The perfect gearbox

[Tim Delles]

Originally Posted by sanddrag

If you were designing the perfect (or as close as possible) gearbox (for FRC robot drive system) what features would it have? Here's some basic points but feel free to add more

Selectable ratios Y/N and how many?
What motors input and how many?
What speed (rpm) output?
Size
Weight
Mounting
Output

And just for fun, if you had to buy all the parts and materials to build this perfect gearbox, how much would you spend on it?

So basically it would be a 2 speed shift on the fly transmission. The motors powering it would of course be the 2 Chips (and possibly the minibike). The arrangment would be that of a triangle, with the 2 chips at the bottom and the minibike at the top.

The gearbox would be geared for 11ft/sec (633.75 rpms using 4 inch wheels) high, and 5 ft/sec (297.99 using 4 inch wheels) low.

I would give around 8 pounds for each of the transmissions, but then again it is like the most important part of the robot, so if it needs to be a little heavier she can be.

Assuming that we are given the same chassis as we have been given for the past 2 years it would sit down within the chasis, with 2 output sprockets running to each end of the drive train.

[vansivallab]

hey
are the dewalt gearboxes compatible w/ the CIMs?

[EricH]

Originally Posted by vansivallab

hey
are the dewalt gearboxes compatible w/ the CIMs?

Yes, with some modifications. See the Nothing But Dewalts whitepaper for details.

[Ben Piecuch]

While I like the 2:1 or 2.5:1 ratios that most gearboxes provide, I REALLY like the 3-speed ratios that the Dewalt's provide. Using the CIM, it provides 3:1, 4:1 and 12:1 ratios, and only requires the use of one motor. The "stump puller" ratio, as I like to call it, gives plenty of torque with a one motor setup. (Granted, at the sacrifice of a bit of speed.) While the other two ratios provide plenty of speed to get across a wide open field, a la this 2006 game...

Overall, the planetary setups provide the smallest, lightest packages possible. Let's face it, 3/8" face, 50 tooth gears are never going to be the lightest for a FIRST robot. Look at the success of the Banebot's gearboxes this year. Cheap, light, small, and a lot of people are using them, even though their quality may be a bit questionable... Make a similar gearbox for a drivetrain (with a bit more robustness) and I think you've got a winner.

My only gripe about most gearboxes is that they take up a lot of volume. Specifically, they tend to be quite wide. Folks using an off-the-shelf gearbox for their onmi-drive setups, or even just a standard 4wd find that the overall length of the motor + gearbox setup becomes very long. Andy Brockway and the 229 crew have solved this problem nicely with their gearboxes. Maybe something like that can be integrated into a planetary setup.

Also, if you look at Wildstang's, Simbots, or even Beatty's (and I'm sure others') custom drive gearboxes on all their swerve setups, you'll find a beautiful, lightweight package. Let's see the whitepapers on those bad-boys!

I believe the kit gearbox is brilliant, and why some under funded, under manned teams shy away from it is beyond my grasp. It's a tough package to beat for reliability and ease of use. You need to match it's performance and ease of use if you want to sell into this group.

Though, overall, I think a lot of work can be done to help teams integrate their motors into a nice, off-the-shelf gearbox. The motor rpm's this year are either really fast, or really slow, and teams are finding that it's tough to get something running in the 500 to 1000rpm range with a small, light package. Adapter plates, mounting brackets, etc... take the pain away from teams with just a drill press and a hack saw.

I know this got a little off-topic, but I think making things easier for the smaller teams will greatly increase the competitiveness of all the robots. If you can make it easier, AND add a performance increase (through a shifting transmission or whatnot) you'll find yourself with a winning package.

BEN