So we know that chain is something that many FRC teams use now if not have used in the past. Using it last year, and debating on using it this year, one problem that comes to my mind, especially when traveling across short distances, is how hard the chain is to tension. I was wondering if anyone had any special tricks to adding tension the chain or to more easily get the right amount of links. Also, without building a sliding tension-er or removing a link, once the chain has stretched after running for a while, is there a good way to just add tension or stretch it in or out to remove slack?
Thanks in advance!
It seems you’re under the wrong impression about chain. It does not need to be so taught that it’s rigid. In fact, it doesn’t need to be very taught at all. After 89 matches our robot’s .25 drive chains were loose, but still functional. We didn’t use any tensioners, and the chain runs were 6 inches c-c.
You can get the right amount of links by using a chain calculator. Just Google and you’ll find many, and remember if you use an odd number of links you will need a half link. Or you can just make the center to center distance of your sprockets a multiple of 0.25 (assuming you have two of the same sprockets) or 0.125 if you are willing to use a half link.
The shorter the run of chain, the less important it is to be able to tension it. Consider using pre-stretched chain if you can buy it or use from last year’s robot.
There are lots of great resources out there… For example, designing your sprocket distances based on the chain type and sprocket sizes you are using…
A simple googling can get you some various chain calculator that you can adjust easily.
That way you can design with the strength chain you need and determine lengths you can work with… #25 chain is good for many things and easier to determine center to center distances, but I like #35 for our drive trains, much less stretch.
Using the Versa Blocksystems with their cam makes for easy adjustments.
Since I am out in the middle of the ocean, chain is much easier to keep on hand than a large variety of belts, besides there is no belt shop out here , mopeds, lots of those…:ahh:
Good luck,
Aloha!
Others have said it. The best way to address chain issues is to design the correct center-to-center distances so that you don’t need tensioners for things like the drivetrain. Using high angles of chain wrap can also help - you’re pretty unlikely to slip a chain if it’s wrapped more than 180 degrees around a sprocket.
If you’re the adjustable type or simply must have tight drive chains you can’t beat the vexpro cam-adjusted versa blocks. Design with center-to-center distance exact and then use the cam system to get it all perfect.
There are other ways to tension nuisance systems. Floating sprockets between the chains are a good near frictionless way. Plastic blocks held together by zip ties were a thing once. Or a sprocket on a bearing that you can adjust against the chain also works.
Some teams are getting precise enough in their control systems that a slightly loose chain or gear-mesh stack-up causes enough backlash in the system that it negatively affects their control scheme. I doubt you’re at that point, but if so then talking to a team like 971 about ways to reduce backlash might get you started in the right direction.