pic: Hex Bearings

[T^2]

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[Travis Schuh]

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

[Bryce2471]

Originally Posted by Travis Schuh

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

+1

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

[wilsonmw04]

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.

[T^2]

Originally Posted by Travis Schuh

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

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.

[Travis Schuh]

Originally Posted by T^2

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.

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.

[T^2]

Originally Posted by Travis Schuh

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.

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.

[magnets]

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.

[Aren_Hill]

You guys have such fun timing,

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

-Aren

[Richard Wallace]

Originally Posted by Aren_Hill

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

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

[FrankJ]

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?

[Aren_Hill]

Originally Posted by Richard Wallace

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

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

-Aren

[Tungrus]

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.

[Aren Siekmeier]

Originally Posted by Tungrus

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

[Richard Wallace]

Originally Posted by Aren_Hill

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

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).