big motor, for ATV steering, unusual feedback

<P style="MARGIN: 0px">Anyone have suggestions for a big motor, 12 or 24v that could be used to drive the steering mechanism for an ATV? Our estimates are that when the vehicle is standing still (the hardest steering task) we're looking at 25 lb-ft.... desired ~100rpm. Would the big NPC motors work for this?
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<P style="MARGIN: 0px">Additionally, there's slop in the steering mechanism.. and we'd like to use the roboteq board in position control mode. So we're actually thinking a linear potentiometer between the wheel and the frame as the feedback... so we actually know where the wheel ended up rather than an encoder. Anyone know of a problem off hand with that?
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<P style="MARGIN: 0px">Thanks!
<P style="MARGIN: 0px">Thomas

<P style="MARGIN: 0px">NPC publishes dynamometric tests for some of their motors. See <A href="www.npcrobotics.com/products/viewprod.as...;cat=20&mode=gfx" target=_blank>www.npcrobotics.com/products/viewprod.as...;cat=20&mode=gfx
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<P style="MARGIN: 0px">As you will see, 25 lbs/ft is not much of a load for some of these motors. NPC should be able to help you refine your choice if you call them.
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<P style="MARGIN: 0px">You will need to use a pot as you need absolute position feedback. The trick is finding the right spot to place it and have the right amount of travel on the pot vs mechanical travel of the steering.
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<P style="MARGIN: 0px">Another important consideration is to use an extremely reliable pot, as it will be moving a lot (far more than in typical application, e.g. volume pot) and will be exposed to elements depending where you mount it.
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<P style="MARGIN: 0px">One of our users and DARPA participant used a pot for aerospace application. It was quite expensive from what we've heard but looked extremely robust. See <A href="www.phantasm1.com/GALLERY.html" target=_blank>www.phantasm1.com/GALLERY.html

<P style="MARGIN: 0px">Thanks for the tips. We're shopping around for a rugged, high precision POT right now.
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<P style="MARGIN: 0px">Please report your findings on the Message Board. This would be useful reference information for many.
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<P style="MARGIN: 0px">You may also consider non-contact hall angular sensors. As the name implies, there is no mechanical whiper so they should work literally forever. See example at <A href="www.beiduncan.com/html/products/non_cont...ng/noncontacting.htm" target=_blank>www.beiduncan.com/html/products/non_cont...ng/noncontacting.htm
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<P style="MARGIN: 0px">I would love to know if you found a motor/pot solution, I have a similar project underway and I've been considering the AX2850.
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<P style="MARGIN: 0px">the only other "plug &amp; play" option I've found is the <FONT face=Arial>SSPS105S180 </FONT>
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<P style="MARGIN: 0px"><A href="vantec.com/ssps105.htm" target=_blank target=_blank>vantec.com/ssps105.htm
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<P style="MARGIN: 0px">but I'm a bit sceptical that this servo is going to turn the steering assembly on an ATV.
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<P style="MARGIN: 0px">any suggestions for a low rpm motor/pot solution to use with the above controller on a large scale rc vehicle for steering and throttle/brake?

While it hasn't been totally implemented yet (funding! <img src="www.websitetoolbox.com/images/boards/smilies/biggrin.gif" align="middle" border="0">), here's what we bought:

NPC Robotics, T-64
www.npcrobotics.com/products/viewprod.as...;cat=20&mode=gfx
That thing is huge though, so be wary of weight. Parker makes some motors we've been looking at for something else... check out their BE series

Pot
www.celesco.com/linearpot/index.html
The CLWG.

The idea being, roboteq tells motor what to do, linear pot is attached to rack and pinion to provide the closed loop.

We haven't actually hooked it all up yet (yeah, I know I posted this a long time) but we have those parts and are planning on using them

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<P style="MARGIN: 0px">We used a linear actuator and a belcrank to steer a powerwheels car and it worked great. They have all kinds of choices. Length of travel, speed, torque etc..
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<P style="MARGIN: 0px"><A href="www.firgelliauto.com/" target=_blank>www.firgelliauto.com/
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<P style="MARGIN: 0px">Good Luck