High Strength Transmission

VEX Robotics Competition Discussion VRC > Starstruck (16/17)
1

Hi Forum,
I’m trying to make a transmission for my robot, which should be pretty simple, but the catch is that the whole mechanism needs to be able to withstand a massive amount of stress because it will be involved with our catapult. Additionally, we would like to do this with a motor instead of pneumatics. I have never built a transmission before, and tips would be appreciated. I’ve .seen many videos of pneumatic transmission, but the only motorized one was not built well. Gear skipping has been a major issue with our robot, and we’d like to eliminate it if possible.

1 Like
2

Clarification: I’m assuming this is for a power transfer from motor power to catapult to perhaps a hang?

3

Sort of… But sure, let’s go with that.

4

Instead of a shifting transmission, you could use a ratchet transmission. When it spins one way, power the catapult. When it spins the other way, power the hanging mechanism. This is assuming you are still using a catapult and only need to spin the motors 1 direction (did I really just say those words?).

Ratchet and pawl:
Ratchet transmission:

5

Note: Transmissions are the coolest, but definitely a time commitment. Make sure the transmission creates a really creates a distinct advantage, as you do have to dedicate a motor or pneumatic to shift and lose a bit of power due to extra friction.

I made a PTO setup earlier this year for a lift to climb power shift, so I got some experience with working with a high torque transmission.

  1. Most important: try and do the shifting early in the gear reduction, ensuring minimal stress is applied to the shifting axle and gears.
  2. Bevel gears. (https://vexforum.com/t/how-to-bevel-gears/38163/1)
  3. Minimize the length of the shifting axle by adding a supporting plate in between shifting gears. (I attached a pretty nice example by another team.)
    g3fMc6R.jpg
    g3fMc6R.jpg1728×1152 296 KB
6

Unfortunately our catapult needs to be able to go in both directions.

7

I think drilling out the planetary holes in the gears and shifting on standoffs should help transfer torque better. Look at Green Eggs or VCAT’s transmissions to see what I’m talking about.

8

Not unless you do it like us :smiley:

Final product is finished on one side of our new base. It works very well.