Help: Torque to Linear force conversion

[Oblarg]

Originally Posted by pfreivald

You'll likely want a ratcheting system to take the load before you do that....

I'm afraid that this season we're going to see a lot of shifting winches that work well at first, and then suffer a bad case of broken teeth and sadness.

Back in 2010, ratchet failure due to broken/gouged teeth was the biggest problem our robot faced (well, second-biggest; our ratchet-tooth-click-counter approach to setting the kicker power was probably the biggest). Our kicker was supremely powerful (could score from the rear zone), but I've always avoided similar mechanisms since then for just that reason. Disengaging teeth under that much force without damaging them is not a trivial matter.

[pfreivald]

Originally Posted by Oblarg

Back in 2010, ratchet failure due to broken/gouged teeth was the biggest problem our robot faced (well, second-biggest; our ratchet-tooth-click-counter approach to setting the kicker power was probably the biggest). Our kicker was supremely powerful (could score from the rear zone), but I've always avoided similar mechanisms since then for just that reason. Disengaging teeth under that much force without damaging them is not a trivial matter.

We're using a 3/8" stainless ratchet and pawl. What were you using?

[Oblarg]

Originally Posted by pfreivald

We're using a 3/8" stainless ratchet and pawl. What were you using?

Something similar. I can snap a picture of the assembly and the damage and upload it (either later today or tomorrow) if you'd like.

We were disengaging our pawl to release our kicker, and the primary failure point was the pawl gouging out the ratchet teeth over time.

[pfreivald]

Originally Posted by Oblarg

Something similar. I can snap a picture of the assembly and the damage and upload it (either later today or tomorrow) if you'd like.

We were disengaging our pawl to release our kicker, and the primary failure point was the pawl gouging out the ratchet teeth over time.

Yeah, I'd love to see it.

[Dan.Tyler]

Relieve the load on the teeth before releasing the pawl.

You designed to have enough power to pull it back? Pull it back a half tooth more while disengaging the pawl.

Similarly, if using a dog gear method... Drive the motor forward and backdrive while pulling the dog.

[Oblarg]

Originally Posted by pfreivald

Yeah, I'd love to see it.

Here's a picture of the ratchet. You can see two severely gouged teeth, and these are on the lighter side of the damage we saw that year (we regularly rotated/swapped out ratchets as the teeth became useless). The pawl, too, took a beating in that mechanism, but I don't have it to show as it appears to have been lost.

http://imgur.com/8kZIYzK

To give a reference for the amount of force we were using on this thing, here's a shot where you can make out two of the (very heavy-duty) springs we used to power it:

http://www.flickr.com/photos/robotproject/5049734546/

In this picture it is set up for half-power, our full-power setup used four springs.

Originally Posted by Dan.Tyler

Relieve the load on the teeth before releasing the pawl.

You designed to have enough power to pull it back? Pull it back a half tooth more while disengaging the pawl.

Similarly, if using a dog gear method... Drive the motor forward and backdrive while pulling the dog.

Alas, we could not do this as we used the same motor to both tension and release our ratchet.

[pfreivald]

Originally Posted by Oblarg

Here's a picture of the ratchet.

Is that aluminum?

[Oblarg]

Originally Posted by pfreivald

Is that aluminum?

I had thought it was steel, but looking closer at the pic it might be aluminum. I'll check.