VexPro Bearings
 

Our team was planning to use VexPro hex or thunder hex bearings to support a hex shaft in a low load, high RPM application (14k RPM) . Has anyone come across any specs or ratings for hex or thunder hex bearings that they offer?

I know that I can get 1/2" bearings rated to up to 15k or 30k but turning the shaft to a round does not support our application.

In addition, what is the risk to using the VexPro bearings at that RPM?

Thanks!

Re: VexPro Bearings
 

There are no specs publicly available, but teams have used the hex bearings in small wheel shooters in 2013 which spun at similar speeds.

I would suggest ThunderHex so that you don't have any minor issues with runout / concentricity, which aren't always noticeable in a normal hex bearing application but might be at high speed.

Re: VexPro Bearings
 

Honestly the fact that vexpro doesn't have specs online really bugs me.

In the industry we have to consider all of these aspects and bearing selection is a major part of the design.
I don't know what speed vexpro hex bearings are rated for so I can't say exactly if they will work or not. However since they decided to withhold the specs I would assume that the bearing won't work.

I am going to let you in on a bit of info that 5817 learned this season. We changed out the hex bearings on the shooter with bearings from McMaster (who give specs on their bearings) with an appropriate rpm rating, our shooter spun around 1000 rpm faster with just a bearing swap.

I don't know why vexpro doesn't give us this info, I am assuming it is either 1: they don't accurately know, or 2: posting the data will harm their sales.

Let's say that the bearings have a low speed rating this could affect uses in a lot of frc applications besides shooters perhaps even some gearboxes. Vexpro also knows that students might not look into specs and thus never bring up any concern.

Re: VexPro Bearings
 

1. It doesn't look like McMaster sells 1/2" hex bore bearings, or anything close to thunder hex size, so it sounds like you might be comparing apples to pineapples or something.
2. Have you tried asking anyone at Vex for ratings, if they're that important? I suspect the main reason the specs aren't listed is because they're in excess of nearly every FRC application.

Re: VexPro Bearings
 

The McMaster Carr bearings are round bearings not half inch hex, if you lathe down the shafts you can use the round bearings. So I am not comparing apples to pineapples or something.

No I haven't reached out to vex however I still believe they should put the bearing specs on their website. And I don't believe that the bearings specs are in excess for every single frc application. I believe that their max rpm is a lot lower than everyone "assumes". I will reach out to vex about their bearing specs. But 1000 rpm difference with only a bearing swap is very significant in my eyes.

Re: VexPro Bearings
 

Did you miss the part where the OP said turning his shaft to round won't work for his application?. That basically means McMaster bearings won't work and he's "stuck" using commercially available hex bearings.

For what it's worth, I've never seen a problem with any of the hex bearings we've used - either custom applications or as provided in some commonly used gearboxes.

If you can contact vex and get a spec for them, you'll know for sure if it'll hold up for your application. If it doesn't, you could try something my team did last night... For one application, we have a hex shaft that we needed to put a specialty bearing (specifically a one way bearing... Those things are so cool!) right in the middle, and a hex bearing just wouldn't work. So instead we got a 3/4 ID version of the bearing, a 3/4 shaft, and bored a 1/2" hex hole in the middle. That lets us put the bearing on the 3/4 shaft, and the 3/4 shaft on the hex shaft wherever we want it, while preserving the hex on either side of the bearing for other applications.

Re: VexPro Bearings
 

Here is an old trick.... get a bearing that fits a 5/8 shaft, get a bushing that is 1/2 ID and 5/8 OD. Broach the bushing, and put it inside of the bearing. Now you have a simple hex bearing.

The one major issue with this is that I have not found a 5/8 shaft bearing with a 1.125 OD, but if that doesn't matter to you this is a good stand in solution, that many teams used to used before hex bearings were common.




On a side note, I also have been meaning to ask what the specs of the hex bearings are, both in RPM, load, and rated life. We have some that during prototyping (spinning at only moderate speeds) seemed to get really loose quickly, I assumed it was either an old bearing or we were beyond the spec. We changed the design, but it would be good to know for the future.

Re: VexPro Bearings
 

Sorry, were you using half inch round Vex bearings and then switched to half-inch round McMaster bearings? If so, then I'll agree that the McMaster bearings were an improvement over the Vex.

If you're talking about switching from half-inch HEX bearings to half-inch ROUND bearings, then that's a whole different ballgame. Vex notes in a few places that hex shaft in hex bearings can have some tolerance issues, and I would expect them to have some minor issues running at higher speeds. So apples to pineapples.

Re: VexPro Bearings
 

We used Vex 1/2" hex bearings for a prototype shooter that ran with 775 pro motors at full speed with no issues.

Re: VexPro Bearings
 

Early on in the design process I tried looking up the specs for both Vex Pro and Andymark's 0.5" hex and round bearings to no avail. Still we are using them anyways in our shooter simply because there's not a good alternative.

It would be interesting to get a spec sheet and some data from practical testing through typical FRC uses (shooters, drive trains, high load applications, etc) so teams can make better informed design decisions.

Re: VexPro Bearings
 

I read the op I was just posting what we were able to do.

Vex emailed me back with no info, but they said they would be contacting soon in this thread.

I am just so surprised at these reactions, all I was saying is that bearing specs should be posted and how going from 1/2 hex to the McMaster high speed round bearing made a difference.

Re: VexPro Bearings
 

To be fair, you did accuse Vex of withholding damaging information from customers to bolster sales of their product. Which is is kind of a serious accusation.

Re: VexPro Bearings
 

ding ding ding we have a winner... Basically steelerborn, you come off as a jerk. I'm sure you didn't intend for that but there it is. Not posting product data because it will harm their sales... mkay.

Re: VexPro Bearings
 

I said that it was only one possibility, let's say that the half inch hex bearings are rated for only 1000 rpm, I would imagine that would affect their sales. I like vexpro I think they are doing a great job.

However I don't think it is too much to ask a supplier to post the load specs for their hardware. Especially when in the workforce students will one day have to understand bearing selection and the reasons why.

I can't be the only one who thinks they should put those specs online.

Re: VexPro Bearings
 

I'm sure you aren't, but there are about 100 better ways to ask for it than the way you did.

Re: VexPro Bearings
 

I'm an advocate of getting the students to understand the reasoning behind selecting those bearings, and not just go with what vexpro uses. If that makes me a jerk or a bad person l, oh well. My life doesn't revolve around this forum.

I feel that it is odd for them not to post that information, especially since I know how much vexpro cares about making sure the students learn and understand engineering principles.

Re: VexPro Bearings
 

*blows ref whistle* Okay, okay. Now let's all take a deep breath and take a break for an hour or three. I've PM'd Aren Hill, and steeler emailed Vex and they've said they're working on information for this thread. I think we've all vented enough to express our opinions at this point, so let's wait for some data.

Re: VexPro Bearings
 

Kevin B.,

We actually have never been asked to put up the specifications on our web site. My team is working on getting the specifications for all of the bearings since most of them are standard ABEC 1 (or ISO 492 Normal Class for the Metric Bearings) bearings.

The total ratings (mostly the load ratings) have zero applicability in FRC for many reasons (I will make another more detailed post about this later), however the speed rating is important.

So, the Thunderhex bearing limiting speed is 31,000 RPM

The standard 3/8 and 1/2 hex bearing theoretical limiting speed is also 31,000 RPM.

However, the nature of hex bores make them oversized a bit in order to practically install the shaft. So there will be clearance between your shaft and the hex bearing (this is true with ALL hex bearings no matter who makes them or what they tell you). This clearance causes extra load at high speeds.

The reason you can only find AM and VEX (and at one point WCP) who make the 1/2" hex is because it is extremely custom for our application. Most bearing volume usage is for industrial, high precision applications and the Hex tolerance is unacceptable for that use case. For most FRC applications that don't involve high speed shooting, the hex has served us well.

Now, I absolutely despise hex bearings for many reasons. I almost despise them as much as mecanum wheels but that is a story for another day.


We wanted something more from a hex compatible bearing that could give us the flexibility of the hex bearing and the precision of a regular ball bearing.

For this reason, we decided to create the Thunderhex bearing. Bearing manufacturers are really good at making round things round with very little total indicated runout. As a matter of fact, no one does that better than bearing companies. However, they are not very good at making hex holes in bearings. We inspect 100% of our hex bearings to make sure they meet our drawings. The factory scraps about 20% of the hex bearings they manufacture for us before anything gets shipped because they do not meet our specs. The Thunderhex bearing scrap rate is below 0.1%. The reason is simple: Thunderhex bearings are just round bearings with a special inside diameter of 13.75mm.

So my recommendation is use Thunderhex shaft with Thunderhex bearings and you will never have an issue. By the way, for high speed applications we recommend a slight press fit between the bearing and the shaft in order to keep the system balanced at high speed.

The basic issue for high speed applications with Hex bearings is that the clearance to make the hex shaft install properly causes eccentric loads on the bearing which causes premature wear and higher loads on motors, which is the most probable reason you saw a speed difference.

So let me be clear, the VEXpro bearings all use standard industrial balls and bearing raceways and can attain the speeds of their industrial counterparts.

One last thing: my team does not use hex bearings anywhere. We use Thunderhex exclusively and Thunderhex shaft in most places. It has made life so much easier.

I hope this helps.

Paul

Re: VexPro Bearings
 

Thanks Paul!

Re: VexPro Bearings
 

This would be why I was questioning if steller was switching from hex bearings to plain round bearings. I knew hex bearings were not equivalent to round in some ways, though I didn't know the specifics.
And so much this. My team was claiming we were out of thunderhex bearings, so they swapped in some "normal" hex bearings. I informed them that the hex bore bearings were only for use as a last resort, and week 2 was not last resort time. Thunder hex just makes life easier. The real problem is that Versaplanetary outputs only come in true hex, not thunder hex. So i have to turn them down for any high speed applications.

Re: VexPro Bearings
 

Thank you Paul for the technical input. I also appreciate the prompt response from your team. It would be great to see the bearing spec ratings on the VexPro website, similar to how other suppliers provide a rating and similar to how you provide full disclosure on your other products (ie 775Pro).

This gives us confidence this year to continue using the product without modification to our design. We just started using thunder hex this year for intake rollers, drive train and shooter. The high RPM application was our only concern.

You mentioned getting the fit right is important when you turn down hex stock to use thunder hex bearings (13.775mm round). When using the thunder hex stock are there any tips and tricks to get the right diametrical clearance, understanding the oversizing from the manufacturer? When working on the lathe and a 3 jaw chuck we had to try a few times and experiment to get the fit a "slight press fit". As soon as the tool started removing material from the part was too much to get a press fit. We also tried a live center to keep it straight. It took a couple times and some scrap material to finally get it right. When we were able to turn down the shaft to achieve the correct fit the cuts were still inconsistent. This may have to do with the lack of eccentricity of the part vice thunder hex stock, I'm not sure how to get it perfect. It is unfortunate that the thunder hex stock still requires precision machining to get the "slight press fit". This burned a lot of our manufacturing time this year.

Is this something VexPro is looking to change in the future?

Thanks again for your help!

Re: VexPro Bearings
 

Did you try using some emery cloth instead of a cutting tool to take off the necessary material?

We've done that for all of our thunderhex this year and it just takes a few seconds. You could even chuck the thunderhex in a drill press, mill or hand drill and take off the necessary material with emery cloth, no lathe required.

-Mike

Re: VexPro Bearings
 

This. Since you are only taking off a couple 0.0001's of an inch you won't be able to hold that tolerance cutting unless you have a really nice lathe. We sand the thunderhex stock on the lathe with emory cloth until the axle turns a certain shade of silver and get very consistent results.

Re: VexPro Bearings
 

Have not tried Emory cloth to get the shaft to the right diameter. Seems like that might work better. Will give that a shot for the next few. The drive axles are made from steel hex so our only real option was to use a lathe and cutting tool to get the 13.75mm.

Re: VexPro Bearings
 

Emery cloth, the original finished to fit option for machinists of old. "Oh, it doesn't fit?" "Just work down the high spots a tad"

Re: VexPro Bearings
 

The Emory cloth is absolutely the way to go. Basically, we take off the anodizing on the round part of the thunderhex and it is a nice slip fit.

However, right now since the thunderhex is slightly oversized it is the perfect size for a press fit. We use our small arbor press to get the shaft in the bearings.

With that said, the Thunderhex used with thunderhex bearings is supposed to be a nice slip fit. The bearings are completely within our expected tolerance but the thunderhex stock is a few 10 thousandths large. This is large enough to make it a slight press fit. It is so close that when it is about 30-35 degrees here in Texas the shafts are a slip fit!

In any case, once we run out of the current inventory we will make sure the next batch is within our size requirements at 75deg F.

Paul

Re: VexPro Bearings
 

So... you're saying I just need to toss my shaft in the snow for a few minutes and it'll fit. Hmm, I wonder where I'll find that around here :p

Re: VexPro Bearings
 

Interesting, I'll have to remember this. Ain't thermodynamics great?