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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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cheap linear motion solution?
Hi,
I would like to make a long rod move forward 4 1/2 feet along it's axis and then return to the starting point with constant velocity and a period of about 3 seconds. This is like the piston in a car engine but slower and larger distances. Using piston terminology if I turn the crankshaft then the piston will move up and down. But the piston doesn't move at constant velocity since the crank shaft is moving in a circle. If i built a big version of a piston I'd have to have a crank shaft 4 1/2 feet in diameter which is pretty big. If I go with the piston type set up it will all be plywood and bolts just so you have an idea of what I'm working with. Any clever solutions? Thanks, Peter |
#2
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depends on required force and velocity - hydraulic ram, air piston, linear
motor, screw motor, parallelogram linkage, the list goes on - how constant a motion do you require?. an acme screw and a parallelogram is one simple way to do it wrote in message oups.com... Hi, I would like to make a long rod move forward 4 1/2 feet along it's axis and then return to the starting point with constant velocity and a period of about 3 seconds. This is like the piston in a car engine but slower and larger distances. Using piston terminology if I turn the crankshaft then the piston will move up and down. But the piston doesn't move at constant velocity since the crank shaft is moving in a circle. If i built a big version of a piston I'd have to have a crank shaft 4 1/2 feet in diameter which is pretty big. If I go with the piston type set up it will all be plywood and bolts just so you have an idea of what I'm working with. Any clever solutions? Thanks, Peter |
#3
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wrote in message oups.com... Hi, I would like to make a long rod move forward 4 1/2 feet along it's axis and then return to the starting point with constant velocity and a period of about 3 seconds. This is like the piston in a car engine but slower and larger distances. Using piston terminology if I turn the crankshaft then the piston will move up and down. But the piston doesn't move at constant velocity since the crank shaft is moving in a circle. If i built a big version of a piston I'd have to have a crank shaft 4 1/2 feet in diameter which is pretty big. If I go with the piston type set up it will all be plywood and bolts just so you have an idea of what I'm working with. Any clever solutions? Thanks, Peter Peter Is there any way you could make use of the concept where a line, like a string, could be attached to a 9 foot long shaft?? If the string is attached to one end and at the middle, then looped around a perpendicular shaft so when that perpendicular shaft is twisted it pulls the 9 foot shaft along its axis. 4 1/2 feet is used for the "thrust mechanism and the other 4 1/2 feet it your extending shaft. I suppose this isnt clear unless you already know what I'm referring to. I have seen this "string around a shaft" used to tune old radios where a dial is moved left to right as the tuning knob is turned.. Jerry |
#4
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wrote in message oups.com... Hi, I would like to make a long rod move forward 4 1/2 feet along it's axis and then return to the starting point with constant velocity and a period of about 3 seconds. This is like the piston in a car engine but slower and larger distances. Using piston terminology if I turn the crankshaft then the piston will move up and down. But the piston doesn't move at constant velocity since the crank shaft is moving in a circle. If i built a big version of a piston I'd have to have a crank shaft 4 1/2 feet in diameter which is pretty big. If I go with the piston type set up it will all be plywood and bolts just so you have an idea of what I'm working with. Any clever solutions? Thanks, Peter 2 sets of same sized bicycle sprockets and chains on opposite sides of the rod with a tab on the chains to hook a tab on the rod. Timing is everything! Two timed semicircles would to the same thing but at the speed and length you want, they get kind big : ) |
#5
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On Sat, 26 Mar 2005 21:25:41 -0800, "william_b_noble"
wrote: depends on required force and velocity - hydraulic ram, air piston, linear motor, screw motor, parallelogram linkage, the list goes on - how constant a motion do you require?. an acme screw and a parallelogram is one simple way to do it wrote in message roups.com... Hi, I would like to make a long rod move forward 4 1/2 feet along it's axis and then return to the starting point with constant velocity and a period of about 3 seconds. This is like the piston in a car engine but slower and larger distances. Using piston terminology if I turn the crankshaft then the piston will move up and down. But the piston doesn't move at constant velocity since the crank shaft is moving in a circle. If i built a big version of a piston I'd have to have a crank shaft 4 1/2 feet in diameter which is pretty big. If I go with the piston type set up it will all be plywood and bolts just so you have an idea of what I'm working with. Any clever solutions? Thanks, Peter How about a cam operated lever driving a loop around two pulleys with a link to operate the rod. Gerry :-)} London, Canada |
#6
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Thanks for the replies! I like Geralds idea quite a bit because it
seems simple. Itis like the piston business but solves the problems I was having. However, how do you attach the link to the loop? Maybe the loop is a chain? |
#8
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On 26 Mar 2005 21:05:42 -0800, wrote:
Hi, I would like to make a long rod move forward 4 1/2 feet along it's axis and then return to the starting point with constant velocity and a period of about 3 seconds. This is like the piston in a car engine but slower and larger distances. Using piston terminology if I turn the crankshaft then the piston will move up and down. But the piston doesn't move at constant velocity since the crank shaft is moving in a circle. If i built a big version of a piston I'd have to have a crank shaft 4 1/2 feet in diameter which is pretty big. If I go with the piston type set up it will all be plywood and bolts just so you have an idea of what I'm working with. Any clever solutions? Thanks, Peter Pneumatics with a long stroke cylinder with adjustable restrictor valves in both air lines. I think Ive a brand new Festo...... Something like this http://catalog.festo.com/enu/asp/Def...D=532447&L=001 Gunner Every normal man must be tempted, at times, to spit on his hands, hoist the black flag, and begin slitting throats. H. L. Mencken |
#9
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wrote in message ups.com... Thanks for the replies! I like Geralds idea quite a bit because it seems simple. Itis like the piston business but solves the problems I was having. However, how do you attach the link to the loop? Maybe the loop is a chain? I've seen these in McMaster carr for timing belts. Bet they have one for chain also. Karl |
#10
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Thanks Karl. I found Roller Chain Attachments on page 922 online. I
cannot find the equivalent for timing belts. Maybe I'm not searching for the correct words. I did browse about 100 pages around the timing belts. Any idea where it is in the catalog? Peter |
#11
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In article . com,
says... Thanks Karl. I found Roller Chain Attachments on page 922 online. I cannot find the equivalent for timing belts. Maybe I'm not searching for the correct words. I did browse about 100 pages around the timing belts. Any idea where it is in the catalog? This is a good source... http://www.misumiamerica.com/ for example... http://www.misumiamerica.com/Categor..._pdf/p1077.pdf Breco or Brecoflex is another manufacturer. Ned Simmons |
#12
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