SIMPLE 2 Neo Custom Gearbox

2 Neos, 12:48 belt reduction, 3" wheels

Still figuring out proper belt lengths and some details but concepts are here. Ideal for a small zippy minibot


Hella pro, Marcus - I love it. If you’re worried about belt tension, I’d consider putting the idler bearing shaft in a slot, though I’m sure you’ve already thought of that.

I love the single stage, single plate setup. Based on the perspective it looks like a 9mm wide, 5mm pitch HTD belt - I’m curious why you didn’t select the 15mm wide option for extra security in the drive. I’m sure there’s a reason but it’s too hot out here for me to think.

Thanks for sharing!

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2 NEOs with a 4:1 reduction and 3" wheels gives a free speed of 18.6 ft/s. That is a very zippy bot!

One other thing to pay attention to is the belt’s minimum back bend radii. As Aren Hill pointed out to me in my similar gearbox, the minimum recommended radius for 5mm HTD belt is 1.25". For FRC purposes you probably don’t need to follow that spec exactly, but I don’t know that I would break it so severely. If you switch those tiny bearings out for “FRC standard” 1.125" OD bearings, that will probably be a lot better for the belt lifespan.

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You might want to actually reduce the top speed as you probably will never reach that speed and will prefer a higher acceleration

That idler will not hold up. Too small, too cantilevered.

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I’m not sure there is a readily available 15mm wide pulley for an 8mm shaft.

I’m inclined to think this is correct.

It would be very easy to fix the cantilevered issue, adding a second plate on the other side of the belt to support the motor and output shafts would make everything stronger and probably run more efficiently.

Like Adam said though, how tightly the belt is wrapping around that pulley, while likely okay in other applications, on a drive train is probably too tight of a bend radius to hold up long term. Also I think the overall output speed of this thing is just way too high, regardless of whether its for a lighter robot or not.

I get the appeal for a single reduction gearbox, but I don’t think it’s that much of a loss to do 2 stages on a flipped gearbox. Conversely, if you don’t need the motors flipped, running a single reduction is very feasible now with the smaller pinion gears that VEX sells. I know for example 971 used the 9T pinions on their drive this season and it performed well.

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Would it work to use 18mm pulleys for everything, but use 2 9mm belts, with one going to each motor?

Nice compact and lightweight concept!

From the second render, it looks like there might not be room for chain ruins to go above and below the standoffs in the tube, I would add placeholders to the CAD to make sure.

I would also be very concerned about running a belt that close to the ground. It seems like going over a small piece of field debris could easily damage it.

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