pic: Team 192's 2014 Gearbox

Originally Posted by DampRobot

I believe they at least partially develop thse gearboxes in the fall.

Champions are made in the offseason.

[Marc S.]

What size belts and pulleys did you use? Have you seen any issues with the belts so far?

[Joey Milia]

Over the past few years, prototypes have been built in the fall to test the new ideas and designs that are part of each gearbox. This has been very important because over the last three years the gearboxes have used untried and unproven concepts. The construction techniques and gear choices of the worm and bevel gearboxes were new and needed to be proven to work before we could decide to use them duing the season. This year the main thing that needed to be proven was the redesigned ball shifting shaft. We liked the ball shifting concept but thought the vex design could be improved. This design has as single piece output shaft, and use open bearings in the gears instead of the bushings.

Originally Posted by Marc S.

What size belts and pulleys did you use? Have you seen any issues with the belts so far?

The belts are 9mm wide, 3mm pitch Gates GT2 belts. The pulleys on this gearbox are 20T aluminum and 48T nylon filled ABS. I don't know how they're preforming on this gearbox so far but we used the same belts on last years drive gearbox, shooter gearbox, and the prototype for this gearbox with no problems when the belts are tensioned.

[AdamHeard]

Originally Posted by Joey Milia

Over the past few years, prototypes have been built in the fall to test the new ideas and designs that are part of each gearbox. This has been very important because over the last three years the gearboxes have used untried and unproven concepts. The construction techniques and gear choices of the worm and bevel gearboxes were new and needed to be proven to work before we could decide to use them duing the season. This year the main thing that needed to be proven was the redesigned ball shifting shaft. We liked the ball shifting concept but thought the vex design could be improved. This design has as single piece output shaft, and use open bearings in the gears instead of the bushings.




The belts are 9mm wide, 3mm pitch Gates GT2 belts. The pulleys on this gearbox are 20T aluminum and 48T nylon filled ABS. I don't know how they're preforming on this gearbox so far but we used the same belts on last years drive gearbox, shooter gearbox, and the prototype for this gearbox with no problems when the belts are tensioned.

You'll be happy with the belts in that application. They're plenty strong.

Hard to say how I feel about the engagement on the two CIM belt though.

[Joey Milia]

Originally Posted by AdamHeard

You'll be happy with the belts in that application. They're plenty strong.

Hard to say how I feel about the engagement on the two CIM belt though.

Yeah, I expect no problems with the strength of the belts.

The prototype used 16T pulleys and an idler to get proper tooth engagement. That was stepped up to 20T to hopefully make an idler unnecessary and still have enough engagement.

[Nathan Streeter]

This gearbox is simply gorgeous! Really love how it looks, obviously... but it certainly looks like it's filled with so much design!

I assume it's just the two stages, given the space on the gearbox and your speeds (19.5 and 8.5 fps)? Are those numbers theoretical, adjusted, or actual? I'm curious how you find the 3 CIMs combined with such high gearing... Seems like - especially for a full weight robot - that could be very battery-intensive.

[Rauhul Varma]

Originally Posted by Nathan Streeter

I assume it's just the two stages, given the space on the gearbox and your speeds (19.5 and 8.5 fps)? Are those numbers theoretical, adjusted, or actual? I'm curious how you find the 3 CIMs combined with such high gearing... Seems like - especially for a full weight robot - that could be very battery-intensive.

Those are the speeds adjusted by a .85 speed loss constant, as for the battery drain: our robot is looking to be 75 to 90 pounds so the loading is appropriately scaled down.

[Wayne TenBrink]

This is beautiful, and it is a great example of my biggest problem with FIRST material usage rules. You can buy a gearbox that is developed and built specifically for FRC in the offseason, test it any way you want, and then use it without restriction. If you design and build one yourself, you can't (without restrictions). It definitely does not inspire teams to do what you did. Excellent work!

[lukedude43]

Hey, I really like how you used the pulleys as the first reduction off the cims. I found what I think are the same pulleys and they seem to have 2 8-32 set screws. Did you guys just crank one of the set screws into the keyway of the cim, and if so how has that been working out for you?

[Rauhul Varma]

Originally Posted by lukedude43

Did you guys just crank one of the set screws into the keyway of the cim, and if so how has that been working out for you?

The pulleys are manufactured with two M3x.5 set screws, we then drill the bore out to 8mm and broach a 2mm square key way and use that to transfer torque.

[Ekcrbe]

Of course it's fabulous. I remember strolling over to your pit with our captain at Champs last year while you guys were gone to a match. We ended up marveling at the spare transmission you had on display for about a half hour and talking to a pit crew member about it. That's still the most amazed I've ever been by seeing an FRC robot part in person. This year, it looks like you've stepped it up again, and I commend your efforts. There might not be another team that condenses so much art into a transmission year in and year out.

[nuclearnerd]

Originally Posted by Rauhul Varma

loading photo ...

That sure is purty. Did you consider using a double sided belt (http://sdp-si.com/ss/pdf/80502117.pdf) and running it around all three motors in a serpentine path? (You would also have to relocate the motors a bit). That would let you get rid of some of the overhang, and flatten the gearbox width a bit. That said, it's pretty compact as-is. How did it perform?

[Rauhul Varma]

Originally Posted by nuclearnerd

Did you consider using a double sided belt and running it around all three motors in a serpentine path?

When I was creating initial sketches of the gearbox, I played with using double sided belts but found that I would need multiple idlers to achieve proper tooth engagement on the cims and that a double sided belt would actually lead to a larger gearbox with more empty space inside it. I decided that the marginally lower CoG due to that type of motor placement did not outweigh a smaller gearbox with little to no dead space.

Originally Posted by nuclearnerd

How did it perform?

As for the performance of the gearbox, we have not had to replace anything on them after 2 regionals and the drive base (the robot with the upper structure unbolted), as a whole, is operating around 53-58 dB.

[Seth Mallory]

Our gearbox won the Excellence in Engineering Award at the three Regional's that we went to this year.

[asid61]

Hi,
I was wondering what the weight of this gearbox was? Did you cheesehole any of the gears?