18-04-2007 18:31

AdamHeard

Re: pic: 1683 8 wheel drivetrain completed

Looks good overall...

just a few questions.

-Weight?
-Speeds?

Also, it looks like you have live axles going into bushings rather than bearings. Wouldn't bearings be better and have a lot less friction?

18-04-2007 19:56

Re: pic: 1683 8 wheel drivetrain completed

Looks good, but keep in mind one thing: if you're doing static wheels, your tensioner needs to be very precise, or you may have chain issues.

Also, I high recommend swapping the bushings out for bearings. You'll notice a huge performance increase. I built our 06 drivetrain in bushings, and I'm never doing it again.

18-04-2007 20:16

MrForbes

Re: pic: 1683 8 wheel drivetrain completed

I wonder how igus bushings would work for the drivetrain? just an idea...they seem to be "good stuff" and worth considering using wherever you can.

I don't see nearly enough room for electronics

How much work is it to change a wheel out?

18-04-2007 21:14

GBIT

Re: pic: 1683 8 wheel drivetrain completed

Just a question would it be tank or skid steering.

18-04-2007 21:37

EnderWiggin

Re: pic: 1683 8 wheel drivetrain completed

Every good 4+ wheel drive train has an odd number of wheels on each side. This is because the center wheel is dropped to allow the robot to "spin on a dime" because it rocks on the center
When you start pushing someone or they start pushing you, the robot basically turns into a 4 wheel drive system by falling to one side. Either the front or back wheels barely touch the ground when this happens.

In your system here, you COULD drop the two sets of center wheels if you so desired (this is what team 48 did with their tank drive system) but i doubt it would rock very well on those four wheels unless you move them closer together.

18-04-2007 21:48

sdcantrell56

Re: pic: 1683 8 wheel drivetrain completed

We used bushings this year and they seemed to work very well. Switching out to bearings would work but the cost would be much greater, also how thin of bearings can you buy? I am wondering because the plates are only .25" thick. I do agree that they would probably be more efficient, but honestly bushings worked so well for us and really didn't have much friction. I will definitely look into bearings though.
The total weight for the drivetrain is around 40lbs. I believe each module is about 17lbs in inventor. That weight is with motors. It uses the andymark 2 speed transmissions, and on the design as pictured the speeds are around 5fps and 12fps, but we might up the speed a little.
The 2 middle wheels are lowered on each side to provide some rocking effect. There shouldn't be much problem with it turning as the middle wheels have a larger track width than the length. Essentially it is a wide 4 wheel drive base which generally doesn't have any problems.

18-04-2007 21:55

Re: pic: 1683 8 wheel drivetrain completed

Quote:

Originally Posted by sdcantrell56 We used bushings this year and they seemed to work very well. Switching out to bearings would work but the cost would be much greater, also how thin of bearings can you buy? I am wondering because the plates are only .25" thick.

18-04-2007 22:00

sdcantrell56

Re: pic: 1683 8 wheel drivetrain completed

Could you tell me where you got them from and how much. The thinnest I can find are 7/16". 1/4" would be perfect and would allow us to press fit them. Also why do you not like bushings? Multiple teams use them including 121 and they seem to work well. Just wondering. Thanks for your help.

18-04-2007 22:02

Alpha 997

Re: pic: 1683 8 wheel drivetrain completed

Quote:

Originally Posted by squirrel I don't see nearly enough room for electronics

19-04-2007 00:42

AdamHeard

Re: pic: 1683 8 wheel drivetrain completed

Quote:

Originally Posted by EnderWiggin Every good 4+ wheel drive train has an odd number of wheels on each side. This is because the center wheel is dropped to allow the robot to "spin on a dime" because it rocks on the center When you start pushing someone or they start pushing you, the robot basically turns into a 4 wheel drive system by falling to one side. Either the front or back wheels barely touch the ground when this happens. In your system here, you COULD drop the two sets of center wheels if you so desired (this is what team 48 did with their tank drive system) but i doubt it would rock very well on those four wheels unless you move them closer together.

19-04-2007 00:52

Re: pic: 1683 8 wheel drivetrain completed

Quote:

Originally Posted by sdcantrell56 Could you tell me where you got them from and how much. The thinnest I can find are 7/16". 1/4" would be perfect and would allow us to press fit them. Also why do you not like bushings? Multiple teams use them including 121 and they seem to work well. Just wondering. Thanks for your help.

19-04-2007 02:20

sdcantrell56

Re: pic: 1683 8 wheel drivetrain completed

I looked at mcmaster and I saw those bearings. If I were to use bearings over bushings, they would have to be flanged, and be thinner than 1/2". Also I can't tell if the electronic thing is a joke or not but I think there's plenty of space for electronics. The controller will probably be on a second layer above the rest of the stuff.