[FTC]: Any teams using dead axles for arms?

[Rick]

Have any teams used a dead axle setup for an arm/manipulator? We are having some issues with the split clamps and our live axle setup, and I was wondering if anyone has any details or pictures about such a setup?

[ttldomination]

What do you mean dead axle?

[Rick TYler]

Originally Posted by ttldomination

What do you mean dead axle?

The axle is stationary and the wheel spins on it.

[jgraber]

Originally Posted by Rick TYler

The axle is stationary and the wheel spins on it.

FTC136 has a parallogram arm using the bronze bushings as pivots. Lets try a word picture:
Have two C channel uprights, with the arm pivoting between them. Stick a bronze bushing from inside the arm into the upright on both sides. Stick an axle through the whole thing, while threading spacers between the bushings to keep them from sliding to the inside. Screw a split clamp to the upright and clamp the axle to keep it from sliding. Alternately, use locking collars on each side to keep the axle in place.
So the axle merely holds things in place, and the sliding joint is between the large holes in the C channel, and the bronze bushing.
It seems like a 40 and 120 tooth gear bolted together could rotate on a bronze bushing in the same way. Hope this helps.

[jbbjjbt]

I don't have a solution, but we share the problem. It irritates me that we have these very powerful motors but only clamps to transmit the power. We have tried lots of ideas out to overcome this issue , but none have worked successfully very long.

[wilsonmw04]

We had the same problem when we were brain storming arm ideas. Because of the weak clamps we opted for live axles. I hope FIRST is reviewing these posts and will be making improvements for next year's season.

[dooey100]

Originally Posted by jgraber

FTC136 has a parallogram arm using the bronze bushings as pivots. Lets try a word picture:
Have two C channel uprights, with the arm pivoting between them. Stick a bronze bushing from inside the arm into the upright on both sides. Stick an axle through the whole thing, while threading spacers between the bushings to keep them from sliding to the inside. Screw a split clamp to the upright and clamp the axle to keep it from sliding. Alternately, use locking collars on each side to keep the axle in place.
So the axle merely holds things in place, and the sliding joint is between the large holes in the C channel, and the bronze bushing.
It seems like a 40 and 120 tooth gear bolted together could rotate on a bronze bushing in the same way. Hope this helps.

We have a setup a lot like this and it works great.

[gregsanCHEVY121]

Could any of the teams that do use dead axles post pictures of their steup? thanks

[gdo]

are you guys using these deadaxle on the intermediates in your Arm's gear train. If so, try to bolt the two gears together with a long screw. Because I remember you guys saying they kept failing at the competition, meaning that one would no longer turn the other, if they were physically bolted together and the clamps "failed", but still remained physically attached, as long as they kept in the proper place in allignment, then you wouldn't have to worry about them fail. You could juts put a shaft collar at each end of the axel to hold the gears on the axel.

[gregsanCHEVY121]

the problem we were having was that the clamps at the top gear of our arm were failing. we have a medium and small gear(i dont know the teeth number) on one axle, that sits between the big gear that is attached to the axle on the arm and a small gear that is on the motor. The center axle and gear setup does not slip or anything, it is always just the clamps that attach the big gear to the axle. We ended up figuring a way to get a clamp on each side of the big gear and putting a screw through the gear and two clamps. That seemed to fix our problem but it was an "on the spot" thing and we need to make it final or use something different such as the dead axle idea.

[dooey100]

Would it be possible for you to attach the gear directly to the arm? Mabey using a clamp as spacing?

[gregsanCHEVY121]

yes, that is one idea of ours. We might add another big gear to the arm that would attach directly to the arm so the clamp is not needed. We would then have a total of four big gears at the top of our arm, but if thats what it would take then it would be worth it. We may be able to get away with only using one big gear on each side that is attached directly to the arm.

[BradMello]

We could do this greg, Mt. Hope showed me how they did it

[ptan]

Take a look at pictures of robots from the FTC tournaments. Here's one with an arm attachment

http://picasaweb.google.com/lh/view?q=ftc&uname=iSPACEPhotos&psc=G&cuname=iSPACEP hotos&filter=1&orderby=date#5300514601670105874

[FTC 2891]

Our team had a problem with slipping clamps too. However, we were running compound gearing on the arm so we had to have live shafts. We attached two split clamps to each gear by drilling out the threads on one clamp and putting a 1.5" socket head screw across the drilled out clamp, gear, and into the threaded clamp on the other side of the gear. The addition of a thread locker would be helpful too.