philipat

I'd like to build some idler adjusters for my Bulldog. I'm borrowing an idea already presented here (http://www.rcuniverse.com/forum/m_9321613/tm.htm). But, I don't want to have to lop off the hub to make it work. So, I was thinking about using M3 screws, which will fit inside of the space between the wheels. The problem is that the shaft on an M3 screw is about 2.94mm and the hole in the wheel is about 5.25mm in diameter. I was thinking that I could fill this gap with some ball bearings. But, the only thing that I can find at these sizes are 3x5-mm needle bearings from Boca Bearings (http://www.bocabearings.com/bearing-.../KT357TN-3x5x7). Their width is perfect, but I don't think these are the right kind of bearings.

Anyone have any ideas for where Imight find these bearings? Or a different way to approach the problem?

Bagheera

Hi Philip

Would help Duratrax http://www.duratrax.com/caraccys/bearing.html

Did you have a good Christmas

John

philipat

Okay...thanks. I may have to look at slightly enlarging the hole in the wheels.

Panther G

You can use a needle bearing. They are much stronger than a ball bearing in the first place. Much more contact area means much more support of the weight.
As long as the case fits in the spot you need it to your fine.
Think of it this way. The drive shaft on your car uses needle bearings, think how much stress that is. They will work fine in your idler wheels. Actually better. NO Wobble at all.

philipat

Sweet...thanks. another bearing question:

does each diameter have to be exact? The actual diameter of the M3 appears to be about 2.95mm and the inner diameter and the inner diameter of the idlers is 5.2mm. The inner diameter appears to be a perfect fit. But, will the diameter of the idler wheel be too much?

Thanks.

Panther G

The 2.95 dimension should be fine. Remember thats just .05 of a Millimeter, that aint much. The 5.2 may need some cleaning up of the inner diameter of the idler wheel. 1 or 2 passes with a small round file should do the trick. If you go to far over then you could get the bearing woobling in the wheel and you dont want that so be very careful.

Panther G

Looks like I got the 5.2 going the wrong way. Just use some rubber cement to secure the bearing in the idler wheel. this should be fine. .2 of a millimeter is very small also.

philipat

Sounds good. I'll give a try. Thanks.