Chris Bell at Highpath engineering here in England can make rings to fit directly to the TA cranks...
Check out:
Hilary Stone, Bristol, British Isles
John Clay wrote:
> Thanks Thomas and everybody else for the input! Somebody I ran into (and can't find again) mentioned having a 19t chainring with a 50.4mm BCD for direct mounting to the inside of the TA flange. You could then set up something like a 44/20 to make a dandy touring double.
>
> I'm pretty partial to the range I got with my 44/32/20 and modified straight 8 (13-17, 20, 26, 34), I did need/appreciate the 20/34 more than a few times; it was fabulous in some small choppy mountains I encountered. Lately though it's occurred to me that I could do pretty much the same thing with a double - and the one thing that I didn't like with my triple was the very wide tread. This would solve it, so I'm looking.
>
> Thanks again
>
> John
> Tallahassee, Florida
> USA
>
> --- On Mon, 12/28/09, Thomas Adams <thomasthomasa@yahoo.com> wrote:
>
>> From: Thomas Adams <thomasthomasa@yahoo.com>
>> Subject: Re: [CR] TA Pro5, Stronglight 49 Crank/Chainring (and shifting) Questions
>> To: "John Clay" <jmedclay@yahoo.com>, "John Wood" <braxton72@gmail.com>
>> Cc: "Classic Rendezvous" <classicrendezvous@bikelist.org>
>> Date: Monday, December 28, 2009, 6:54 PM
>> Dear John:
>>
>> The smallest normal inner ring on a TA is 26
>> teeth. So I presume you're imagining two outer
>> rings. One, I don't know of a supply for the micro
>> outer rings, and two, the TA arms are not set up to clamp
>> two outer rings to the arms. So you would have to set
>> up everything from scratch: get a longer set of the 5
>> fixing bolts, find some kind of spacers to space the inner
>> ring, and then try several bottom bracket spindles to get
>> the sizing right. I have no experience with this kind
>> of set up, but I wonder if a vintage frame will have
>> clearance/chainline issues with such a tiny chainring.
>>
>>
>> It's also hard to envision a riding situation
>> where a 32 or 34 tooth rear cog and a front 26 would not be
>> sufficient. Perhaps you are trying to micro size
>> you're rear cluster? I tried this once with a
>> short chainstay bike with a 13-24 rear and a 52/42/24 front
>> triple, and never was happy with chainline or
>> shifting. A better set up to emulate might be Sheldon
>> Brown's wide range double with the TA cranks on his
>> Hetchins: 50x28 with a 12-28 cluster for a 27 inch low
>> gear.
>>
>> http://sheldonbrown.org/
>>
>> A 32/34 rear cog would get you a serious low gear
>> with decent chain line. I suspect though that longer
>> chainstays make this work better.
>>
>> A 20 tooth front chainring would be an interesting
>> project, but I'd be skeptical of how well it would work,
>> and I suspect the 20 tooth ring would wear very quickly
>> indeed. And getting a derailleur to shift it would be
>> tough, especially as the TA arms don't like modern
>> knobby caged front derailleurs. The arm sits so tight
>> to the chainrings that vintage straight up and down front
>> cages are the rule.
>>
>> Good luck.
>>
>> Tom Adams
>> Manhattan, KS
>>
>> --- On Mon, 12/28/09, John Wood
>> <braxton72@gmail.com> wrote:
>>
>>
>> From: John Wood <braxton72@gmail.com>
>> Subject: Re: [CR] TA Pro5, Stronglight 49 Crank/Chainring
>> (and shifting) Questions
>> To: "John Clay" <jmedclay@yahoo.com>
>> Cc: "Classic Rendezvous"
>> <classicrendezvous@bikelist.org>
>> Date: Monday, December 28, 2009, 2:56 PM
>>
>>
>> On Mon, Dec 28, 2009 at 11:34 AM,
>> John Clay <jmedclay@yahoo.com>
>> wrote:
>>
>>> The context of all of this is that I'm thinking
>> about making a 44-20ish
>>> touring double. Have any of you ever set up anything
>> like that? If so, did
>>> it shift reliably? I'd expect the shifting to be
>> anything but crisp and
>>> quick, but it needs to be reliable, non-jamming. Do
>> any of you have any
>>> insight or experience with similar arrangements?
>>>
>> Hi John,
>> The closest I have come to the above is a 46/29, and that
>> shifted fine, but
>> I did have to play around a bit with front
>> derailleurs. I wound up using a
>> mid to late 90's Campy Chorus FD.
>> I would think the ideal FD for the set up you describe
>> would be the new SRAM
>> XX, assuming you can make it work with whatever shifter
>> you're using.
>>
>>
>>
>> --
>> John Wood
>> Missoula, Montana, USA