Advertise on Bikeforums.net



User Tag List

Page 2 of 2 FirstFirst 12
Results 26 to 44 of 44
  1. #26
    tuz
    tuz is offline
    Senior Member
    Join Date
    Dec 2006
    Location
    Toronto/Montréal
    My Bikes
    Homemade mixte, track, commuter and road, Ryffranck road
    Posts
    1,145
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    It's good to read some good-old Jobst Brandt

    It looks like if you put the caliper in front of the blade, the reaction force will push the wheel in and the QR won't loosen from the load cycling. Otherwise, a through-axle is the way to go. Along with beefy blades or with Frank's ingenious design!
    homebuilt commuter, mixte, road and track (+ Ryffranck road)
    bla bla blog

  2. #27
    Randomhead
    Join Date
    Aug 2008
    Location
    Happy Valley, Pennsylvania
    Posts
    12,549
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    tried drawing a quick free body diagram and just confused myself. Looks like putting the caliper in front does help the immediate wheel launching problem. Probably not a bad idea to add lawyer lips in any event.

  3. #28
    Senior Member calstar's Avatar
    Join Date
    Mar 2012
    Location
    santa barbara CA
    Posts
    784
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by tuz View Post
    ..It looks like if you put the caliper in front of the blade...
    Has this been done, anyone build or see this design?

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

  4. #29
    Senior Member
    Join Date
    Sep 2012
    Posts
    1,496
    Mentioned
    6 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by ftwelder View Post
    Here ya go. You mount the caliper on a bracket that goes directly to the axle and can rotate on the axle on a bearing (bushing). Near where the caliper mounts to the bracket, there is another small bushing. This is called a lower stay rod bushing. The upper stay rod bushing bolts to the fork crown.

    When the bike is moving and you apply the brake, the caliper pulls down on the stay rod causing the brake force to move upward directly toward the upper stay rod bolt where it belongs, in a nice thick chunk of metal.

    Welding a gusset on a skinny tapered blade is so very bad. There is nothing about a tapered fork blade that should be near a disk brake caliper unless it is very large, thick and straight. Torch brazing on the fork blade will jeopardize the condition of the material in a critical area. ending the gusset at the drilled hole is so wrong it's not even funny.
    road-brake by frankthewelder, on Flickr
    Frank -

    I remember the early 70's Proteus Framebuilding book (it had a yellow/tan cover) had a similar design for making a strong fork when heavy duty blades were lacking. That design placed a flexible plate under the top headset bolt with two holes in the outer end of it. Then a pair of seat stays ran from the front dropouts up to the flex plate where a 6mm bolt through the flex plate and into a plug brazed into the head of the stay. Don't remember any mention of effects on brakes (of course this was pre-disk era). Don't remember ever building one and about this time I got access to forged Cinelli full sloping crowns which solved the problem well enough and looked great.

    Here is a quick sketch from memory of the Proteus design recommendation;

    Fork Reinforcement.jpg

  5. #30
    Senior Member calstar's Avatar
    Join Date
    Mar 2012
    Location
    santa barbara CA
    Posts
    784
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Anyone know of pics of and unraked fork somewhere?

    Thanks, Brian


    edit: just noticed there was a very similar thread on this subject (Dec 2012, I even posted on it! damn that short term memory), still nice to have further discussion on the subject
    Last edited by calstar; 03-25-13 at 06:07 PM.
    "The older I get the better I was" (from Old Guys Rule t-shirt)

  6. #31
    Member
    Join Date
    Feb 2013
    Posts
    45
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by calstar View Post
    Has this been done, anyone build or see this design?

    thanks, Brian
    I've built a bunch of bikes with the caliper on the front of the right fork leg. It means the braking force is pushing the hub into the dropouts, not pulling it out.
    http://www.kinetics-online.co.uk

  7. #32
    Senior Member calstar's Avatar
    Join Date
    Mar 2012
    Location
    santa barbara CA
    Posts
    784
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by BenCooper View Post
    I've built a bunch of bikes with the caliper on the front of the right fork leg. It means the braking force is pushing the hub into the dropouts, not pulling it out.
    Got any pics? What type of tab mount do you use? thanks, Brian
    "The older I get the better I was" (from Old Guys Rule t-shirt)

  8. #33
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    540
    Mentioned
    31 Post(s)
    Tagged
    0 Thread(s)
    Silk Road fork in #5, keeps the caliper on the left, has dropouts, that open end is the front.
    I expect they have them made for themselves.. .

  9. #34
    Senior Member
    Join Date
    Jul 2011
    Posts
    1,473
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by unterhausen View Post
    there have been plenty of reports of blades un-raking. I guess it depends on the user as much as anything. I am not sure I understand the dislike for unicrown forks. They look better than segmented forks and many forks with crowns to me.
    It probably is traditional, but it is associated with tig or Walmart. If they didn't exist they would be a hit at NABHs for the first guy to show them, but as it is...

    Those segmented forks seem like a poor place to start building an extra strong fork. There is a good thread on one that failed somewhere, with the whys and wherefores. I would build a plate crown first. Sturdy and all plate fabable.

    http://www.velocipedesalon.com/forum...ned-16537.html

    I have this CS from my first order from Nova. I got a standard touring CS, a tandem, and then a TANDEM. Holy moly that thing is like a easton baseball bat, but made of steel. Still not recommending it. I think probably the only advantage to the lopsided forks is the modest weight savings, and the look at me I am an engineer factor. There can't be any ride advantage left, and weight wise, one has to pretty much abandon all hope with that kind of set-up. I think just hefty but not crazy all the way is probably better.

  10. #35
    Senior Member
    Join Date
    Jul 2011
    Posts
    1,473
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by ftwelder View Post
    Here ya go. You mount the caliper on a bracket that goes directly to the axle and can rotate on the axle on a bearing (bushing). Near where the caliper mounts to the bracket, there is another small bushing. This is called a lower stay rod bushing. The upper stay rod bushing bolts to the fork crown.

    When the bike is moving and you apply the brake, the caliper pulls down on the stay rod causing the brake force to move upward directly toward the upper stay rod bolt where it belongs, in a nice thick chunk of metal.
    r

    That kind of rig is common on choppers though they normally tether to the fork at brake height. I have never built one for a bike, but have suggested it often enough, so far no takers, no how. These days the strut could be amsteel at about zero weight and fab cost. It is also a good method to retro a disc.

  11. #36
    Senior Member
    Join Date
    Jul 2011
    Posts
    1,473
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    The caliper in the front was one of the first things I read about when I was pushing my way through this stuff X years ago. Still, you basically never see them...

  12. #37
    Member
    Join Date
    Feb 2013
    Posts
    45
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Got any pics? What type of tab mount do you use? thanks, Brian
    Mostly IS mounts, though I'm building a setup for a Brompton at the moment which will have double discs, both post-mount, and the right one will probably go on the front.
    http://www.kinetics-online.co.uk

  13. #38
    tuz
    tuz is offline
    Senior Member
    Join Date
    Dec 2006
    Location
    Toronto/Montréal
    My Bikes
    Homemade mixte, track, commuter and road, Ryffranck road
    Posts
    1,145
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    check here. Every failure has it's own circumstances so a picture doesn't tell the whole story. However, basic physics tells me that light blades and disks is a bad idea.
    homebuilt commuter, mixte, road and track (+ Ryffranck road)
    bla bla blog

  14. #39
    Senior Member
    Join Date
    Sep 2006
    Location
    Bozeman MT
    My Bikes
    Kirk
    Posts
    180
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Good morning Gents,

    I don't chime in here very often but I do enjoy looking in and see what everyone is up to.

    I thought I'd share my findings and thoughts on disc brakes on steel forks. I've done a lot of long term testing and have been using different versions of steel disc forks for coming on two years now. I certainly think that one can make a very good, reliable and safe fork to work with discs if it is done right and I also think that if you just stick some tiny tabs on a lightweight steel fork that bad things can happen. The tough part about talking about this on the web is that a poorly conceived fork looks for the most part like a well conceived fork at first glance.

    Cutting to the chase here is what I've found. There are a few key things to keep in mind when designing and building the fork IMO.

    First is that diameter and wall thickness are your friend. Tapered blades almost always come much longer than is needed and most of the time folks bend the blades, stuff the tips in and then cut them to length by taking length off the large end. If one cuts the blade to length by cutting off the small end then the part of the blade dealing with most of the braking loads can be considerably larger than if the length is taken off the top. It can make fitting the tips a PITA but it helps a lot. It's also a very good idea to use blades with a heavy wall. This will make them stiffer and more resistant to de-raking.

    Next up is the design of the dropout - I use a dropout with a very low angle or even 0° slot. This means that is the rider doesn't use the QR properly that the wheel will not get pulled out of the drops due to braking torque. If the slot angle is proper then the axle gets pushed sideways in the slot instead of out of it. It's also important to make sure you can offset the drop to the inside edge of the blade so that the rotor will not hit the inside of the blade.

    Next are the disc tabs - there are two key things to consider here IMO - how far up the blade they go and where they mount to the blade rotationally. The first part of this is pretty obvious to most folks.............by making the tab extend up the blade it spreads the load and changes the leverage on the blade imparted my braking force. Because the blade is tapered you end up transferring a good bit of the load to a larger diameter section of the blade with an extended tab - a good thing. If done right it will also give the upper part of the tab more surface area where is meets the blade to lessen the point loads and any chance of the 'can opener' effect. The other thing to consider is where the disc tabs mount to the blade in a rotational sense (must be a better way to say that). When viewed from above it's important that the tab be mounted so that it meets the blade tangentially and not perpendicularly. By having it mount tangentially the tab does not try to push through the blade and collapse the tube but instead tries to twist it..........and the blade deals with that very well. Getting the tabs to sit on the blade in this fashion requires that you think ahead a good bit and not just make the fork and then see where then tabs land. Since the tabs mount in a fixed relationship to the drops it's the blade that needs to be moved in/out to get this alignment. One can do this with fork crown width and picking how the drops sit in the blades. A bit of a pain but worth it in the long run. The fact that the tab doesn't load the tube straight means that it is less prone to making the tube cross section change shape. I haven't tested this well enough to prove it but I feel strongly that the tab pushing on the blade and wanting to change the shape of the cross section of the blade can contribute to the de-raking effect. Mount the tab low and perpendicularly to the blade and it can flatten the tube which of course will pull the blade backward lessening the rake.

    I went through many designs before I found one that performed the way I wanted with no weird twisting or shudder. I then worked on making sure the fork would stay together over the long term. In the end I have a fork I feel good about. I rode and tested the final version for a year before offering anything for sale. I can't tell you how sore my hands got riding down endless washboard dirt roads while using the front brake hard. In the end I have a fork that holds its geometry and alignment, handles and rides well and should stay together for them long term.

    I hope that my findings help others make safer forks. A high tide raises all boats.

    Have fun.

    dave

  15. #40
    __________ seeker333's Avatar
    Join Date
    Feb 2004
    Posts
    2,681
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    You guys over-think this. Surly sells their Disc Trucker fork in black, for 26 or 700 wheel, for as little as $90 shipped - less than you can make them. Buy one, ride it - it works, looks good too. Crown rack boss is a neat feature.

    Let Tange do the hard stuff (maxway makes the frames, fork steerer is branded tange).

    http://classic.aebike.com/product-li...5-m27576-qc30/

  16. #41
    Senior Member GrayJay's Avatar
    Join Date
    Sep 2009
    Location
    EagleRiver AK
    Posts
    1,225
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by seeker333 View Post
    You guys over-think this. Surly sells their Disc Trucker fork in black, for 26 or 700 wheel, for as little as $90 shipped - less than you can make them. Buy one, ride it - it works, looks good too. Crown rack boss is a neat feature.

    Let Tange do the hard stuff (maxway makes the frames, fork steerer is branded tange).

    http://classic.aebike.com/product-li...5-m27576-qc30/
    Plenty of reasons to try something different, there are good reasons we build frames instead of just getting a LHT.

    The bend in those LHT forks is all concentrated in the middle of the leg, looks more like a (human) leg with a bent knee than a fork nicely raked along lower 1/3 of the leg.

    Dropouts are verticle instead of forward facing as they should be for disk.

    Builder might want different A-C, rake, width measurements or just astheticaly might want a differet crown style that fits rest of the bike together.

  17. #42
    tuz
    tuz is offline
    Senior Member
    Join Date
    Dec 2006
    Location
    Toronto/Montréal
    My Bikes
    Homemade mixte, track, commuter and road, Ryffranck road
    Posts
    1,145
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Thanks for the input Mr. Kirk!
    homebuilt commuter, mixte, road and track (+ Ryffranck road)
    bla bla blog

  18. #43
    Senior Member calstar's Avatar
    Join Date
    Mar 2012
    Location
    santa barbara CA
    Posts
    784
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by tuz View Post
    Thanks for the input Mr. Kirk!
    A big +1. And heres a link to a Kirk Frameworks sequential build, very nice.

    http://www.kirkframeworks.com/jk_cross1.htm

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

  19. #44
    Senior Member
    Join Date
    Sep 2004
    Posts
    244
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    A friend pointed me to this thread.

    I made the dropout on my fork, it is not a Willits dropout. I have a small CNC mill and made the dropout in my basement. I make most of my own front dropouts. It is different from most in that it is designed to take a rear caliper, not a front. Rear calipers sit closer to the axle than front dropouts, and I did that for aesthetic reasons. My dropout is also cut to match the curve of the fork blade, while the Willit's is designed to go against a straight blade fork. They are bent (usually not very nicely) to fit on curved fork blades. If you look closely you can almost always see the distortion from the bend.

    Otherwise Dave Kirk already wrote a lot of what I did on this fork. I cut the blades from the bottom, not the top, to increase the diameter of the fork blade at the dropout. I also used a sloping crown (not normally my preference) to get more fork blade to trim. The fork blades were the thickest in my inventory (they are Columbus Thron).

    The fork has about 1500-2000 miles on it these days and has had no issues.

    There is one issue with it. When choosing to use the rear ISO mount I read the disk mount drawings carefully and have everything aligned for that. However I didn't read the hub standards and neglected to notice that rear hubs put the disk 5mm farther from the dropout than front hubs. This means that the caliper is closer to the rotor than any calipers are designed for. I corrected for this by modifying the ISO to post mount adapter and because the BB7 caliper is very flexible in setup. However it is unlikely to work for something like a Shimano Servowave brake.

Page 2 of 2 FirstFirst 12

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •