Chain Backdriving

[ThunderPorpoise]

Hi all,
One thing I've noticed in many of the Ri3D videos is that the chain or pull lifted mechanisms tend to slip a little bit while they are not powered. Is there a simple and elegant way of preventing this problem? I'm aware of leadscrew anti-backlash nuts and I'm wondering if there is something similar for chain.

[Team3266Spencer]

You could use a worm gear or some form of brake.

[Dunngeon]

In the past, we've used lever actuated disc brakes from mountain bikes.

http://i.imgur.com/o9vWxK2.jpg
The disadvantage is it's relative size and the required alignment between the caliper and the disc. They can be difficult to package if your team doesn't have the ability to create precise holes.

[BBray_T1296]

See the Choo-Choo people built last season. Team JVN used a ratcheting wrench on board, and loads of people (including us) machined their own paul-and-ratchet. Just install on any sprocket in the system, and design it to pneumatically (or otherwise) release when you want to go down