Tank Style CVT gearbox

What’s the final reduction for this gearbox? It looks like you have some reduction in the motor belt, some in the CVT belt, then two more gear reductions before the output shaft. Why so many?

Final reduction is (I think) 8:1 - 20:1

A definite improvement!

Are you planning to run this with a supported axle, or cantilevered WC style? Especially if the latter, you might find it advantageous to relocate (or remove) the NEO nearest the output shaft, to reduce the shear load on your shaft and the radial load on the output bearing. You may also be able to find a way to replace the initial belt with gears, which would likely have less friction than your serpentine belt - or perhaps you could use double-toothed belt and mount a motor to run inverted from the others to ditch the idlers. Which way to move from here is going to be dependent on how this fits into your chassis.

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I’m planning on running this in WC style chassis, but I don’t see why that matters as long as the NEO clears the frame? The double sided belt does seem to be a really good idea though. As for using gears, initially, (like way in the beginning) the NEO’s went to a central gear first, instead of the belt +pulley I have now, and then later switched it to the system you see now, after a couple people in this thread suggested it based on the fact that having a gear reduction would put a lot more torque near the first pulley which means it will be more likely to slip. What could happen is I can “undo” the reduction by that first stage with a second gear cluster after the motor input, but that would be a lot more space, gears, and bearings, so it seemed like the belt was a more elegant solution , even considering the slight reduction it introduces. I think from this point on, I need to start creating prototypes to iterate belt formats and such and really see what it takes to get the belt to slip, so more to come once I’m done the school year and have a 3D printer.

You should try to mount cantilevered wheels (and other loads) fairly close to the bearing to reduce the load on the bearings. As your output shaft extends several inches beyond the NEOs, which leads me to believe that you will putting the wheels out past the NEOs, and this is why I suggested moving the NEO out of the way. If the wheels are small enough that they fit within the NEOs’ depth, then simply making the shaft shorter would address the issue.

Here is another update. BIG thanks to @dirtbikerxz for the renders, he did an amazing job!

231 ![233|690x410]

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I know I am late to this, but couldn’t you have the three neos immediately drive the cvt, in a simmilar fashion to how the belt is shaped now? you could get rid of a stage that doesn’t do much other than combine all of the motors onto one shaft. Also, idk what your ratio is after the cvt, but you might be able to cut out one of the gear stages after the cvt if your ratio from the motors to the cvt is large enough. My only concern with this idea is that the pulley on your drive motor might be too small and could slip, but idk if this will happen. idk exactly how to do the math, but this might help shrink your gearbox

This is probably as far as this individual design will go, as yeah it’s a bit too big right now to be useful. but the neo’s are directly driving the neos

Can you show a picture with the neo shafts facing us with the plate hidden? I want to see the path of all the belts on the neos and how much wrap they have

image

Someone with more belt experience can comment on this. Whats the accepted number of teeth or wrap angle you want for a belt pulley to prevent slipping? Looks like you have about ~60 degrees on each pulley? Is that enough? I think these low torque high-rpm pulleys so maybe that makes it okay compared to using a belt as the last stage on a WCD for example.

Other than that it looks really good. I’me xcited to see how it turns out once you start making it.

Sorry, that’s not exactly what I meant. You currently run a belt stage to drive a small pulley that is attached which then drives the cvt pulley. What I meant was that why not directly drive the cvt pulley with the three motors. You might need to make custom pulleys if you can’t find ones that can directly attach to the motors, but this could cut down a stage or two.

this is why

wait mb someone already said this. I can’t read :confused: . This makes sense tho

Edit: If the concern is the amount of contact the pulley has with the belt, can’t you set two idlers around the cvt pulley to increase the wrap around the pulley, and then pull the belt outwards to shrink it? this could inverse the effect that you are referring to, since the pulley would have the least contact when at its smallest, but this could still be ~180 degrees if you put the idlers close.

Well, That isn’t possible, as the CVT pulley can only have 1 belt wrapped around it at a time

K, I’m really bad at explaining, but the three motors would immediately drive the cvt pulley. I noticed this was already discussed (thank you amrelk), however I might have a solution to that issue.

If the concern is the amount of contact the pulley has with the belt, can’t you set two idlers around the cvt pulley to increase the wrap around the pulley, and then pull the belt outwards to shrink it? this could inverse the effect that you are referring to, since the pulley would have the least contact when at its smallest, but this could still be ~180 degrees if you put the idlers close.

At this point, the thing needs some testing. In about a week, I’ll have ordered what parts I need in about a week (once I finish exams). That should determine what works and what doesn’t.

cough cough check out our CAD cough cough

Yeah i saw this yesterday, someone on the discord sent it to me.

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