#25 Chain

[Joe Johnson]

At first blush, it seems that #25 chain should be able to provide more torque to the wheels than traction from the carpet (unless you are using teeny tiny sprockets) BUT, with drive systems, I don't mess around. There is nothing that lowers your draft potential as fast as driving in circles for a match because your robot threw a chain.

I recommend #35 chain unless you are completely painted into a corner and there is just no way to make it work.

YMMV.

Dr. Joe J.

[gblake]

Originally Posted by Sh1ine

Hi Folks,

Typically we use belt for our drive train. This year with the bigger wheels we are decided that we wanted a stronger transfer method so we switched to #25 chain. We are running 8" AndyMark Pneumatic wheels, with a WCP Dual Speed Gearbox. Our low end is about 6 fps and the high is about 12 fps. We keep breaking chain. Is anyone else having problems with the large wheels breaking the chain? Some on the team want to switch to #35 chain, but that seems like overkill to me. I feel like we must be doing something wrong, not that the chain is too weak.

Thanks!

Search through the past Chief Delphi discussions about the relative merits of #25 and #35 chains and you will find plenty of facts, experiments, opinions and anecdotes.

One thing that should become apparent during your search is that your machine is a system made of many parts, that it is operating in varying environments, and that it is being asked (by its operators & software) to do more than one thing. That makes it easy to reach the conclusion that you have to ask the right question (one that takes into account all the important independent variables) before you can answer whether #25 or #35 is the right chain for your machine.

I don't say this to make the topic sound too hard. I say it to help you quickly reach a valid, complete answer. Answers to incomplete questions are incomplete answers, and letting incomplete answers churn your design is not good.

Bottom Line: As is often the case, the right place to start is by learning what has already been recorded; so that you can stand on the shoulders of the ones who have gone before you.

Blake

PS: Some engineers and shade-tree mechanics might just decide to do a quick experiment. That would be adding some dead weight and/or rotating mass to your robot to approximate the effects of switching to #35 chain+sprockets, and then (using the current #25) deciding if the robot is likely to perform well enough when it has to move the the more massive, and stronger, #35 chain+sprockets. If it does still perform well enough, switch to the stronger and "more forgiving" chain this season (before next season do more sophisticated experiments).

PPS: There is more than one type of #25 chain ..., and more than one type of #35 chain.

[evanperryg]

Originally Posted by Sh1ine

Hi Folks,

Typically we use belt for our drive train. This year with the bigger wheels we are decided that we wanted a stronger transfer method so we switched to #25 chain. We are running 8" AndyMark Pneumatic wheels, with a WCP Dual Speed Gearbox. Our low end is about 6 fps and the high is about 12 fps. We keep breaking chain. Is anyone else having problems with the large wheels breaking the chain? Some on the team want to switch to #35 chain, but that seems like overkill to me. I feel like we must be doing something wrong, not that the chain is too weak.

Thanks!

#25 chain is very sensitive to alignment, if one sprocket is 1/8" further out than the other, it'll bind up and have problems. Make sure you don't over-tension your chain, as this also makes it more likely to snap. There should be a little bit of slack in your chains, but not enough for the chain to be noticeably floppy. Especially with a game like this, #35 chain is definitely not overkill, and it's much less sensitive to alignment. We're using #25 for mechanisms, but #35 on the drivetrain is definitely a good option.

[mman1506]

We're running a versachassis with 6 8" wheels on 25 chain with standard sprockets (18t?) and haven't had any issues after a full competition with plenty of defence crossing and hard defence. We did have one failure during practice due to a tensioner backing out but it was an easy swap.