Chain vs. Belts?!?

[Ginger Power]

Originally Posted by orangemoore

My FTC team is looking at it as complete replacement for gears and chain.

I wouldn't trust it in high torque situations such as drivetrains, as I haven't worked with it yet. If anybody can speak to polycord's power transfer ability before slipping that'd be awesome. I can't wait to test the stuff in many different applications.

[ASD20]

Originally Posted by Ginger Power

I wouldn't trust it in high torque situations such as drivetrains, as I haven't worked with it yet. If anybody can speak to polycord's power transfer ability before slipping that'd be awesome. I can't wait to test the stuff in many different applications.

We tried using it this year for driving our intake. Our intake was designed to pinch the ball between the wheels and a churro and we could not spin the ball out. The polycord would just slip. We were attempting to use it more like a traditional belt, which was probably our mistake, and only had 2 cords. However, in 2015 we used it for a conveyor belt and it worked fine. I think the main dlfference is we had a lot more cords (4 or 5) and it was a lower torque application.

[S1LK0124]

I know for a fact that my team has published a paper evaluation this very topic. If you'd like, I can post a link to it!

[S1LK0124]

You can find it here, scroll down until you find the "Belts vs Chains presentation" PDF.

[C.Lesco]

Chains suck if you dont know how to instal them or get that finicky half link in however used correctly i think its fine. As for belts, a good belt is better in my opinion "but belts might stretch" people argue. Youre using the thing for 6 hours flat out total at most, it doesnt matter in the time span of build and comp unless youre using a multiyear old belt. BELLLTSSSS

[Jay O'Donnell]

Originally Posted by C.Lesco

Chains suck if you dont know how to instal them or get that finicky half link in however used correctly i think its fine. As for belts, a good belt is better in my opinion "but belts might stretch" people argue. Youre using the thing for 6 hours flat out total at most, it doesnt matter in the time span of build and comp unless youre using a multiyear old belt. BELLLTSSSS

For FRC applications belts shouldn't stretch. Chains will stretch though.

[Chak]

Originally Posted by Jay O'Donnell

For FRC applications belts shouldn't stretch. Chains will stretch though.

I've heard that multiple times, but I've always wondered what "FRC applications" means. After all, one team's robot might go through tons of matches and hours of practices. Another team's robot might go through just one competition with minimal practice time. Doesn't the difference in runtime affect how much chains/belts stretch?

[Jay O'Donnell]

Originally Posted by Chak

I've heard that multiple times, but I've always wondered what "FRC applications" means. After all, one team's robot might go through tons of matches and hours of practices. Another team's robot might go through just one competition with minimal practice time. Doesn't the difference in runtime affect how much chains/belts stretch?

For chains definitely. Belts just don't really stretch under normal loads of an FRC robot.

[Cothron Theiss]

Originally Posted by Chak

I've heard that multiple times, but I've always wondered what "FRC applications" means. After all, one team's robot might go through tons of matches and hours of practices. Another team's robot might go through just one competition with minimal practice time. Doesn't the difference in runtime affect how much chains/belts stretch?

Because of the fiberglass tensile members in the belts we use, there isn't much 'stretch' in the belt at all, regardless of loading. Basically, if you're putting enough load on the belt to stretch it, it's about to snap, and cause a complete failure. Belts do not stretch appreciably over time. Theoretically, the teeth of the belt will deflect under shock loading because the tensile members do not support the teeth themselves, but that doesn't really affect wear and tear, that just increases the likelihood of ratcheting when you're overloading the belt's hold on the pulley.

[Oblarg]

Originally Posted by Chak

I've heard that multiple times, but I've always wondered what "FRC applications" means. After all, one team's robot might go through tons of matches and hours of practices. Another team's robot might go through just one competition with minimal practice time. Doesn't the difference in runtime affect how much chains/belts stretch?

Yes, but even given the variation in runtime between different FRC robots, the runtimes of all FRC robots are on a scale that's orders-of-magnitude smaller than that of these parts in actual industry, so "FRC applications" remains a very meaningful distinction.

[ollien]

Originally Posted by Jay O'Donnell

For FRC applications belts shouldn't stretch. Chains will stretch though.

How does one account for stretch? Tensioners like delrin rods on bolts?

[asid61]

Originally Posted by ollien

How does one account for stretch? Tensioners like delrin rods on bolts?

Basically having tensioners at some point, yes. There's a lot of ways to do it, including using idler sprockets, bare tensioners like you describe, or moving the bearing blocks farther away from each other via a Vex cam.
I heard from someone on 1296 that they used preloaded chain to account for chain wear-in so that they could run direct C-C without any change in tension over the course of a season.

[Jay O'Donnell]

Originally Posted by ollien

How does one account for stretch? Tensioners like delrin rods on bolts?

All sorts of different ways to tension chain. You can find nice ones on McMaster but are expensive, but if you don't over tension you can get away with Delrin of some sort.

Be careful to not over tension. Cost 229 a chance at a regional win this year.