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Ofmega crank question

Old 02-19-24, 12:37 PM
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Ofmega crank question

Posting here rather than mechanics sub forum as it seems like a vintage manufacturing question. Iím working on an 1980s bike with an Ofmega crank that I got used nearly 3 years ago. I know no history of it, but it seems low miles but stored poorly for maybe 30 years and probably seldom if ever serviced. Pulling the crank showed marks in the taper in the crank. I just thought perhaps at one time someone used an improper crank puller, although the rest of the crank wasnít scratched up.





Kinda hard to photograph, but this is how it is along with the nds crank also. Things tighten up fine and no riding problems. Searching the internet however for similar Ofmega cranks shows the same thing. People selling these cranks donít picture it, but on most one can get a sense of it from pics. Here are photos from the net:





So, what is this? Was it something to do with the manufacturing process? My Park tool puller didnít cause this, and it seems that most have this.
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Old 02-19-24, 12:52 PM
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I don't see any such marks on the Ofmega and Avocet (made by Ofmega) cranks I have here. The blemishes look consistent with galling damage. Has the bike been left outdoors and/or in a corrosive environment (e.g. road salt, ocean breeze)?
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Old 02-19-24, 01:57 PM
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No history on bike, but no salty environment around here. I just found it curious that these gouges were all at 45 degrees to the taper flats and were present in so many others that I saw pics of. They appear to be mechanically caused and there wasn’t any sign of any other metal or debris upon disassembly either. These marks are also at the very outside ends of the taper where galling shouldn’t happen as the crank spindle didn’t reach that far.
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Old 02-19-24, 02:24 PM
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I think someone used an extractor with a mushroomed part.
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Old 02-19-24, 02:35 PM
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The hole was made - possibly tapered - but round; then the taper was machined. What you see is the part of the hole not removed as the taper was made - that's why you see it of the outer part of the taper flat and the bolt seat (the taper is smaller there).

It's not a problem, the crank doesn't bear on the axle at that place but on the corners.
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Old 02-19-24, 03:03 PM
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Originally Posted by oneclick
The hole was made - possibly tapered - but round; then the taper was machined. What you see is the part of the hole not removed as the taper was made - that's why you see it of the outer part of the taper flat and the bolt seat (the taper is smaller there).

It's not a problem, the crank doesn't bear on the axle at that place but on the corners.
That is exactly what I was wondering, especially seeing it on many others. If I was to ever sell this bike in the future, I wanted to not hide flaws, so this is the answer I suspected.
As a side note, these cranks seem quite light with a sort of delicate look and feel. 144bcd doesnít do it for me though.
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Old 02-19-24, 04:03 PM
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Just make sure you never combine the cranks to a different brand BB as Ofmega uses a proprietary BB with tapers that only works best with Ofmega cranksets.....
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Old 02-19-24, 04:33 PM
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Interesting on the bb tapers. This 1984? Torpado has a Campagnolo bb and I am about 99% sure it is stock. I’m not planning on switching anything out on it. It would be another bit of Italian confusion such as I read about other campy bottom brackets and cups.
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Old 02-19-24, 05:54 PM
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I have experienced a case where LBS was unable to remove an Ofmega crank arm - their extractor tips (multiple tools)
were too large in diameter, hanging up on the top of the crank arm rather than sliding through to engage the crank spindle end.
They almost stripped out the extractor threads by exerting too much force.

My solution was to cut a piece of drill rod stock so that it extended beyond the end of the crank spindle. I inserted
the drill stock and then set the crank extractor tool so that it made contact on the drill stock, which was centered
in the spindle. The crank came off cleanly.

There is a residue of marking on the crank arm similar to yours.
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Old 02-19-24, 06:01 PM
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Originally Posted by sd5782
... marks in the taper of the arm.
Same here. ​​​​​​I have an Ofmega arm hanging on a wall, and just noticed it, like the very middle of each taper wall is deeper than the rest.
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Old 02-19-24, 06:02 PM
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I thought of that, but the marks go nearly to the bottom of the tapers. The cranks would have surely popped free long before the extractor would have been threaded that deep. The many others seen on internet searches would have all have suffered the same fate.
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Old 02-19-24, 06:11 PM
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Old 02-19-24, 06:21 PM
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Exactly
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Old 02-19-24, 06:22 PM
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Originally Posted by cyclophilia
I have experienced a case where LBS was unable to remove an Ofmega crank arm - their extractor tips (multiple tools)
were too large in diameter, hanging up on the top of the crank arm rather than sliding through to engage the crank spindle end.
They almost stripped out the extractor threads by exerting too much force.

My solution was to cut a piece of drill rod stock so that it extended beyond the end of the crank spindle. I inserted
the drill stock and then set the crank extractor tool so that it made contact on the drill stock, which was centered
in the spindle.
A flange-headed screw, with the flange cut to a square, lives (along with a wingnut to keep it there) in the hole in the handle of the crank extractor here.
Every crank extraction that screw gets placed in the end of the axle, and the extractor bears on it.
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Old 02-20-24, 10:41 AM
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A close-up of a new old stock arm might help solve the mystery.
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Old 02-20-24, 12:52 PM
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Originally Posted by Chombi1
Just make sure you never combine the cranks to a different brand BB as Ofmega uses a proprietary BB with tapers that only works best with Ofmega cranksets.....
applies to SOME but not to EVERY Ofmega spindle, likewise do not assume it applies to each and every Avocet (rebranded Ofmega) spindle, either. Best to consult Sutherlands for the fine points.
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Old 02-21-24, 06:20 PM
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Originally Posted by unworthy1
applies to SOME but not to EVERY Ofmega spindle, likewise do not assume it applies to each and every Avocet (rebranded Ofmega) spindle, either. Best to consult Sutherlands for the fine points.
I wasn't aware of Ofmega proprietary spindle tapers. I replaced the original 144mm Ofmega cranks on the Bianchi with newer 130mm Bianchi-branded cranks that may well have been made by Ofmega, as well.
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Old 02-22-24, 12:02 AM
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Originally Posted by John E
I wasn't aware of Ofmega proprietary spindle tapers. I replaced the original 144mm Ofmega cranks on the Bianchi with newer 130mm Bianchi-branded cranks that may well have been made by Ofmega, as well.
And I should take my own advice and actually refer to Sutherlands rather than rely on memory, cause it says in this section for "Avocet" that 2 of those spindles (marked "20 and 30" and "USA" are closest to a Campy taper whereas the spindles marked "2 and 3" (and apparently made in Italy or not specified) use the "special" Ofmega taper, that is the ends are smaller that Campy (or clones) or other ISO.

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Old 02-22-24, 07:24 AM
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Originally Posted by Chombi1
Just make sure you never combine the cranks to a different brand BB as Ofmega uses a proprietary BB with tapers that only works best with Ofmega cranksets.....
Only true for early production Ofmega. By the late 70s, Ofmega adopted the same taper as Campagnolo. If your crank uses the early taper, it will sit too far out on a Campagnolo-type taper spindle.
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Old 02-22-24, 09:50 AM
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Some pics for you folks fluid in Italian and Campagnolo. The only other Italian one I have is a Shimano that I used for a short time on a Frejus I no longer have. That one in 109mm allowed me to use a first generation Superbe crank on that 64 Frejus instead of the cottered 47-50. The Torpado I am cleaning up is stamped 84 on the BB. Shell is 70mm and the spindle is 115.5 withe the drive side being about 2.5mm longer than the nds.



Loosely mounted for photo



Thick cup vs thin?



NDS



Quite a difference in center section, both marked 70



Tapers appear the same


The spindle side by side photo is distorted as the front Shimano spindle is 109mm and the back Camp that is on this bike is longer at 115.5.
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Old 02-22-24, 12:12 PM
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Originally Posted by JohnDThompson
Only true for early production Ofmega. By the late 70s, Ofmega adopted the same taper as Campagnolo. If your crank uses the early taper, it will sit too far out on a Campagnolo-type taper spindle.
IIRC, The Ofmega Mistral cransets I had used on a few builds, might have still required Ofmega BBs to get the chain lines to run correctly, and those cranksets were already from the 80's.....
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Old 02-22-24, 12:17 PM
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I'll never understand the Italians copying the looks and designs of one another. Did they not have a proper patent system?

Whenever I see Ofmega cranks, I immediately see Campagnolo, maybe with the arms "mexicaned" out like E. Merckx' bike.
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Old 02-22-24, 05:11 PM
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Originally Posted by Chombi1
IIRC, The Ofmega Mistral cransets I had used on a few builds, might have still required Ofmega BBs to get the chain lines to run correctly, and those cranksets were already from the 80's.....
I didn't measure chainline, but a Mistral crank on a Campagnolo spindle seems within what Suntherlands would call an acceptable fit:

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Old 02-22-24, 05:21 PM
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I notice that one has the marks that I have mentioned and pictured.
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Old 02-22-24, 07:23 PM
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I am not an engineer, but I wonder if that little bit of space in the middle of the flat would make it less likely to seize?

As oneclick said, the middle of the flat shouldn't be bearing any load.
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