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  1. #1
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    Frame Prep and Powder Coat

    I am just finishing up my first frame. TIG welded 4130 CroMo. All thats left are the small braze ons and slotting the seat tube. Leading to my questions....

    1) Should I have the seat tube reamed before I slot it? My concern is the tube reamer/cutter catching on the slotted edge, and the tube is only .6mm in that area.

    2) I'm taking it to Class Act for Powder here in Portland, OR. I am going to have to take it to a bike shop for proper chasing/facing/reaming. Logic tells me to prep the frame before paint, but it would also be good after paint to get overspray off the faced areas.

    3) Lastly, has anyone had experiences where the baking process in powder coating relaxed the stresses in the steel and warped the frame out of alignment? I don't know much about the powder coating process, not worried much if it's only baking for 15-20 mins.

    Anyone who chimes in is a saint. Thanks for input.

  2. #2
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    Hi Drew -

    Saint me! Or buy me a beer if you're in SLC (the land of the latter-day saints, no less!)

    1. Slot, then ream. Slotting after reaming will just mean you have to run the reamer through again to get rid of the burrs from slotting.

    1A. If your seat tube is .6mm at the top and you have not sleeved/lugged it somehow you should not waste your money on a powdercoat, because it is going to come apart pretty fast. For TIG 1.2mm or so is the minimum wall thickness that will last at that ST/TT/SS cluster area. If you've got a sleeve on there, you're good.

    2. You will have to re-do all your ream/face/chase work after the powdercoat anyway so just do it afterwards.

    3. The powdercoating will not affect the 4130 in any meaningful way, if the frame is in some kind of alignment now it'll stay that way.

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  3. #3
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    Thanks Walt! What do you mean by the powdercoat not lasting on thin wall tubing? To clarify, this is a road bike frame so it's not going to see the abuse that my mountain bike sees. I also did not add a sleeve or lug, but it's not too late. I have about 20mm from the top of the top tube, to the top of the seat tube. Plenty of meat to braze in a sleeve.

  4. #4
    Nemophilist
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    No...

    He meant the FRAME won't last without a ST sleeve, so putting a finish on it is a waste of money. .023" is pretty darn thin, especially for the business end of a tube. Unless you weigh a 100lbs, I'd be nervous about that. Unless it's an exercise bike....
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  5. #5
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    Yes, that's what I meant. We may be misunderstanding you but here's my guess as to what happened:
    -When you went to buy tubes, you picked a tube you liked that was listed as a seat tube. It was probably single-butted .9/.6.
    -You correctly figured out that the thick part went at the bottom, so you left the thin part at the top.

    What you did not know (and could not have) was that those tubes are intended for lugged frames, so the entire seat tube/toptube/seat stay cluster joins the lug, which fits over and reinforces the .6mm top of the seat tube. If you build with fillet or TIG, you can still use those seat tubes, but only by making a sleeve (faux lug) of your own to join your seatstays and toptube to. The .6mm wall is otherwise much too weak to deal with the forces involved (the usual failure mode is for the seatstays to try to push through and crack the back of the seat tube) and the frame will crack quickly.

    I actually would be surprised if you can even ream the seat tube, there is probably insane distortion.

    So unless I've misunderstood, this first frame is unfortunately basically garbage/wall art.

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  6. #6
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    Quote Originally Posted by Walt View Post
    So unless I've misunderstood, this first frame is unfortunately basically garbage/wall art.

    -Walt
    Well, he could cut out the top tube, clean the ST up and sleeve it, put a new TT back in it. But yes, baring doing any of that, talking finishing at this point is a waste of time and money.

  7. #7
    Randomhead
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    you could ride it bare and see what happens

  8. #8
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    OK;

    This is going to sound crazy to some, but it might be effective, and salvage a lot of work on a personally valuable piece. Why could you not make a split sleeve to reinforce the area? Get the proper size sleeve material. Cut to length, then spit it in half. Miter the halves to fit around the existing nested tubes. TIG the tube joints and the split seams, then silver or braze the ends of the "sleeve."

    Do I think this is something that everyone should seek to do? Obviously not. Like I said, it sounds crazy, and I can hear the eyes rolling around their sockets as they read this. It would be a ton of fiddly work. However, a first frame is a ton of work already to this point. A pro building lots of frames would just slap himself upside da head and chuck it in the scrap bin, but chucking it now would "hurt" most hobby builders. If you're ornery like me, take the opportunity to give this a go. It's not ideal, but it will be great practice, and it will make for an interesting story if you do a nice job.
    Most people ply the Well Trodden Path. A few seek a different way, and leave a Trail behind.
    - John Hajny, a.k.a. TrailMaker

  9. #9
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    Quote Originally Posted by unterhausen View Post
    you could ride it bare and see what happens
    That's what I would do. I didn't powder or paint anything until #7. #1 is still raw and somehow it's still in one piece, who knows if anything for sure will break.

  10. #10
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    Rattle can it, ride it, retire it when you find the first cracks.

  11. #11
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    I have done this and it will work. It is WAY more effort than it sounds like, though. Plus if the seat tube is distorted enough it'll be impossible to fit all the puzzle pieces together around the cluster.

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  12. #12
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    Damn, thanks everyone. Walt, you nailed the scenario. I bought a cheap NOVA road tubeset to make my first frame. I'm a TIG welder by trade, so I am pretty good with heat control, but you are correct; The top of the ST ovaled a small bit. One way measures 28.9, the other way measures 28.5

    I'm not looking into fixing the frame, it was a $100 investment and learning experience, and I loved every minute of building this bike. And will look forward to building the next one. Now that I've got the sequence, and the know how, I'm going to spring for some True Temper tubing and make it right with an external butted ST.

    One more question, are there any other tubes I should be concerned about? The main tubes I was planning on using are double butted, .8/.5/.8 and chainstay/seatstay 1.1 on dropout side and .7 on other side with Paragon hooded dropouts. I will admit that welding .7mm seatstay to .6mm seat tube was harsh. I was running 15-20 amps and pulsing with my foot to keep the heat lower.

    The ultimate plan is to ride this cheap steel bike (I love steel) and see how the geometry fits me. If it's all good, eventually I'll replicate the bike with stainless or TI and swap over my components to the new frame.

    Again, thank you everyone!

  13. #13
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    You'll look back and laugh and your next bike will be way, way better because of this (plus all the other stuff you learned while building it).

    On tubes, you can do some searches and find lots of recommendations, but I always tell people to just use 9/6/9 for everything (TT "Verus" series is usually drawn to that thickness, call the fine folks at Henry James) and forget about weight. Don't try to build your dream bike on the first try and get the cheapest and thickest butted tubes you can find because that'll make mistakes cheap and mitering/welding easy.

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  14. #14
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    Good conclusion, put it together, sort out the geometry, deal with area's needing addressing, build another with corrections done. Not too much money spent. You will enjoy the 2nd one better. If you were brazing, thinner tubing would not have bothered me, but Tig has the need for practice. You could cut this one up for practice and weld segments of the thin wall, eg .8 to .8 on some, .5 for others and tune your Tig into it.

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

  15. #15
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    Here's a seat tube that work's well for tig, they have different lengths too.
    28.6 EXTERNAL BUTT SEAT TUBE 1.2/0.6/0.9 x 520 :: EXTERNAL BUTT SEAT TUBES :: ROUND TUBES :: MAIN TUBES :: TUBES STEEL :: Nova Cycles Supply Inc.
    cheers
    andy walker

  16. #16
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    Could he use one of the Paragon 304 stainless machined collars and insert that to the tube? I've welded stainless to steel in the past in other applications and worked well. I didn't see any steel collars on their site. If not using a ex butted tube, is there a source for these press in collars in steel?
    Andy
    Blitz Cycleworks
    Green Bay, WI
    www.blitzcycleworks.com

  17. #17
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    That won't work, as the ID of the seat tube (~27.2) is the same as the ID of the collars Paragon sells. Those are intended to insert into 31.8mm OD seat tubes.

    You *could* make a plug for a 25.4 post (Thomson makes one that size) and press/braze it in. But it will probably still crack.

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  18. #18
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    Thanks everyone for your suggestions. I got my new tubeset (columbus zona 8/5/8) and I've already begun the build. I don't think I need practice with the welding, I got that on lockdown. It's what I do 50-80 hours per week. But the advice on tube selection is greatly appreciated.

    Frame Prep and Powder Coat-img_0826.jpg

  19. #19
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    Are you just going circumferentially all the way around the tube? Because just FYI, you should be doing it in quarters and alternating sides to minimize alignment problems.

    IMO Zona is a very expensive form of 4130 - that stuff is scary soft when you miter it.

    Welding obviously looks good - glad to see the first setback hasn't discouraged you!

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  20. #20
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    Hey again Walt. I am welding in quarters. I like to think of it like tightening lug nuts on a car wheel. I don't place my tacks on centerlines (12, 3, 6, and 9 o'clock), but rather at 2, 4, 8, and 10ish then connect the tacks. Weld across the front centerline first, then the back centerline, then the sides. You cannot see it because of the light glare, but there is a tie-in right where the glare is. Likewise, a restart in the same spot on the left side of the photo.

    The zona set was actually pretty affordable ($130) for the set, plus the external butted seat tube ($25). The tolerances for wall thickness are a bit more sloppy than the previous Nova set I had, but the Columbus welds much cleaner.

    I actually had some Nova tubing that had such a bad warp in the end of the tube, you could lay it on a table, roll it, and watch the end bounce about .25", like a warped pool stick. I'd still like to try some True Temper, that will probably be my 29er tubing.

    Lastly, Walt, I didn't realize until just now that you are Walt from Waltworks. I just noticed it in your signature below your postings. I've been following your blogs for a while now, gaining advice and drooling over your builds. Cheers.

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