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Thread: BMX forks

  1. #1
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    BMX forks

    This is my first post here so i want to say hello to all! Lots of cool stuff being built in this section!

    I need a set of forks built for my cyclecraft crusier and i had some question's that maybe someone could give me some pointer's on?? Here's the fork's that i need built....

    (1)


    (2)


    (3)



    Here's my current cruiser forks (same make) that i was gonna use for the measurements....

    (a)


    (b)


    (c)


    (d)

  2. #2
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    Here's some of my question's/concern's....

    1) What type of tubing should i use, butted or straight gauge like the steerer tube?

    2) How do i go about finding rings or whatever to make the crown/race in picture (a)?

    3) What plate should i use to make these simple drop outs in picture (c), any advice??

    4) I found the tap to make the thread's but what about the slot that is machined in there (d), any advice there?

    5) Is it me or did they just weld some washer's to end the tubing or what?? (3&b)

    I've got more question's but this is a loaded plate here, i'm a little prepared. Thank's to anyone who has the time to read all this and help me. Thanks, again!

    Tyler

  3. #3
    Randomhead
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    Paragon and Nova both sell the crown race rings. See the supplier thread at the top of the forum. Any steel plate will do for the dropouts. I wouldn't worry about the weight, go with straight gauge for the tubes. The steerers can be bought from Nova, I don't know if they have a keyway or not. The tubing caps are non-critical, so washers would work but don't use galvanized.

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    6) If i use straight gauge tube what thickness would you recommend?

    7) As for the "crown" section in pic (a), it has a very thin piece above the welded section, is it all one piece that is just welded from below? My fork has to have one of these 27.0 mm crown's:


  5. #5
    Randomhead
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    .056" 4130 might be a little heavy, but it would work.

    The thin part of the crown race ring is turned or cut down to be a press fit into the inside diameter of the headset crown race that you show.
    See this page for Paragon's crown race

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    Thanks Unter!! That's more my speed there! Its got a few measurements there...

    "The race diameter is accurately machined to size, 26.43 mm/26.49 mm, and the largest diameter is 1 1/4"

    I'm guessing the 27.0mm crown in the picture would work fine then??

    Thank's again Unter, you're helping see a light at the end of the tunnel!!

  7. #7
    Andrew R Stewart Andrew R Stewart's Avatar
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    Tomknox- You want a small interference fit between the, brazed onto the fork, crown race seat and the crown race. So a head set crown race with a 27.0mm ID would want a seat with a 27.1 (or there abouts) OD. The 26.43/9 seat is for races of 26.4 (the "Campy" standard). Some seats are available in a larger size that is then, after brazing, machined down to the needed OD. Or you could make your own on a lathe. Andy.

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    Thanks for the reply Andrew! Being that it's old 80's bmx sizing i kinda figured that something would have to made because everything is modern sized nowadays. As for the "brazing", i was thinking it just needs welding, are you saying it need's both?

    In this case, would you recommend i have the crown welded on the steerer tube first and then have it lathed?

  9. #9
    Randomhead
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    I was assuming your fork was 1", which is still used on custom steel bikes. There were a few 1 1/8" threaded steerers, but they are rare. Paragon says you need to have brazing under the crown ring or it will eventually break. I assume this is from long, sad experience. I'm sure a lot of forks were built with just the weld.

  10. #10
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    Unter: Yes it's the old 1'' steerer, not saying that the company that made them(cyclecraft) didn't know better but i highly doubt they brazed under it. There is no sign of it if they did, back then they probably just welded it on and sent it down the road! Paragon refers to cane creek's research, i'm not sure but i don't think they even existed back when these were built, don't quote me on that though. I'm assuming that i will need to mill down the stock crown from Paragon, whatcha think??
    Last edited by tomknox; 09-19-12 at 12:40 PM. Reason: typo

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