Rookie team drive tream idea

[edomus]

Originally Posted by maxlobovsky

Team 1257 (Parallel Universe or something like that.... don't ask me, I just build the thing ) is a rookie team this year without too much mentor support. We have started to settle on drive train idea but i have a few questions that no calculation or estimate could answer us well. We plan to use one Chiaphua per side (in a tank type steering system) in a four wheel drive with identical wheels front and back. We want to use a worm gear to gear it down about 15 times then a sprocket system for an additional 1.8 or so for a total of about 27. Assuming the the Chiaphua can give us 4000 rpm while driving the robot, that should give us a max speed of something like 8 ft/s.

1. Are two Chiaphua's sufficient to drive it and reach this speed?are the drills better for this situation?

2. Is it worth it to try to assemble the worm-gear-to-spur-gear gearbox ourselves (keep in mind it will be mainly students with access solely to drill presses and other basic power equipment), or should we buy it? If we should buy one, where do we get a gearbox like this for a reasonable price (I was thinking the seat motor, thats a reasonable price )?
3. Will the skyway wheels provide sufficient traction?

4. Will tank type steering with wheels be possible when our robot has a relatively large aspect ratio (something like 1.5:1, assuming wheels are about at the corners of it)?

5. Any other suggestions?

I would recomend buying planetary gearsets and then sprockets to gear the chip's down. We reconfigured our drive train post season and this worked well. Planetary gearsets can be purchased for a relatively small amount and they are very lite. we ran this with a 3:2 4 wheel drive chain/sprocket setup. works great

[KenWittlief]

is there some reason why you dont want to use one of the two drivetrains that FIRST supplied? we built a baseline/pratice robot from the ones they gave us last year (the 90° ones) and it works very well.

at least consider doing that as your plan B.

[Sachiel7]

^ See Reference Image (my avatar)

27:1 seems like a little too much of a reduction. Especially if you're running at 40 amps. You can get a good reduction simply with sprockets and chain.
We typically run a drive similar to what you've specified.
We run 1 chip per side, each at a 18:1 sprocket reduction, 40 amps/motor. We use 8" wheels; remember your wheel size will make your speed vary.
If you're gearing down the Chip's 27:1, you will not hit 8 fps, unless you have a large enough wheel. Having a wheel that size will compromise your gearing thus making it pointless.
Also, remember when your worm gear stops motion, your drive wheels won't want to move. In pushing matches or in conflicting forces in your drive, depending upon your worm gear configuration, you may be risking breaking your worm gear assembly. Trust me, I've seen it done. If you want to brake your drive instead of coasting, there are better options than a worm gear.
I'm glad to hear of some rookies trying something other than the drive supplied in the kit.
I would suggest that you shoot for 20:1 at most if you're running at 40 amps. The 12" wheels in the kit should get ok traction, but the 12" size can be a bit of an overkill, unless you're planning on driving up the side of the platform.
Either way, it sound like you guys are off to a good start!

[Max Lobovsky]

Originally Posted by Sachiel7

^ See Reference Image (my avatar)

27:1 seems like a little too much of a reduction. Especially if you're running at 40 amps. You can get a good reduction simply with sprockets and chain.
We typically run a drive similar to what you've specified.
We run 1 chip per side, each at a 18:1 sprocket reduction, 40 amps/motor. We use 8" wheels; remember your wheel size will make your speed vary.
If you're gearing down the Chip's 27:1, you will not hit 8 fps, unless you have a large enough wheel. Having a wheel that size will compromise your gearing thus making it pointless.
Also, remember when your worm gear stops motion, your drive wheels won't want to move. In pushing matches or in conflicting forces in your drive, depending upon your worm gear configuration, you may be risking breaking your worm gear assembly. Trust me, I've seen it done. If you want to brake your drive instead of coasting, there are better options than a worm gear.
I'm glad to hear of some rookies trying something other than the drive supplied in the kit.
I would suggest that you shoot for 20:1 at most if you're running at 40 amps. The 12" wheels in the kit should get ok traction, but the 12" size can be a bit of an overkill, unless you're planning on driving up the side of the platform.
Either way, it sound like you guys are off to a good start!

We are right on with our ratios, you forgot to take into account the difference in wheel size, ours 12 and yours 8:
12/8=1.5
1.5*18=27

Why is a 12" "overkill"? We thought it would make the steps significantly easier and, in addition, we already have two to play with.

The reason i wanted to do a worm gear is because i didn't want to deal with building a complex multiple axle gearbox. I understand the problem with the worm gear, but i still really don't want to try a gearbox like this. If anyone knows a way to simplify this 27:1 gearing (buy if possible), that would be great.

[edomus]

Originally Posted by maxlobovsky

Why is a 12" "overkill"? We thought it would make the steps significantly easier and, in addition, we already have two to play with.

There is absolutely no need to climb the stairs in this game.

[Max Lobovsky]

Originally Posted by edomus

There is absolutely no need to climb the stairs in this game.

There is no need to do just about anything in this game.

[Cory]

Think twice about the steps. You could get up them with far smaller wheels. Also, make sure you make your robot narrower than 30", or that your driver is darn good. It's going to be real tough for anyone to manuever around the fixed goal in such a tight space at such an angle.

Just some things to think about

Cory

[Max Lobovsky]

Originally Posted by Cory

Think twice about the steps. You could get up them with far smaller wheels. Also, make sure you make your robot narrower than 30", or that your driver is darn good. It's going to be real tough for anyone to manuever around the fixed goal in such a tight space at such an angle.

Just some things to think about

Cory

Hence the high aspect ratio of the bot's profile. And from everyone's suggestions, sounds like 8 inch wheels may be a better choice