pic: Frog Force 503 Omnitank Drivetrain (rAC)

[Paul Richardson]

Originally Posted by Bryce Paputa

We are using 25 chain, it isn't getting loose, it began loose. The tension on the chain doesn't change when shifting with this setup. Once we get the next iteration of this built with the initial chain tension issues fixed we'll be able to test if the 25 is sufficient or not, but teams have shown that it is (118).

Originally Posted by Electronica1

Didn't 118 have double strands of 25 chain like this?

While not a member of 118, I have had their systems explained to me by their students, so I can provide a little insight into why they do what they do.

They like the chain in tube because of the small space savings (and no bearing blocks to manufacture) but mostly because it requires no tensioning. The chain may stretch, but there is nowhere for it to go, so losing a chain isn't possible. Note that this doesn't mean the chain is necessarily strong enough for whatever load you are applying, it just means it won't derail as long as you stick it in a small enough space.

The double sprockets don't actually run double chain. Remember that the center wheel(s) are connected to the wheel in front of and behind it, so they have two chain runs on their axles. The people designing/building the drive found it simpler to just put double sprockets on all the axles rather than make spacers just for some of them.