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Info on these unusual TA cranks

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Info on these unusual TA cranks

Old 03-26-13, 07:52 AM
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ericbaker 
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Info on these unusual TA cranks

Ugh, I can't get pics to upload right now. Photobucket is rebelling.

They are 3 arm TA Pista cranks with a 1" pitch TA duraluminum chainring.

The unusual part is that the back of the pedal threads are closed in so the back of the arm is smooth. Much like the very fist campy cranks, or top line cranks. Has anyone seen this or know what the story is?
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Old 03-26-13, 08:00 AM
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The closed pedal threads are not that rare among TA cranks, and can be found in their 5-pin versions as well, but I don't know if there was a particular time frame in which they were made. I have a pair of them. The 1" pitch chainring sounds interesting! Can't wait to see pics.
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Old 03-26-13, 08:35 AM
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Old 03-26-13, 08:51 AM
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Closed back on TA is not all that unusual. I have the same on my Lejeune tandem. As to why...never gave it a thought. It's French.
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Old 03-26-13, 08:58 AM
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Well we know the TA Pro-3 made their debut circa 1969, so they are boom era. It's really hard to say how long they retained this feature as the TA catalogues used Rebour line drawings as opposed to photographs. Existing illustrations were probably reused a lot and they may not have neceassarily reflected subtle changes in the design. Additonally, the caps were easily popped out when the pedal washer was not used, so looking at surviving cranksets doesn't help much. That doesn't look like a TA chainring. That BCD was very popular, so there are numerous possibilities.
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Old 03-26-13, 08:59 AM
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Originally Posted by CV-6 View Post
Closed back on TA is not all that unusual. I have the same on my Lejeune tandem. As to why...never gave it at thought. It's French.
Your so right as they have a highly individual way of looking at things. I first discovered this on buying my first French car (a Citreon Dyane) and wondered what the triangular wedge of wood could be for in the tool kit. After much scratching of the head I realised it was a wheel chock.
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Old 03-26-13, 09:09 AM
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Thanks T-Mar, that's what I was looking for.

The ring is a TA though, it has the standard TA stamp and another "duralumin forged" something or other. I'll take a closer pic in a bit.
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Old 03-26-13, 10:50 AM
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I'm glad some one got those I was eyeballing them all day!
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Old 03-26-13, 03:05 PM
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I have a 3-pin set on my '75 Motobecane Grand Record...standard equipment. Not with an inch-pitch ring, however.
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Old 03-26-13, 05:28 PM
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if the 3-pin came out in '69ish, it seems as though inch pitch would have been more or less obsolete by then, or at least uncommon
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Old 03-26-13, 05:57 PM
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one reason the closed back may be unfamiliar to some readers is that TA cranks tended to come on french bicycles which came with french pedal threads. when people wanted to change the model of pedal on their bike they often ended up tapping out the pedal threads to 9/16". whereupon "pop" would go the little disc.

Last edited by juvela; 03-26-13 at 05:58 PM. Reason: spelling correction
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Old 03-28-13, 02:29 AM
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I just read (CR list) that the 3-pin TA cranks use a unique 9mm diameter bolt hole and so a unique size bolt...the 5-pin Cyclotouriste does not use that size.
Never have taken mine apart (yet) so never had occasion to learn that, but if it's true: hang on to those bolts!
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Old 03-28-13, 08:16 AM
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Originally Posted by ericbaker View Post
The ring is a TA though, it has the standard TA stamp and another "duralumin forged" something or other. I'll take a closer pic in a bit.
I've never seen TA Pro 3 rings with that big of a radius in the corners of the cutouts. I've got about a dozen NOS TA Pro 3 chainrings in the shop they all have a much smaller radius. I'm wondering if this was hand cut from a blank? The openings don't seem to be consistent. The one to the immediate right of top dead centre has a left hand end that is one long curve whereas it's right hand end has a short straight section. It looks like if you trraced the outline of one opening and overlaid the others on it, they wouldn't all match.

Originally Posted by ericbaker View Post
f the 3-pin came out in '69ish, it seems as though inch pitch would have been more or less obsolete by then, or at least uncommon.
I hear where you are coming from. However, if you look in Camapgnolo catalog 16 (1969) you see they still show 1" pitch track chainrings, so it doesn't appear to have been just TA.

Originally Posted by unworthy1 View Post
I just read (CR list) that the 3-pin TA cranks use a unique 9mm diameter bolt hole and so a unique size bolt...
Not quite, but close. The 9mm bolt hole is not unique to the TA 3 pin cranks. However, it is used only on 3 pin cranks with 116 BCD. The 9mm hole was the standard for three pin cranks with this BCD. It was used by most, if not all of the manufacturers who offered them, including Campagnolo, Magistroni, Nervar, Solida, Stronglight , TA and Zeus, among others.

Last edited by T-Mar; 03-28-13 at 08:20 AM.
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Old 03-28-13, 11:09 AM
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Here are the pics of the stamps on the rings, I see what you are saying about the shape of the cutouts, perhaps they were widened? There does appear to be file marks perhaps, though I've nothing to compare it to except the inner diameter of the ring itself, which is smooth.



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Old 03-28-13, 02:08 PM
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The cutouts in mine look like they were stamped. There are no file marks. The inner diameter was machined.
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Old 03-28-13, 05:27 PM
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Originally Posted by T-Mar View Post
Not quite, but close. The 9mm bolt hole is not unique to the TA 3 pin cranks. However, it is used only on 3 pin cranks with 116 BCD. The 9mm hole was the standard for three pin cranks with this BCD. It was used by most, if not all of the manufacturers who offered them, including Campagnolo, Magistroni, Nervar, Solida, Stronglight , TA and Zeus, among others.
Ah! Good info (as ALWAYS!) so these may be different from all the piles of crank-bolts in my stash (mine are all from various 5-pin cranks) but shouldn't be at all hard to find replacements. My mind is eased, thanks.
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