(MBBO#05 Class 2) Flashback GT - Done!

Discussion in 'MBBO 2016 BIKES' started by tjwilson, Sep 7, 2016.

  1. tjwilson

    tjwilson Pro Member

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    Thanks, that's quite a compliment.
     
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  2. tjwilson

    tjwilson Pro Member

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    Thanks.

    To be honest I've been so concerned about the strength up and down that I haven't really considered side to side forces. It seems like that is were there might be an issue with the dimpled tubes. Not sure, I'm not an engineer and am just building by best guess. True though that dimpling of tubes for clearance on factory frames are (always?) horizontal along the tube instead of vertical? Once I have the frame complete I plan to take some measurements and run the bike through a few cautious test rides. I'll remeasure to see where and if there is any movement and then if required plan additional reinforcements. The good thing is that there is plenty of room on the inside of the stays to add material. The bad thing, it could potentially be a very short test ride!
     
  3. pholTmonx

    pholTmonx

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    After the rest of bars are there I'm sure you'll be able to even torque test it to see with the clearances u have going on :).
    I just checked my cranbrook.. the seat stays have no dimples... They are carrying the weight and load to the rear axle, top brace is a bit past the dimples of the chain stay.... In your case it's more like a fixed swing arm as far as how load will transfer.
     
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  4. tjwilson

    tjwilson Pro Member

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    Latest progress, bending the side stays. Symmetry is hard! They ended up closer to each other than the image of the tubing in the bender would indicate... close enough anyway. I added a plug to one end, packed the tubes with sand, plugged the other end, and welded the tubes together. Then I ran the twin tubes through the bender. (Probably important to note that I made sure that the plugs didn't seal the ends completely. This prevented pressure from building up in the tubes as they were welded.)

    tubingBenderAndSides.jpg

    Bottom end reinforcement. I'll weld this in place after cleaning up the previous welds.

    bottomEndReinforcement01.jpg

    bottomEndReinforcement02.jpg

    bottomEndReinforcement03.jpg

    Side stays in-process and in position. I plan to make some adjustments. The rear end of the side stays will be trimmed and the sides rotated a bit. The upper ends will be trimmed and tube extensions added to follow what will be the bottom edge of the seat. I'm also thinking of tapering the tube from 3/4" to 1/2" along that edge and shortening the seat length a bit. These are the handlebars that are the winning choice... so far.

    rear3qtrDetail.jpg

    rear3qtr.jpg

    frnt3qtr.jpg

    sideNonDrive.jpg

    sideDrive.jpg
     
  5. OneHorsePower

    OneHorsePower

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    Sick!!:rockout::41:
     
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  6. assa9

    assa9

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    Love the flow of this bicycle it is unique for sure. Looks nimble
     
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  7. pholTmonx

    pholTmonx

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    And there it is... Awsome..
     
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  8. LukeTheJoker

    LukeTheJoker Moderator

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    Love those curves!

    Luke.
     
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  9. GuitarlCarl

    GuitarlCarl

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    update update update...

    Carl.

    sent from a crowded phonebooth...
     
  10. tjwilson

    tjwilson Pro Member

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    Hey Carl...

    Not a lot to update, was out of town this past weekend. Did get a start on prepping some of the pieces that will probably make their way into the side / seat stays. Also worked up a digital mock-up to experiment with how much I want to shorten the seat and refine how the seat flows into the side stays.

    Here's a pict of the pieces and parts. The tapered pieces are donor chain stays, .75" to .5". Really thick wall, .120" x .5", tubing was used for the tight bends. These will be for the back of the seat, maybe. Might try for a tighter radius. The two longer bent pieces are .049" x .5". These were filled with sand, plugged, welded together, and sent through the bender.

    seatStayPieces.jpg

    This side view has the pieces in approximate position. For comparison the left side shows the pieces in mock-up, right shows the existing frame end digitally removed and the intended seat profile added.

    seatShorten.jpg

    No picts but, pulled everything apart last night and cleaned up the welds that will be hard to get to once the side stays and bottom brace are welded on. I've got time set aside this coming weekend so hopefully there will be more to show soon.
     
  11. OneHorsePower

    OneHorsePower

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    Really nice frame! i love how the seat flow with the top tube and there is nothing under it , makes it look light and fast :113:
     
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  12. kingfish254

    kingfish254 CHECK OUT MY SALE THREAD FOR COOL STUFF! Pro Member

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    WOW!!! What a curvy work of art!!!
    It's so surreal it is sorta like a Salvador Dali build!
     
  13. LukeTheJoker

    LukeTheJoker Moderator

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    Looking awesome!

    Luke.
     
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  14. OddJob

    OddJob

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    Yep. All it needs are wheels like these.... daliwheels.jpg
     
  15. LukeTheJoker

    LukeTheJoker Moderator

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    I think I have some like that in my parts pile...

    Luke.
     
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  16. tjwilson

    tjwilson Pro Member

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    Flashback -> Daliesque -> "Persistance of Memory"
    Oh how I wish I could say that was intentional.

    ... tacos!
     
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  17. tjwilson

    tjwilson Pro Member

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    A little weld clean up. Most of the tubing is relatively thin .049" wall so I was a little concerned about doing too much smoothing. Just enough to keep the filler from having to be too thick.

    weldCleanup01.jpg

    weldCleanup02.jpg

    Most of the weekend was spent working on the seat/side stays. I started by making a cardboard template to find the angle of the curved sides extending back to the end of the seat. Then I tacked the pieces and parts previously bent together using the template as reference.

    seat01.jpg

    seat02.jpg

    seat03.jpg

    seat04.jpg

    seat05.jpg

    seat06.jpg

    seat07.jpg

    The sides were trimmed and solid rod inserts were used between the sides and the new seat base.

    seat08.jpg

    seat09.jpg

    seat10.jpg

    sideview10172016.jpg

    The frame backbone was trimmed and new pieces bent and cut to tie the end of the seat to the frame.

    seat11.jpg

    Next up will be final welding the tacks!
     
  18. OddJob

    OddJob

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    I like that shot between the handlebars. Symmetry.....
     
  19. assa9

    assa9

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    That's one smooth looking beast. Looks quick even when still. Excellent design
     
  20. QUEASY RIDER

    QUEASY RIDER

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    Excellent metalwork sir!


    Sent from my iPad using Tapatalk
     

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