pic: Triple 775 gearbox.

Three 775pro gearbox, should be easy enough to make on a manual mill. The air holes on the 775 are going to have to be hand fit, but I’m still happy with how I got this.

My inventor skills are improving a lot the more I work on this stuff.

I posted the dual 775 version yesterday, I originally wanted this to be a 3 motor gearbox but they didn’t fit the way I drew it, and then I realized if I rotate the two side motors 20degrees I could make them fit around the 60tooth gear.

This looks very similar to one I’ve been working on (Here is a drivetrain using it)

What gear ratios are you using?
The first stage seems to be 12:60, not sure about the second stage.

What wheel size did you have in mind designing it?

And what speed does JVN say it will go?


Nice design and good luck with inventor!

I strongly recommend that you put holes in the mounting plate for the motors to breath. I love 775Pro motors but you have to let the air flow through them if you want to work them hard without them overheating.


Dr. Joe J.

I actually based it originally on this guys
two motor box and had tried to fit three motors,
I couldn’t figure it out originally,
and ended up with the dual input box I drew the other day(https://www.chiefdelphi.com/media/photos/45206)
Before I realized that I could rotate the mounting holes for the 775’s 20degrees and make three fit on the 60tooth gear

It’s 12:60 first stage at 14:46 second stage.
There will then be a 18t-22t sprocket reduction to get the ratio of about 18:1 total that I want.
JVN.calc says about 13fps adjusted
4" wheels with option to go 6"

Yeah we are going to have to hand make the air holes on our manual mill. Definitely going to be in there.

This should work just fine. We did this on our shooter this year and didn’t have any overheating issues. To save time, I’d recommend just making the hole pattern with the same drill you use to cut the mounting holes. We did a total of 10 holes. 2 for mounting and 8 for airflow.


Did you just use the same bolt hole circle that the 775 mounts to?

Definitely gonna add that to the next revision

yep. Same bolt circle. One issue found was with using the same bolt circle it’s now possible to install the motor in several different “orientations”. It really only mattered during assembly where we had a bolt head interfering with our belt path. Explicit instruction gets around that pretty easily.

Ok nice.
Thanks for the idea