Frame #2 - 160mm FS 29er- Mtbr.com
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  1. #1
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    Frame #2 - 160mm FS 29er

    And frame #2 is done! This time around, I went for a full suspension bike.

    I wanted a high-pivot bike and I wanted to keep it single pivot to simplify maintenance. As it ended up, it's basically a single pivot, but with pullrods to reduce the shock's effective eye-to-eye length in order to be able to package it (kinda) vertically. This only adds 2 additional bearings, bringing the total up to 4 (plus 1 shock bushing, at the lower mount), so the bearing count is still low compared to other designs.

    I designed the kinematics using a homemade spreadsheet, aiming for 100% AS, or a little over, around the sag point in the larger cogs. I was also aiming for as linear a motion ratio as possible ( I ended up with about 6% variation over the whole range).

    The frame is chromoly for both front and rear triangles. I'm not super good at documenting what I do, but I do have a few pics of the build process which I included below.

    Specs:
    ~63 HTA
    ~77 STA
    450mm reach
    ~350mm BB height
    435mm chainstays
    160mm F/R
    Attached Thumbnails Attached Thumbnails Frame #2 - 160mm FS 29er-2019-04-24-15.46.46.jpg  

    Frame #2 - 160mm FS 29er-kinematics.png  

    Frame #2 - 160mm FS 29er-2019-03-02-12.02.10.jpg  

    Frame #2 - 160mm FS 29er-2019-04-11-17.29.37.jpg  

    Frame #2 - 160mm FS 29er-2019-04-19-15.41.11.jpg  

    Frame #2 - 160mm FS 29er-2019-04-19-16.35.42.jpg  


  2. #2
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    That's rad. Would love to see a video of the suspension cycling. I can't wrap my head around how the pull rods go without a rocker link.

  3. #3
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    It's neat to see the idler bikes coming back into fashion. I thought I wouldn't see that design again as of 20 years ago, but it's back!

    Great work!

    -Walt

  4. #4
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    Thanks Walt! It's appreciated.

    Shirk, here's a video of the suspension cycling:

    https://youtu.be/jfdUyta0xNA

    Basically, the pullrods don't move relative to the shock. They're bolted directly together up top at the trunnion mount, and there's a bearing at the lower end where the pullrods connect to the rear triangle.

  5. #5
    will rant for food
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    Too cool!
    Disclaimer: I run Regular Cycles (as of 2016). As a profiteer of the bicycle industry, I am not to be taken very seriously.

  6. #6
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    Awesome Build! I want to make a high idler bike for my next build. I used a similar method for the front triangle jig, seems to be a easy and inexpensive way to build a jig. Let us know how it rides!

  7. #7
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    Yeah the front triangle jig worked super well and was really easy to make.

    I took the bike out to Highland & Burke, as well as a couple of days in local trails, and I'm super happy with how it turned out. The high-pivot rear end and the super slack front make it a real tank, it just wants to plow through everything. Surprisingly, it climbs pretty well; the steep STA keeps weight on my front wheel. I'd even say it's an overall better climber than my old bike, a 2014 Devinci Atlas. Although I can definitely feel the extra drivetrain friction, the slower handling makes it easier to point the bike where I want it to go, and I haven't had any issues with wheel flop. I'm super happy with it so far!

  8. #8
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    Damn that's a cool build. Way to go.

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