Bearings vs Bearing Blocks

[Mr V]

Originally Posted by Chak

I thought we were talking about the vexpro bearing blocks here.
Even so, I still don't see how bearings blocks can help you go over bumps, whether it be the vexpro variety or a professional "pillow block".

The pillow block style can be mounted below the frame so you have more floor to frame clearance with the same diameter wheel.

[Ari423]

Originally Posted by Chris is me

First, COTS bearing blocks have the advantage of a precision bore to retain bearings - for teams without machining resources, this is simply the only way they're going to pull off a reliable live axle drivetrain.

Actually for the past three years we, using only a handsaw and hand drill, have built live axle drivetrains without using bearing blocks. The tricks is to use a piece of plastic block (I believe we use HDPE) with a semicircle cut into it on one side. The block is bolted onto the chassis semicircle side down and the live axle sits in the semicircle. The weight of the robot and the bolts holding on the gearbox keep the axle seated in the cutout, and the plastic has so little friction that the axle turns as if the plastic were a bearing. This also allows us to easily remove the gearbox, wheel, and axle without having to remove the bearing, while avoiding cantilevering the drive axles.

This may be a confusing explaination and I don't have any pictures from home, but if anyone is interested I can try to explain in more detail and get pictures the next time I'm in the shop.

[asid61]

We use bearing blocks for slots or other moving connections. Otherwise we just use plates with mounting holes, or bore directly into aluminum box tubing when it's applicable.
It really depends on the application.
We generally aim for a 1.124" or 1.123" hole (the latter for undersized measurements on bearings) by boring it out on the Bridgeport mill, manually. It's arduous but generally only takes around 5-6 minutes with an experienced student. I dream of one day having a 1.124" reamer and 1-7/64" drill bit to do bearing bores. We could go to 1.125", a regular size, but then we'd probably have to locktite it.

[RoboChair]

1678 used to use a 1-1/8th wood cutting spade bit that I hand ground down a little on up to 0.125 aluminum plate using our old tiny drill press(still use it for rapidly iterating prototypes) >_> then we upgraded to a step drill. Man, that was only 4 years ago... Some days I really do miss the shipping crate "machine shop".

[carpedav000]

Originally Posted by Chak

Can you further explain this point please? I don't understand how bearing blocks would help bumps, since they should be just as rigid as popping bearings in.

Rigidity is not what I was looking at. I was looking at the fact that bearing blocks can make the wheels stick farther down from the frame and give the robot more clearance between the floor and the bellypan.

And no, I did not search "bearing block" in google images.