Roger Longbottom
Guest
W
Last edited:
W
- Thread starter Roger Longbottom
- Start date
Page may contain affiliate links. Please see terms for details.
ColinJ
Puzzle game procrastinator!
- Location
- Todmorden - Yorks/Lancs border
SkipdiverJohn
Deplorable Brexiteer
- Location
- London
If you want to permanently manipulate steel you have to take it beyond it's yield point, otherwise it will just spring back exactly to where it was to start with.
As to whether something made of steel will bend to your will, or simply snap, the answer is it really depends what sort of steel you are dealing with. The lower grade it is, ironically the "safer" it is to mess around with due to the metallurgical properties. Steel has two important strengths, the Yield Strength and the Ultimate Tensile Strength. If you load it below the yield point, then remove the load, it will return elastically to it's original state. if you load it to above it's yield point, but below it's UTS, it will deform permanently to a degree, but not actually fail. If you go beyond the UTS, it fails.
Now, you don't need to be a rocket scientist to realise that if the yield strength and UTS are a long way apart, bending the material is relatively risk-free, but if the yield strength and UTS are very close together (as in the case of some "exotic" high strength steel alloys such as Reynolds 753), then forcing the steel to yield in order to adjust it, if overdone, could easily result in total failure.
So, the first thing you need to ask yourself is "what sort of steel am I dealing with"?
As to whether something made of steel will bend to your will, or simply snap, the answer is it really depends what sort of steel you are dealing with. The lower grade it is, ironically the "safer" it is to mess around with due to the metallurgical properties. Steel has two important strengths, the Yield Strength and the Ultimate Tensile Strength. If you load it below the yield point, then remove the load, it will return elastically to it's original state. if you load it to above it's yield point, but below it's UTS, it will deform permanently to a degree, but not actually fail. If you go beyond the UTS, it fails.
Now, you don't need to be a rocket scientist to realise that if the yield strength and UTS are a long way apart, bending the material is relatively risk-free, but if the yield strength and UTS are very close together (as in the case of some "exotic" high strength steel alloys such as Reynolds 753), then forcing the steel to yield in order to adjust it, if overdone, could easily result in total failure.
So, the first thing you need to ask yourself is "what sort of steel am I dealing with"?
FrankCrank
Old layabout
Have done several frame adjustments using a car jack, for steel the risk is low. Over stretching is needed to allow for springback, considerably more than you might think. Make sure that each side of the triangle is moving out equally. When done, check dropout alignment and adjust if needed, and you're good to go 
SkipdiverJohn
Deplorable Brexiteer
- Location
- London
As a general rule this is what you want to happen, but not here. In this case we have localised damage/distortion to one side of the frame and we want to reverse this without changing the correct position of it's opposite frame member. The way to achieve this is to temporarily strengthen the side you want to leave alone, and force the applied load to move only the part of the frame that is misaligned. The simplest and most obvious way is you clamp something strong & stiff to the side you don't want to change to reinforce it, so the applied force goes down the path of least resistance and bends out only the stay that was previously hit by the car.
FrankCrank
Old layabout
.....good call Skippy, may be more to this one than meets the eye. Maybe the Op can post a pic or three.........
HMS_Dave
Grand Old Lady
Would it not be better to use a long bolt through the drop out and wind a nut out to spread the frame? similar to this
View: https://www.youtube.com/watch?v=YdibmxBuMy0
Then align the drop outs using this
View: https://www.youtube.com/watch?v=PsU8IkkFaok
Perhaps ive completely misunderstood mind...
View: https://www.youtube.com/watch?v=YdibmxBuMy0
Then align the drop outs using this
View: https://www.youtube.com/watch?v=PsU8IkkFaok
Perhaps ive completely misunderstood mind...
FrankCrank
Old layabout
....indeed, another way to skin a cat. Done this before just placing the bike on the floor, one foot on the lower triangle, and yanking the other side into submission. Have seen bikes with a high sprocket count with asymmetrical stays, so that's another consideration. Without more info from the Op it's just supposition really.....
PaulSB
Squire
- Location
- Chorley, Lancashire
As a truly non-mechanical person I would ask myself can I do this?
If you're unsure or have little experience with such things would it be sensible to ask the LBS to fix it?
You've suggested it is +/- 6mm. To my mind a spacer sounds like the first option. I think my LBS would say the same. A car jack sounds like the nuclear option!
If you're unsure or have little experience with such things would it be sensible to ask the LBS to fix it?
You've suggested it is +/- 6mm. To my mind a spacer sounds like the first option. I think my LBS would say the same. A car jack sounds like the nuclear option!
SkipdiverJohn
Deplorable Brexiteer
- Location
- London
I would not panic about cold-setting 531 if done in small bites and checked for progress as you go, although I have only personally cold-set hi-tensile.
The brick wall trick will not help, nor will laying the frame on the ground and putting your foot on the good side. The only way you can stop the good side spreading is to make it more difficult to bend than the bad side, which means bracing it with additional material clamped at each extremity of the stay. My preferred method would be a length of angle iron along the RH chainstay going from the RH dropout all the way to the BB junction past any chainstay bridge built into the frame, and clamped to the chainstay with several G clamps. A big bench vice might work, if you can hold the good side whilst still giving access to the bad side.
A car jack might sound brutal, but if it's a wheel-changing jack with a fairly fine pitch thread, you can exert a lot of force but in a very controlled manner. It is infinitely preferable to merely grabbing hold of the frame and physically wrenching it apart - which could be overdone and cause unwanted damage.
Last edited: