Gearbox/ Dual Motor Setup

[matt111]

Hello all,

I am a member on team 1024, The Kil-a-Bytes.

We are looking for any plans or blueprint of a gearbox or a dual motor setup. This off-season we are trying to build a faster drive train. If you have any thing you think could be of assistance, please share it with us. Thanks in advance.


Matt
Lead CAD

[dlavery]

Look in the White Papers section. There are several designs already posted. Take your choice.

-dave

[NateBot16]

Our team has never mastered the art of gear boxes, but you can really do some great things with a few chains and sprockets. We are using this as a possible basis for the new robot. Looks like it should run very fast.

[Greg Perkins]

gotta love a ballsy battlebot chassis awesome! using those motors, it will be sooo robust!!

[Tristan Lall]

If you look closely at the above picture, you'll notice the chains being used to reduce the output from the motor are connected to a small sprocket on the shaft of the motor itself. There are three possible problems that might crop up with this arrangement.
Having such a small sprocket on that chain limits the maximum power it can reliably transfer. This was part of the reason that Blizzard 4 suffered several chain failures during the season. (Our drive sprocket was too small--25-pitch, 20-tooth.) Linked here is a (13 MB) reference that contains charts of maximum power for various sizes of chain (in terms of rotational speed and size of sprocket). These start on page A-6 (or 17 in Acrobat).
Related to Blizzard 4's chain troubles, there doesn't seem to be any idler system on that chain. While this can work (and has worked on many robots), the lack of an idler can put you at greater risk of chain slippage. If the chain isn't exactly the right size, you might find yourself missing a chain at an inopportune moment (and with chain, "exactly" isn't always a plus/minus one link situation).
Lastly, watch for the possibility of side loads on that motor. Some motors are more tolerant of this than others, depending on the way that their shafts are mounted in their bodies, and whether or not they incorporate internal gearheads. In general, a load (such as that introduced by an over-tightened chain) will tend to wear the motor at a significantly increased rate. (You might remember the warnings to never subject the Globe motors to a large side load, for this reason.)

[sanddrag]

Originally posted by Tristan Lall
(and with chain, "exactly" isn't always a plus/minus one link situation).

That is why they make half links

[Tristan Lall]

Which are half as strong ...
(Well, not quite half, but they are generally weaker than the regular links. And you know what they say about the weakest link...)

[sanddrag]

We never had a problem with them and we used drills and chias linked together for a total of a four motor drive. 1 drill + 1 chia per side. You can make out a half link in this pic

EDIT: This is also a pic of one way to do a dual motor drivetrain. You'll find a couple more pics here As a note, do not use nylon spacers under the pilllow blocks like we did. Make your own pillow blocks the correct height or use aluminum or steel spacers. While structurally safe, the nylon compressed when the mounting bolts were tightened making for horrible alignment at times.

[Rob Colatutto]

If your looking for a very simple 4 motor drive, probably one of the most simple I've seen that don't use gears would be from my high school teams (263) 2001 robot. Simply just the fp/bosch. (2001 was before the Atwood was added to the kit for anyone newer) fp(with its gearbox) geared up 1:3 to mate with the bosch(and its gearbox in low) and then geared 1:3 back down to a 12 inch wheel and ran about 5.5ft/s. Simple and elegant, 2001 LI regional winner and 2001 LI Delphi Driving Tomorrow's Technology winner. you could take that from the bosch and gear 1:1 to an 8 inch wheel and go approx 10ft/s if you are looking for a faster drive. A good approx of the robot speed can be done by taking
(wheel rpm X wheel diameter X pi) / 12 / 60
There are many old threads on this if you just look for them.
Another 4 motor drive example without gears is a timing belt combiner. (263 2002) The Atwood added in 2002 had a cluster gear given with it that mated with its output shaft. Then we attached a small 5:1 timing belt reduction onto that and it mated well with the bosch (and its gearbox in low). Then we did a sprocket reduction to the wheel. However both these designs required us to take appart the bosch gearbox and modify the output shaft to a standard 3/8 axel. Not a hard modification to do on your own.