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Square holes in a round bar.
How would one make nice sharp-cornered, clean-sided (I'm not sure of the
surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Alternately, how might one make those same holes in a cylinder machined out of that same bar, with a wall thickness of about 0.06", without distorting the cylinder by more than a couple of thousandths (I am assuming that one would have to do some post-operations to clean up the cylinder after making the holes, unless one hand-filed them). This is a thought experiment for making cylinder liners for 2-stroke engines of about 0.2 in^3 displacement; the holes would be the transfer ports, and the cylinder liners need to have their diameter controlled to about 0.001" on the outside and less than that on the inside for proper sealing (or if not controlled, then at least matched to the crankcase that they slide into, and the piston that slides in them). -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com |
Square holes in a round bar.
On Thu, 15 Mar 2012 10:54:15 -0500, Tim Wescott
wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Alternately, how might one make those same holes in a cylinder machined out of that same bar, with a wall thickness of about 0.06", without distorting the cylinder by more than a couple of thousandths (I am assuming that one would have to do some post-operations to clean up the cylinder after making the holes, unless one hand-filed them). This is a thought experiment for making cylinder liners for 2-stroke engines of about 0.2 in^3 displacement; the holes would be the transfer ports, and the cylinder liners need to have their diameter controlled to about 0.001" on the outside and less than that on the inside for proper sealing (or if not controlled, then at least matched to the crankcase that they slide into, and the piston that slides in them). EDM? |
Square holes in a round bar.
Tim Wescott wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Alternately, how might one make those same holes in a cylinder machined out of that same bar, with a wall thickness of about 0.06", without distorting the cylinder by more than a couple of thousandths (I am assuming that one would have to do some post-operations to clean up the cylinder after making the holes, unless one hand-filed them). This is a thought experiment for making cylinder liners for 2-stroke engines of about 0.2 in^3 displacement; the holes would be the transfer ports, and the cylinder liners need to have their diameter controlled to about 0.001" on the outside and less than that on the inside for proper sealing (or if not controlled, then at least matched to the crankcase that they slide into, and the piston that slides in them). -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com Wouldn't this normally be just a milled slot? Square on the top and bottom (relative to the piston stroke) with the edges running off the cylinder leaving square "knife edges" at the ends? At 0.1" perhaps a pass with a slotting saw rather than a super small and delicate end mill. |
Square holes in a round bar.
On Thu, 15 Mar 2012 10:54:15 -0500, Tim Wescott
wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Alternately, how might one make those same holes in a cylinder machined out of that same bar, with a wall thickness of about 0.06", without distorting the cylinder by more than a couple of thousandths (I am assuming that one would have to do some post-operations to clean up the cylinder after making the holes, unless one hand-filed them). This is a thought experiment for making cylinder liners for 2-stroke engines of about 0.2 in^3 displacement; the holes would be the transfer ports, and the cylinder liners need to have their diameter controlled to about 0.001" on the outside and less than that on the inside for proper sealing (or if not controlled, then at least matched to the crankcase that they slide into, and the piston that slides in them). I think that the only ways are non-traditional machining. The most obvious is EDM, as Pete says. I also suspect it's the only *practical* way to do it. Laser would be a problem on the corners and perhaps on the finish. Other energy-beam methods, likewise. ECM (electrochemical machining) would do the job very nicely but that's a production method that requires a lot of custom setup. You can get mirror finishes with conventional, or sinker-type EDM. If corner radii can be 0.002", no problem. Sharper corners are possible but require really good technique and equipment. I wouldn't try to do it with home-made EDMs. You'll have a problem with surface finish and it would be really slow. This is a job for a jobbing EDM shop -- usually mold shops -- that is sympathetic to your interest and that would give you a good rate. Burn rates should be very quick. That's not where your money would go. Electrodes would be simple -- you could make them at home. It's setup time that could cost you. If you find a shop and visit, you should be able to figure out how to fixture the parts and get specs for making electrodes (graphite or copper). If you deliver parts already loaded in a simple-to-mount fixture, that could make the whole job really cheap. -- Ed Huntress |
Square holes in a round bar.
On Mar 15, 9:54*am, Tim Wescott wrote:
How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Alternately, how might one make those same holes in a cylinder machined out of that same bar, with a wall thickness of about 0.06", without distorting the cylinder by more than a couple of thousandths (I am assuming that one would have to do some post-operations to clean up the cylinder after making the holes, unless one hand-filed them). This is a thought experiment for making cylinder liners for 2-stroke engines of about 0.2 in^3 displacement; the holes would be the transfer ports, and the cylinder liners need to have their diameter controlled to about 0.001" on the outside and less than that on the inside for proper sealing (or if not controlled, then at least matched to the crankcase that they slide into, and the piston that slides in them). EDM and you really, really don't want sharp corners. Nice stress risers if you do. Have a look at some weedwhacker motors. You also don't want a configuration that'll grab your piston rings. Stan |
Square holes in a round bar.
On Thu, 15 Mar 2012 10:20:42 -0600, Pete C. wrote:
Tim Wescott wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Alternately, how might one make those same holes in a cylinder machined out of that same bar, with a wall thickness of about 0.06", without distorting the cylinder by more than a couple of thousandths (I am assuming that one would have to do some post-operations to clean up the cylinder after making the holes, unless one hand-filed them). This is a thought experiment for making cylinder liners for 2-stroke engines of about 0.2 in^3 displacement; the holes would be the transfer ports, and the cylinder liners need to have their diameter controlled to about 0.001" on the outside and less than that on the inside for proper sealing (or if not controlled, then at least matched to the crankcase that they slide into, and the piston that slides in them). -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com Wouldn't this normally be just a milled slot? Square on the top and bottom (relative to the piston stroke) with the edges running off the cylinder leaving square "knife edges" at the ends? At 0.1" perhaps a pass with a slotting saw rather than a super small and delicate end mill. Schnuerle ported engines want transfer ports that direct the gas toward the cylinder wall away from the exhaust port -- that tends do a good job of blowing out mostly spent combustion products, while retaining the most possible unburned fuel/air mix. More power, better fuel efficiency, cleaner burn -- what's not to like? (Except for the difficulty in machining, of course). -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com |
Square holes in a round bar.
On Thu, 15 Mar 2012 09:36:39 -0700, Stanley Schaefer wrote:
On Mar 15, 9:54Â*am, Tim Wescott wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Alternately, how might one make those same holes in a cylinder machined out of that same bar, with a wall thickness of about 0.06", without distorting the cylinder by more than a couple of thousandths (I am assuming that one would have to do some post-operations to clean up the cylinder after making the holes, unless one hand-filed them). This is a thought experiment for making cylinder liners for 2-stroke engines of about 0.2 in^3 displacement; the holes would be the transfer ports, and the cylinder liners need to have their diameter controlled to about 0.001" on the outside and less than that on the inside for proper sealing (or if not controlled, then at least matched to the crankcase that they slide into, and the piston that slides in them). EDM and you really, really don't want sharp corners. Nice stress risers if you do. Have a look at some weedwhacker motors. You also don't want a configuration that'll grab your piston rings. Stan Well, square-ish then. One wants square holes for more gas flow, but at the same time one doesn't want one's cylinder liner to break. Weedwhacker motors aren't exactly on the same point in the production volume/performance potential/cost curve that I'm trying to address -- if I go looking at bigger engines I'll be looking at race bikes. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com |
Square holes in a round bar.
On Thu, 15 Mar 2012 12:25:19 -0400, Ed Huntress wrote:
On Thu, 15 Mar 2012 10:54:15 -0500, Tim Wescott wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Alternately, how might one make those same holes in a cylinder machined out of that same bar, with a wall thickness of about 0.06", without distorting the cylinder by more than a couple of thousandths (I am assuming that one would have to do some post-operations to clean up the cylinder after making the holes, unless one hand-filed them). This is a thought experiment for making cylinder liners for 2-stroke engines of about 0.2 in^3 displacement; the holes would be the transfer ports, and the cylinder liners need to have their diameter controlled to about 0.001" on the outside and less than that on the inside for proper sealing (or if not controlled, then at least matched to the crankcase that they slide into, and the piston that slides in them). I think that the only ways are non-traditional machining. The most obvious is EDM, as Pete says. I also suspect it's the only *practical* way to do it. Laser would be a problem on the corners and perhaps on the finish. Other energy-beam methods, likewise. ECM (electrochemical machining) would do the job very nicely but that's a production method that requires a lot of custom setup. You can get mirror finishes with conventional, or sinker-type EDM. If corner radii can be 0.002", no problem. Sharper corners are possible but require really good technique and equipment. I wouldn't try to do it with home-made EDMs. You'll have a problem with surface finish and it would be really slow. This is a job for a jobbing EDM shop -- usually mold shops -- that is sympathetic to your interest and that would give you a good rate. Burn rates should be very quick. That's not where your money would go. Electrodes would be simple -- you could make them at home. It's setup time that could cost you. If you find a shop and visit, you should be able to figure out how to fixture the parts and get specs for making electrodes (graphite or copper). If you deliver parts already loaded in a simple-to-mount fixture, that could make the whole job really cheap. "I wouldn't try to do it with home-made EDMs." Do you wave red towels in front of bulls, too? My first alternative is to just use an end mill, and accept that a round hole isn't going to pass as much gas as a square one. Or use an end mill to establish the hole position and angle, then use a plain old file, elbow grease, and patience to establish the squareness. If I actually find myself wanting to build more than one motor then yes, I'll consider finding a sympathetic shop; that's a good idea. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com |
Square holes in a round bar.
On Thu, 15 Mar 2012 09:36:39 -0700, Stanley Schaefer wrote:
On Mar 15, 9:54Â*am, Tim Wescott wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Alternately, how might one make those same holes in a cylinder machined out of that same bar, with a wall thickness of about 0.06", without distorting the cylinder by more than a couple of thousandths (I am assuming that one would have to do some post-operations to clean up the cylinder after making the holes, unless one hand-filed them). This is a thought experiment for making cylinder liners for 2-stroke engines of about 0.2 in^3 displacement; the holes would be the transfer ports, and the cylinder liners need to have their diameter controlled to about 0.001" on the outside and less than that on the inside for proper sealing (or if not controlled, then at least matched to the crankcase that they slide into, and the piston that slides in them). EDM and you really, really don't want sharp corners. Nice stress risers if you do. Have a look at some weedwhacker motors. You also don't want a configuration that'll grab your piston rings. Piston rings? How many piston rings are there on a lapped piston? -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com |
Square holes in a round bar.
On Thu, 15 Mar 2012 12:13:55 -0500, Tim Wescott
wrote: On Thu, 15 Mar 2012 12:25:19 -0400, Ed Huntress wrote: On Thu, 15 Mar 2012 10:54:15 -0500, Tim Wescott wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Alternately, how might one make those same holes in a cylinder machined out of that same bar, with a wall thickness of about 0.06", without distorting the cylinder by more than a couple of thousandths (I am assuming that one would have to do some post-operations to clean up the cylinder after making the holes, unless one hand-filed them). This is a thought experiment for making cylinder liners for 2-stroke engines of about 0.2 in^3 displacement; the holes would be the transfer ports, and the cylinder liners need to have their diameter controlled to about 0.001" on the outside and less than that on the inside for proper sealing (or if not controlled, then at least matched to the crankcase that they slide into, and the piston that slides in them). I think that the only ways are non-traditional machining. The most obvious is EDM, as Pete says. I also suspect it's the only *practical* way to do it. Laser would be a problem on the corners and perhaps on the finish. Other energy-beam methods, likewise. ECM (electrochemical machining) would do the job very nicely but that's a production method that requires a lot of custom setup. You can get mirror finishes with conventional, or sinker-type EDM. If corner radii can be 0.002", no problem. Sharper corners are possible but require really good technique and equipment. I wouldn't try to do it with home-made EDMs. You'll have a problem with surface finish and it would be really slow. This is a job for a jobbing EDM shop -- usually mold shops -- that is sympathetic to your interest and that would give you a good rate. Burn rates should be very quick. That's not where your money would go. Electrodes would be simple -- you could make them at home. It's setup time that could cost you. If you find a shop and visit, you should be able to figure out how to fixture the parts and get specs for making electrodes (graphite or copper). If you deliver parts already loaded in a simple-to-mount fixture, that could make the whole job really cheap. "I wouldn't try to do it with home-made EDMs." Do you wave red towels in front of bulls, too? Ha-ha! If you get into that, you're enterring a new hobby unto itself. Seriosly, for the type of work you're contemplating, I'd consider building an ECM before an EDM. You can't buy small ones and you'd be a pioneer for hobby work, but the power supply and the servos are *vastly* simpler. It would be a good project for a hobbyist who wanted to experiment. My first alternative is to just use an end mill, and accept that a round hole isn't going to pass as much gas as a square one. Or use an end mill to establish the hole position and angle, then use a plain old file, elbow grease, and patience to establish the squareness. As one who has squared the ports in several Power Products go-cart engines (and who five-ported one, with someone else doing the milling and the brazing), I remember that work. That's a lot of filing in a PP engine. It probably would be quicker and lighter work with a jeweler's file in those little engines you're working with. If I actually find myself wanting to build more than one motor then yes, I'll consider finding a sympathetic shop; that's a good idea. It's one operation that, IMO, would be a Sisyphean job if you started with a home-built EDM. Just getting those things to cut right is an accomplishment. And when you do, you have a 1950s-type EDM. You need at least a 1980s type to get the finish and surface quality that you'd want. Good luck! -- Ed Huntress |
Square holes in a round bar.
Tim Wescott wrote: On Thu, 15 Mar 2012 10:20:42 -0600, Pete C. wrote: Tim Wescott wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Alternately, how might one make those same holes in a cylinder machined out of that same bar, with a wall thickness of about 0.06", without distorting the cylinder by more than a couple of thousandths (I am assuming that one would have to do some post-operations to clean up the cylinder after making the holes, unless one hand-filed them). This is a thought experiment for making cylinder liners for 2-stroke engines of about 0.2 in^3 displacement; the holes would be the transfer ports, and the cylinder liners need to have their diameter controlled to about 0.001" on the outside and less than that on the inside for proper sealing (or if not controlled, then at least matched to the crankcase that they slide into, and the piston that slides in them). -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com Wouldn't this normally be just a milled slot? Square on the top and bottom (relative to the piston stroke) with the edges running off the cylinder leaving square "knife edges" at the ends? At 0.1" perhaps a pass with a slotting saw rather than a super small and delicate end mill. Schnuerle ported engines want transfer ports that direct the gas toward the cylinder wall away from the exhaust port -- that tends do a good job of blowing out mostly spent combustion products, while retaining the most possible unburned fuel/air mix. More power, better fuel efficiency, cleaner burn -- what's not to like? (Except for the difficulty in machining, of course). -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com I'm having a little difficulty picturing exactly what you're trying to do. Perhaps drill and broach? You can make your own broach a bit more easily than the ECM and EDM lines of thought. Come to think of it, perhaps rotary broaching might do what you need. |
Square holes in a round bar.
On Thu, 15 Mar 2012 12:10:40 -0600, Pete C. wrote:
Tim Wescott wrote: On Thu, 15 Mar 2012 10:20:42 -0600, Pete C. wrote: Tim Wescott wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Alternately, how might one make those same holes in a cylinder machined out of that same bar, with a wall thickness of about 0.06", without distorting the cylinder by more than a couple of thousandths (I am assuming that one would have to do some post-operations to clean up the cylinder after making the holes, unless one hand-filed them). This is a thought experiment for making cylinder liners for 2-stroke engines of about 0.2 in^3 displacement; the holes would be the transfer ports, and the cylinder liners need to have their diameter controlled to about 0.001" on the outside and less than that on the inside for proper sealing (or if not controlled, then at least matched to the crankcase that they slide into, and the piston that slides in them). -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com Wouldn't this normally be just a milled slot? Square on the top and bottom (relative to the piston stroke) with the edges running off the cylinder leaving square "knife edges" at the ends? At 0.1" perhaps a pass with a slotting saw rather than a super small and delicate end mill. Schnuerle ported engines want transfer ports that direct the gas toward the cylinder wall away from the exhaust port -- that tends do a good job of blowing out mostly spent combustion products, while retaining the most possible unburned fuel/air mix. More power, better fuel efficiency, cleaner burn -- what's not to like? (Except for the difficulty in machining, of course). -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com I'm having a little difficulty picturing exactly what you're trying to do. Perhaps drill and broach? You can make your own broach a bit more easily than the ECM and EDM lines of thought. Come to think of it, perhaps rotary broaching might do what you need. http://en.wikipedia.org/wiki/Schnuerle_porting. See the picture in the upper right. Now imagine that instead of having two transfer ports feeding gas to the cylinder, there's four; the two shown, plus two more that are rotated more away from the exhaust. Then, if that's not enough, a fifth "boost" port directly opposite the exhaust, and pointing toward the top of the cylinder. The whole idea is that the transfer gas hits the pocket at the cylinder/ piston junction, then rises up the back of the cylinder in a fairly unified mass; because this mass is increasing in volume, it naturally pushes the spent gas out the exhaust port. Cross-flow scavenging (the kind where there's a fence on the piston) tends to mix the gases a lot more. There's a lot of hand-waving explanation for why it works, but the bottom line is that it works better than cross-flow scavenging! -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com |
Square holes in a round bar.
On Thu, 15 Mar 2012 13:43:35 -0500, Tim Wescott
wrote: On Thu, 15 Mar 2012 12:10:40 -0600, Pete C. wrote: Tim Wescott wrote: On Thu, 15 Mar 2012 10:20:42 -0600, Pete C. wrote: Tim Wescott wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Alternately, how might one make those same holes in a cylinder machined out of that same bar, with a wall thickness of about 0.06", without distorting the cylinder by more than a couple of thousandths (I am assuming that one would have to do some post-operations to clean up the cylinder after making the holes, unless one hand-filed them). This is a thought experiment for making cylinder liners for 2-stroke engines of about 0.2 in^3 displacement; the holes would be the transfer ports, and the cylinder liners need to have their diameter controlled to about 0.001" on the outside and less than that on the inside for proper sealing (or if not controlled, then at least matched to the crankcase that they slide into, and the piston that slides in them). -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com Wouldn't this normally be just a milled slot? Square on the top and bottom (relative to the piston stroke) with the edges running off the cylinder leaving square "knife edges" at the ends? At 0.1" perhaps a pass with a slotting saw rather than a super small and delicate end mill. Schnuerle ported engines want transfer ports that direct the gas toward the cylinder wall away from the exhaust port -- that tends do a good job of blowing out mostly spent combustion products, while retaining the most possible unburned fuel/air mix. More power, better fuel efficiency, cleaner burn -- what's not to like? (Except for the difficulty in machining, of course). -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com I'm having a little difficulty picturing exactly what you're trying to do. Perhaps drill and broach? You can make your own broach a bit more easily than the ECM and EDM lines of thought. Come to think of it, perhaps rotary broaching might do what you need. http://en.wikipedia.org/wiki/Schnuerle_porting. See the picture in the upper right. Now imagine that instead of having two transfer ports feeding gas to the cylinder, there's four; the two shown, plus two more that are rotated more away from the exhaust. Then, if that's not enough, a fifth "boost" port directly opposite the exhaust, and pointing toward the top of the cylinder. The whole idea is that the transfer gas hits the pocket at the cylinder/ piston junction, then rises up the back of the cylinder in a fairly unified mass; because this mass is increasing in volume, it naturally pushes the spent gas out the exhaust port. Cross-flow scavenging (the kind where there's a fence on the piston) tends to mix the gases a lot more. There's a lot of hand-waving explanation for why it works, but the bottom line is that it works better than cross-flow scavenging! Shoot. You're five-porting. 1960 go-carting, here we come! g -- Ed Huntress |
Square holes in a round bar.
Tim Wescott wrote:
On Thu, 15 Mar 2012 12:10:40 -0600, Pete C. wrote: Tim Wescott wrote: On Thu, 15 Mar 2012 10:20:42 -0600, Pete C. wrote: Tim Wescott wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? ? ?? Alternately, how might one make those same holes in a cylinder ?? ?? machined out of that same bar, with a wall thickness of about 0.06", ?? ?? without distorting the cylinder by more than a couple of thousandths ?? ?? (I am assuming that one would have to do some post-operations to ?? ?? clean up the cylinder after making the holes, unless one hand-filed ?? ?? them). ?? ?? ?? ?? This is a thought experiment for making cylinder liners for 2-stroke ?? ?? engines of about 0.2 in^3 displacement; the holes would be the ?? ?? transfer ports, and the cylinder liners need to have their diameter ?? ?? controlled to about 0.001" on the outside and less than that on the ?? ?? inside for proper sealing (or if not controlled, then at least ?? ?? matched to the crankcase that they slide into, and the piston that ?? ?? slides in them). ?? ?? ?? ?? -- ?? ?? My liberal friends think I'm a conservative kook. My conservative ?? ?? friends think I'm a liberal kook. Why am I not happy that they have ?? ?? found common ground? ?? ?? ?? ?? Tim Wescott, Communications, Control, Circuits ? Software ?? ?? http://www.wescottdesign.com ?? ? ?? ? Wouldn't this normally be just a milled slot? Square on the top and ?? ? bottom (relative to the piston stroke) with the edges running off the ?? ? cylinder leaving square "knife edges" at the ends? At 0.1" perhaps a ?? ? pass with a slotting saw rather than a super small and delicate end ?? ? mill. ?? ?? Schnuerle ported engines want transfer ports that direct the gas toward ?? the cylinder wall away from the exhaust port -- that tends do a good ?? job of blowing out mostly spent combustion products, while retaining ?? the most possible unburned fuel/air mix. More power, better fuel ?? efficiency, cleaner burn -- what's not to like? (Except for the ?? difficulty in machining, of course). ?? ?? -- ?? My liberal friends think I'm a conservative kook. My conservative ?? friends think I'm a liberal kook. Why am I not happy that they have ?? found common ground? ?? ?? Tim Wescott, Communications, Control, Circuits ? Software ?? http://www.wescottdesign.com ? ? I'm having a little difficulty picturing exactly what you're trying to ? do. Perhaps drill and broach? You can make your own broach a bit more ? easily than the ECM and EDM lines of thought. Come to think of it, ? perhaps rotary broaching might do what you need. http://en.wikipedia.org/wiki/Schnuerle_porting. See the picture in the upper right. Now imagine that instead of having two transfer ports feeding gas to the cylinder, there's four; the two shown, plus two more that are rotated more away from the exhaust. Then, if that's not enough, a fifth "boost" port directly opposite the exhaust, and pointing toward the top of the cylinder. The whole idea is that the transfer gas hits the pocket at the cylinder/ piston junction, then rises up the back of the cylinder in a fairly unified mass; because this mass is increasing in volume, it naturally pushes the spent gas out the exhaust port. Cross-flow scavenging (the kind where there's a fence on the piston) tends to mix the gases a lot more. There's a lot of hand-waving explanation for why it works, but the bottom line is that it works better than cross-flow scavenging! I don't see why you need holes with square sharp corners to achieve those port configurations. |
Square holes in a round bar.
On Thu, 15 Mar 2012 14:07:34 -0500, jim wrote:
Tim Wescott wrote: On Thu, 15 Mar 2012 12:10:40 -0600, Pete C. wrote: Tim Wescott wrote: On Thu, 15 Mar 2012 10:20:42 -0600, Pete C. wrote: Tim Wescott wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? ? ?? Alternately, how might one make those same holes in a cylinder ?? ?? machined out of that same bar, with a wall thickness of about 0.06", ?? ?? without distorting the cylinder by more than a couple of thousandths ?? ?? (I am assuming that one would have to do some post-operations to ?? ?? clean up the cylinder after making the holes, unless one hand-filed ?? ?? them). ?? ?? ?? ?? This is a thought experiment for making cylinder liners for 2-stroke ?? ?? engines of about 0.2 in^3 displacement; the holes would be the ?? ?? transfer ports, and the cylinder liners need to have their diameter ?? ?? controlled to about 0.001" on the outside and less than that on the ?? ?? inside for proper sealing (or if not controlled, then at least ?? ?? matched to the crankcase that they slide into, and the piston that ?? ?? slides in them). ?? ?? ?? ?? -- ?? ?? My liberal friends think I'm a conservative kook. My conservative ?? ?? friends think I'm a liberal kook. Why am I not happy that they have ?? ?? found common ground? ?? ?? ?? ?? Tim Wescott, Communications, Control, Circuits ? Software ?? ?? http://www.wescottdesign.com ?? ? ?? ? Wouldn't this normally be just a milled slot? Square on the top and ?? ? bottom (relative to the piston stroke) with the edges running off the ?? ? cylinder leaving square "knife edges" at the ends? At 0.1" perhaps a ?? ? pass with a slotting saw rather than a super small and delicate end ?? ? mill. ?? ?? Schnuerle ported engines want transfer ports that direct the gas toward ?? the cylinder wall away from the exhaust port -- that tends do a good ?? job of blowing out mostly spent combustion products, while retaining ?? the most possible unburned fuel/air mix. More power, better fuel ?? efficiency, cleaner burn -- what's not to like? (Except for the ?? difficulty in machining, of course). ?? ?? -- ?? My liberal friends think I'm a conservative kook. My conservative ?? friends think I'm a liberal kook. Why am I not happy that they have ?? found common ground? ?? ?? Tim Wescott, Communications, Control, Circuits ? Software ?? http://www.wescottdesign.com ? ? I'm having a little difficulty picturing exactly what you're trying to ? do. Perhaps drill and broach? You can make your own broach a bit more ? easily than the ECM and EDM lines of thought. Come to think of it, ? perhaps rotary broaching might do what you need. http://en.wikipedia.org/wiki/Schnuerle_porting. See the picture in the upper right. Now imagine that instead of having two transfer ports feeding gas to the cylinder, there's four; the two shown, plus two more that are rotated more away from the exhaust. Then, if that's not enough, a fifth "boost" port directly opposite the exhaust, and pointing toward the top of the cylinder. The whole idea is that the transfer gas hits the pocket at the cylinder/ piston junction, then rises up the back of the cylinder in a fairly unified mass; because this mass is increasing in volume, it naturally pushes the spent gas out the exhaust port. Cross-flow scavenging (the kind where there's a fence on the piston) tends to mix the gases a lot more. There's a lot of hand-waving explanation for why it works, but the bottom line is that it works better than cross-flow scavenging! I don't see why you need holes with square sharp corners to achieve those port configurations. Well, you don't, in general, which is why I'll probably just use round holes to start. But if you want the maximum flow in the minimum space, you do. -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com |
Square holes in a round bar.
Tim Wescott wrote: On Thu, 15 Mar 2012 14:07:34 -0500, jim wrote: Tim Wescott wrote: On Thu, 15 Mar 2012 12:10:40 -0600, Pete C. wrote: Tim Wescott wrote: On Thu, 15 Mar 2012 10:20:42 -0600, Pete C. wrote: Tim Wescott wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? ? ?? Alternately, how might one make those same holes in a cylinder ?? ?? machined out of that same bar, with a wall thickness of about 0.06", ?? ?? without distorting the cylinder by more than a couple of thousandths ?? ?? (I am assuming that one would have to do some post-operations to ?? ?? clean up the cylinder after making the holes, unless one hand-filed ?? ?? them). ?? ?? ?? ?? This is a thought experiment for making cylinder liners for 2-stroke ?? ?? engines of about 0.2 in^3 displacement; the holes would be the ?? ?? transfer ports, and the cylinder liners need to have their diameter ?? ?? controlled to about 0.001" on the outside and less than that on the ?? ?? inside for proper sealing (or if not controlled, then at least ?? ?? matched to the crankcase that they slide into, and the piston that ?? ?? slides in them). ?? ?? ?? ?? -- ?? ?? My liberal friends think I'm a conservative kook. My conservative ?? ?? friends think I'm a liberal kook. Why am I not happy that they have ?? ?? found common ground? ?? ?? ?? ?? Tim Wescott, Communications, Control, Circuits ? Software ?? ?? http://www.wescottdesign.com ?? ? ?? ? Wouldn't this normally be just a milled slot? Square on the top and ?? ? bottom (relative to the piston stroke) with the edges running off the ?? ? cylinder leaving square "knife edges" at the ends? At 0.1" perhaps a ?? ? pass with a slotting saw rather than a super small and delicate end ?? ? mill. ?? ?? Schnuerle ported engines want transfer ports that direct the gas toward ?? the cylinder wall away from the exhaust port -- that tends do a good ?? job of blowing out mostly spent combustion products, while retaining ?? the most possible unburned fuel/air mix. More power, better fuel ?? efficiency, cleaner burn -- what's not to like? (Except for the ?? difficulty in machining, of course). ?? ?? -- ?? My liberal friends think I'm a conservative kook. My conservative ?? friends think I'm a liberal kook. Why am I not happy that they have ?? found common ground? ?? ?? Tim Wescott, Communications, Control, Circuits ? Software ?? http://www.wescottdesign.com ? ? I'm having a little difficulty picturing exactly what you're trying to ? do. Perhaps drill and broach? You can make your own broach a bit more ? easily than the ECM and EDM lines of thought. Come to think of it, ? perhaps rotary broaching might do what you need. http://en.wikipedia.org/wiki/Schnuerle_porting. See the picture in the upper right. Now imagine that instead of having two transfer ports feeding gas to the cylinder, there's four; the two shown, plus two more that are rotated more away from the exhaust. Then, if that's not enough, a fifth "boost" port directly opposite the exhaust, and pointing toward the top of the cylinder. The whole idea is that the transfer gas hits the pocket at the cylinder/ piston junction, then rises up the back of the cylinder in a fairly unified mass; because this mass is increasing in volume, it naturally pushes the spent gas out the exhaust port. Cross-flow scavenging (the kind where there's a fence on the piston) tends to mix the gases a lot more. There's a lot of hand-waving explanation for why it works, but the bottom line is that it works better than cross-flow scavenging! I don't see why you need holes with square sharp corners to achieve those port configurations. Well, you don't, in general, which is why I'll probably just use round holes to start. But if you want the maximum flow in the minimum space, you do. -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com Looking at the pic, it still looks like you could get the desired port with a small dia slotting saw. It will leave you a bit of a funnel opening on the outside leading in to your square / rectangular port. |
Square holes in a round bar.
On 03/15/2012 10:14 AM, Tim Wescott wrote:
On Thu, 15 Mar 2012 09:36:39 -0700, Stanley Schaefer wrote: On Mar 15, 9:54 am, Tim wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Alternately, how might one make those same holes in a cylinder machined out of that same bar, with a wall thickness of about 0.06", without distorting the cylinder by more than a couple of thousandths (I am assuming that one would have to do some post-operations to clean up the cylinder after making the holes, unless one hand-filed them). This is a thought experiment for making cylinder liners for 2-stroke engines of about 0.2 in^3 displacement; the holes would be the transfer ports, and the cylinder liners need to have their diameter controlled to about 0.001" on the outside and less than that on the inside for proper sealing (or if not controlled, then at least matched to the crankcase that they slide into, and the piston that slides in them). How about you turn it inside out so it's an external slotting/milling operation? :-) That's not as nutty as it sounds...mill your transfer ports into the outside of the cylinder proper, than press a hollow tube (sleeve) over the outside. Presto, you have transfer ports! One thing that is going to be a problem though: steel/iron doesn't get the heat out very well, and two strokers have a lot to get rid of. Good luck, Bill |
Square holes in a round bar.
"Tim Wescott" wrote in message http://en.wikipedia.org/wiki/Schnuerle_porting. Tim Wescott Is this a good job for a home-made filing machine? jsw |
Square holes in a round bar.
"jim" wrote in message ... If a thin wall is a problem then it's usually better to first bore the cylinder to an undersize condition and slot the ports using whatever convenient means is available, finally finishing the cylinder bore by holding from the part outside diameter in a collet or some type of full grip vise jaw type of fixturing device. holes with square sharp corners Does not exist--the best you can do is to approximate by specifying the max allowable mismatch and corner radii. |
Square holes in a round bar.
On Thu, 15 Mar 2012 14:48:50 -0600, Pete C. wrote:
Tim Wescott wrote: On Thu, 15 Mar 2012 14:07:34 -0500, jim wrote: Tim Wescott wrote: On Thu, 15 Mar 2012 12:10:40 -0600, Pete C. wrote: Tim Wescott wrote: On Thu, 15 Mar 2012 10:20:42 -0600, Pete C. wrote: Tim Wescott wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? ? ?? Alternately, how might one make those same holes in a cylinder ?? ?? machined out of that same bar, with a wall thickness of about 0.06", ?? ?? without distorting the cylinder by more than a couple of thousandths ?? ?? (I am assuming that one would have to do some post-operations to ?? ?? clean up the cylinder after making the holes, unless one hand-filed ?? ?? them). ?? ?? ?? ?? This is a thought experiment for making cylinder liners for 2-stroke ?? ?? engines of about 0.2 in^3 displacement; the holes would be the ?? ?? transfer ports, and the cylinder liners need to have their diameter ?? ?? controlled to about 0.001" on the outside and less than that on the ?? ?? inside for proper sealing (or if not controlled, then at least ?? ?? matched to the crankcase that they slide into, and the piston that ?? ?? slides in them). ?? ?? ?? ?? -- ?? ?? My liberal friends think I'm a conservative kook. My conservative ?? ?? friends think I'm a liberal kook. Why am I not happy that they have ?? ?? found common ground? ?? ?? ?? ?? Tim Wescott, Communications, Control, Circuits ? Software ?? ?? http://www.wescottdesign.com ?? ? ?? ? Wouldn't this normally be just a milled slot? Square on the top and ?? ? bottom (relative to the piston stroke) with the edges running off the ?? ? cylinder leaving square "knife edges" at the ends? At 0.1" perhaps a ?? ? pass with a slotting saw rather than a super small and delicate end ?? ? mill. ?? ?? Schnuerle ported engines want transfer ports that direct the gas toward ?? the cylinder wall away from the exhaust port -- that tends do a good ?? job of blowing out mostly spent combustion products, while retaining ?? the most possible unburned fuel/air mix. More power, better fuel ?? efficiency, cleaner burn -- what's not to like? (Except for the ?? difficulty in machining, of course). ?? ?? -- ?? My liberal friends think I'm a conservative kook. My conservative ?? friends think I'm a liberal kook. Why am I not happy that they have ?? found common ground? ?? ?? Tim Wescott, Communications, Control, Circuits ? Software ?? http://www.wescottdesign.com ? ? I'm having a little difficulty picturing exactly what you're trying to ? do. Perhaps drill and broach? You can make your own broach a bit more ? easily than the ECM and EDM lines of thought. Come to think of it, ? perhaps rotary broaching might do what you need. http://en.wikipedia.org/wiki/Schnuerle_porting. See the picture in the upper right. Now imagine that instead of having two transfer ports feeding gas to the cylinder, there's four; the two shown, plus two more that are rotated more away from the exhaust. Then, if that's not enough, a fifth "boost" port directly opposite the exhaust, and pointing toward the top of the cylinder. The whole idea is that the transfer gas hits the pocket at the cylinder/ piston junction, then rises up the back of the cylinder in a fairly unified mass; because this mass is increasing in volume, it naturally pushes the spent gas out the exhaust port. Cross-flow scavenging (the kind where there's a fence on the piston) tends to mix the gases a lot more. There's a lot of hand-waving explanation for why it works, but the bottom line is that it works better than cross-flow scavenging! I don't see why you need holes with square sharp corners to achieve those port configurations. Well, you don't, in general, which is why I'll probably just use round holes to start. But if you want the maximum flow in the minimum space, you do. -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com Looking at the pic, it still looks like you could get the desired port with a small dia slotting saw. It will leave you a bit of a funnel opening on the outside leading in to your square / rectangular port. Well, I disagree. I think that if I did that I'd end up with undirected, turbulent flow in exactly a spot where I wanted directed laminar flow. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com |
Square holes in a round bar.
On Thu, 15 Mar 2012 14:11:59 -0700, Bill Martin wrote:
On 03/15/2012 10:14 AM, Tim Wescott wrote: On Thu, 15 Mar 2012 09:36:39 -0700, Stanley Schaefer wrote: On Mar 15, 9:54 am, Tim wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Alternately, how might one make those same holes in a cylinder machined out of that same bar, with a wall thickness of about 0.06", without distorting the cylinder by more than a couple of thousandths (I am assuming that one would have to do some post-operations to clean up the cylinder after making the holes, unless one hand-filed them). This is a thought experiment for making cylinder liners for 2-stroke engines of about 0.2 in^3 displacement; the holes would be the transfer ports, and the cylinder liners need to have their diameter controlled to about 0.001" on the outside and less than that on the inside for proper sealing (or if not controlled, then at least matched to the crankcase that they slide into, and the piston that slides in them). How about you turn it inside out so it's an external slotting/milling operation? :-) That's not as nutty as it sounds...mill your transfer ports into the outside of the cylinder proper, than press a hollow tube (sleeve) over the outside. Presto, you have transfer ports! One thing that is going to be a problem though: steel/iron doesn't get the heat out very well, and two strokers have a lot to get rid of. Good luck, The standard construction for model airplane engines of this sort is to have a cylinder lining of steel or (if you have friends in the right sorts of shop) hard chromed brass. It's a thin tube, usually with a lip on top, that slides into the crankcase. The crankcase has passages cast or milled into it for the transfer and for the exhaust. So the gas travels up from the crank case to the port along the outside of the sleeve, then turns 90 degrees to go into the cylinder. Meanwhile, the exhaust is exiting through its port without (we hope) leaking into the crankcase because the liner is sealed to the case by a close mechanical fit. I'm not sure of the detailed heat-flow -- I just know that it must be adequate, or all my engines would have burnt up long ago. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com |
Square holes in a round bar.
Tim Wescott wrote: On Thu, 15 Mar 2012 14:48:50 -0600, Pete C. wrote: Tim Wescott wrote: On Thu, 15 Mar 2012 14:07:34 -0500, jim wrote: Tim Wescott wrote: On Thu, 15 Mar 2012 12:10:40 -0600, Pete C. wrote: Tim Wescott wrote: On Thu, 15 Mar 2012 10:20:42 -0600, Pete C. wrote: Tim Wescott wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? ? ?? Alternately, how might one make those same holes in a cylinder ?? ?? machined out of that same bar, with a wall thickness of about 0.06", ?? ?? without distorting the cylinder by more than a couple of thousandths ?? ?? (I am assuming that one would have to do some post-operations to ?? ?? clean up the cylinder after making the holes, unless one hand-filed ?? ?? them). ?? ?? ?? ?? This is a thought experiment for making cylinder liners for 2-stroke ?? ?? engines of about 0.2 in^3 displacement; the holes would be the ?? ?? transfer ports, and the cylinder liners need to have their diameter ?? ?? controlled to about 0.001" on the outside and less than that on the ?? ?? inside for proper sealing (or if not controlled, then at least ?? ?? matched to the crankcase that they slide into, and the piston that ?? ?? slides in them). ?? ?? ?? ?? -- ?? ?? My liberal friends think I'm a conservative kook. My conservative ?? ?? friends think I'm a liberal kook. Why am I not happy that they have ?? ?? found common ground? ?? ?? ?? ?? Tim Wescott, Communications, Control, Circuits ? Software ?? ?? http://www.wescottdesign.com ?? ? ?? ? Wouldn't this normally be just a milled slot? Square on the top and ?? ? bottom (relative to the piston stroke) with the edges running off the ?? ? cylinder leaving square "knife edges" at the ends? At 0.1" perhaps a ?? ? pass with a slotting saw rather than a super small and delicate end ?? ? mill. ?? ?? Schnuerle ported engines want transfer ports that direct the gas toward ?? the cylinder wall away from the exhaust port -- that tends do a good ?? job of blowing out mostly spent combustion products, while retaining ?? the most possible unburned fuel/air mix. More power, better fuel ?? efficiency, cleaner burn -- what's not to like? (Except for the ?? difficulty in machining, of course). ?? ?? -- ?? My liberal friends think I'm a conservative kook. My conservative ?? friends think I'm a liberal kook. Why am I not happy that they have ?? found common ground? ?? ?? Tim Wescott, Communications, Control, Circuits ? Software ?? http://www.wescottdesign.com ? ? I'm having a little difficulty picturing exactly what you're trying to ? do. Perhaps drill and broach? You can make your own broach a bit more ? easily than the ECM and EDM lines of thought. Come to think of it, ? perhaps rotary broaching might do what you need. http://en.wikipedia.org/wiki/Schnuerle_porting. See the picture in the upper right. Now imagine that instead of having two transfer ports feeding gas to the cylinder, there's four; the two shown, plus two more that are rotated more away from the exhaust. Then, if that's not enough, a fifth "boost" port directly opposite the exhaust, and pointing toward the top of the cylinder. The whole idea is that the transfer gas hits the pocket at the cylinder/ piston junction, then rises up the back of the cylinder in a fairly unified mass; because this mass is increasing in volume, it naturally pushes the spent gas out the exhaust port. Cross-flow scavenging (the kind where there's a fence on the piston) tends to mix the gases a lot more. There's a lot of hand-waving explanation for why it works, but the bottom line is that it works better than cross-flow scavenging! I don't see why you need holes with square sharp corners to achieve those port configurations. Well, you don't, in general, which is why I'll probably just use round holes to start. But if you want the maximum flow in the minimum space, you do. -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com Looking at the pic, it still looks like you could get the desired port with a small dia slotting saw. It will leave you a bit of a funnel opening on the outside leading in to your square / rectangular port. Well, I disagree. I think that if I did that I'd end up with undirected, turbulent flow in exactly a spot where I wanted directed laminar flow. Another option would be to mill a wider slot out of the side of the bar, say .125" wide, make a matching half moon shaped insert to fit the slot, mill your three square channels in the insert, TIG weld the insert into the bar and then machine your cylinder liner from the resulting bar with included channels. You could also make a punch and die set to punch the channels in the cylinder liner tube once it's at your 0.060" wall thickness or slightly thicker and then hone the inside to clean up any ridges around the ports. |
Square holes in a round bar.
On Thu, 15 Mar 2012 15:20:36 -0700, PrecisionmachinisT wrote:
"jim" wrote in message ... If a thin wall is a problem then it's usually better to first bore the cylinder to an undersize condition and slot the ports using whatever convenient means is available, finally finishing the cylinder bore by holding from the part outside diameter in a collet or some type of full grip vise jaw type of fixturing device. That's exactly what I intend to do -- the last thing I want to do is go hacking at the holes when I don't have enough meat in the cylinder liner to correct any problems. holes with square sharp corners Does not exist--the best you can do is to approximate by specifying the max allowable mismatch and corner radii. I just want something that's significantly more square than it is round. -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com |
Square holes in a round bar.
On Thu, 15 Mar 2012 18:14:51 -0500, Tim Wescott
wrote: On Thu, 15 Mar 2012 14:11:59 -0700, Bill Martin wrote: On 03/15/2012 10:14 AM, Tim Wescott wrote: On Thu, 15 Mar 2012 09:36:39 -0700, Stanley Schaefer wrote: On Mar 15, 9:54 am, Tim wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Alternately, how might one make those same holes in a cylinder machined out of that same bar, with a wall thickness of about 0.06", without distorting the cylinder by more than a couple of thousandths (I am assuming that one would have to do some post-operations to clean up the cylinder after making the holes, unless one hand-filed them). This is a thought experiment for making cylinder liners for 2-stroke engines of about 0.2 in^3 displacement; the holes would be the transfer ports, and the cylinder liners need to have their diameter controlled to about 0.001" on the outside and less than that on the inside for proper sealing (or if not controlled, then at least matched to the crankcase that they slide into, and the piston that slides in them). How about you turn it inside out so it's an external slotting/milling operation? :-) That's not as nutty as it sounds...mill your transfer ports into the outside of the cylinder proper, than press a hollow tube (sleeve) over the outside. Presto, you have transfer ports! One thing that is going to be a problem though: steel/iron doesn't get the heat out very well, and two strokers have a lot to get rid of. Good luck, The standard construction for model airplane engines of this sort is to have a cylinder lining of steel or (if you have friends in the right sorts of shop) hard chromed brass. It's a thin tube, usually with a lip on top, that slides into the crankcase. The crankcase has passages cast or milled into it for the transfer and for the exhaust. So the gas travels up from the crank case to the port along the outside of the sleeve, then turns 90 degrees to go into the cylinder. Meanwhile, the exhaust is exiting through its port without (we hope) leaking into the crankcase because the liner is sealed to the case by a close mechanical fit. I'm not sure of the detailed heat-flow -- I just know that it must be adequate, or all my engines would have burnt up long ago. Greetings Tim, I don't know how many of these you need. If I had to make just a few I would mill out the square holes with a .062 dia endmill and then finish the square corners with a square needle file. I would grind the teeth off one side first to make a safe side on the file. But I have a surface grinder that would make the job easy. A fellow could stone off the teeth too since the file is so fine and narrow. If I had to do a lot I would grind a broach to square up the corners but I would still mill out most of the metal. First a .094 drill, then mill, then broach. The tubing I would mount on a mandrel to support it, that would keep distortion within your tolerance range. Having a safe side on the file makes it easy to just remove material from the corner while not removing material from the side. Furthermore the safe side will burnish the side. Eric |
Square holes in a round bar.
On Thu, 15 Mar 2012 13:43:35 -0500, Tim Wescott
wrote: http://en.wikipedia.org/wiki/Schnuerle_porting Set up a fixture to hold the cylinder liner at the angle you want the port. Drill a hole to the largest diameter that fits your square port and file to final shape. If you are persnickety then leave the sleeve bore a few tenths underside and lap of hone to final diameter after finish filing the ports. -- Cheers, John B. |
Square holes in a round bar.
On Fri, 16 Mar 2012 10:41:45 +0700, John B.
wrote: On Thu, 15 Mar 2012 13:43:35 -0500, Tim Wescott wrote: http://en.wikipedia.org/wiki/Schnuerle_porting Set up a fixture to hold the cylinder liner at the angle you want the port. Drill a hole to the largest diameter that fits your square port and file to final shape. If you are persnickety then leave the sleeve bore a few tenths underside and lap of hone to final diameter after finish filing the ports. I'm thinking that he will have a file stroke length of around 6/10 of an inch... -- Ed Huntress |
Square holes in a round bar.
On Thu, 15 Mar 2012 23:52:55 -0400, Ed Huntress wrote:
On Fri, 16 Mar 2012 10:41:45 +0700, John B. wrote: On Thu, 15 Mar 2012 13:43:35 -0500, Tim Wescott wrote: http://en.wikipedia.org/wiki/Schnuerle_porting Set up a fixture to hold the cylinder liner at the angle you want the port. Drill a hole to the largest diameter that fits your square port and file to final shape. If you are persnickety then leave the sleeve bore a few tenths underside and lap of hone to final diameter after finish filing the ports. I'm thinking that he will have a file stroke length of around 6/10 of an inch... I've had to deal with similar filing jobs before. And a few gouges along the diameter of the cylinder wouldn't be all that bad if they were in the plane of the ports, anyway, and happened before lapping. (And lapping has to happen no matter what: that's how you achieve the cylinder-piston fit). -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com |
Square holes in a round bar.
On Thu, 15 Mar 2012 23:52:55 -0400, Ed Huntress
wrote: On Fri, 16 Mar 2012 10:41:45 +0700, John B. wrote: On Thu, 15 Mar 2012 13:43:35 -0500, Tim Wescott wrote: http://en.wikipedia.org/wiki/Schnuerle_porting Set up a fixture to hold the cylinder liner at the angle you want the port. Drill a hole to the largest diameter that fits your square port and file to final shape. If you are persnickety then leave the sleeve bore a few tenths underside and lap of hone to final diameter after finish filing the ports. I'm thinking that he will have a file stroke length of around 6/10 of an inch... I don't think he mentioned the engine size but I've done essentially that with .049, .15 and larger engines with out getting too many scars on the opposite side of the bore :-) With good sharp, clean, jewelry files 6/10" is a long stroke. :-) -- Cheers, John B. |
Square holes in a round bar.
On Fri, 16 Mar 2012 01:20:44 -0500, Tim Wescott
wrote: On Thu, 15 Mar 2012 23:52:55 -0400, Ed Huntress wrote: On Fri, 16 Mar 2012 10:41:45 +0700, John B. wrote: On Thu, 15 Mar 2012 13:43:35 -0500, Tim Wescott wrote: http://en.wikipedia.org/wiki/Schnuerle_porting Set up a fixture to hold the cylinder liner at the angle you want the port. Drill a hole to the largest diameter that fits your square port and file to final shape. If you are persnickety then leave the sleeve bore a few tenths underside and lap of hone to final diameter after finish filing the ports. I'm thinking that he will have a file stroke length of around 6/10 of an inch... I've had to deal with similar filing jobs before. And a few gouges along the diameter of the cylinder wouldn't be all that bad if they were in the plane of the ports, anyway, and happened before lapping. (And lapping has to happen no matter what: that's how you achieve the cylinder-piston fit). You're a patient man, Tim. -- Ed Huntress |
Square holes in a round bar.
On Mar 15, 11:52*pm, Ed Huntress wrote:
I'm thinking that he will have a file stroke length of around 6/10 of an inch... -- Ed Huntress perfect application for a filing machine. |
Square holes in a round bar.
On Fri, 16 Mar 2012 18:26:26 +0700, John B. wrote:
On Thu, 15 Mar 2012 23:52:55 -0400, Ed Huntress wrote: On Fri, 16 Mar 2012 10:41:45 +0700, John B. wrote: On Thu, 15 Mar 2012 13:43:35 -0500, Tim Wescott wrote: http://en.wikipedia.org/wiki/Schnuerle_porting Set up a fixture to hold the cylinder liner at the angle you want the port. Drill a hole to the largest diameter that fits your square port and file to final shape. If you are persnickety then leave the sleeve bore a few tenths underside and lap of hone to final diameter after finish filing the ports. I'm thinking that he will have a file stroke length of around 6/10 of an inch... I don't think he mentioned the engine size but I've done essentially that with .049, .15 and larger engines with out getting too many scars on the opposite side of the bore :-) With good sharp, clean, jewelry files 6/10" is a long stroke. :-) I did. About 0.20. -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com |
Square holes in a round bar.
On Mar 16, 10:17*am, rangerssuck wrote:
On Mar 15, 11:52*pm, Ed Huntress wrote: I'm thinking that he will have a file stroke length of around 6/10 of an inch... -- Ed Huntress perfect application for a filing machine. And couldn't you program a CNC mill to do the work of a filing machine? |
Square holes in a round bar.
On Thu, 15 Mar 2012 20:27:03 -0700, etpm wrote:
On Thu, 15 Mar 2012 18:14:51 -0500, Tim Wescott wrote: On Thu, 15 Mar 2012 14:11:59 -0700, Bill Martin wrote: On 03/15/2012 10:14 AM, Tim Wescott wrote: On Thu, 15 Mar 2012 09:36:39 -0700, Stanley Schaefer wrote: On Mar 15, 9:54 am, Tim wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Alternately, how might one make those same holes in a cylinder machined out of that same bar, with a wall thickness of about 0.06", without distorting the cylinder by more than a couple of thousandths (I am assuming that one would have to do some post-operations to clean up the cylinder after making the holes, unless one hand-filed them). This is a thought experiment for making cylinder liners for 2-stroke engines of about 0.2 in^3 displacement; the holes would be the transfer ports, and the cylinder liners need to have their diameter controlled to about 0.001" on the outside and less than that on the inside for proper sealing (or if not controlled, then at least matched to the crankcase that they slide into, and the piston that slides in them). How about you turn it inside out so it's an external slotting/milling operation? :-) That's not as nutty as it sounds...mill your transfer ports into the outside of the cylinder proper, than press a hollow tube (sleeve) over the outside. Presto, you have transfer ports! One thing that is going to be a problem though: steel/iron doesn't get the heat out very well, and two strokers have a lot to get rid of. Good luck, The standard construction for model airplane engines of this sort is to have a cylinder lining of steel or (if you have friends in the right sorts of shop) hard chromed brass. It's a thin tube, usually with a lip on top, that slides into the crankcase. The crankcase has passages cast or milled into it for the transfer and for the exhaust. So the gas travels up from the crank case to the port along the outside of the sleeve, then turns 90 degrees to go into the cylinder. Meanwhile, the exhaust is exiting through its port without (we hope) leaking into the crankcase because the liner is sealed to the case by a close mechanical fit. I'm not sure of the detailed heat-flow -- I just know that it must be adequate, or all my engines would have burnt up long ago. Greetings Tim, I don't know how many of these you need. If I had to make just a few I would mill out the square holes with a .062 dia endmill and then finish the square corners with a square needle file. I would grind the teeth off one side first to make a safe side on the file. But I have a surface grinder that would make the job easy. A fellow could stone off the teeth too since the file is so fine and narrow. If I had to do a lot I would grind a broach to square up the corners but I would still mill out most of the metal. First a .094 drill, then mill, then broach. The tubing I would mount on a mandrel to support it, that would keep distortion within your tolerance range. Having a safe side on the file makes it easy to just remove material from the corner while not removing material from the side. Furthermore the safe side will burnish the side. This is a hobbyist thing, so one or a few is what I'm looking at (or maybe it's just mental masturbation -- time will tell if I actually _build_ something). If I were doing it in production I'd certainly be thinking EDM or broach. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com |
Square holes in a round bar.
On Fri, 16 Mar 2012 08:57:24 -0700, rangerssuck wrote:
On Mar 16, 10:17Â*am, rangerssuck wrote: On Mar 15, 11:52Â*pm, Ed Huntress wrote: I'm thinking that he will have a file stroke length of around 6/10 of an inch... -- Ed Huntress perfect application for a filing machine. And couldn't you program a CNC mill to do the work of a filing machine? Wouldn't that look bizarre? I think you could, though. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com |
Square holes in a round bar.
On Thu, 15 Mar 2012 12:10:40 -0600, Pete C. wrote:
Tim Wescott wrote: On Thu, 15 Mar 2012 10:20:42 -0600, Pete C. wrote: Tim Wescott wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Alternately, how might one make those same holes in a cylinder machined out of that same bar, with a wall thickness of about 0.06", without distorting the cylinder by more than a couple of thousandths (I am assuming that one would have to do some post-operations to clean up the cylinder after making the holes, unless one hand-filed them). This is a thought experiment for making cylinder liners for 2-stroke engines of about 0.2 in^3 displacement; the holes would be the transfer ports, and the cylinder liners need to have their diameter controlled to about 0.001" on the outside and less than that on the inside for proper sealing (or if not controlled, then at least matched to the crankcase that they slide into, and the piston that slides in them). -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com Wouldn't this normally be just a milled slot? Square on the top and bottom (relative to the piston stroke) with the edges running off the cylinder leaving square "knife edges" at the ends? At 0.1" perhaps a pass with a slotting saw rather than a super small and delicate end mill. Schnuerle ported engines want transfer ports that direct the gas toward the cylinder wall away from the exhaust port -- that tends do a good job of blowing out mostly spent combustion products, while retaining the most possible unburned fuel/air mix. More power, better fuel efficiency, cleaner burn -- what's not to like? (Except for the difficulty in machining, of course). -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com I'm having a little difficulty picturing exactly what you're trying to do. Perhaps drill and broach? You can make your own broach a bit more easily than the ECM and EDM lines of thought. Come to think of it, perhaps rotary broaching might do what you need. I didn't know that rotary broaching existed. It doesn't look like it makes the surface finish that I'm interested in (and I was kinda looking for home-shop sorts of solutions) but it does look like it'd work well. Isn't there a process that uses a diagonal bit in some perverted fixture that makes it cut square holes? -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com |
Square holes in a round bar.
On 03/15/2012 04:14 PM, Tim Wescott wrote:
On Thu, 15 Mar 2012 14:11:59 -0700, Bill Martin wrote: On 03/15/2012 10:14 AM, Tim Wescott wrote: snip The standard construction for model airplane engines of this sort is to have a cylinder lining of steel or (if you have friends in the right sorts of shop) hard chromed brass. It's a thin tube, usually with a lip on top, that slides into the crankcase. The crankcase has passages cast or milled into it for the transfer and for the exhaust. Oh, ok. I see what you are doing now. you are making a sleeve, as opposed to an actual cylinder, there is already a vertical path for gas flow in the outer wall. So the gas travels up from the crank case to the port along the outside of the sleeve, then turns 90 degrees to go into the cylinder. Meanwhile, the exhaust is exiting through its port without (we hope) leaking into the crankcase because the liner is sealed to the case by a close mechanical fit. I'm not sure of the detailed heat-flow -- I just know that it must be adequate, or all my engines would have burnt up long ago. My experience is just with high output 2-strokes, as in Kart racing engines. A steel sleeve would not do it there...you must match the piston expansion with heat as closely as possible. Nikasil on Al is pretty much the only game now, except for air cooled iron sleeve types. The Al cylinders work much better, run tighter clearances, last longer. Bill |
Square holes in a round bar.
On 2012-03-16, Tim Wescott wrote:
On Thu, 15 Mar 2012 12:10:40 -0600, Pete C. wrote: [ ... ] I'm having a little difficulty picturing exactly what you're trying to do. Perhaps drill and broach? You can make your own broach a bit more easily than the ECM and EDM lines of thought. Come to think of it, perhaps rotary broaching might do what you need. I didn't know that rotary broaching existed. It doesn't look like it makes the surface finish that I'm interested in (and I was kinda looking for home-shop sorts of solutions) but it does look like it'd work well. Isn't there a process that uses a diagonal bit in some perverted fixture that makes it cut square holes? There is a triangular bit with a floppy shank in a guiding holder which cuts square holes. Not sure how deep it will go, or how thick your workpiece is. If the workpiece is too thin, I would expect warping. Good Luck, DoN. -- Remove oil spill source from e-mail Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
Square holes in a round bar.
On Fri, 16 Mar 2012 13:58:03 -0700, Bill Martin wrote:
On 03/15/2012 04:14 PM, Tim Wescott wrote: On Thu, 15 Mar 2012 14:11:59 -0700, Bill Martin wrote: On 03/15/2012 10:14 AM, Tim Wescott wrote: snip The standard construction for model airplane engines of this sort is to have a cylinder lining of steel or (if you have friends in the right sorts of shop) hard chromed brass. It's a thin tube, usually with a lip on top, that slides into the crankcase. The crankcase has passages cast or milled into it for the transfer and for the exhaust. Oh, ok. I see what you are doing now. you are making a sleeve, as opposed to an actual cylinder, there is already a vertical path for gas flow in the outer wall. So the gas travels up from the crank case to the port along the outside of the sleeve, then turns 90 degrees to go into the cylinder. Meanwhile, the exhaust is exiting through its port without (we hope) leaking into the crankcase because the liner is sealed to the case by a close mechanical fit. I'm not sure of the detailed heat-flow -- I just know that it must be adequate, or all my engines would have burnt up long ago. My experience is just with high output 2-strokes, as in Kart racing engines. A steel sleeve would not do it there...you must match the piston expansion with heat as closely as possible. Nikasil on Al is pretty much the only game now, except for air cooled iron sleeve types. The Al cylinders work much better, run tighter clearances, last longer. Aluminum pistons in hard-chromed brass or aluminum sleeves is "it" for model airplane engines. I'm pretty sure the piston is high-silicon, because the idea is that the sleeve expands faster than the piston -- when cold, there's just a slight pinch at the top of the stroke that goes away as soon as the engine warms up. (And you never, ever, want to run them really rich -- then the fit gets too loose). I'll be doing a steel piston in a steel sleeve, then if I find myself getting serious about it I'll see about making friends with a shop that can hard chrome the inside of an itty bitty brass cylinder. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com |
Square holes in a round bar.
On Thursday, March 15, 2012 8:54:15 AM UTC-7, Tim Wescott wrote:
How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Why not mill a square slot in the end of the bar, then attach a cap? It's certainly easy to do, and the bar is big enough to take a variety of cap-fastening schemes (weld, rivet, bolt, pin, threaded section). |
Square holes in a round bar.
On Sat, 17 Mar 2012 13:41:59 -0700, whit3rd wrote:
On Thursday, March 15, 2012 8:54:15 AM UTC-7, Tim Wescott wrote: How would one make nice sharp-cornered, clean-sided (I'm not sure of the surface finish, but mirror-bright would be nice) square holes, about 0.1" on the sides, off center from the axis of the bar (so not square to the bar surface), in a round steel bar about 0.75" in diameter? Why not mill a square slot in the end of the bar, then attach a cap? It's certainly easy to do, and the bar is big enough to take a variety of cap-fastening schemes (weld, rivet, bolt, pin, threaded section). Because when I'm done making the holes, I'm going to bore the bar into a tube with 50-mil thick walls. -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com |
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