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

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?

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.

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

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

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

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

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

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

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

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.

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

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

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.

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

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.

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

"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

"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.

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

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

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.

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

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

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.

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

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

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.

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

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.

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

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?

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

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

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

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

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 ---

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

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).

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