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.

[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

[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.

[Michael Hill]

Originally Posted by nuclearnerd

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

We used something very similar. Our chassis in 2015 was made of 0.050 2024-T3, which is structurally sound, but .050 is a little thin to retain bearings, so we made up some similar parts as above out of 0.090 6061-T6 sheet to rivet on to help relieve the bearing stresses. They seemed to work out really well adding mass only where it needed to be.

[FrankJ]

Assuming you don't have a CNC handy, drilling 1-1/8 bearing holes in thin aluminum (<1/4") a step drill works well. You can pilot drill a small hole through the channel to locate the step drill. You don't the spring back or grabbing that you get with a twist drill. For anything under .1" I would recommend a doubler plate to get more thickness.

What I like about the VEX bearing blocks

1. You don't have to be near as accurate drilling holes in the channel
2. It allows for tension adjustment for belts & chains
3. It locates the hole in the Z direction.
4. bearing retainer built in
5. Greater distance between bearings gives you better support moments.
6. smaller holes in channel gives you more strength. (Since you are taking material out of the center, this is a small thing.

The biggest disadvantage is there are a lot more expensive.

[JCharlton]

We got one of these a couple of years ago. A bit fiddly but does an accurate hole through a single sheet or stacks of custom bearing blocks. At $70 don't know why I didn't buy it ages ago.

http://www.busybeetools.com/products...ank-arbor.html

[GeeTwo]

Originally Posted by JCharlton

We got one of these a couple of years ago. A bit fiddly but does an accurate hole through a single sheet or stacks of custom bearing blocks. At $70 don't know why I didn't buy it ages ago.

http://www.busybeetools.com/products...ank-arbor.html

Let me be the first to admit that I have no idea what this piece is, does, or fits into. Nothing on it looks like a cutting surface/edge to me.

[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.

[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".