06-03-2012 18:10

Sb28000

Re: pic: Brakes.. Deploy!

Having a "brake" like that is an impressive idea! Is it pneumatic-powered, or driven by some motor? Also, why does 3451 have a blue bumper on half of its front side? I hope they built them sturdy enough to put up with that much weight applied to them!

06-03-2012 18:21

Jeffy

Re: pic: Brakes.. Deploy!

What extra functionality do those "brakes" give you over the typical servo w/ pawl into the gearbox?

06-03-2012 18:34

V_Chip

Re: pic: Brakes.. Deploy!

Thank you!
The brakes are purely pneumatic.
Luckily 3451's bumpers were still intact, though we did leave an imprint.

Our brake system guarantees that once deployed, we do not move AT ALL. Say if an alliance member went to double balance with us, we usually offer to be the immobile member of the balancing act. Once on the bridge, we plant our brakes. If unbalanced and tipped in our direction, the brakes guarantee that we do not slip and roll off.

Our current configuration of plaction tread wheels may have plenty of grab on the carpet, but are quite slippery on lexan. The pneumatic brakes have an insured non-slip grip pad on the bottom. If the brakes are down, we're not going anywhere.

Here are some of the pictures we took at BAE GSR.
http://buzzrobotics.org/node/193
There is a close up of our deployed brakes.

06-03-2012 23:14

jblay

Re: pic: Brakes.. Deploy!

This seems like a greeat way to get the coopertition bridge for 1 point if the clock is running out.

You guys looked great at gsr and I can't wait to play with you guys at CT again.

Also not sure on this but those might be in violation of the metal traction device on the field rule. I hope there is tread or something like that on the bottom.

07-03-2012 09:38

Sb28000

Re: pic: Brakes.. Deploy!

My understanding of the rule regarding metal traction devices was about using a metal brush or "file card" (as I believe is the official "Manual" term for it) to gain a large amount of traction, and be nearly impossible to push. This is from memory, but I believe the rule began because a team used brushes somewhat similar to a wire brush used to clean grill racks, or wood files, that ultimately could cause damage to the field carpet. Perhaps someone who was around then, or has a more specific knowledge of it can back me up on that. But I don't believe the intent rule is against having metal at all in contact with the carpet - As long as it is smooth and not intentionally rough or desctructive, I'd imagine it could be used as skids, or in this case, a deployable brake.

07-03-2012 09:53

V_Chip

Re: pic: Brakes.. Deploy!

Thanks jblay! We're excited to compete at CT; so many great teams are in attendance.

We have rubber pads on the bottom of the brakes so that they are in compliance with the field rule. It took numerous traction/friction tests but we finally came across a material that suffices.

07-03-2012 15:40

Madison

Re: pic: Brakes.. Deploy!

I am excited to see another team with brakes -- especially one as good as 175.

Brakes win matches. They're almost the best thing a team could ask for when it comes to balancing bridges.

07-03-2012 16:12

AcesJames

Re: pic: Brakes.. Deploy!

After looking at your machine at BAE, I thought I spotted your brakes covered in black roughtop tread, am I right?

I only ask because you posted that the wheels are slippery on lexan but not on carpet, while the brake pads are grippy on both, and I had thought that the material on your brakes appeared to be the same material as the tread on your wheels.

From the testing I did, roughtop tread had a reasonable CoEF on the bridge, so part of me wants to say the reason you found you were sliding off the bridge before adding brakes wasn't because of the tread's CoEF, but because of the fact that your drivetrain PWMs were probably in coast mode, and you simply rolled off the bridge (your CIMs were backdriving).

Of course, I definitely could be wrong. I'd love an official 175 answer.

08-03-2012 03:06

pigpenguin

Re: pic: Brakes.. Deploy!

Yeah, that is correct. I was not around at the time but I went to a lecture thing (lack for a better term) and the mentor brought it up. The team would, from what I recall, pull its self along. It was immovable due to the iron wool getting mixed in with the carpet. Eventually some one did move it, how ever it took two robots and instead of the bot moving the carpet was ripped out after that year it became illegal. So yeah good times.

08-03-2012 17:58

V_Chip

Re: pic: Brakes.. Deploy!

Official 175 answer:
"It's top secret."

The PWMs are in fact in coast mode.

The tread used on the brakes is black roughtop that we've used for tread in past seasons. The material is a little harder than what is currently on the wheels.