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Thread: Vari-wall order

  1. #1
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    Vari-wall order

    I got some tubes from vari-wall for the current frame build. Pricing was competitive/cheaper than other suppliers with similarly appropriate tubes. Pretty psyched with the product- the finish is the best i've seen (according to my totally untrained eye), and each tube was individually plastic bagged with a moisture removal packet with the tube spec on a sticker on the outside. I wasn't able to spot the high spot by rolling the tubes on a surface plate, had to use a tool. I'll definitely order from them again.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

  2. #2
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    I agree, I've had a fantastic experience with them so far. Definitely know their stuff and provide a great product. I don't think we lost much when TT went away, we really gained a better supplier in the end.

    Anyway, +1 from me.
    Myth Cycles handbuilt bike frames
    Durango, CO
    http://www.mythcycles.com

  3. #3
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    Do people really roll tubes to find the high spots? I always thought that was a joke.

    On topic: Vari-wall makes great stuff.

    -Walt

  4. #4
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    Quote Originally Posted by Walt View Post
    Do people really roll tubes to find the high spots? I always thought that was a joke.
    I do what i'm told. It only takes a moment, and it's interesting how much straighter some tubes are than others.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

  5. #5
    pvd
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    I look for the spine of tubes. I feel it is useful to align the miters to the existing bend in the tube. Some tubes are far worse than others.

  6. #6
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    Quote Originally Posted by Walt View Post
    Do people really roll tubes to find the high spots? I always thought that was a joke.
    Two v-blocks and an indicator to find the high spot. That becomes the tube centerline always oriented with the vertical plane. If it's up or down depends on which tube it is and it's purpose in the mix.

  7. #7
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    Huh. I have never bothered. If a tube is straight visually, it's straight enough for me. And I've never seen one that was visually bent.

    Seems like extra work for nothing. I just find the butts, weigh the tube to make sure it's to spec, and go.

    But to each their own.

    -Walt

  8. #8
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    I fit into the Walt camp of thought. It does not matter if you find a millimetre. Try and straighten a tube? Don't go there. Use the PVD method. Make sure it's axis is vertical, you will never notice.
    The tubes are drawn out in straight mandrels so there should not be really huge differences in a round tube. With Butted tubes, because they are actually stretched in the butting process the potential for a slight 'bend' is possible. Aero/oval tubes are another story though.

    Eric
    If I don't make an attempt, how will I know if it will work?

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    Honest question: if the axis wasn't vertical, and the tube was out by, say, a millimeter, would anyone be able to tell when riding the bike (or when looking at it)?

    It seems like one of those traditions like spending a bunch of time buying a surface plate ground to .001" and using a dial indicator to check alignment - when your shell is only faced to +/- .005" or something and that error translates to 35 times that amount at the head tube. Might be satisfying, but a waste of time.

    On the other hand, I meet (professional, sometimes) builders regularly who either don't check butts (they are out of spec all the time!) or don't weigh the tubes to make sure they're at least close to spec. Or they don't do *either* one. I know people (cough, cough, me) who didn't check butts and had stuff break because the butts weren't where the spec sheet said.

    -Walt

  10. #10
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    I was told to do it because you don't want the tube to distort out of plane when you weld. As a mediocre metalworker I'll take every precaution I can.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

  11. #11
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    Why would the tube distort out of plane when you weld it (assuming you weld it in some sort of competent manner/decent sequence)?

    It's the *middle of the tube* that you're measuring the bow at. Weld heat gets nowhere near it.

    Seriously, that makes zero sense. When I build a bike with a curved toptube or downtube (VERY curved ones) I don't end up with a different head tube or seat tube angle than I was going for because the bend somehow increased (or decreased) after I welded it in. The bend is totally unaffected by me welding the tube in.

    That said, it's not hurting anything to orient the tubes however you want.

    -Walt

  12. #12
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    I figured it out, I think.

    This is a holdover from building lugged bikes. If you've got a bowed tube with a lug bike, there's a decent chance you'll create a bit larger gap on one side of the lug than the other, when you fit the tubes into the lugs. When you go to flow silver through, that side will probably pull a bit more than the other, and potentially pull your frame out of alignment.

    Combine that with much crappier tubes available 100 years ago, and you've got the formula for a once-useful tradition to be handed down from builder to builder after it's long lost it's usefulness.

    That's the best I've got.

    -Walt

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    I'm also with Walt here, I aligned the tube's spine vertically for my first couple frames and haven't done it since. My reasoning is that my frame jig references the parts of the frame that the main tubes attach to, not the main tubes themselves. So as long as my jig is keeping the HT and ST in line with eachother, and perpendicular to the BB, who cares if the TT takes a slight arc to get between them? It's only a visual benefit, IMO and if your eye can notice a TT arcing .003" or .005" out of straight, then congratulations, you're a human straight edge.

    I think it mattered a lot more when frame jigs held on to the TT and DT themselves instead of the HT and ST. In that case, a tube bowing left or right could cause the HT to be way more out of whack. Like Walt said, a holdover from days of yore.

    Also, I check where the butts are on every tube I build with. They're not in the right place way more often than one would think.
    Myth Cycles handbuilt bike frames
    Durango, CO
    http://www.mythcycles.com

  14. #14
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    Finding the bow and orienting it complementary to the design is just part of my process. No one told me to do it. Using an indicator to find the high spot is just the easiest way for me to locate where my centerline goes, the actual measurement means nothing. For measuring butts I hold the tube up to a light and sight down the ID with a filler rod to transfer measurement and run it up against the published specs, so there's that.

    I get the argument going the other way, too and don't believe that the tube's bow orientation dictates any sort of noticeable or measurable ride characteristic. However, I'll dig deep and throw these out there; Building a frame with a focus on standover concerns... why not locate the top tube bow downward? Rider has issues with close knee stance... why not locate the top tube bow vertical to avoid possible interference to one side? Bending/rolling a tube radius... why not orient the bow with the arc to get ahead of the game? Late night and your mitering game is getting sloppy... why not orient the bow with the spindle plane to keep the cuts closer to tube cl? Yes, I see how these examples are relative "non-issues" and could have alternative arguments to why they could be entirely avoided with some other consideration.

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    Dude, we're talking like a few thousandths of bow, though. Your knees/crotch aren't going to get saved by .010" to one side or the other or up/down. The bows we're talking about are thinner than the paint on the tubes!

    As for mitering, unless you're holding the middle of the tube and mitering the end or something weird like that, bow is absolutely meaningless. Even the burliest milling machine on the planet running $200 Strawberry cutters isn't going to cut that perfectly on center anyway. Hell, my centering system consists of a piece of tape on the X axis of my mill. Just line it up by eyeball and start mitering. It's probably off by 20 thou or more one direction or another every time I set it up after tramming back from another station.

    I think Eric's idea might make more sense than mine. It would indeed cause problems if you were holding the toptube/downtube instead of the BB shell/head tube/seat tube like most modern jigs do. There was a lot of jigless building happening back in the day, too, and I could see it saving some effort there.

    -Walt

  16. #16
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    Walt, you are right on all points. Lugs did pose this problem. I don't think it's a big deal. A slight bow is what? I have seen frames with cable guides brazed on the top tube that look really bad as they sunk into the tube a little, causing the tube to bow.

    Eric
    If I don't make an attempt, how will I know if it will work?

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    Most of the Supertherm tubes are bowed by ~1mm. Some by more than that. It takes a few seconds to look at the tube on a flat surface and draw a center line on the tube.

    The Vari wall ones are much straighter, but I'd still take the few seconds to avoid a huge mistake.

    A frame's "compliance" is elasticity. In this way, a frame is like a big spring. How the tubes are oriented could affect how a frame acts under load.

  18. #18
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    I'd bet a large amount of money (in effect, I already have, since I've sold ~700 frames without doing anything to find the bow in the tubes) that you could not detect any difference (either riding, or looking at the bike) in a 1mm bowed tube, no matter how you oriented it.

    But as I said before, a lot of this process is about what is satisfying *to you*. It's not hurting anything to check.

    -Walt

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