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  1. #1
    Senior Member calstar's Avatar
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    Fork blade bending

    What are your thoughts on blade bending with and without the drops brazed on, pros and cons? Do the drops help align the blade in the bender, make it easier or harder? I know blades bent with the drops can have a straight section from the tips for a few inches (which is not objectionable to me), anything else different? And how many of you use sand fill to prevent rippling? Posted same question on mtbr, looking for more input here.

    thanks, Brian
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  2. #2
    Andrew R Stewart Andrew R Stewart's Avatar
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    Bend the blades without drop outs. If done with you can get a crimple at the end of the drop out where the blade won't bend any more. If you like the bend to be as close to the drop out as possible this is more likely to happen. If you want the bend to finish off well before the drop outs (which I think looks cheap) then you'll be fine with the drop out in place. Andy.

  3. #3
    tuz
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    I'm not sure that having the drops in would help in properly raking the blades? I guess it's easier to hook the blade but you could still bend it crooked if you were careless. I makes sense if you braze the entire fork with straight blades, true it, and then bend both blades simultaneously.

    I've never used sand to rake blades. I think that if you use a wooden mandrel you don't need it.
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    Depends on your bender I suppose - I always braze ends in first, and with the Hammill bender I use I don't get a straight section at the end. Never use sand.
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  5. #5
    Senior Member calstar's Avatar
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    Quote Originally Posted by tuz View Post
    .....then bend both blades simultaneously.
    Have you/do you do this? You have two mandrels attached side by side? I've thought this would be a good idea but have never seen/heard of anyone(small builders) doing it.

    Brian
    "The older I get the better I was" (from Old Guys Rule t-shirt)

  6. #6
    Older I get, Better I was velonomad's Avatar
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    I have only made 6 or 7 forks. Since my bender is fairly crude I can't insure the bend is precisely on the center line so I leave the drop-outs off until after I make my bend.

    I have used sand in bending mild steel tubing, In my experience it only seems to work well when packed with foundry sand ( mixture of silica sand,clay and oil) I have never used it on a fork blade

  7. #7
    tuz
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    Quote Originally Posted by calstar View Post
    Have you/do you do this? You have two mandrels attached side by side? I've thought this would be a good idea but have never seen/heard of anyone(small builders) doing it.

    Brian
    There is a local shop that has this system. I dont remember the details but it's basically a foot wide strip of steel that is curved. You hook the dropouts and pull on the steer tube. There are some videos from the 80's of some big Italian shops showing this technique. Can't find them...
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    Quote Originally Posted by calstar View Post
    What are your thoughts on blade bending with and without the drops brazed on, pros and cons? Do the drops help align the blade in the bender, make it easier or harder? I know blades bent with the drops can have a straight section from the tips for a few inches (which is not objectionable to me), anything else different? And how many of you use sand fill to prevent rippling? Posted same question on mtbr, looking for more input here.
    thanks, Brian
    OP Brian -

    Most modern folks (that are bent at all) are given a gradual bend over the bottom half (or so) of the fork. In non-modern times it was common to put most of the bend near the drop-out end aka near the tips. I have heard this called a "continental fork" basically meaning that is how the Brit's and the French used to do it. Look in the C&V for many examples of the old style and in any on-line bike store webpage for the modern style. If you were to want to decide if one is better than the other, that is a separate question to ask.

    For today, I'll recommend searching this forum for "fork bending" or "fork bender" and you should find several threads with detailed photo's of easy to make bending jigs/tools that will get the job done very well and consistantly. The ones made of simple hardwood really work well. You should be able to clone those in a decent Saturday afternoon for few dollars and be bent and brazing by supper time. Reminder though (just in case it needs to be said) that the amount you bend the fork is interactive with the other design aspects of the frame, so it can't generally be taken as an independent decision.

    Hope that helps
    /K
    Note; No rocket scientist were harmed in formulated inconstructing this response [

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    Both methods give good results, so neither is really better. One advantage to not brazing the ends in is that you have leverage from the tip end also, to force the bend in where you want it. If you are tip trimming anyway.

    I think the factories bent forks, not blades, I`m sure some start with pre-bents also. But I have seen big machines that were designed to bend both sides. It makes sense to have such machines in shops that tune up forks also, since they are forced to deal with the fork in finished form. Beats sticking them under a door. Obviously a machine on that scale is more expensive to build.

  10. #10
    Old fart JohnDThompson's Avatar
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    Quote Originally Posted by tuz View Post
    There is a local shop that has this system. I dont remember the details but it's basically a foot wide strip of steel that is curved. You hook the dropouts and pull on the steer tube. There are some videos from the 80's of some big Italian shops showing this technique. Can't find them...
    That's how we did it at Trek. I prefer the look of a blade that curves all the way to the dropout, though, so I bend them before brazing on my bikes.

  11. #11
    tuz
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    I visited that shop I mentionned today. Here's a pic of the bender. I guess you need to calibrate the length of the straight blade vs. the desired rake and have indexed stops for a few rakes values.
    bender.jpg
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