Difference between roller and rollerless chain?

[Steven Smith]

I looked for a good video or diagram to show you, but I can't find what I'm looking for. I'll give it a shot via words, but a picture might be needed.

What's the difference between roller and rollerless chain?

Per the Wikipedia link you posted, on the schematic under variants in design, it is the presence or lack of part #5, the roller. In #25 or #35 chain which covers most FRC applications, there is just a bushing. If you look at the #25 or #35 chain, you can actually see a slit in the bushing, and if you grab the bushing with needlenose plies and try to rotate it, you will see that it doesn't easily move in reference to the inner plate. The primary movement you see/feel is the inner plate moving relative to the outer plate.

If you did have a roller, it now be a "bearing", in that the roller could also rotate and spin freely around the bushing.

Why would one want 'rolling' bushings instead of non-'rolling' bushings?

Mostly for sprocket wear. This is where I could use a better picture, but look at this basic one here, and picture that sprocket is being driven by an outside force causing it to rotate clockwise. On the top, the chain is contacting near the midpoint of the sprocket tooth on the bushing as the tooth engages the chain. The chain then gets pulled into the root between the teeth, and then comes back out on the slack side. With a bushing, this is all sliding movement between the bushing and the sprocket, causing more wear than if you had a roller.

I notice that most sprockets on Andymark use x5 chains. Is there a reason for this?

In the "lighter" series chain, the benefits of the rollers are less important. Even at "drivetrain speeds" our chains are usually run in the low to mid hundreds of feet per minute, which is reasonably low versus their rating. Additionally, you might only run a robot for 5-50 hrs in its lifetime, versus a car, or motorcycle, or fan, etc. that might have 1000-10000 of hours in its lifetime. The sprocket wear is likely dominated by material choice of the sprocket, tension of the chain, etc, not by the presence or lack of a roller.

Good question though, forced me to revisit the topic myself and play with a bit of chain Others, feel free to correct me if I missed something.

[ollien]

Awesome! Thanks so much! Out of curiosity, could you use a x5 on a x0 sprocket and visa versa, or are they totally not compatible with each other?

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?

[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.