pic: ABS-110, lightweight 2-speed PTO gearbox

[Chris is me]

Originally Posted by tickspe15

Most teams that run PTO's do not disengage the drivetrain when the PTO is engaged. You can get around disengaging the drive by either lifting the wheels off the ground before engaging the PTO(see 254 or 118*in reveal video* 2013), or using the drivetrain to assist the action being performed by the PTO(see 254 or 1114 in 2010)

In the case of both 254's and 1114's 2010 robots, the PTO did disengage the wheels. With 254 this is evident when you watch the robot extend its arm - it has to stop driving to unfold the hanging arm. I don't know where you're getting this information from. There are serious risks to trying to align something when the PTO is moving you away from your target. You almost never want your wheels engaged while your PTO is doing something else.

In 2013, if 254's PTO didn't disengage its wheels, that's just because the wheels had already left the ground at that point, so the feature wasn't necessary. This is unique to the 2013 hanging task.

[Travis Covington]

Originally Posted by Chris is me

In the case of both 254's and 1114's 2010 robots, the PTO did disengage the wheels. With 254 this is evident when you watch the robot extend its arm - it has to stop driving to unfold the hanging arm. I don't know where you're getting this information from. There are serious risks to trying to align something when the PTO is moving you away from your target. You almost never want your wheels engaged while your PTO is doing something else.

In 2013, if 254's PTO didn't disengage its wheels, that's just because the wheels had already left the ground at that point, so the feature wasn't necessary. This is unique to the 2013 hanging task.

This is correct. In 2010 we disengaged and in 2013 we did not. In 2013 the drive wheels were already off the ground so we had no need for the three position cylinder. When we were hanging, the drive wheels were also spinning back and forth. No big deal.

Be careful with the three position cylinders though. They do not behave exactly the same as two 2-position cylinders stacked back to back. See this post here for details: http://www.chiefdelphi.com/forums/sh...75#post1276175

[asid61]

Originally Posted by Travis Covington

This is correct. In 2010 we disengaged and in 2013 we did not. In 2013 the drive wheels were already off the ground so we had no need for the three position cylinder. When we were hanging, the drive wheels were also spinning back and forth. No big deal.

Be careful with the three position cylinders though. They do not behave exactly the same as two 2-position cylinders stacked back to back. See this post here for details: http://www.chiefdelphi.com/forums/sh...75#post1276175

Thank you, that's very helpful. So the holding force in the middle position is quite low then.
In that case, I might just switch to two stacked cylinders.

[Travis Covington]

Originally Posted by asid61

Thank you, that's very helpful. So the holding force in the middle position is quite low then.
In that case, I might just switch to two stacked cylinders.

Yes, it is. It is worth considering. We got away with it in 2010, but it was a little sketchy. Sometimes it wouldn't shift. We ended up having to shift to the other gear before shifting back to neutral. Not ideal.