Andymark rhino drivetrain discussion

[Knufire]

Originally Posted by Tom Line

A whole lot of teams are going to be a whole lot of disappointed if those treads slide off when pushed sideways.....

And a whole lot of teams are going to learn how to play some pretty effective defense.

[MrJohnston]

The Rhino treads are very well secured and will be extremely difficult to knock off so long as the robot's pit crew keeps up with standard maintenance checks and makes sure that everything is kept tight.... Assuming proper upkeep, it would take a tremendous hit to cause any problems.... No, we don't intend to subject our robot to too many violent hits before competition...

At the same time, we recognize that there is a potential weakness here, so are developing game play strategies that will minimize such collisions.... Robot damage happens, no matter how robust your design might be... We even had our chassis bent at a district event last year - due to a violent autonomous collision with a member of our own alliance who's routine went haywire in a very bad way.....

[dradel]

I am pretty confident the tracks will stay on when pushed from the side. The pulleys have a V groove which the the belt has an inverted v that fits in the groove. Is it possible that they could slide off when pushed from the side and the bot is trying to move forward or backward? Sure it's possible, but if the drive just lays off the controls for a couple seconds they won't "slide" off. Keep in mind someone can only push for 5 seconds and then has to back off.

[JamesCH95]

I too am interested to see how these treads work out with full-weight robots, especially with open-field hits.

What makes me nervous is the turnbuckle used to tension the treads that relies on the eyelets to stay bent closed. The first thing I would do with one of those tread modules is to weld those eyelets closed. My intuition is that it will only take one or two hits to open those up.

Of course, I might be completely wrong...

Originally Posted by dradel

I am pretty confident the tracks will stay on when pushed from the side. The pulleys have a V groove which the the belt has an inverted v that fits in the groove. Is it possible that they could slide off when pushed from the side and the bot is trying to move forward or backward? Sure it's possible, but if the drive just lays off the controls for a couple seconds they won't "slide" off. Keep in mind someone can only push for 5 seconds and then has to back off.

You might want to check G22... ROBOTS can only pin for 5s. I think that you would have a hard time arguing that being pushed in an open field counts as a PIN.

[dradel]

Granted, but where is this open field you refer to?? It isn't like the Airial assist field! A quick back up or move forward and your touching the outer defense and bam foul.
Now I'm not saying there won't be defense played hard this year, but the potential for hits like in 2014 are going to be rare. Plus I would think most would be more worried on breaking defenses and or scoring in the tower. But we shall see

[JamesCH95]

Originally Posted by dradel

I am pretty confident the tracks will stay on when pushed from the side. The pulleys have a V groove which the the belt has an inverted v that fits in the groove. Is it possible that they could slide off when pushed from the side and the bot is trying to move forward or backward? Sure it's possible, but if the drive just lays off the controls for a couple seconds they won't "slide" off. Keep in mind someone can only push for 5 seconds and then has to back off.

Originally Posted by dradel

Granted, but where is this open field you refer to?? It isn't like the Airial assist field! A quick back up or move forward and your touching the outer defense and bam foul.
Now I'm not saying there won't be defense played hard this year, but the potential for hits like in 2014 are going to be rare. Plus I would think most would be more worried on breaking defenses and or scoring in the tower. But we shall see

Therein lies the rub.

An open-field pin, or more precisely: an open field t-bone, doesn't require a high-speed impact. All it requires is a defender applying steady pressure to the side of another robot to completely ruin their ability to maneuver. I would encourage you to try this out with two or more robots, it is comically effective and easy to do.

[RacerX]

The turnbuckles are in compression to keep the belt tight, not in tension. It would take quite a bit to get to the point where the eye bolts are opening. If things get that out of hand, the eye bolts opening will likely be the least of our worries....

As a suggestion, it would be a good idea to have jam nuts on one end of the turnbuckles to make sure they stay where you want them.

[dradel]

Originally Posted by JamesCH95

Therein lies the rub.

An open-field pin, or more precisely: an open field t-bone, doesn't require a high-speed impact. All it requires is a defender applying steady pressure to the side of another robot to completely ruin their ability to maneuver. I would encourage you to try this out with two or more robots, it is comically effective and easy to do.

I understand what you are saying, but when I hear (read) T-bone I am thinking full speed violent hit. But I see your point. I know we will be testing that hopefully this weekend. Will try and grab some video to post here.

[JamesCH95]

Originally Posted by RacerX

The turnbuckles are in compression to keep the belt tight, not in tension. It would take quite a bit to get to the point where the eye bolts are opening. If things get that out of hand, the eye bolts opening will likely be the least of our worries....

As a suggestion, it would be a good idea to have jam nuts on one end of the turnbuckles to make sure they stay where you want them.

I know that the turnbuckles are in compression, which is what concerns me. It may be fine as-is, but the 2 grams of mass it would take to weld it closed seem more than worth it to me.

[dradel]

Originally Posted by JamesCH95

I know that the turnbuckles are in compression, which is what concerns me. It may be fine as-is, but the 2 grams of mass it would take to weld it closed seem more than worth it to me.

I hadn't thought about them opening up, which is plausible if a hard impact is taken on the front. And now that I think about it I will be welding ours.

[Jon K.]

Originally Posted by JamesCH95

I know that the turnbuckles are in compression, which is what concerns me. It may be fine as-is, but the 2 grams of mass it would take to weld it closed seem more than worth it to me.

I would be more worried about weakening the aluminum at the weld. We at AndyMark did extensive hit tests on these turnbuckles at full speed with a fully weighted chassis into a piece of diamond plate that was backed by a full pallet of roller chain, so it had no where to go. We are working on putting up some videos of our testing so that the community can see what we have done to test the modules before we were comfortable selling them.

[Michael Corsetto]

Originally Posted by Jon K.

I would be more worried about weakening the aluminum at the weld. We at AndyMark did extensive hit tests on these turnbuckles at full speed with a fully weighted chassis into a piece of diamond plate that was backed by a full pallet of roller chain, so it had no where to go. We are working on putting up some videos of our testing so that the community can see what we have done to test the modules before we were comfortable selling them.

Jon,

As part of your video tests, can you run a test of the Rhino track system being pushed sideways by another robot (both at 140lbs)? Specifically:

Robot A - Rhino Tracks (~140lbs)
Robot B - Kitbot (~140lbs)

Robot B pushes square onto the side of Robot A.
Robot A does not move.
As Robot B pushes Robot A, Robot A attempts to drive forward/backward.

If you could test the above scenario, that would be awesome!

Thanks,

-Mike

[RacerX]

If it becomes an issue with the tread being pushed off the wheels with side load, which I doubt will happen with a properly tensioned belt, can the Rhino Teams add a plate to the sides of the wheels, slightly larger than the wheel, so it overlaps the white part of the belt?

This would be similar to the other belt pulleys that are used.

In addition to the plates, perhaps a mechanism to deflate pneumatic tires could also be added?

[EricDrost]

Originally Posted by RacerX

In addition to the plates, perhaps a mechanism to deflate pneumatic tires could also be added?

Not comparable. Treads coming off a tread drive (ANY tread drive) from base to base interaction is a chassis that cannot withstand the rigors of FRC. Poking holes in pneumatic wheels is damaging and deliberate contact inside the frame perimeter.

Causing a team with under inflated tires to pinchflat under heavy defense is the parallel.


I'd be very interested in seeing the results of the test Mike has outlined.

[JamesCH95]

Originally Posted by Jon K.

I would be more worried about weakening the aluminum at the weld. We at AndyMark did extensive hit tests on these turnbuckles at full speed with a fully weighted chassis into a piece of diamond plate that was backed by a full pallet of roller chain, so it had no where to go. We are working on putting up some videos of our testing so that the community can see what we have done to test the modules before we were comfortable selling them.

The eyelets in the turnbuckles are aluminum? What alloy?

They appear as zinc-plated steel eyelets with an aluminum body, but you would of course know better!

Posting test videos would be a great way to address concerns of their robustness given the long the somewhat sordid history of treads in FRC drives. I look forward to seeing them!