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MrCrankyface

3D printed RC truck V3: Gearbox V3A

by MrCrankyface Aug 5, 2016
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could you share the .sldrpt files of this gearbox? i'm making your amazing truck but i need to adapt an other motor, with diferent holes. thank you!!!

trés bien,la gearbox V3A. merci

What kind of post processing do you do? I'm having trouble getting the pieces to fit inside one another and I'm printing at .1 layer height and with a .90 extrusion multiplyer. Should I scale the shafts down slightly or do i simply have to sand the pieces down and get creative?

At most I give my parts a very very light sanding across the layers with 120 grit sandpaper. I usually print at 0.2mm layers but layer height shouldn't matter as long as it's under 0.2.
Print calibration cubes and measure with calipers to make sure you're getting within at least 0.05millimeter.

These all V3 parts are awesome and so far I have made both the axle, center differential and gearbox. But the major issue u am facing is the parts not fitting. Some are damn tight to fit and some are so snug that once they fit when I try to pull it just breaks off. What is your suggestion on this?

I suggest printing calibration cubes and measure with calipers to make sure you're getting within at least 0.05millimeter.
You could also do a very light sanding across the layers to reduce the locking effect of layers-against-layers if your prints are slightly oversized.
Parts printed against the bed can also tend to "flare out" a tiny bit and might need chamfering or adjusting your bed to get rid of it.

I know its asking for a lot, but can I get the original files for your gearbox? I want to remake it to work with a cheap brushless motor.

could someone tell me the gear ratio on this?

Yes, exactly...what is the gear ratio??

Well. The motor sprocket is 10 teeth and that connects to 31 teeth.
Then you have a second gear ratio of 13 teeth to 31 teeth.

Soooo
10/31 = 0.32
13/31 = 0.42
0.32*0.42 = 0.1344
For every revolution of the motor, you get 0.13 on the output shaft.
I guess this makes for a 10000:1344 gear ratio.
Or ~100:13

nice approx 8:1...or 7.44:1

Very very cool!!!!!!

Now if I can just figure out how to upscale it and see if I can put it between a gasoline motor and the drive sprocket on a gocart...this way can eliminate that huge 60 tooth gear between the wheels...make it 12 teeth top, 12 teeth bottom...let the gearbox handle the reduction (it's usually 5:1 though) [as a test of course]

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Absolutely perfect project! Great design and engineering! Thank You for it!
Just one question. Please, how many turns per minute has Your motor? Could You give a link on it? I have no idea, how strong motor to buy.
Thank You.

a stock rs540 is around 17-18k rpm
in brushless thats just under 2300KV with a 2S battery

Thank you! My motor is a no-name 540-sized brushed motor which I think has a max rpm of ~18000.
A slower motor could work quite well as well as it will only slow your top speed a bit.

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Has anyone thought of using pulleys printed from abs and using O rings or tooth belts instead of gears? Its a relatively low rpm setup just curious how it would hold up...

Well the motor outputs nearly 20k RPM, not sure how it'd work in the long run. Might work better with a lower KV motor.

Great gearbox thinking about printing one to see how it would in a semi

Totally awesome! Definitely going to the axles, and gearbox =). How well are these holding up?

Thanks! They hold up pretty good I'd say! I've printed them in my cheapest PLA and the only thing that's broken is a driveshaft so far(first shaft from gearbox to center differential), and that was when I went full throttle at a jump/ramp.

What are the bearing specs for the V3 Gearbox?

Good thing you asked, I see I missed writing those down in 'Thing details'!
They are 6700zz bearings(10x15x4), same as in the V3 axles.

Thank you for making this! I was thinking of remixing the openrc truggy to solid axle but you've gone and made a solid axle rc already! Will add this to my print list.

Glad you like it! :)