Non backdrivable drill transmission

[bs7280]

Hello all,

We are trying to find a non backdrivable drill transmition/gearbox that we can modify or comes with a way to use a pneumatic piston. I have been able to find some winches and gearboxes that are not backdrivable and gearboxes that have a dog gear/clutch, but nothing that has both. I have had very little luck researching drill transmitions and think that could be a good option, especially after seeing the team 1114 2008 robot.

[atucker4072]

Why not use a worm gear box? You can't back drive those. The link below is to one from Andy Mark.

http://www.andymark.com/mobile/Product.aspx?id=38147

[Mark Sheridan]

the dewalt xrp series is non-backdrivable. I used them a few years ago. It was kinda pricy from the service center. I had to get a motor too in order to cut off the pinion. they don't sell the pinion separate. It did require a bit of machining to do. There is a good white paper called "Nothing but Dewalts" by Dr. Joe that is a little outdated but would explain mostly how to do it.

Nowadays, I much rather have a ratcheting wrench on a hex shaft. If you need to rotate in both directions your gonna need to find a good drill. I think 33 found a better one but I can't find which thread they mention it.

[bs7280]

Originally Posted by atucker4072

Why not use a worm gear box? You can't back drive those. The link below is to one from Andy Mark.

http://www.andymark.com/mobile/Product.aspx?id=38147

We have been looking at this and think that it will be great, if we can figure out how to use this with a clutch, we are golden. The only problem is that we have no idea how to do that. We want to somehow incorporate a tube that will slide on and off the hex shaft. I saw one example of this (sorta) from 2010 but I am struggling to find any examples on chief delphi

[GrantN27]

We are also looking into some type of a non-reversible transmission with the clutch.

Ri3D used a Modulox gear box and a mechanical clutch unit to accomplish this and it can be seen in this youtube video at about 1:30. Definitely worth a look.

http://www.youtube.com/watch?v=SWO9OE8JZZk

I would like to help in any way I can but my team is a bit stumped with this system.

[Aren_Hill]

Originally Posted by atucker4072

Why not use a worm gear box? You can't back drive those. The link below is to one from Andy Mark.

http://www.andymark.com/mobile/Product.aspx?id=38147

Just a heads up this is a multi-start worm and backdriveable.

[bs7280]

Where can I get a gearbox that will not backdrive?

[DonRotolo]

Originally Posted by atucker4072

Why not use a worm gear box? You can't back drive those.

Just beware: some worm gear drives are backdriveable. As with many things, it depends upon the exact design of the worm gearbox.

[bs7280]

What about this one:
http://www.andymark.com/RAW-Box-p/am-2372.htm

Sorry if it is obvious, I have not been able to find anything

[magnets]

Originally Posted by bs7280

What about this one:
http://www.andymark.com/RAW-Box-p/am-2372.htm

Sorry if it is obvious, I have not been able to find anything

This too is a four start worm, and will easily backdrive on a vibrating and shaking robot once it's worn in.

Try using a ratcheting mechanism or clutch bearings from http://www.bocabearings.com/bearing-...h-bearing-csk-

[bs7280]

But wouldn't this prevent us from reversing the winch/gearbox which would prevent us from changing the power of our catapult. Can you recommend an alternative gearbox?

[Dan Richardson]

Originally Posted by GrantN27

We are also looking into some type of a non-reversible transmission with the clutch.

Ri3D used a Modulox gear box and a mechanical clutch unit to accomplish this and it can be seen in this youtube video at about 1:30. Definitely worth a look.

http://www.youtube.com/watch?v=SWO9OE8JZZk

I would like to help in any way I can but my team is a bit stumped with this system.

The CAD for this gearbox was also posted on the Robotin3days.com website here: http://wp.me/p2Y6Na-eL

Should provide more information on how it was assembled.

We were happy with the performance of the ratcheting wrench. The tightening torque on grade 8 1/4-20 bolt is 12 ft lbs which would make me assume the average ratcheting wrench would able to handle this load or slightly higher.

[artdutra04]

Originally Posted by DonRotolo

Just beware: some worm gear drives are backdriveable. As with many things, it depends upon the exact design of the worm gearbox.

To further expand on the science behind this, we start with the notion that all worm drives are backdriveable. This holds true if we have infinitely strong unobtainium worms and worm gears and/or infinitely awesome unobtainium grease that lowers coefficient of friction to zero.

What prevents some configurations of worm drive from backdriving is a high coefficient of friction between the worm and the worm gear, which means an exceptionally large backdrive force is needed. This exceptionally high backdrive force needed to overcome the friction means that the gear teeth will shear off before that level of force is reached.

A simple explanation for this principle uses the principle that a screw is just a inclined plane wrapped around a cylinder. Using only one angle component, we can see from the diagram below that the backdrive force F will cause the worm to backdrive if Fsinϴ > Fcosϴμ, where μ is the coefficient of friction between the two gears.

Since F cancels out, and sin/cos = tangent, in simplistic terms you can state that a worm drive will backdrive if μ < tanϴ and F is less than the force required to shear worm teeth.