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Old 09-11-12, 05:13 PM   #1
nfmisso
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modifying a fillet brazed 531 tandem frame

Hi;

I want to explore options.

I have Jack Taylor #7640 http://forums.bicycletutor.com/thread-4198-page-1.html

In the SF Bay Area, how much would it cost to have the frame height reduced from 25" to 22"? Is this even practical?

The lengths of the cockpits is good for us, just a bit too tall.

I have no experience in this area, and am thinking to have the front top tube angled, leaving it is in the same position on the headset and dropping the position on the seat tube, keep the rear top tube horizontal and inline with back end of the front tube; shortening the seat post, and re-angling the seat stays.

With this sort of modification, I understand that the paint would need to be striped. I am thinking of powder coating for durability. The box lining would be very difficult to duplicate .

I would appreciate any advice on this, and would especially like to have some discussion with a person who can do this sort of work.

Thank you
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Old 09-11-12, 05:58 PM   #2
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it's unwise to reuse any of that tubing. You might find someone that is willing to do it. If they charge you less than $1000 before paint, they are subsidizing a bad idea.
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Old 09-12-12, 06:19 AM   #3
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One problem is that the Jack Taylor is a classic and could be valuable to a collector. You might want to consider selling the frame and replacing it with one of more appropriate geometry.

I almost got a Jack Taylor tandem 40 yrs. ago. I ended up with two matching JT Touring single bikes and a Rene Herse tandem. The Herse is a great classic bike, but the rear top tube is fairly short by current standards. I later built one for myself using the longest 531 I could get. The Herse is 23.5" rear TT. My homebuilt is 25" and currently bikes are 28 or 29" which provides a lot more room for the stoker. Just something to consider.
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Old 09-12-12, 08:28 AM   #4
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link to a post showing why this is not a good idea
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Old 09-12-12, 05:32 PM   #5
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Unlike the above replies i'll try to remain neutral. (But the above replies are good food for thought). I have done this with a single. Made a tall bike that ended up with a crack just below the seat lug. Gave the customer (once a friend but that's another story) his deposit and moved on. Chopped off the TT and seat stays and installed new lugs/tubes. As the frame had a short TT for the size after "downsizing" the TT was pretty normal for the new size. The frame sold to another friend and saw many (VERY MANY) thousands of miles.


Being a tandem the issues are a bit more. One of the potentials after cutting off the top tubes you'll find hidden stresses are released and the frame will twist out of line. Same with the stays. I supose you could install a new TT (or pair of TT's) before cutting off the old then deal with the stays...


If I were a builder (and not a seasoned hobby guy) I'd try to talk you out of this. But it's your $ and your bike. Andy.
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Old 09-13-12, 05:46 AM   #6
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Thank you for all the well thought out replies - I definitely will not be modifying the frame.
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Old 09-18-12, 10:32 AM   #7
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I supose the best answer is to find someone with a smaller frame to swap with. If not that, then Andrew's suggestion that you could have new pair of TT's installed before cutting off the old then deal with the stays... shows merit. I would also think it might be viable to tack a long length of 2" square tube on each side, just below where the new tubes would be located. That could also provide the alignment retension or at least the hope for that. Overall just hate to be cutting up a vintage frame that is really a vintage frame...
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