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  1. #1
    ihd
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    Fork bend discontinuities

    Hi all.

    I recently received a new steel fork and frame, and am concerned that the forks may not have been built correctly, or at least not with due care.

    I'd like your views so that I'm a bit better educated before I speak to the framebuilder.

    The forks have a rake of about 55mm, which as I understand it is fairly standard for this "sporty touring" type of frame. The issue is that the inside elbows of both fork bends have slight indentations that break up the continuity of the fork tubing. These are perceptible both by touch and by eye - I have attached a (not-great) photo, where reflections on the enamel make the irregularities appear deeper, sharper and much more ridge-like than they are. In reality they more closely resemble the slight impression a finger might leave when gently pressed against a fork made of putty (not the most reassuring mental image, I know!).

    I'm also conscious that the overall bend isn't as smooth as it could be (and as it is on my other bikes, ranging from the cheap to a similarly-specc'ed Reynolds frame), but seems to subtly form an angle at the elbows.

    I imagine these effects all relate to the necessary process of bending the fork blades to produce the rake. Yet no other steel fork I've closely inspected has anything like these ripple-like irregularities or corrugations, not even to the slightest perceptible degree.

    What worries me most, of course, is that they might weaken or are signs of weakness in the fork. Is there some tolerance level that is acceptable here? Or should I just send these back and insist on replacements without these imperfections, however 'slight' they may be?
    Attached Images Attached Images

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    Did he build the fork, or did he re-radius an existing fork? And if the latter, who's idea was that (ok to do that, just asking)? My fork bending jig is a smooth bend of material, so it couldn't indent a fork like that unless the fork collapsed a little. Except it only works on individual blades before they are assembled. Bending a whole fork is a much larger bender, that I have thought would be fun to make, but I imagine most shops don't have, small factory scale thing. They would make forks up without bend, and then zap the bend into them as required. Leaves people without a dual bender adding bend by doing weird things like wedging the fork under doors, in vises, tweaking with frame tools...

    It isn't good for strength, basically you never want to see a dent (period) that is deeper than a wall thickness, which at that point can be quite stout. Probably fine on the fingertip analogy. You have to consider that normal riding does not bend forks, and that it therefore takes a lot more violence to get a bend in than is likely in non-destructive riding. If that violence does not cause the forks to break or fade during the bending process, then the riding probably won't asuming the crimp isn't fataly deep.

    Whether one should pass on a fork with dents is another mater, and could depend on who told what to whom on a spectrum from: "don't really like to do that to a fork with my tool set, by I can try if you insist" through to "really that is what the big shops do, those dents reduce air resistence"...

  3. #3
    ihd
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    Thanks for those thoughts. Any idea how I could go about measuring the depth of indents accurately? I have a digital Vernier caliper, but it looks like it wouldn't be easy with all the bends, ovalizing and tapering around there...

    Did he build the fork, or did he re-radius an existing fork?
    This I don't know, but I suspect I'll be finding out soon enough. The geometry is this builder's standard for the type of frame, so I had no direct influence on any of those decisions.

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    You could take a piece of something flexible like sheet metal, and flex it over the fork, following thecurve, then eyeball the space. You can also use a feeler gage, or caliper the whole assembly, then subtract the sheet thickness. If the dent is more around the corner, then it might be harder to measure, but also less likely to mater.

    Keep in mind that if the fork blade is .9 mm, then at the thin end, all that metal has been swedged into the smaller section so it would take a massive dent to be out of line with the wall thickness. For a custom though, you shouldn't have to put up with a non-structural dent, let alone one with structural potential.

  5. #5
    Randomhead
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    I hate to say anything based on such a bad picture. Looks like a buckled blade.

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    I haven't buckled one yet, but I was surprised both dents seem similar, and they aren't at the point of greatest load, or don't seem to be to my eye. They are a little off center from what I can tell, and I don't quite get how they got that way either from pressure points or the tube collapsing.

  7. #7
    meech151
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    It almost looks as if there was something not uniform about the jig, like a large burr or something because the indentation looks to be in the same exact area on both blades. It does look like it started to collapse but wouldn't it be more in the center of the blade? Regardless, its not eye candy.

  8. #8
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    That fork looks pretty bad. You should be able to determine if it was damaged in shipping or not. If it wasn't, it never should have been sent out of the workshop. It should be considered sub-standard in any decent frame shop. If it was from a reputable builder, he or she should have known better and redone it before it every got near a shipping box. If it was from one of the myriad of new, wanna-be framebuilders he or she should have known better, and will take this as a learning lesson. Either way, and no matter how much or little you paid for it, you didn't pay for that kind of work. Send it back.

  9. #9
    ihd
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    Sorry about the poor picture, I'm going to borrow a digital camera and take some better ones tomorrow (which I need to do anyway before sending the fork back to the framebuilder). I'm also going to bring it to some of the better bikeshops around town and see what people think.

    About the indentations being off-centre, that's correct: none is at its deepest facing directly forward. I've started measuring this and that, and the dropout distance is about 98.5mm, which I suppose isn't great, but wouldn't have alarmed me in itself. Next, I'm going to put in a true and perfectly-dished wheel, to see if there's any alignment issues.

    Will report back with pics ASAP.

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    Randomhead
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    Quote Originally Posted by meech151 View Post
    It almost looks as if there was something not uniform about the jig, like a large burr or something because the indentation looks to be in the same exact area on both blades. It does look like it started to collapse but wouldn't it be more in the center of the blade? Regardless, its not eye candy.
    I was thinking there may be something wrong with the builder's bender as well. It does look exactly the same on both blades, and I wouldn't expect to see dents on the sides. OTOH, it may be the bad quality of the pic, and we are just seeing the edge of a buckled area that goes across the fork blade.

  11. #11
    ihd
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    Photos

    OK, here's some better pictures of the fork. Because the enamel finish makes any unevenness more visible, I've tried to include some where this plays less of a role (C, E). In some pictures not included here, you'd think the forks had holes because of the circular highlights created by the indentations - obviously nothing so dramatic is going on.

    However subtle, you can always feel the ripples under your fingers, as well as discern the worst indents in silhouette just by eye. I wasn't able to take the fork to bikeshops today but will still do so before shipping it back. (Oh and there is no way this could have happened during the shipping to me - I doubt the fork could collapse but the bubble wrap remain unburst...)
    Attached Images Attached Images
    • File Type: jpg A.jpg (85.5 KB, 33 views)
    • File Type: jpg B.jpg (66.1 KB, 43 views)
    • File Type: jpg C.jpg (46.2 KB, 32 views)
    • File Type: jpg D.jpg (96.2 KB, 23 views)
    • File Type: jpg E.jpg (68.0 KB, 27 views)
    • File Type: jpg F.jpg (71.2 KB, 36 views)

  12. #12
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    don't rule out shipping damage because the packing materials are intact. I've had frames damaged by UPS and the boxes / packing materials looked fine.

    I'd bet that is not how the fork left the builders shop - and if he knew what it looked like now he would run to your house to get it back.

    Why go showing it around a local bike shop? You aren't happy, that is enough - send it back to the builder and he will replace it asap. He'll be glad to do it asap and he could probably tell you what happened to it. The builder won't want that fork floating around bike shops and forums representing his work.

    Again, doubtful it left the shop like that.
    Last edited by GAAP; 08-27-09 at 07:12 AM.

  13. #13
    ihd
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    Quote Originally Posted by GAAP View Post
    don't rule out shipping damage because the packing materials are intact. I've had frames damaged by UPS and the boxes / packing materials looked fine.
    The frameset came in a big, roomy carton, with the frame and fork wrapped in many layers of bubble wrap, and the fork firmly attached to the seat stays. There's some minor denting of the box but nothing that could have impacted upon the fork from an appropriate angle (let alone left no other trace of itself other than the buckling of the fork blades). To bend the blades you'd need to brace the fork against something - the packaging style they use just doesn't allow that.

    I've also spoken to the tube manufacturer, who understand this kind of fault very well and how it hapens, and what they do when it happens to forks in their factory (they throw them away).

    Quote Originally Posted by GAAP View Post
    I'd bet that is not how the fork left the builders shop - and if he knew what it looked like now he would run to your house to get it back.
    A nice notion, but in fact on their business terms I've had to cover the cost of shipping the faulty fork back to them (more on the upshot to this below).

    Quote Originally Posted by GAAP View Post
    Why go showing it around a local bike shop? You aren't happy, that is enough - send it back to the builder and he will replace it asap. He'll be glad to do it asap and he could probably tell you what happened to it. The builder won't want that fork floating around bike shops and forums representing his work.

    Again, doubtful it left the shop like that.
    You seem to be mistaking this framebuilder/manufacturer for one with your own business values. I showed this fork to others more knowlegeable than myself because when I contacted the manufacturer I was greeted with extreme scepticism and the suggestion that I was being overly perfectionist. I had no reference point for how much "uneveness" was allowable for a fork blade, so needed to consult others, in order to avoid paying both for return shipping of the fork to the manufacturer and (if they thought it non-defective) their cost of shipping it back to me. About $50.

    I can understand your empathising with the builder, but I haven't told those bikeshops who built this fork, nor this forum (and boy, did those bikeshops want to know). But since my concern extends to customers as well as framebuilders, I may yet do so. Any business can have an untypically bad day, but when it's indicative of habitual sloppiness, then I think others should know about it, don't you?

    So now for an update to this unedifying tale: upon receiving the returned fork, the manufacturer agreed there was indeed "something wrong" with it, and replaced it with another. Which would been the end of the matter, except that the replacement:

    - has an approximately 2mm fore-aft misalignment of the dropouts,

    - a loose piece of flux rattling around in one of the blades,

    - and is missing the countersink for the recessed brake hole.

    There's a bulge of some sort above the bolt hole (I can't tell without scratching at it whether it's excess paint or how this fork crown was cast), leaving the bolthead flush againt the fork on only one small part of its circumference, which isn't very reassuring. The other fork did at least have that countersink.

    You'd think that with a replacement for a defective item, they'd take a bit of extra care - but clearly, no.

    So I'm now considering taking the fork to another workshop that can at least align the blades, and countersink the brake bolt hole (they obviously won't be able to do anything about the rattling flux), because I despair of ever getting anything "perfect" from this manufacturer (by "perfect" I mean "built with due care and attention").
    Last edited by ihd; 09-01-09 at 11:13 AM.

  14. #14
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    These guys shouldn't be in business anymore. Let us know who it was so we can avoid them. The need to make this perfect for you, and refund your shipping costs *now*.

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    Senior Member PaPa's Avatar
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