Tank Tread Help
 

We are in need of some help...

We are making a robot that is about 3.5 ft. by 2 ft. wide. We are going to put some sort of tank tread on it but what we currently are using is not working. Currently our tread is two lines of chain that go around two sprockets each. They are connected with strips of Lexan that are riveted into the chain every fourth link. On the sprockets every fourth link is cut off so that the rivet pieces of Lexan line up with the cut out teeth on the sprocket. This system would work, but all of the holes on the Lexan pieces don’t line up, so the chain slips off often and then it simply doesn’t work. We are wondering if anyone has suggestions how to fix this, because if we can’t fix it we will have to come up with a new idea. We are thinking timing belts and pulleys, but we can’t find any that are wide enough. Does anyone have any suggestions on how wide the belt would have to be to be effective, and where we could find a fairly affordable belt that size?

Or are we approaching this entirely wrong?

Re: Tank Tread Help
 

we used timing belts for our robot this year. We bought them at http://www.brecoflex.com/ With them you can get custom treads at any size

Re: Tank Tread Help
 

I couldn't quite follow the description of what you are doing. Is it possible to post a pic?

Re: Tank Tread Help
 

Also could you tell us what "affordable" is? Under $100? Under $1000? Under $10,000?

Re: Tank Tread Help
 

This year our Breakaway robot used a tank tread drive system. In order to save money, we designed it to use triple-wide drive chain run on two sprockets, rather than buying belts from Brecoflex. I think the chain was available through some surplus store; I don't know where we bought it. This worked out well for us since the chain was wide enough that we could use it as a track and it never slipped in competition. To make it legal, we attached small pieces of hose using bolts, as you can see in this picture.

Re: Tank Tread Help
 

Check out the local tractor supply store, you might find something that will suite your needs. In Oklahoma there was a team (i think it was 2824) that used some treads from a tractor supply equivalent and they never threw a belt and had crazy pushing ability. The treads I am thinking of were about 6 inches wide.

Re: Tank Tread Help
 

I am waiting for the pictures to be approved or whatever so I can give you the link on Chief Delphi. Also for the price question under a thousand is a must, and honestly under 500 would be ideal. The cheaper the better because we already have invested a decent amount of money into the system we have which is not really working, and we don’t have a large budget to work with.

Re: Tank Tread Help
 

I recommend buying a pulley/belt system from a company called "Polytech", our team was EXTREMELY unsatisfied with our Brecoflex belts. Not only were they delivered way behind schedule, but also they snapped after only 3 or 4 matches, whereas the comparable polytech belts lasted an entire regional (12-14 matches) and an entire day of practice on our own field.

http://www.polytechdesign.com/

anyway,

I liked 578's style of afordable belts, they worked well at FLR where we competed against/with them.

Re: Tank Tread Help
 

on this year's winning NASA Lunar excavation robot, there were these tracks.

Thy consisted of aluminum C-stock fastened to chain that had special links that allowed things to be attached to them without modifying the sprockets. you can find them here: http://www.mcmaster.com/#roller-chain/=6s0umt Scroll down to the bottom and click on accessories. Unfortunately, they're only available for 35 pitch chain.

EDIT: Here's a pic of the link.

Re: Tank Tread Help
 

I've never done this before, but I would suggest timing belt since it requires fewer modifications than chain, and has fewer moving parts and joints. also, I would check to make sure the chain/belt is tensioned properly and hasn't stretched.

Re: Tank Tread Help
 

Handmade..cheap...and the best treads i've seen. http://www.maikenmagic.com/?ref=show...20Build&num=23

Re: Tank Tread Help
 

here's an innerworking picture http://www.maikenmagic.com/?ref=show...20Build&num=11

Re: Tank Tread Help
 

May I first ask why you think you need tank tracks/treads?

Re: Tank Tread Help
 

The simple and cheap solution may be to go with a higher pitch chain. I would think #35 at the smallest, but even higher may be necessary so the teeth of the sprockets have more chain to dig into as the whole assembly rotates.

I'd also recommend you fix the "holes don't line up" issue. It sounds like you have many lexan pieces and they all need to be identical. A jig, automated process, or assembly line may be in order. Look for defects as they come out of cutting/drilling and discard any grossly imperfect pieces.

Re: Tank Tread Help
 

Well honestly i do not think we need tank treads, however our team is set on tank treads.

Re: Tank Tread Help
 

We actually looked at those and our considering getting them. This is what we currently have.


This is our drive system with shocks...we still need a dynamic tensioner so currently we are just trying to get it working with the shocks locked and static.

This is the tread but we will be putting something over the lexan pieces so they grip the ground better.

This is a close up of the sprocket. If you look to the right of the sprocket you can see where we cut off the teeth so we could rivet the lexan pieces to the chain.

Re: Tank Tread Help
 

We used tank treads exclusively in the mid-late 90s. Given, this was for carpet with FRC, but your pushing ability is absolutely unmatched, but your speed tends to be slower, and your maneuverability is arc and circle limited.

We used something similar to the brecoflex treads with very high levels of success. We never slipped a tread after our ~first year using them. You need to be very careful how you design your tensioner and idler and where you place your bogies.

Re: Tank Tread Help
 

Team 578 this year, my team, was considering the same thing when we found triple starnd chain. its the same Idea but you bolt the lexan to the outer stands and run a regular sprocket on the inner strand. it will work exactly as you want it to. it can be bought from any specialty chain store online. alas it is expensive.

Re: Tank Tread Help
 

Might be above your cost range, but we've been very happy with the Outback track systems. Effectively it's a Brecoflex self centering belt riding on pulleys between milled aluminum, but it could probably be simplified down to a brecoflex belt on pulleys with some cheaper structure. If you're interested, Outback MFG is a Brecoflex reseller, so you can get some FIRST legal belts through them. (You'll need to contact them for details... I'm not current on what belts they carry in stock, or costs, or even availability...)

If we had more information about your application, I'm sure we could help you out with more accurate information....

Re: Tank Tread Help
 

The outback systems from what I heard didn't work out well. I only saw 2-3 Robots at Worlds with Treads, the both had belt treads. http://maikenmagic.com/?ref=showphot...%20Build&num=8
We handmade our using Kevlar belting, ABS plastic, and Rivets....lots of rivets.

Re: Tank Tread Help
 

We never had a single mechanical failure. Neither did any of the other track bots at our regional. I'm not going to say that it was an instant win due to treads, that would be lying. But we were never outpushed, and we never broke down due to mechanical reasons. A testament to their power can be found in our haywire autonomous, when we flipped another robot with a full speed hit, and proceeded to drive entirely over their underside.

Re: Tank Tread Help
 

Once again, flipping a robot this year is not a testament to your power but rather a testament to the bumper rules creating a situation where a large moment can be present.

Until they give us a game with sand or some soft surface, teams should really shy away from tank treads as they don't provide any competitive advantage and a whole slew of potential downfalls.

Re: Tank Tread Help
 

Agreed, our robot was simple...6 in. wheels with two cims per side going into andymark gear boxes. Nothing complicated and we could push everyone we wanted, we even bent a tracked bot's drive system some...oops.

Anyway, we are not using this for an actual FIRST competition it is for something else.

Re: Tank Tread Help
 

gonna try this mesage again the links didn't work last time

We actually looked at those and our considering getting them. This is what we currently have.


This is our drive system with shocks...we still need a dynamic tensioner so currently we are just trying to get it working with the shocks locked and static.

This is the tread but we will be putting something over the lexan pieces so they grip the ground better.

This is a close up of the sprocket. If you look to the right of the sprocket you can see where we cut off the teeth so we could rivet the lexan pieces to the chain.