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Author Topic: piston crankshaft help  (Read 1633 times)

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Offline dvdnguTopic starter

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piston crankshaft help
« on: April 10, 2015, 06:45:14 PM »
Hi all,
I am making a pneumatic piston with a rod and a crank shaft system. How would you make it so the crank shaft only rotates in a specific direction? Thanks in advance!

Offline bdeuell

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Re: piston crankshaft help
« Reply #1 on: April 11, 2015, 04:38:17 PM »
start it in only one direction (i.e. starter motor)... inertia will do the rest assuming you fire the piston at the correct time

with multiple pistons you may be able to use firing sequence to start the direction of rotation as well.

Offline dvdnguTopic starter

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Re: piston crankshaft help
« Reply #2 on: April 11, 2015, 05:43:27 PM »
start it in only one direction (i.e. starter motor)... inertia will do the rest assuming you fire the piston at the correct time

with multiple pistons you may be able to use firing sequence to start the direction of rotation as well.

If I am understanding you correctly, you are saying to add a motor specifically for the purpose of giving the crank shaft an initial push in the direction that I want? If that is the case, I would rather not add a motor, as the project I am working on is only allowed to have one motor (which I am using for steering) and one pneumatic piston (which I am using for the propulsion of the robot). I was wondering if there was a specific/clever way in which I build a stereotypical piston/crankshaft system in which it would rotate in one direction only. For example, I was thinking about putting the axle of the crankshaft slightly offset from the plane of the axle of the piston, but I fear that the crankshaft will not rotate at all in this case or high stresses will be created on the system.
« Last Edit: April 11, 2015, 05:45:04 PM by dvdngu »

Offline bdeuell

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Re: piston crankshaft help
« Reply #3 on: April 12, 2015, 03:00:39 PM »
why not use the motor to drive the vehicle and the piston to actuate the steering? Remember the KISS principle it is your friend despite how much you hate it.

anyways if you insist on using the piston to generate rotary motion you can tie the control valve to the rotational position to control what position the piston moves for that angular position, i.e. the piston moves up 0-180 and down 180-360. if your piston only a power stroke in one direction you would need to start in the region of that power stroke, i.e. for a up only power stroke it would need to start in the 0-180 range. if your piston is powered in both directions it could start in either the 0-180 or 180-360 regions but if it started at the top dead center TDC or bottom dead center BDC there would be no torque to rotate the. the possible starting regions will actually be a little smaller because near the TDC and BDC positions the torque would be too low to overcome friction. I suggest you take a look at some steam engines.

 


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