Tank Tread Help

[Jstack14]

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?

[viperred396]

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

[Nevets Amstier]

Originally Posted by viperred396

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

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.

[Ty Tremblay]

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.

[PAR_WIG1350]

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.

[JohnFogarty]

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

[JohnFogarty]

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

[sanddrag]

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

[JesseK]

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.

[Jstack14]

Originally Posted by sanddrag

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

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

[Isaac501]

Originally Posted by Jstack14

Well honestly i do not think we need tank treads, however our team is set on tank treads. This is really unfortunate because you can have just as good if not better handling and off road capability without it.

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.

[yarudl]

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.

[Jstack14]

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.

[Tom Ore]

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

[MrForbes]

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