Straightforward, lightweight, compact, easy maintenance, what’s not to like? Trying to push my team to a similar consideration; we’ll see suitability after the reveal.
We have been tempted to do this in the past because of efficiency, but the weight is a deciding factor against this.
The 72 tooth vex gear is 0.4 pounds and with six of them you are at 2.4 pounds in just spur gears.
Where if you buy the single speed double reduction you weigh just 1.26 pounds per side. Or 1.2 pounds per side with the single speed single reduction box.
Just something to keep in mind if you decide to go with this, albeit great in all other ways, drive train.
Sounds like a fantastic use for WCP pocketed gears. Total weight of the 6x 72t gears drops to 0.85 lbs.
What is the thickness of the belly pan?
Assuming those are 72tooth gears, that only leaves 0.15" of ground clearance between the wheels and the gear teeth. And that’s assuming a totally rigid floor (not carpet) and zero wheel wear. That’s always been too close for comfort for me. If you pursue this design, watch out for carpet fragments getting caught in your gears and try to make sure you don’t spin out your wheels and end up destroying the carpet.
Alternatively, consider stepping up to a 5" wheel and using the new 10tooth pinions. Granted, 5" omni wheels are not a standard size from FRC vendors, although theydoexist.
Up here in leaf land most of our WCP will be bought off of VEXPRO, and they only have the 32 DP.
Makes me tempted to look at some of my old CAD again…
The model might be the 32 DP gears, but if we did this we would be using 20 DP WCP pocketed gears.
I definitely think a 5" wheel would be preferable or a 4" performance wheel with tread.
The belly-pan is just .080 AL sheet. I have .060 as an option as well, but I haven’t had a chance to ensure it passes FEA.
Are you looking at torsional stiffness? Or more for yielding under load x?
What’s a “pass”? Does your superstructure contribute stiffness?
I’m thinking about putting our chassis through FEA but haven’t found a good starting point for loading…
We had a 0.06" thick 7075-T6 belly pan in 2017. We gave it a stiffening rib (1x1 angle) mid span, but otherwise was perfectly fine for holding up our electronics and battery.
What is the belly pan intended to do in this case?
Instead of using lock collars, I would consider tapping ThunderHex and using 1/4-20 screws and washers for retention. Otherwise, it looks like a nice and simple design.