Bearings vs Bearing Blocks

[KeeganP]

Is there an advantage to using bearing blocks instead of just imbedding bearings into the frame of a chassis? If so, what is said advantage?

Historically, our team has just drilled 1.125" diameter holes into the sidewall of our chassis, and then popped the bearings in, and we were done! Worked well, was light, and easy to use. Just had to make sure the holes were in the right place when drilled, but never seemed to be too big of an issue (even for a team with no machining equipment beyond a drill press and a band saw).

I notice a lot of teams with WCD use bearing blocks, and VexPro sells giant blocks to hold bearings -- what's the point? I'm sure there's some big problem that they solve or nobody would use them, so I'm curious.

[carpedav000]

I only find bearing blocks advantageous in two ways:
1.) when there is some form of bump in the field (like the scoring platforms this year)

2.) it is generally easier to make drivetrain repairs

[EricH]

There is a third reason to use bearing blocks. And a fourth that is connected to that third one.

3. Because if you don't drill the holes to the right size, the bearing can fall out. (big ouch) Or it doesn't go in, requiring a bigger drill, which increases the risk of oversizing the hole. Bearing blocks have the hole drilled for you (and generally speaking, right the first time).

4. In case of chain tensioning by sliding the bearing around, the blocks often have built-in tensioners. Oh, and did I mention that this sort of tensioning system generally needs some form of oversized hole/slot (see #3), so a bearing in a hole doesn't work as well?

*Note: #4 does not apply to "tensioning by sliding transmission", which is another possible method.

[Chak]

Originally Posted by carpedav000

I only find bearing blocks advantageous in two ways:
1.) when there is some form of bump in the field (like the scoring platforms this year)
...

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.

[Chris is me]

Using bearing blocks doesn't really have anything to do with obstacles on the field, or being more able to drill a hole in aluminum plate versus tubing, or even ease of maintenance.

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.

Bearing blocks are most often used when you are using a sliding block tensioning system. A sliding bearing block tensioning system moves the axles away from the gearbox until the power transmission is properly tensioned. This allows for perfect tension, adjustable over time, without any loss in efficiency as would be the case with a chain idler or other system.

Additionally, single piece bearing blocks allow for perfect concentricity between the bearings. This improves efficiency greatly. Double piece bearing blocks such as the VersaBlock rely on counterbores and other geometric features to ensure concentricity.

[Monochron]

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.

This is the reason we have used them. Ordering a precision made piece and then adapting it to whatever you need is really powerful. Found out we need to move the shaft .5" further forward? No need to get new pieces and drill new holes, just slide the block down by .5".

Drilling a hole for a bearing is like soldering your electrical connections. Don't get it right the first time and you'll have to rework things a lot more.

That said, drilling a hole can be a lot cheaper and simpler if you have the resources and tolerances.

[GeeTwo]

Originally Posted by carpedav000

I only find bearing blocks advantageous in two ways:
1.) when there is some form of bump in the field (like the scoring platforms this year)

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.

I believe that this refers to using actual bearing blocks, not just sheets of aluminum pre-drilled. Something like asking Google Images for pictures of bearing blocks.

[Chris is me]

Originally Posted by Monochron

Drilling a hole for a bearing is like soldering your electrical connections. Don't get it right the first time and you'll have to rework things a lot more.

Well put.

That said, drilling a hole can be a lot cheaper and simpler if you have the resources and tolerances.

This is actually a fairly annoying manufacturing problem for a lot of teams. 1.125" drill bits aren't exactly commonly lying around. Step drill bits and metal hole saws will get you there, but not very accurately in terms of either location or diameter. I think the way 90% of FRC teams solve this is by milling their holes to size as most things with a 1.125" hole in them are done on a CNC of some sort.

The best way is probably to center-drill, drill that out with a variable-diameter bit to something like 1.12", then ream to desired fit (1.124", for example). The tricky thing is, even if you're willing to invest over $100 in a reamer, a lot of common school shop drill presses can't deal with the 1/2" shank. A hand reamer can do the job as well without the drill press, but they are also expensive and can be difficult to use.

Perhaps there's an obvious, easy solution I'm missing.

Originally Posted by GeeTwo

I believe that this refers to using actual bearing blocks, not just sheets of aluminum pre-drilled. Something like asking Google Images for pictures of bearing blocks.

I think this is an unnecessarily snarky response when the object you're alluding to is often called a "pillow block", and when several FRC specific COTS products that do not have this functionality are called "bearing blocks". It's easy to understand how someone would have trouble associating bearing blocks in an FRC context with increasing ground clearance.

(I do realize that "pillow block" doesn't exclusively mean a bearing block where the bearing sits below / above the flange bolting the block to its surface, I've just seen it used as shorthand in an FRC context like that)

[nuclearnerd]

Originally Posted by Chris is me

Perhaps there's an obvious, easy solution I'm missing.

There is an easy solution. Drill a 1.25" hole and rivet over one of these

[Chak]

Originally Posted by GeeTwo

I believe that this refers to using actual bearing blocks, not just sheets of aluminum pre-drilled. Something like asking Google Images for pictures of bearing blocks.

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".

[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".

[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.

[Monochron]

Originally Posted by nuclearnerd

There is an easy solution. Drill a 1.25" hole and rivet over one of these

We have two of these on our 2015 robot holding a shaft that is passing through a piece of rectangular tubing. Sadly the drilling of the 1.25" hole got a little harry and we needed to spend some quality time with with a file in order to get the rectangular tube smooth enough to rivet the plates on. And locating the plates on either side of the tube so that they lined up perfectly was probably more hassle than it was worth. Would have been a great place to use a VersaBlock or something similar that takes care of the locating problem.