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View Full Version : Double ended cylinders? Self centering controls?


Blender
09-16-2010, 06:59 PM
I'm interested in a small (7-9mm bore) 20-25 mm stroke double ended cylinder for use with a steering system. I've looked at Clippard and McMaster air cylinders, but they are all very long.

I was staring at one of my Leimbach single ended rams and wondered if it would be feasible to combine two single ended rams into one double ended. I'd steal the shaft side cap and reattach it to the back of an existing cylinder. I would need to make/acquire a longer shaft, but that would be easier than a complete scratch built cylinder. I suppose the piston isn't symmetric, so it would block the inlet port while at one end of it's travel limit. I think i remember Lil Giants posting about disassembling a leimbach cylinder on scale4x4. They appear to be glued together and not meant to be re aseembled.

Has anyone messed around with a servo control loop for a self centering system? I need self centering for 4 wheel steer. I suspect the slight speed/force differences would otherwise result in alignment issues between the front/rear axles.


I thought about a linear motion potentiometer along the cylinder to replace the rotary pot in the valve's servo. The linear motion pots are only available in sizes that are way too big. I'd have to remove the valve-servo's pot, so it would likely over extend the valve. I dunno if this would damage the valve, but it would surely stall the servo. I'm too afraid to take apart my valves to see if they could crash internally.

My second option would be to rig up a rotary pot near the pivot point of the steering system. It would be kind of ugly, but it may work okay.

The third option is to somehow add an additional pot outside the servo. If i could connect them in such a way the actual servo position and the ram position would both be fed into the control setup. I suspect this may not act right, or limit travel.


I'll pick up another 3107 servo to cut up just to see what happens.

This is what i'm trying to make: Hydraulic steering with no tierod. Just two short links from knuckle to ram. My last resort would be a single ened ram with a tierod.

pugs
09-16-2010, 07:57 PM
Another possible option, would require more work but is an option, Is to build a hyd rack and pinion.
http://www.hydraulics-pneumatics-engineering.com/hydraulic-oscillating-actuator.html
The 3rd and 4th pics are what I'm talking about. This could perhaps be built and then hook a servo up to the input shaft and use the cylinder sections of it as the pump for the steering cylinder. Once air was bleed from the lines it should zero return right with the servo. This would be completly seperate system from the hydraulic pump and thus would work with out a pump running.

Just a thought anyway.

Colin11123
02-03-2017, 10:00 AM
Did you ever come up with a solution for self centering hydraulic steering? I'm looking at the same thing just now for my Bell dumper and wondered if anyone has found a solution. No point re inventing the wheel :)

Blender
02-04-2017, 12:15 AM
Nope. It has servo steering in it... and it's still not finished.

I'll bet an arduino could be made to do this, but that's beyond my abilities

TheBennyB
02-04-2017, 01:45 AM
eeeks. So a member here has done a demo of the ford trailer assist, wondering if this could be applied to the ram's servo?
https://www.youtube.com/watch?v=ksGVRNkb9es&t=356s

nevermind, forgot all the external accessories needed.