Gearbox Help

[RyanJK]

Hey, so our team is in its rookie year, and we're flying blind when it comes to pretty much everything. We were thinking of using BaneBots's new P80 gearboxes instead of the gearboxes that came with the kit of parts. Here's a link to the gearbox page http://banebots.com/pc/P80A-nnnn-0005-Rn/P80A-4-0005-R2. I was reading that the Banebot gearboxes from last year were unreliable. Is anyone using this gearbox, and if so, is it any good?

[AdamHeard]

Even if the gearbox has been improved, I would pick the AM gearbox that came in the kit of parts. It beats the banebots gearbox in every way possible. This is advice is for the drivetrain though.

Unless this is to be used on a mechanism outside of the drivetrain, I can't see why you would pick a 4:1 gearbox. You would a lot more reduction to get some reasonable speeds.

[Urban Hawk]

I would go with a first choice of the one that came in the kit of parts rather then the banebot one.

[RyanJK]

So if we would need a higher reduction to get a real increase in speed, what would you recommend?

[Urban Hawk]

If speeds what your after, I would still recommend the one that came in the kit of parts. Last year with that part we were able to hit 10 - 15 mph.

[AdamHeard]

Originally Posted by Urban Hawk

If speeds what your after, I would still recommend the one that came in the kit of parts. Last year with that part we were able to hit 10 - 15 mph.

No, you weren't. that's 15-21 fps.

With a single speed gearbox, having 15fps would make your robot nearly impossible to drive and turn.

Most teams with shifters have a high speed of 12-16 fps and use their lower speed for more maneuvering.

With no chain reduction, the kit gearbox will get about 10.5 fps on 6" wheels. That's probably geared too high to be useful, it is also most likely not traction limited.

I would recommend the KOP gearbox with an additional 3:4 reduction in sprockets. That will put you at 8 fps, which is pretty good for a single speed robot.

[Teched3]

Staying single speed in your rookie season is not a bad idea. Banebots has redesigned their transmissions for greater durability, and a planetary transmission takes less space, is easy to mount, and you can change output ratios simply with sprockets. You MUST support the outboard end of the output shaft, and they have a bearing block available to make this easy. The kit transmission will also work well, but you should consider lightening it up. We have used DeWalt XRP transmissions with the CIM motors for the past two years, and they have been bulletproof (with modifications). I would not recommend you doing this outright, but you can do a Search on CD for Joe Johnson's paper "Nothing But DeWalts". You can get up to three speed output, but two speeds are most useable.

[Urban Hawk]

Hey due to our speeds, We wound up crashing into the cafeteria wall, bent some axles and took a few tiles off the wall. The other crash we completely wrecked our robot. Thats why we wound up having to slow ourself down. Never said anything about our control ability at that speed in last post.

[Jonathan Norris]

Originally Posted by AdamHeard

With no chain reduction, the kit gearbox will get about 10.5 fps on 6" wheels. That's probably geared too high to be useful, it is also most likely not traction limited.

I would recommend the KOP gearbox with an additional 3:4 reduction in sprockets. That will put you at 8 fps, which is pretty good for a single speed robot.

The theoretical maximum speed of the robot using the kit gearbox, 6" wheels, and the free speed of the CIM motors is around 10.5 ft/s. But when looking at these values you need to look at more real world speeds out of the gearbox take the normal speed of the CIM motors or make some rough estimations of the inefficiencies of the drive system.

So for a robot with the kit gearbox direct driven to 6" wheels I would expect the maximum speed to be closer to 8 ft/s in real world situations. So when doing rough calculations for drive systems taking the theoretical maximum speed (with motors at free speed) isn't all that useful, I would recommend either direct driving the 6" wheels or sprocketing it down by just a little but not 3:4 (which would be closer to 6 ft/s if you did).

[lynca]

Originally Posted by RyanJK

I was reading that the Banebot gearboxes from last year were unreliable. Is anyone using this gearbox, and if so, is it any good?

The hardened carrier plate has been fixed on the Banebots, we used them last year with a few minor hiccups. I would say banebots and AndyMark are about the same in terms of functionality. I know a lot of people are die hard for fellow FIRST members, but Banebots is a good company as well.