21-09-2014 15:24

Travis Schuh

Re: pic: Hex Bearings

Where were these bearings used? Any details on the situations that caused them to fail?

21-09-2014 15:28

Bryce2471

Re: pic: Hex Bearings

+1

It would also be interesting to here how VEX plans on fixing this problem.

21-09-2014 15:35

wilsonmw04

Re: pic: Hex Bearings

since the suppliers of these items are limited, I am not sure what Vex can do about these. However, AM has already put these out for sale.

21-09-2014 15:46

T^2

Re: pic: Hex Bearings

Both bearings failed as part of the polycarb intake arms. The second one, in particular, was fresh, and failed in its first match. 1678 didn't have any problems with these bearings throughout the 2014 season.

21-09-2014 15:55

Travis Schuh

Re: pic: Hex Bearings

Where in the polycarb arms were they? Do you know what particularly in the match caused these? It sounds like it was a particular impact or something, rather than a life issue.

I guess I am surprised that after all you put that robot through this season, that you just had 2 failures in close succession.

I am curious as to the details so that we can learn from them for next year.

21-09-2014 16:07

T^2

Re: pic: Hex Bearings

They were both in the rear arm, on the end opposite the gearbox. (The second replaced the first.) From what I saw from the stands, neither failure was immediately preceded by any sort of contact with another robot.

21-09-2014 16:09

magnets

Re: pic: Hex Bearings

The failed bearing on the left confuses me.

My experience with hex bearings is that they are hit or miss in terms of quality from all vendors. None of them roll as smoothly as the comparable round bearings, and they have varying degrees of accuracy with runout and hex sizing.

Generally, I'd try to avoid them if it all possible. Even if you think they're strong enough, dealing with availability and variation between suppliers can be frustrating.

21-09-2014 16:12

Aren_Hill

Re: pic: Hex Bearings

You guys have such fun timing,

These guys will be in stock soon (bigger inner race).

-Aren

22-09-2014 05:44

Richard Wallace

Re: pic: Hex Bearings

Looks like the weight went down very slightly. What else is different? Smaller balls and more of 'em?

22-09-2014 10:33

FrankJ

Re: pic: Hex Bearings

The bearings get used on drive trains without that kind of failure. It seem the drive train would have a higher loading. I am a little hesitant to blame this on bearing quality. Maybe the shaft is bending or severely misaligned which is torquing the bearing rather than a axial load?

22-09-2014 10:52

Aren_Hill

Re: pic: Hex Bearings

Well, larger inner race, so yes, that does mean smaller balls and more of them.

-Aren

22-09-2014 11:02

Tungrus

Re: pic: Hex Bearings

The failure may be due to 1 in a millionth chance that it was manufacturing defect (nothing is perfect) but its not common. In past 4 years we have been using both AndyMark as well as VEX bearings on drive and other systems. Never had this issue. We have 7/8" bent aluminum shaft, 3/16 hollow steel shaft but not the bearing.

Looks like both VEX and AM have/are releasing super-bearings this season. Price will stop me from going to these new super bearings.

22-09-2014 11:34

Aren Siekmeier

Re: pic: Hex Bearings

The Andymark bearing went up $1 to $6, but the Vex bearing is the same price as before, $5.

I imagine the failure has something to do with the torsional load seen in 1678's flexible intake arms. Our intake this year had similar flexibility, and when it deformed our intake roller stalled more easily due to the load on the bearings. In a WCD, the load is almost entirely radial, since the double bearing arrangement takes up the torques from the cantilevered wheel and the chain.

EDIT: What Frank said.

22-09-2014 12:25

Richard Wallace

Re: pic: Hex Bearings

Thanks for clarifying, Aren. I could not tell if the inner race was enlarged radially or axially, since there is no pdf on your site yet and I don't have CAD on my tablet (yet).

22-09-2014 12:54

Michael Corsetto

Re: pic: Hex Bearings

I will confess, we should have turned the end of the shaft down to 1/2 round and avoided using a hex bearing in this particular setting. Lessons for next year...

22-09-2014 14:18

PayneTrain

Re: pic: Hex Bearings

secrets secrets are no fun unless they're shared with everyone

We wrecked 3 or 4 bearings this year and I had assumed it was due to bad implementation. It probably still was, but it's nice to know about new and improved hex bearings we can buy to fashion a throne alongside the 3 ft pieces of 1/2" hex shaft y'all sell.

23-09-2014 22:34

bEdhEd

Re: pic: Hex Bearings

Did one of these bearing failures occur during a chicks in charge match that my team was in against you guys? Those matches were quite aggressive. I think I remember watching the shaft pop out of your polycarb intake when everyone was mashing up on the field. Our intake suffered some damage in those matches with a substantial dent in our intake frame. Actually, now that I think of it, our chicks in charge matches had a lot of intakes hanging outside of frame perimiters, which caused a few tangles.

24-09-2014 12:16

billbo911

Re: pic: Hex Bearings

I can confirm the first failure was during the "Chicks in Charge" matches.
The second failure was shortly after that and might have been there very next match.
Both failures occurred while the pickup was outside the frame perimeter.

Honestly, I am VERY impressed that these failures never happened in all of the matches BECA has played in this year. The torsional load on those bearings when the poly flexes back and forth has to be fairly extreme. That is something these bearings are really not designed for. Maybe a floating bearing setup if something like this is needed in the future? Maybe something like this?

08-10-2014 15:41

Aren_Hill

Re: pic: Hex Bearings

The v2 Hex bearings are now in stock,

http://www.vexrobotics.com/vexpro/ha.../bearings.html

-Aren

08-10-2014 16:39

Nathan Streeter

Re: pic: Hex Bearings

I actually disagree... seems like the intake would actually likely have significantly higher impact loads (but probably smaller steady, radial loads).

09-10-2014 01:26

JackFisher

Re: pic: Hex Bearings

On our drive trains, we have shattered these hex bearings two seasons in a row. Its great that vex has a redesigned option now. The part of the bearing that failed on our drives was the corner where the steel was a bit thin due to the hex.

09-10-2014 01:38

AdamHeard

Re: pic: Hex Bearings

We didn't break any in 2013, we just broke so many this year it seemed like both years!

09-10-2014 08:28

RonnieS

Re: pic: Hex Bearings

Are the Vexpro V2 hex bearings the same as andymarks HD hex one? There is a fairly significant price difference.
-Ronnie

09-10-2014 10:03

wilsonmw04

Re: pic: Hex Bearings

I have a feeling they are not.

09-10-2014 10:22

Re: pic: Hex Bearings

Both are improved hex bearings with what seems like similar if not the same improvements. You can look at and compare the new AM Hex HD bearing thanks to Richard Wallace's post here with the new VP Hex bearing V2, found on their website.

If I were to guess I would say the price difference is based off of where the bearing is manufactured. Still, I'd rather just use round bearings.

09-10-2014 10:29

Richard Wallace

Re: pic: Hex Bearings

For reference, the pdf image that I posted in another thread comparing old and new 1/2 inch hex FR8 bearings showed parts from AndyMark. The HD bearing is one that I ordered a couple of weeks ago, while VexPro was out of stock.

By my measurement, the inner race outside diameter of the AndyMark HD bearing is 0.76 inch, which matches the value shown under the heading "Hex Bearing Update" at the bearings page of the VexPro web site.

-----

edit: I see Andrew beat me to one of the points above. To add a technical point, it makes sense that AM and VP would arrive at the same inner race outside diameter for more durable R8 hex bearings. This is because the improvement requires decreasing ball diameter, and bearing balls come in discrete standard diameters. So it is very possible that AM and VP are getting similar bearings from different sources.

The price difference will sort itself out. Markets are wonderful things.

09-10-2014 12:41

Brandon_L

Re: pic: Hex Bearings

Except for when you order hex bearings on AndyMark and get shipped VexPro hex bearings inside a VexPro package inside an AndyMark package. True story.

09-10-2014 16:42

PayneTrain

Re: pic: Hex Bearings

I still can't believe that actually happened.

09-10-2014 16:46

wilsonmw04

Re: pic: Hex Bearings

Agreed, where's the trollooollloll?

09-10-2014 16:53

PayneTrain

Re: pic: Hex Bearings

I'm pretty sure I asked for pictures.

09-10-2014 17:24

Richard Wallace

Re: pic: Hex Bearings

I can believe it, easily. Especially if it happened during FRC build season. Andy and Paul have consistently demonstrated that they will do anything they are able to do (which is a lot, in both cases) to make sure they fill orders. That includes getting the parts from a competitor, when necessary.

FRC teams get parts from competitors all the time, up to and including the finals of MSC, Einstein, and IRI. It happens so often we have come to expect it. Why should AM and VP behave differently? It won't stop them trying to surpass each other when introducing new products.

09-10-2014 17:40

Michael Hill

Re: pic: Hex Bearings

Almost as if there's...co-opertition?