[Ty Tremblay]

Originally Posted by Steven Smith

Hopefully not de-railing the conversation, but if anyone could humor me and take this discussion up a level, or link the relevant threads if it has been adequately discussed before, I'd certainly appreciate it.

#1: What are the pro/con of going to belt in tube if you are currently running chain in tube?
#2: Do you believe the differences are significant? And why?

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What advantages might we be missing out on by continuing to run chain in tube?

The things I can think of:
- We have run 3" high tubing two years in a row, to accommodate extra center drop as well as a slightly larger sprocket to reduce chain loads/sprocket wear/etc. I have justified this in my head by saying the extra profile yields a stronger frame (torsional), but is it needlessly stronger? Would running belts make it easier to go to 2" profile and maintain the high safety factor I would like, even at large diameter wheels?
- Are belts (when properly tensioned) more accurate with less slop when it comes to measuring distance traveled (for auton)? Or is the difference to chain not worth mentioning?
- Is the system more efficient? More robust? Overall lighter (I know the belts are, but the hubs look heavier than an equivalent plate sprocket).
- Other?

Any rate, we will probably do another iteration of our drivetrain before build season next year, and the discussions on the belt in tube have me intrigued. Thanks for any input!

In no particular order:

• There really isn't a weight savings with this specific design. The pulleys are about .5lbs heavier than the sprockets would be, and the belts are about .5lbs lighter than the chain would be.
• While you should always strive to do it right, chain can be a little more forgiving in terms of tension, proper spacing, and alignment, in my opinion.
• You can run chain-in-tube with 1.5"x2" rails like this design. There are some great posts and videos by 2363 in the forums.
• I would say yes, 3" tall tube is needlessly strong. If you've got a welded chassis, 2"x1" is plenty strong even if the front and rear tubes are .0625" wall. A lot of the strength of your chassis comes from a properly designed and attached belly pan.
• When properly tensioned, belts are no more or less accurate than chain in terms of odometry.
• Chain wears in (which some people perceive as stretching) over time. This can often lead to less tension in the chain later in the season, and can sometimes be a cause of issues depending on chain load. Belts wear too, but I don't think they wear as fast and the effects of belt wear aren't as apparent in an FRC robot.
• My main reason for wanting to go with belt-in-tube over chain-in-tube is for pulley wear. In FRC, a chain drive will wear both the chain and the sprocket because most of our sprockets are made from AL. In a belt drive, the AL pulley is much harder than the rubber belt and won't wear nearly as fast (if at all).