Shifting Gears

[MBosompra]

Hello all. I'll keep this short and sweet.
My team and I have decided that we are going to build a multi gear gearbox so that we can shift gears on the fly. We have 2 solid ideas on how too do it and were currently doing all the math. I would just like to here from others any difficulties you had with changing gears. Any words of advice or ideas would be greatly appreciated.

[geo]

Keep it simple so when it do brake down it would be easier to fix.

[sanddrag]

Make it robust so it won't break down. (then it can be as complex as you want)

[Warren Boudreau]

Shifting on the fly is a challenge.
Bevel the teeth (grind them off at a 45 degree angle) of the mating gears. It makes the shifting smoother. Not all the way, mind you. Just on the edges.
We have tried programming a "synchro-mesh" system that would match the motor speeds. But up to now the computer power wasn't there. Maybe this year.
And you don't have to really shift on the fly. Think about what you are doing at the time you want to shift from high gear to low gear and low gear to high gear. You might be surprised what's really going on. I was.

[sanddrag]

You don't have to mesh gears. You could have a shifter dog mechanism.

[Gregory Frechou]

^could you elaborate

[Bill Gold]

Gregory Frechou:

http://www.chiefdelphi.com/forums/sh...ht=Technok at

[DanL]

I second the whole bevel-gears thing... we had lots of problems with the gears meshing until we did this.

Another thing I suggest goes to the programmers. When shifting, even our team's better drivers had problems getting the speed right. In the heat of the battle, it's hard NOT to be going in full throttle. As a result, when we were shifting, all of our drivers were putting too much speed in between gears, and the gears were making the clang-clang-clang noise of dhoom from sliding past each other and not meshing. What we did was we used two digital inputs and four limit switches (wired as shown in the 1-min Paint diagram below) to tell us when we were engaged and when we weren't engaged. At any point in time, the High-Gear OR the Low-Gear input must be 1. If both are 0, that means we're not engaged. When we're not engaged, the program limits the speed to something like 1/5th or 1/6th of the maximum speed - slow enough for the gears to finally mesh. This system is nice because its fully automatic - the driver can push as hard as he wants on the joysticks because the robot automatically limits the max speed.

Depending on how easily your system shifts, you might also consider having the program automatically go forward and backwards. We found that if you jiggle between forwards and backwards, it shifts faster. It's something you need to test out on your system and see how it works for you.

Hope all this made sense... it's 1am and I'm falling asleep, so my grammar probably isn't up to par. If you don't understand something, post and I'll get back to you in the morning.

[Mark Hamilton]

Perform all the math, figure out exactly how strong it needs to be, then build it 3x stronger.

[MBosompra]

http://jaw.iinet.net.au/crustyquinns/gears.html

http://www.chiefdelphi.com/forums/sh...ht=Technok at

I'd like to mention that this design is courtesy of the technokats.

Here are some ideas that we have. Please offer any and all words of advice it's greatly appreciated. We are rookies at building gear boxes. We're not sure which equations to use or even were to start. Please help.

[sanddrag]

Originally posted by MBosompra
http://jaw.iinet.net.au/crustyquinns/gears.html

I would hate to have to make that. Although I would feel very proud after I did.

[Madison]

Why shift gears when you can shift wheels?

[Rpifirst]

Yeah kickers. 190 did this very sucessfuly in 2001. But i think it takes up amuch more weight than a transmission.

[Madison]

Originally posted by Rpifirst
Yeah kickers. 190 did this very sucessfuly in 2001. But i think it takes up amuch more weight than a transmission.

It is heavier, usually, but can offer more advantages as well. Not only does it allow you to change speed and output torque, but other things like wheel base, tread, width and type.

I've helped do it very successfully in 2002 and, with luck, I'm going to do it even better in 2004.

[Specialagentjim]

Originally Posted by Mark Hamilton

Perform all the math, figure out exactly how strong it needs to be, then build it 3x stronger.

I just wanted to point out, that on the shaft we had bend, when we redesigned it to avoid the bending, we made it 8x stronger.