Major problems with tank tread drive

[Chris Fultz]

1. Try to machine a groove in your idler wheels to keep the track in.

2. We made small guides to keep the treads aligned. They are pretty simple.
We used lexan as a plate, and the cantilevered 2" long bolts (like #10's) from them, with metal sleeves over the bolts to act as "rollers" for alignment.
We have one set placed at the front and back of the drives.

These roller guides are spaced just a little bit wider than our track so there is not much friction. The bolts and sleeves came from Home Depot so they should be easy to find.

If the description doesn't make sense - PM me with an email contact and I will try and send a power point picture.

[Kevin Sevcik]

This would be our first experience with treads, as well. Pretty much the exact smae problem you describe, really. We ended up trying to live with never turning during most of the season.

If you're really, really hurting for a quick fix that miiiiiight work, I'll tell you what I recall us doing with our treads. I don't remember the specifics, as I didn't see them constructed, but here goes:

We made our own bootleg self centering belts. I'm sure this was a very painstaking process. All I remember is that we eventuallyran on our old belts, except with a ridge on the back. this might not be an option for you, though. we were running on the belts inside out, ie. the teeth were running on the ground, and the smooth side was running on our idler pulleys.

I think some of the engineers took a spare belt and cut it into a thin strip. Then they laid it on inside of our track belt, smooth side to smooth side, and somehow attached the two together. I'm thinking something like the rivets that hold jeans together, between every tooth, or every other tooth. Maybe a pop rivet and a small washer on the other side? Then, of course, we machined matching grooves in the pulleys.

*shakes head* Now that I think about it, that sounds incredibly crazy and darn near impossible. Maybe we just did the sane thing and bought some new belts in the off-season. My memory is a little fuzzy.

PS. I'm starting to loathe last minute drivetrain testing. We just recently tested our bot on carpet, and the transmission is eating gears up. I'm thinking it's not dealing well with shock loads caused by breakers tripping and then cycling on and turning on the motors at full blast. So we're looking at custom gear sources with very fast turnaround, and some programming changes and driver training to make things nicer on the trannies.

[Lord Nerdlinger]

Originally Posted by Kevin Sevcik

*shakes head* Now that I think about it, that sounds incredibly crazy and darn near impossible. Maybe we just did the sane thing and bought some new belts in the off-season. My memory is a little fuzzy.

.

Would it be legal to buy a new tread and new pulleys and wheels after we ship and then replace our current ones with them at the competition?

If they were exactly the same size and didn't change the design of the robot at all?

[Greg]

Yes, this is legal. The rules say that you can bring "identical spares" to the competition.

[Stu Bloom]

Originally Posted by Greg

Yes, this is legal. The rules say that you can bring "identical spares" to the competition.

HOLD ON A MINUTE GREG ... this is one of those situations that you shouldn't be too quick to answer. I happen to disagree ... I suppose if they were ordered before ship date then the "timing" would be OK ... but if the parts they are referring to are truly "identical" then it seems it would not solve their problem. This is really a question for FIRST.

[Eric Reed]

Originally Posted by Stu Bloom

HOLD ON A MINUTE GREG ... this is one of those situations that you shouldn't be too quick to answer. I happen to disagree ... I suppose if they were ordered before ship date then the "timing" would be OK ... but if the parts they are referring to are truly "identical" then it seems it would not solve their problem. This is really a question for FIRST.

My interpretation (someone go ahead and shoot me down) has always been that you can bring any kind of raw material to the competition that you want, if you intend to build something there. You cannot do ANY kind of alteration to this material during the time between the build period and the event.

"raw material" in this case is anything that you would normally buy rather than make. Bolts, nuts, gears, treads, etc.

I mean, you are allowed to improve your robot on site...including adding brand new mechanisms...seems to me you'd need to bring something to make that stuff from.

If I'm way off, please let me know. We are neither rule-stretchers nor rule breakers, and would regret it if we have been misinterpreting this rule.

Eric.
De Anza Robotics

[SuperJake]

We used treads in 2001 and hated them.. but Robbie Extreme (56) used treads also and had a lot of luck with them. They said that the trick is to put pop-rivets all along the tread down the center. Then on all of your wheels, cut a groove that the pop rivets will slide in. This is basically how tanks do it.

[Lord Nerdlinger]

Originally Posted by SuperJake

We used treads in 2001 and hated them.. but Robbie Extreme (56) used treads also and had a lot of luck with them. They said that the trick is to put pop-rivets all along the tread down the center. Then on all of your wheels, cut a groove that the pop rivets will slide in. This is basically how tanks do it.

could you explain in more depth how to do this?


How do you cut the wheels in the wheel, and what are pop rivets?

[Stu Bloom]

Originally Posted by Eric Reed

My interpretation (someone go ahead and shoot me down) has always been that you can bring any kind of raw material to the competition that you want, if you intend to build something there. You cannot do ANY kind of alteration to this material during the time between the build period and the event.

"raw material" in this case is anything that you would normally buy rather than make. Bolts, nuts, gears, treads, etc.

I mean, you are allowed to improve your robot on site...including adding brand new mechanisms...seems to me you'd need to bring something to make that stuff from.

If I'm way off, please let me know. We are neither rule-stretchers nor rule breakers, and would regret it if we have been misinterpreting this rule.

Eric.
De Anza Robotics

I apologize ... I was the one who answered too quickly ...
I was thinking of a team-manufactured mechanism/alternate configuration brought to the competition which was different than what was on the bot ... I stand corrected [hangs head in shame ].

You have some good suggestions for different fixes here - good luck getting the bot up and running.

[ShadowKnight]

FIRSt actually touches on this subject in the rulebook. It is completely legal to get off the shelf parts bought after the ship dae, however you cannot modify the parts in any way between ship date and the competition. Now, if you want, you can assemble any changes you want to make to the drive train at the competition with the raw materials/ off the shelf parts you purchased between ship date and the competition

[ChrisH]

In addition to the previous suggestions, you might try putting a slight "crown" on your rollers. Particularly the ones at the ends of the robot. It doesn't take much. If the center of the rollers is slightly larger in diameter than the sides, then the belt tends to self center. Most conveyour belts do this but the crown is so slight you can barely see it. 1-5% of the diameter would probably do it.