Are tensioners worth it?

[McDoofus]

My team is having some trouble with a tensioner, and we are wondering if it is worth it. Some of us want to make the window motor swivel on one of it's bolts. Others just want to keep the tensioner. What does CD have to say?

[Swampdude]

We never use tensioners, just slot the motor mount or use 1/2 links.

[scottydoh]

The short answer is yes. With out seeing your actual set up its hard to judge, but it sounds like you're driving an arm with said chain. That makes me assume its is a considerably long run of chain, and you will most certainly need a tensioner to assure the chain does not skip teeth as it stretches. As for which style is better, I'd say a traditional tensioner is probably better because if you have the drive motor pivot, it might loosen as the motor torques when its running.

Edit: You can also just use a block of delrin or a similar material just pushing against the chain...Andy Mark also sells a tensioner that rubber bands pieces of plastic around the chain.

[TubaMorg]

I assume you mean for a chain? A swivel motor mount is also an acceptable way for tensioning. Two things to keep in mind:

1. Whatever tensioning method you use should be robust enough to not spontaneously loosen. For example, simply having a pivoting motor mount would not be enough because it would just pivot back under tension. You would have to figure out a way to lock it in place.

2. Your chains WILL LOOSEN with use. They stretch and will fall off if you do not check them periodically. For that very reason, even if you mount things so that the chain is tight initially, the chain will stretch. Without a tensioning system you may have a lot of heartache.

[Josh Drake]

Another thing to consider with the window motors is that the sprocket you attached is on a nylon splined shaft. The hub needs to be supported on the other end. If you have a good size load on the motor, the sprocket will come out of alignment and cause more chain problems.

[JesseK]

Whichever fixes the problem and will keep the problem fixed is the best solution. Honestly, you have to tension the chain and either option requires more work/maintenance.

[Teched3]

If you choose to go the window motor pivot route, you should install an adjusting bolt in a bracket with double nutting the bolt so it will hold the motor in proper tension position. Similar to what you see on a motorcycle rear wheel axle mount to tension and hold axle position.

[MrForbes]

Originally Posted by McDoofus

What does CD have to say?

Post some pictures of what it is you're trying to tension!

We love pictures.

There are a lot of ways to make chain tension adjustable, the way that's best for what you're doing depends on what you're doing.

This year we used washers as shims to raise the kit transmissions to tension the chains in one direction, and moved the transmission with the slotted bolt holes to tension the chains that go the other way. And we used ABS pipe cut in half lengthwise to tension the chain between the two wheels where the transmission is not. We used a screw in a tapped hole to push a bearing away from the mount, to tension the belt.

Some teams use a "floating" sprocket to tension a chain, it just sits in the middle and is held in by the chain on both sides.

We've made tensioning blocks from oil impregnated nylon rod. Machining required.

btw chains don't "stretch", instead they wear at each joint. The wear looks like stretch because the chain gets longer, but it's just wear.