VEX Pro vs. AM Bearings
 

So today after hours of milling out our chassis rails I noticed something when I was assembling them. Unfortunately the bearings bought from VEX Pro were not to the quality I would have liked. So heres what I noticed. 1. The VEX bearings were not stamped HEX leading me to think that the bearing was broached by VEX unlike AndyMarks which is stamped FR8-ZZ now I dont know whether this is done by the manufacturer so I cant say exactly. 2. The bore/ inner ring on the AndyMark bearings look larger than the ones on the VEX Pro one. 3. when the bearing were press fitted in our Gearbox to take a hex output if would stick in one place./ when press fitted into our chassis rails and bearing blocks the fit was tight and when it did fit the would be wobble in the sprockets and wheel hubs seen in this video https://www.youtube.com/watch?v=EmbLamJat6o (I have about 10 AM Bearings and 34 VEX Pro bearings. Tried them all in different combinations) I'm not saying the VEX Pro parts are bad but just that the fit of the bearings weren't good enough for us. Just a heads up for teams and VEX.

Re: VEX Pro vs. AM Bearings
 

My team and I can confirm this. I have played around with a few of jsasaki's VEX and AM bearings, the Hex VEX bearings are not centered. All other components that I've played with from vex are of excellent quality.

Re: VEX Pro vs. AM Bearings
 

The runout of an R8 bearing is supposed to be several ten-thousandths of an inch, even for ordinary ABEC 1 or ABEC 3 bearings. Your bearings are visibly out of spec by about two orders of magnitude.

You've clearly demonstrated that those particular parts are bad in any conventional bearing application. Since the parts came that way, I'm sure IFI will be happy to speak with you about it. Hopefully their supplier will also be willing to speak to IFI about it.

(Incidentally, the shields upon which the part number is stamped are a standard part; perhaps IFI didn't want to go to the extra expense of having a custom marking put on.)

Re: VEX Pro vs. AM Bearings
 

Heres a video of AndyMark bearings https://www.youtube.com/watch?v=_yZm6RUQ92U notice that these bearings dont shift around like this video at 0:27

Re: VEX Pro vs. AM Bearings
 

I would definitely be contacting IFI and speaking to them. I'm sure they are going to want to know this, so that they can go back to their supplier/Manufacturer.

Re: VEX Pro vs. AM Bearings
 

So I have a few questions from the video and I can clear up some of your assumptions.

First, the bearings are not broached by VEX afterwords. They are broached by the bearing manufacturer prior to hardening and grinding.

Second, the first shot in the first video I don't really know your setup so I can't comment on the wobble. In the second shot are you saying there is wobble in that video? In any case , please contact customer support and we can get you replacement bearings. Please be sure to give them your order number.

Third, the shield is a completely different part from inner race and we used a standard fr88 bearing shield.

Last, the absolute best way to get customer support from VEX is to call the support line or email support@vexrobotics.com

I assure you that the bearings are supposed to be ABEC1 and not have wobble like you show on your video. We use these same bearings in our single speed gearboxes and we do not see this issue.

Please contact customer support and we can resolve this issue.

Re: VEX Pro vs. AM Bearings
 

Is this on all vex bearings or just the ones that have a hex?

Re: VEX Pro vs. AM Bearings
 

What question are you asking and who are you asking?

Re: VEX Pro vs. AM Bearings
 

Hi Paul, sorry for being unclear. We ordered a lot of bearings from Vex this year(FR8-ZZ Hex, FR8-ZZ, FR6-ZZ Hex, FR6-ZZ). This obviously is an unusual problem, but I was wondering if any other teams have found runout problems with their other bearings(specifically the ones we ordered). We haven't recieved our Vex order yet so I want to be prepared to check our bearings for any runout.

Re: VEX Pro vs. AM Bearings
 

In our recent tests with non-hex bearings, VersaWheels, and a perfectly circular axle, the wheel, when turned, moved perfectly straight with no wobble to either side, and the bearings worked as expected.

Re: VEX Pro vs. AM Bearings
 

For various reasons we've gotten .5" hex bearings from both VEXPro (80) and AndyMark (60) , and haven't noticed a problem with either.

I'm sure that the occasional bearing has a problem -- this happens with any large-quantity manufactured good -- but thus far the quality control of both products seems to be quite satisfactory.

Re: VEX Pro vs. AM Bearings
 

Thanks for the reply Paul. Definitely will contact VEX asap. I just want to clear up with you that the VEX Pro bearings were in fact not concentric as you can see in this video at 0:27. I'm just hoping it was a small batch error but no matter what setup the bearings are in, it just wont work.

Re: VEX Pro vs. AM Bearings
 

We only purchased half inch hex bearings from VEX

Re: VEX Pro vs. AM Bearings
 

I would be interested in more details.

Did the VEX bearing stick before you pressed it in your bore? If not, it's possible (if not probable) that your bore could be too tight, or you pressed it in and indented the shield, or somehow damaged the race/ball interface.

Did you try an AndyMark bearing in the same bores that you displayed the runout in your first shot? Did you independently chuck the shaft and hub in a lathe/drill press/something else that spins to verify that each component spins true? Without all 3 of those actions, there's no way of isolating the problem to your bearing.

Re: VEX Pro vs. AM Bearings
 

I'm sure Paul and his staff at VEXPro will get to the bottom of this.

Just because I am addicted to looking at details, I took a two VEXPro FR8ZZ Hex bearings (217-2734) to my lab and set up an indicator to measure run-out while the bearings were supported by a hex shaft clamped in a bench vise. They measured 0.0005" TIR on the outer race and 0.0015" TIR on the inner flange face. I have some AndyMark FR8ZZ Hex bearings (am-0279) on order and will test a couple of them the same way when they arrive.

Re: VEX Pro vs. AM Bearings
 

We don't have experience with the VEX bearings, but do have experience with AM hex bearings. This fall we converted our summer developed dead axle WCD to a live axle design, using hex axles. We ordered a bunch of hex bearings from AM for our bearing blocks. We found them to be frustratingly undersized. We are using standard 7075 1/2" hex extrusion for our axles and AM hex output shafts to direct drive the center wheels. We found that the AM bearings didn't even fit their own hex shafting. This led to hours of hand working the hex shafting to get everything to fit. Using a belt sander to resize the hexes resulted in scrapped axles from taking too much material off.

For our build season drive train, we ordered hex bearings from WCProducts. Whereas in the AM order, 2 of the 14 bearings fit our shafts, in the WCProducts order, 2 of 24 bearings are undersized. Most slide right on our shafts, and if they are snug, a few swipes over sandpaper to get the shaft faces planer (extruding leaves high spots in the faces) gives a good fit.

So, if you are having problems with AM bearings being too tight, or VEX bearings having too great of runout, try the WCProducts bearings. If we had not done so, we would probably abandon hex shafting as too labor intensive a system to be truly useful.

I should also point out that customer service for all these companies is great about replacing parts that don't measure up. But in the world of FIRST robotics, returning bad parts for good ones is not an acceptable option during build season. Getting good parts from a supplier the first time can make the difference between getting your robot built early, having time to practice with it, leading to a great season, and finishing your robot in your pit at your first regional.

Re: VEX Pro vs. AM Bearings
 

Richard,

Remember that we increased the size of the hex in order to accommodate various larger hex stock. If used with the VEXpro shaft there could be as much as .001 gap between the flats of the hex shaft and flats of the bearing

The only true way to get runout indication is clamping the output and rotating the input.

We will perform this test on samples this Monday.

Re: VEX Pro vs. AM Bearings
 

Yep, that is not normal. Call customer support today and give them your order number. We will send you new ones immediately ... After we inspect our inventory. When you get the new bearings there will be a shipping label, please ship the product back to us with the ram number we provide.

Paul

Re: VEX Pro vs. AM Bearings
 

Paul, you are right.

I did the TIR check just for my own curiousity. Actually, the VEXPro 1/2" hex shaft I used was quite a tight slip fit for the bearings -- needed firm hand pressure to get them on. If there were as much as 0.001" clearance I would have been able to feel that. Anyway, the TIR that I saw is consistent with "good" ABEC 1 bearings, in my experience.

Nonethless, you are right about clamping for true runout tests.

Re: VEX Pro vs. AM Bearings
 

Todd,

I am sorry about your troubles with the hex bearings. You will have the same troubles with VEXpro hex bearings as we decided to make them the same nominal size as the AM bearings. WC Products decided to make their bearings larger to accommodate the standard hex shaft.

We chose to solve the problem differently. Standard hex shaft as a really large tolerance of almost +.005". Practically most shafts come in at +.003". We decided the shaft was the problem so made a custom hex shaft that is sized appropriately to fit in both the AM hex bearing and the VEXpro bearing both in 3/8" and 1/2".

I can't really speak for WC Products or AM, but we made a conscience decision to make out bearings the same nominal size as the FRC industry standard.

Paul

Re: VEX Pro vs. AM Bearings
 

Thanks for the info, Paul. We'll take a close look at your stuff for next summer. I somehow missed your vex pro product line until the start of this build season, but I like what I see.

We are attempting to move into the mode of students and mentors working during the summer on drive train development, using as much COTS parts as possible. During the fall we work on skills training for new members, and getting everyone intimately familiar with the hardware. We also pre-purchase all the COTS stuff we think we may need, to avoid the build season rush. Then when build season hits, we tweak our previously developed drive train to work with the game and execute as quickly as possible. This year, we will have a running drive train in less than 50% of the time it took last year, even with the smaller size limitations.

We are trying to raise our level of competitiveness by taking FIRST robotics from a build/competition season activity to a develop/train/build/compete activity that engages students year round.

Re: VEX Pro vs. AM Bearings
 

The bearings fit on the VEX .5" hex shaft snug. On a cnc'd one piece bearing block the shaft would not go all the way through. I've tried most of the bearings and both VEX Pro and AM hex shafts.

Re: VEX Pro vs. AM Bearings
 

We will check around for all of out products but the AM shaft does states on their website with the .5" hex shaft "This dimension is slightly larger than the bore for the 500 Hex Hub and 1/2" Hex Bearing. In order to make this material fit into the hub or bearing, we suggest that the user slightly modify the hex stock. We have found that the best way to do this is to use a belt sander and carefully sand off a small amount of each side of the hex stock until the stock fits into the Hex Hub or Hex Bearing."

small tolerances are manageable but this was just not working out for us.

Re: VEX Pro vs. AM Bearings
 

We are experiencing this wobble in our shaft/bearing/wheel assemblies also, and it is pretty severe. With some experimentation we are confident the problem is with the hex hubs, and is not confined to just the bearings, although they may be contributing. We believe the hex broach is not square/perpendicular, and also possibly not concentric.

To test this we put two plate sprockets, each mounted on their own hex hub, side by side on a spinning hex shaft. Both shafts wobble, sometimes in sync with each other, sometimes opposite of each other. When one is removed and rotated to a different position relative to the other, the wobble with respect to each other changes. This would happen if the hex broach in one or both were not perpendicular.

As a second test we take a wheel assembly with hex hubs and spin it on a bearing-mounted shaft. It wobbles. We note and mark the location of the high points of the wobble. We then put the same wheel on a different shaft and different bearings, and the wobble is identical. This would be the case if the wobble was in the wheel/hub assembly. This same wheel spins true when it is fitted with round bearings, so the wobble is in the hubs, not the wheel.

We also see the hex shafting is not straight. A shaft segment laid on a surface plate will rock in some orientations, and not others.

It is difficult to assess the contribution of each of these factors (bearings. hubs, shaft) but we believe the squareness/concentricity of the hex hubs is the primary problem.

Teams experiencing this problem may want to duplicate these tests and look further at the source of the wobble. In our case it is not just the bearings.

Re: VEX Pro vs. AM Bearings
 

Which models of hex hubs, bearings and shafts are you using?

Re: VEX Pro vs. AM Bearings
 

The VexPro hex shaft stock, hex hubs, and bearings.

Re: VEX Pro vs. AM Bearings
 

If you are experiencing these issues with any of your components please contact customer support and we will replace them

With that said, we have tested all the hubs that we have in inventory and we do not see this issue. In addition, we have not seen this issue with the shafts that you describe.

In any case, return the items you think are not to the appropriate dimensions and we will replace them.

Re: VEX Pro vs. AM Bearings
 

Yes, we will contact customer support and I am confident it will be fully resolved. Just unfortunate that we observed it on a Friday evening. I just wanted to share the observation so others can check their situation and check other factors than the bearing. It can be difficult to diagnose the source of the problem in a turning assembly.

Re: VEX Pro vs. AM Bearings
 

We have experienced this issue with our shifters as well. We think it might not be the bearings -- the shaft is slightly bent and the hole holding it is slightly too big. See video below:


http://youtu.be/sdGAuatJCqw

Re: VEX Pro vs. AM Bearings
 

You guys have your bearing in backwards. The flange is supposed to be on the inside. We also noticed a problem where the standoff pockets are too deep. You will be receiving washers to fix this problem. The bearing is moving because it is not seated in the plate properly due to the reversed installation.

Please contact customer support to get more details.

Paul

Re: VEX Pro vs. AM Bearings
 

Paul,

The video may not show this well, but the flange is on the inside of the plate. The bearings are not in backwards. The bearing is moving despite this, partially due to excessive clearance in the bore that holds it. The outer race spins freely by hand, and can be visibly moved side-to-side within the plate. You are correct that the standoff pockets are too deep on our gearbox; we would appreciate shipment of the correct washers used to mitigate this issue.

We were also wondering whether the design intent of these gearboxes is such that the shaft is self-supported by the cantilever, or whether the output shaft must be supported at the far end.

Thanks.