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Mr.Chips
11-14-2003, 05:55 PM
I am going for a rigid construction so I made the gantry sides and top cross piece two layers thick of 3/4" MDF. The top cross piece section is mortised through the inner sides of the gantry, It is rigid but HEAVY.
Mounted the inline skate bearings on 1" angle iron using two bearings on the topside and two on the bottom.
Everything looked good during the early stages of the alignment of the gas pipe. Then it became more difficult to move the gantry. Looking closer I discovered that the top bearings had started to wear through, and becoming difficult to move.
All gantry movement was by hand, purchased a pair of inline skates and removed thoes bearings.
The outer race of the bearing is very thin, and just stamped sheet metal. I remember front bicycle bearings had real metal construction, will consider thoes types if the four fail.

I know the gantry is heavy, but I was wondering if anyone has had a problem like this.

Since this failure I have reconfigured the angle iron with four bearings on the top side. So far so good but I will run it end to end about 50 times before I make any decision if the bearings are OK or not.

Hear is a photo of the failed bearing.

balsaman
11-14-2003, 09:10 PM
Those are cheap stamped bearings. Use bearings made for inline skates available and sports stores and also Kmart etc.

Eric

DaSigntist
11-14-2003, 09:37 PM
Thats' what I call a blowout!

I agree with Balaman.

Mine are inline skate ones and they are rated @ 1000 lbs duty.

see the URL below on eBay:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=36624&item=3631817725

Don't let the price fool you these are nice.

Regards,
DaSigntist

Mr.Chips
11-14-2003, 10:33 PM
Thanks for the info.
When I receive the bearings I will do a comparison photo and details of what to look for, so others donít make the same mistake. I bought a used pair of roller blades, and they looked good and the bearings didnít seem worn out. I did take one of the broken ones apart and it was only stamped metal.

I just ordered them.
Hager

DaSigntist
11-14-2003, 10:38 PM
Great, I had no clue myself I just bought them without knowing a thing about them.

Sorry for the misspelling Balsaman!

HuFlungDung
11-15-2003, 11:03 AM
"Real" ball bearings are not all that expensive, perhaps even the same price, guys, and most likely a hell of a lot more durable than roller skate bearings.

Roller skate bearings are something that McGyver would use in a pinch :D

You do pay a premium for tiny, but there is a good price break in certain common bearings:
6202 2RS = C$2.66 (35mm Od x 15mm Id)
6203 2RS = C$2.34 (40mm Od x 17mm Id)

These bearings can also be purchased with imperial sized bores, 5/8" or 3/4". The "real world" uses metric ball bearings. Inch sizes are all specials, particularly Imperial outside diameter.