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I need to do this to a frame. I usually put the bb shell on a post and bend it that way, but in this case I haven't figured out how to get the bb out. Apparently takes a special tool. I started a thread on it in here while back, it's a Dutch 3 speed and it's currently spaced at 140mm :twitchy:
I'm usually a little obsessive about bending frames. A framebuilder I respect always recommends the axle method, but I figure that on older bikes the drive side chainstay is almost always more compliant than the non-driveside chainstay due to the extra dimple for crank clearance. So it will never work |
140 is wider than 135 whats wrong with It as Is?
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I have used Sheldon's method a half dozen times or more. You do have be ready to over bend it a little bit so that it springs back to the intended final spot. Some that I've modified have bent very easily, however, and I ended up way over correcting. But steel is pretty resilient and you can just keep tweaking until it is right.
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Curious as to what the group thinks about a method I've tried. I too always thought the threaded rod left a bit to be desired...so I started with a couple of pieces of hardwood attached to the inside of the dropouts using small bolts through the fender brace eyelets. Approximating axle location on the wood blocks, I used a 1" diameter by 3/16" thick grinding stone to carve a depression in them more or less following the seat stay angle. From these crude jigs, I inserted and spread progressively larger Turnbuckles. Due to their right and left threading, the spread was controlled, and equalized, in both directions at the same time. Might not be ideal for correcting a problem, but seemed to be fairly quick and accurate for something straight to begin with. Word of warning, the mechanical device used, (turnbuckle), is no where near as secure as the threaded rod with washers when exerting pressure. Use some type of fail safe in the operation. Zip ties, cable, something looped through the eyebolts and the frame to prevent accident should it slip free. Kind of a long setup initially, but as I said, it seemed to yield good results for me.
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Originally Posted by kalash74
(Post 18386333)
My vintage English 3-speed has a chainline issue. I finally traced it to the RH chainstay being pushed over to the right side. Using Sheldon's string method described here
Bicycle Frame/Hub Spacing I determined that the difference between right and left with respect to the seat tube is about 8mm. (I ran fishing line around the head tube, tied it off to both rear fork ends, and used a ruler to measure the difference between the seat tube and the string on both sides. The right side was +8mm more than the left. Incidentally, the rear clearance is around 118 mm--a bit wide for the standard 110 mm spacing on these old hubs. Pushing the right stay 8mm inward would both close this gap and fix the alignment issue). I called the LBS, and upon mentioning "frame misaligned" they declined to do the work. I did locate a guy who is in town and is a framebuilder (and has a frame alignment table), but he mentioned that I would need to install a bottom bracket insert. I'm not sure if these inserts will fit my bottom bracket or not. The bike is an old English 3-speed with cottered cranks. So should I attempt the Sheldon method on my garage floor. Are there any improvements to the method that I should try? The method seems pretty crude, but I do trust Sheldon's wealth of knowledge. The frame is lugged steel, and is pretty mild--unlike more modern steels. just take it to the frame builder and let him do after all he actully knows what hes doing right, what i would do anyhow. |
Originally Posted by wedgeSG
(Post 18400289)
Curious as to what the group thinks about a method I've tried. I too always thought the threaded rod left a bit to be desired...so I started with a couple of pieces of hardwood attached to the inside of the dropouts using small bolts through the fender brace eyelets. Approximating axle location on the wood blocks, I used a 1" diameter by 3/16" thick grinding stone to carve a depression in them more or less following the seat stay angle. From these crude jigs, I inserted and spread progressively larger Turnbuckles. Due to their right and left threading, the spread was controlled, and equalized, in both directions at the same time. Might not be ideal for correcting a problem, but seemed to be fairly quick and accurate for something straight to begin with. Word of warning, the mechanical device used, (turnbuckle), is no where near as secure as the threaded rod with washers when exerting pressure. Use some type of fail safe in the operation. Zip ties, cable, something looped through the eyebolts and the frame to prevent accident should it slip free. Kind of a long setup initially, but as I said, it seemed to yield good results for me.
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Originally Posted by wedgeSG
(Post 18400289)
Curious as to what the group thinks about a method I've tried. I too always thought the threaded rod left a bit to be desired...so I started with a couple of pieces of hardwood attached to the inside of the dropouts using small bolts through the fender brace eyelets. Approximating axle location on the wood blocks, I used a 1" diameter by 3/16" thick grinding stone to carve a depression in them more or less following the seat stay angle. From these crude jigs, I inserted and spread progressively larger Turnbuckles. Due to their right and left threading, the spread was controlled, and equalized, in both directions at the same time. Might not be ideal for correcting a problem, but seemed to be fairly quick and accurate for something straight to begin with. Word of warning, the mechanical device used, (turnbuckle), is no where near as secure as the threaded rod with washers when exerting pressure. Use some type of fail safe in the operation. Zip ties, cable, something looped through the eyebolts and the frame to prevent accident should it slip free. Kind of a long setup initially, but as I said, it seemed to yield good results for me.
If you still want to use this method, I would double-check that the entire frame is aligned. The string method is the quick & easy. |
Originally Posted by Steiner74
(Post 18400352)
just take it to the frame builder and let him do after all he actully knows what hes doing right, what i would do anyhow.
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Originally Posted by kalash74
(Post 18401669)
I'm not sure if the frame builder's jig will fit my bottom bracket. It's an old English bottom bracket from the 1950s. If I understand correctly, the frame is laid sideways on the frame table and secured at the bottom bracket. Mine has fixed cups, I think? Not sure if it would work with a modern setup.
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