192 2014 Gearbox Parts

[Rauhul Varma]

Here are a few parts from our gearbox this year; these were run through all three of our competitions this year.

(All the images below can we found in full resolution at: http://imgur.com/a/eERy6)

Output Shaft (7075-T6 Aluminum)


44T Vex Pro Gear w/ Custom Shifter Bore


34T Vex Pro Gear w/ Custom Shifter Bore


Cluster Shaft (Vex Pro 1/2" Hex Stock)


24T Vex Pro Gear

[Rauhul Varma]

14T Vex Pro Gear


Shifter Shaft (4340 Steel)


Pneumatic Hub (6061-T6 Aluminum)


89T & 94T Belts (3mm Pitch 9mm Wide GT2)

[Chowmaster4695]

Nice parts. I see belts but I don't see any pulleys??

[asid61]

Snazzy. Is the shifter shaft hardened?
I remember one of our mentors dislike ball shifters, because his experience with them in the past has been that the balls wear out the inside of the output shaft. Can you cross-section it on one of the ball holes to see if that is the case?

[Rauhul Varma]

Originally Posted by asid61

Snazzy. Is the shifter shaft hardened?
I remember one of our mentors dislike ball shifters, because his experience with them in the past has been that the balls wear out the inside of the output shaft. Can you cross-section it on one of the ball holes to see if that is the case?

The shifter shaft was not hardened as the prototype did not show enough wear to warrant hardening the shaft.

I'll try to get a picture of one of the ball cavities, but last I checked there was very little wear on the shaft and no visible wear on the balls.

[asid61]

Originally Posted by Rauhul Varma

The shifter shaft was not hardened as the prototype did not show enough wear to warrant hardening the shaft.

I'll try to get a picture of one of the ball cavities, but last I checked there was very little wear on the shaft and no visible wear on the balls.

I meant the inside of the main shaft. I heard that the inside of the ball cavity can wear out.

[mman1506]

Did you machine the output shaft with a 4th axis?

[kitare102]

Originally Posted by mman1506

Did you machine the output shaft with a 4th axis?

From what it looks like, all you'd need is a 3-axis mill and lathe. Turn the sucker down, mill the two holes and set up the piece in a rotary table to make the hex end.

[highlander]

What was the rationale behind not adding more ball's for each gear to make engagement faster when you shift? Also, what is the benefit of adding ball bearings (my guess at what those depressions in the gears are for) as opposed to the bushings that VexPro sells with their ball shifter gears?

Thanks for posting these pictures; very useful into seeing how this great gearbox was made

[Rauhul Varma]

Originally Posted by mman1506

Did you machine the output shaft with a 4th axis?

Originally Posted by kitare102

From what it looks like, all you'd need is a 3-axis mill and lathe. Turn the sucker down, mill the two holes and set up the piece in a rotary table to make the hex end.

We used a lathe to turn the counter and bore, then mounted the shaft in an indexer on a manual mill and made the ball cavities and the hex with 2 work holdings.

Originally Posted by highlander

What was the rationale behind not adding more ball's for each gear to make engagement faster when you shift? Also, what is the benefit of adding ball bearings (my guess at what those depressions in the gears are for) as opposed to the bushings that VexPro sells with their ball shifter gears?

With a .625” OD this driveshaft is smaller than the drive shafts on the Vex Pro gearboxes. In addition it’s 7075 aluminum not hardened steel, so introducing a fourth ball could have made the shaft susceptible to shear failure. Even if the shaft was strong enough for a fourth set of balls, it would have taken too much time in analysis to prove for the marginal gain in shift speed.

I used bearings in the gears because they’re more efficient than the bushings. They are slightly bigger but that didn’t hinder the design very much.

Originally Posted by highlander

Thanks for posting these pictures; very useful into seeing how this great gearbox was made

No problem! Just wait for next year's gearbox, we have big things in store.