help! is this bad?
 

right now, we have for each wheel, on the kit axle. a kit 12in wheel between 2 kit ball bearings on kit pillow blocks. a sprocket is outside one side of one bearing.

like this

B......W........B ........S
E.......H.........E.........P
A===E=====A=====R=====
R.......E .......R.........O
I .......L..........I..........C
NG ................NG.......KET

kinda get the idea? well, you see the sprocket is outside the 2bearings.
do you think we should put another bearing outside the sprocket too?
like this


B......W.........B ..........S..........B
E......H ........E .........P .........E
A===E=====A=====R=====A
R......E .........R .........O.........R
I......L............I ..........C........I
NG ..............NG .........KET......NG


is that 3rd bearing needed? it is too late for us to try to put the sprocket inside the 2 bearings next to the wheel.
we are too close widthwise to make the wheel go onto the otherside of the bearing so the sprocket is between, but the wheel is not.

please tell us what you think. if we should try to put the 3rd one on, or not.
it would help if you could give us some good reasons why or why not too.

please keep in mind that trying to put the 3rd ones on will be very akward on our present design.
thanks!

Re: help! is this bad?
 

On our bot we've got the third bearing on the inside of the sprockets (meaning closer to the center of the bot). I think it is a good idea to have a bearing on either side of the sprocket cause it can decrease axle wobble and keep tension for the chain. A chain drive can have a tendency to tug on the axle quite a bit. But it might be ok if the sprocket is quite close to the outer bearings. Hope this is what you mean.

Re: help! is this bad?
 

how close is quite close? ours is about 2 inches maybe?

Re: help! is this bad?
 

That is probably ok, but try running it and watch for any visible problems, like wobble, etc. it depends on how far apart the other bearings are, cause the further apart, the steadier the axle.

Re: help! is this bad?
 

Lining up three bearings on a single shaft requires a bit of precision. Otherwise, you'll deflect or bend the shaft in a way that might result in increased friction or binding.

Cantilevering the load against your sprocket outside the bearings isn't a great idea, either, but I think it's the lesser of two evils in your case.

Re: help! is this bad?
 

I would defenitley say yes because we have our wheels outside of our bearings and we've been driving for a week without any problems. Logically, if a wheels that is getting bumped around and torquing the axle in all the wrong ways runs fine, then a protected sprocket torquing in the right way will be fine.

Re: help! is this bad?
 

Once again, I will ask an engineer to back me up on this...

It can be a real problem having three bearings on a single shaft.

It is very, very easy for them to bind up! Avoid this at all costs unless you have a flexible coupling in there somewhere.

The kit shaft is very strong. A cantilevered sprocket should be no problem as long as the sprocket is close to the bearing.

-Mr. Van
Coach, 599

Re: help! is this bad?
 

Will this be the end of the world to have it cantilevered... no. Optimal? Not really.

The easy answer to whenever you have 3 bearings in a line... what is the middle one for? Can't you just remove it? Since they're bearings, they must be lined up on rigid surfaces. It should be as simple as running the sprocket and wheel in between the two bearing and mounting blocks...

I hope this helps.

Matt

Re: help! is this bad?
 

yes, it is possible, only if we choose to do that, the bearing to bearing will be almost 12 inches.
that or a cantilever then.
which should i do :(

Re: help! is this bad?
 

Without seeing your device up close, I would think it would be OK. There is always a source of trouble in this setup with implementation. The pillow blocks work well for slightly misaligned shafts but the torque on the wheels and the sprocket tend to try and drive the blocks out of alignment. The surface to which they are mounted and the mounting hardware must be sturdy enough to prevent movement of the assembly. If the blocks move, the chain will loosen, the wheels will not run true or they may even begin to drag on the robot body. You are using the big shaft right? I don't think you will be able to bend that without doing some harm to other parts of the drive.