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-   -   Shrinking a frame? (http://www.bikeforums.net/framebuilders/933855-shrinking-frame.html)

RaleighSport 02-11-14 06:53 PM

Shrinking a frame?
 
I don't know if this is the right place for this, but it was the best place I could come up with.

Is it possible to remove the filler from lug work on an old steel road bike, then to cut down the tubing to a shorter predetermined length and then rejoin the frame with the same lugs and tubes with fresh filler? Will I have to change the geometry?

I also understand this is fairly silly and a lot of you wouldn't bother, but I have a frame hanging that's just too large for me and has minimal capital into it as well as not being a great looker so not exactly a tradeable either.

ftwelder 02-11-14 07:59 PM

The short answer is yes, the correct answer is no. Rebuilding a frame is not less expensive than a new one. Labor 50% of the cost of a custom frame while materials are 10-15% and no-one takes apart frames for it's components unless they are very rare.

unterhausen 02-11-14 08:49 PM

taking a bike apart and putting it back together should cost you 10x what a new frame would cost, if not more.

Andrew R Stewart 02-11-14 09:27 PM

This is really only cost practical with the top tube height (frame size). And if the height reduction is enough then there's no need to take apart lugs/pull out tubes. Pretty much the same as replacing a tube except the disassembly goes quicker. Just a quick hack saw cut just below the upper head lug and the seat lug, only the seat stays will need pulling off.

I have done this once before. I had started building a frame for a, then, friend. He was very short torsoed and had no upper body flexibility. So while the height was about a 60cm the top tube was only 56.5. After the seat stay attachment I cracked the ST when center punching the binder slot's stress relief hole (ironic, I know). I had well over heated the thin ST between the lug then the SS brazing steps. How I dealt with my "friend" is another thread. But after that I cut off the TT and SS as described above. Then I installed a new TT, seat and head lugs and SS. Learning from the first mistake the results were far better. Now I had a 56cm ST size with a 56.5cm TT frame. Found a buyer and he enjoyed his bike for many thousands of miles and years.

In this case the keel of the bike remained the same, the CS, DT, HT and most of the ST all were unchanged angle and lengths. Andy.

tuz 02-12-14 08:45 AM

2 Attachment(s)
I have an excuse to post those pics :)

http://bikeforums.net/attachment.php...hmentid=364003http://bikeforums.net/attachment.php...hmentid=364004

It's possible but it's a lot of work. I don't think you would be able to salvage the lugs; simplest would be to cut the ST and HT below the lugs, remove the seat stays and then use new tubes and lugs.

hueyhoolihan 02-12-14 09:21 AM

couplers?

RaleighSport 02-12-14 09:24 AM

Thanks guys, you've been helpful mostly. I was just curious since it seemed a good way to try my first frame layup.

Andrew R Stewart 02-12-14 09:41 AM

Quote:

Originally Posted by RaleighSport (Post 16489472)
Thanks guys, you've been helpful mostly. I was just curious since it seemed a good way to try my first frame layup.

So your thought was that you'd start the building thing by cutting down an existing frame? Nothing wrong in this model though many will point out the drawbacks. One positive thing about working on frames that others have made is that you see how others did some of the process, for better or worse.

Regardless of the manor you start up your building the need for practice and destruction/cutting up of the practice pieces is still there. Andy.

RaleighSport 02-12-14 10:37 AM

Quote:

Originally Posted by Andrew R Stewart (Post 16489505)
So your thought was that you'd start the building thing by cutting down an existing frame? Nothing wrong in this model though many will point out the drawbacks. One positive thing about working on frames that others have made is that you see how others did some of the process, for better or worse.

Regardless of the manor you start up your building the need for practice and destruction/cutting up of the practice pieces is still there. Andy.

The main triangle of the frame in question is 531, I like the geometry but the frame's just too big also it's fairly worthless.. I should note I don't even have a simple jig yet so it's not like this is a feasible any time soon project.

busdriver1959 02-13-14 07:06 AM

Realize that what the experienced voices are saying is that taking apart a frame is often a lot harder than putting one together, good for learning but a major PITA. It may have been pinned and is probably put together with brass. Some may disagree but many think that a brass brazed frame shouldn't be repaired because of the heat required. Also you might be cutting off the butted sections when you resize it.
Straight gauge 4130 tubes and inexpensive pressed lugs are easier to start practicing with.

JohnDThompson 02-13-14 12:06 PM

Quote:

Originally Posted by busdriver1959 (Post 16492165)
Realize that what the experienced voices are saying is that taking apart a frame is often a lot harder than putting one together...

Especially if you intend to take it apart in a manner that will allow you to rebuild it in a rideable state.

In principle, it's possible; in practice, it's not worthwhile.

RaleighSport 02-13-14 05:46 PM

Quote:

Originally Posted by busdriver1959 (Post 16492165)
Realize that what the experienced voices are saying is that taking apart a frame is often a lot harder than putting one together, good for learning but a major PITA. It may have been pinned and is probably put together with brass. Some may disagree but many think that a brass brazed frame shouldn't be repaired because of the heat required. Also you might be cutting off the butted sections when you resize it.
Straight gauge 4130 tubes and inexpensive pressed lugs are easier to start practicing with.

Very good to know.. so for my next idiotic question for you guys.

Could I build a fixed jig around a bike frame I absolutely love and try and make copies of it? Or is this silly and I should just invest in a real jig instead of some hokey pokey redneck DIY homejob?

Andrew R Stewart 02-13-14 09:04 PM

If you are going to be building for a while, and once started it's hard to give it up, i'd invest in a jigging solution that can grow with you as you do other frames. There are table top solutions that are very flexible and don't cost any where near as much as a self contained jig.

But you have to start somewhere so try whatever you can to get going. Just don't spend much $ and don't expect in a year to have the same ideas about what you need or want. Andy.

CustomSteel 02-13-14 10:03 PM

This ^^^

And I wouldn't cut the 531 tubes. Sell the frame and get yourself a straight gauge frame to practice on.

*edit: Schwinn Varsity frames are plentiful, just saying...

fietsbob 02-16-14 04:23 PM

.02 .. only with a parallel seat and head tube could you take out an equal amount from Both.

Frame Repairs same dimensions, can replace tubes and reuse the lugs ..
but it needs to be worth a lot to you..

or the customer to pay .. had a Masi it went out and back to the shop I worked in 25 years ago

sold it at a few bucks more than it cost , but I got the Guys Alan frame in the trade in. ..
and rode it for a few years..


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