Hi, my team uses one chain on each side of the shooter to help it pivot, but were are having an issue where we can never get both chains tensioned at the same time. We can tension either side, but then the other side is always too loose. Does anyone know what the problem could be?
Edit: I hope we will be able to get the chains to tension with the AndyMark tensions we have bought, but, in case we can’t, does anyone know if/where we can buy #35 inline chain tensions of different lengths?
What is your chain tensioning mechanism? Are the sides separate from each other, or linked where both are tensioned at the same time with a linked mechanism? Can we see a photo?
Thanks for asking for clarification! We have a hex shaft in the belly of our robot driven by a neo with a 90-degree gearbox. On the top of the robot (the pivot for the shooter), we have a SplineXL. On both ends of the hex shaft and Spline XL, we have a gear. We have two separate chains. A chain runs on both sides to connect the gear on the SplineXL to the gear on the hex shaft. I believe we are using #35 inline chain tensioners from AndyMark.
Something I would check is to match sure the teeth on your sprockets are clocked to the same position on each side, and that each chain has the same number of links. Don’t know if that would cause this issue, but seems like a good idea regardless.
We lined up the clocking of the sprockets today, and we still couldn’t get the chains to tension at the same time. We’ll make sure to check the length of the chains tomorrow. Thanks!
If they are clocked the same this shouldn’t be necessary, but if you have room for a tensioner on either side of the run (so with 2 chain loops, that’s 4 total tensioners) you should be able to get all the slack out, but again, if they are clocked that shouldn’t be an issue. With hex shaft it’s hard to get every last bit of slop out, so you can also try to preload the shooter so the motor is always pulling against the preload. My team is using surgical tubing for this to pull the shooter down. When the robot aims the motor is always stretching the tubing which keeps it from bouncing around.
With tensioners like that, you should be able to get pretty close to equal. Let me ask you this? Did you just recently put the chain on, or only just start running it? Like, the last day or so? Because you should expect chain to stretch for a little while before it gets to it’s fully stretched length, and you’ll need to keep tensioning until it settles.
They’re never going to be perfectly equal, one chain is always going to be doing more of the work, and that chain is then going to stretch, and then the other one will take the load, and then it will stretch, passing the work back and forth over the course of days. You’re likely going to have to keep tweaking the tension while you run it, and eventually it’ll stop stretching (depends on how much you run it and how long the chain is).
Thank you so much for both those solutions! We may have some extra tensioner laying around that we could use. We also have some surgical tubing that is a little bit bigger in diameter, so, if doubling up on chain tensions doesn’t work, we’ll try that.
We actually did slowly pivot the shooter with one of the chains while we were waiting for the tensions to arrive, so it is very possible that one is stretched out more than the other. Thank you so much for your response!
I would also consider shimming the hex shaft. Hex-hex interfaces are notorious for backlash and can contribute to the tensioning issue, especially as the shooter is moved.
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