COTS & Custom Worm Gearboxes

[craigboez]

We are working on designing a shooter gearbox that can pull back a spring, release it quickly, and adjust up or down as necessary. In order to hold the spring load the gearbox must be non-backdriveable.

The common way of preventing backdrive is to use a ratchet. The downside to this is that if you dial up your shooter and then decide you want to lower it back down, you can't. You could if your gearbox used a worm gear that had a low enough pitch angle to be non-backdriveable, then you could spin the input motor either direction to adjust tension. It wouldn't be particularly efficient, but that is the tradeoff.

It seems there are only two COTS worm gearboxes, the AndyMark WormBox and RawBox. I saw a post about the WormBox stating that it is easily backdriveable, I havne't seen much info on the RawBox.

Can anybody with a RawBox comment on it's backdriveability?

Can anybody with custom worm gearbox experience comment on the process, and the parts sourcing?