Quote:
Originally Posted by Andrew Lawrence
I'm referring to OP's use in a drivetrain. There is no question about the application in question. OP asked a question, I answered it with the answer OP was looking for. No hypotheticals - just a straight answer. The 17" number was based off of the older frame dimensions where the longer lengths around that number would lengthen more over a season.
Precision for chain isn't difficult to do, since you just need a multiple of the pitch, which is in eighths and easily measurable with a tape measure or ruler. It doesn't take precision fabrication to get C-C distance with hand measurements and an electric drill (something I've done for the past 4 years as a student on 256). While power is indeed a variable to look at, this returns to the fact that OP was referring to a drive system, where judging by even the really extreme systems shows that 35 chain can consistently and reliably handle the loads thrown at it, as it has for years.
I agree that adding a tensioner is simple in a WCD. I'm not saying it's not. OP asked if it's needed. I'm saying it's not.
You are correct in that there is much more that is being overlooked, but judging by OP's question I do not doubt that this is the question they wanted answered and that - possibly - an excess of extra information like others have been posting may take away from the original point of this thread.
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Yes the OP asked a simple question but with a complex answer.
Giving him a answer based on your experience without some context can be slightly misleading. There is a lot of "it worked for me so it has to work for you" type stuff floating around here, and often that is not the case. There are many types of drive trains out there and the OP didn't specific anything about them. (He could be talking about swerve for all we know) and just many variables at play. As I said, C-C chain can work, but it doesn't always usually based a team's experience and testing. The drive base is one of the most important part of a FRC robot, and is something you want 100% confidence in. Planning some tensioners, even not used, can save a lot of headache down the road.
And drilling holes for C-C with a hand drill and a tape measure... I reckon that it needs to be within at least +-.04in for it to work effectively... probably you want something closer +/- to .01in. Sure this is possible to do on a drill press, but isn't trivial. It isn't "precision" machining but it isn't just sharpie some marks and go for it and the OP should be aware of this and is a important part of getting C-C to work.
This is a question that comes up a lot "do we need tensioners" on the robot. And leaving a bit of information for the OP to think about and explore with off season prototyping and research is never a bad thing.