Difference between roller and rollerless chain?

[Steven Smith]

It usually isn't a problem you have to worry about

At lower load applications, #25 and #35 chain are just standard. At higher load, the #40/#50/#60 become standard.

The critical dimensions regarding sprocket fit the pitch, or distance from pin to pin, which is defined by the first number #2x is .25", #3x is .375", #4x is .5" etc, and the roller (or bushing) diameter, and the distance between inner plates. Changing from #40 to #41 changes the roller diameter from 5/16" to 0.306", which may affect the fit slightly. Similarly, the inner plate distance changes, so a sprocket sized for #40 might not fit in a #41. I don't have a lot of practical experience working the the larger chains though, so I can't say 100% for certain if it would or wouldn't.

Generally in FRC, you should be fine with #35 chain as a practical maximum upper limit. If you find yourself thinking you need to run larger chain, you could look for ways to reduce the load in the chain, such as running a higher diameter sprocket. It's still interesting from an educational standpoint, but in 99% of FRC applications you will likely use "standard" #25 or #35 chain. Also, as it is not as standard of a product, you will likely pay quite a bit more for it (if it's even available).

EDIT: Also, just to clarify, roller chain would be fine for FRC, but there's no reason to use it because non-roller works just fine for our low-speed/low-use application?

Note that #25 chain is roughly ~0.1 lbs per foot, #35 is ~0.21 lbs per foot and #40 is 0.4 lbs per foot. If you have a 30" long drivetrain module, you could easily have 7 feet of chain per side, or say ~15 ft across your robot. Adding an extra 1.5 lbs to go from #25 to #35 or an extra 3 lbs to go from #35 to #40 shouldn't be done without a solid reason. It's also more of a penalty that simple static weight on the robot, as it is moving mass. Every time you speed up, slow down, reverse direction, you are having to accelerate several pounds of weight from a velocity of zero to a couple hundred feet per minute, superimposed on the need for the entire system (robot) to accelerate.

If you mean from a strictly academic sense of could we use a rollered #20 or #30 chain instead of the #25 or #35 chain (without adding a lot of extra weight), then yes that would probably be ok. By adding the roller though and maintaining the same maximum diameter, you have to decrease the diameter of the bushing/pin, which will reduce the load rating of the chain, for little appreciable gain in efficiency/sprocket wear in the context of FRC.