Custom Transmission - #1

I started designing this last night. I was getting a little bored and this is the kind of stuff I do when that happens. Usually its Chassis’ though not transmissions.

This is my first transmission I have ever designed, so its not going to be amazing, and I am really looking for some Structural Criticism.

“Front” View](
“Rear” View](
Internal View


  • Geared for 11.75 ft/s *
  • Reduction 9.9:1
  • pushing force is 207.20 *
  • Max RPM is 448.8
  • Gearing:
    12 tooth:45 tooth
    17 tooth:45 tooth
    -Output shaft is from ToughBox Nano (extended shaft)
  • Encoder mount on output shaft

*with 6" wheel

Criticize away, and any Tips or Comments would be awesome :slight_smile:

Thanks to Justin Montois (FRC Top 25) for helping me get started :slight_smile:

(PS! this is my 400th post!)

What’s the application? (Number of driven wheels per transmission, wheel mounting style, type of wheel, robot objective, etc…)

How does it attach to the robot?

What machining processes do you expect to have available, and what’s the budget?

Also, needs more shifting. (Or more to the point, what does it do that an AndyMark product couldn’t? Price and design experience are valid criteria here.)

it would be used on a chassis, for a 6 to 8 Wheel Tank Drive. The wheels will be direct driven by the output shaft, to a hub (from AndyMark). Any 6 Inch wheel would work, others would to but may not have the best speed and torque wanted.

it would just get bolted to the robot, the outside plate (side with output shaft) would be bolted, right onto frame of bot.

I would most likely get this Water-Jetted, from Sponsor. We have lathes and Mills to make shafts (except output shaft which is from AndyMark)

I wanted a Single speed transmission for my first transmission, so that’s why its not a two speed.

I have no knowledge of any Benefits so far. May be cheaper, and lighter but I never tried to compare. This was strictly for me to get use to designing transmissions.

Could you provide a pic of the internals, it’s hard to say much just seeing the plates.

Consider how you are mounting the gearbox. Having that angle on the bottom won’t help and I don’t see any mounting holes already.

It doesn’t seem to be a shifting transmission in which case it can be a lot thiner.

You should also reconsider your uses of a 17 tooth gear, I don’t know where you plan to get it but something like 16 teeth is much more common.

Tristan has a good point, what benefit does this have over an andymark product? If your goal is to make something smaller/lighter than you could start with toughbox gearing and go from there.

The Bolts will be longer and the nuts just get put on the other side of chassis (sheet metal chassis)

Could be a lot thinner, but its my first transmission so i don’t have any experience trying to compact it.

this is a 17 Tooth gear from Andy Mark.

Its just for Fun. I dont plan on making it better than AndyMark.

EDIT: Pic of Internals is now in Original post

with going for design experience, it isn’t bad. Personally, i like having a ring (different color and shaped like the actual teeth outermost point) on all gears to represent teeth to make sure i make the spacing correct and provide proper clearance.

Have you set up the mates for gear ratio and tested the output torque/speed of rotation? This is an important part of transmissions in CAD. If you have done this part(or when you do it), have someone (or more then one) who knows how to calculate it by “hand” do so and compare to make sure you did it right. If you are having issues doing this, feel free to ask (keep in mind my only experience designing transmissions is in Solidworks).