Steel 29er Hardtail V2.0- Mtbr.com
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  1. #1
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    Steel 29er Hardtail V2.0

    [Aside: I canít seem to find the catch-all frame building thread that I posted my first build in a couple of months ago. Has it been deleted for some reason? There was a ton of good information in that thread.]


    A couple of months ago I posted my first steel hardtail project, but before I had finished that one I knew I wanted to make a second version of it. The primary motivator was that I wanted much more tire clearance. It also helped that I had learned much about the fabrication process the first go around so I knew I could make it far better the second time. So I went back to the drawing board (or AutoCAD, for that matter), and designed my Hardtail V2.0.


    Here is the geometry:
    HT Angle: 67˚
    ST Angle: 74˚
    Stack: 649mm (inc. headset)
    Reach: 480mm
    Chainstay Length: 425mm
    Front-Center: 788mm
    Wheelbase: 1210mm
    BB Drop: 55mm
    BB Height: 325mm (w/ Ý760mm tires)
    ST Length: 445mm
    HT Length: 110mm (plus 20mm headset)
    Fork Axle-Crown: 537mm (130mm Fox 34)
    Fork Offset: 51mm
    Stem Length: 45mm
    Tire Clearance: 29x2.6Ē
    Max Chainring: 36 tooth
    Saddle Height: 815mm (from center of BB) (I'm 6'2" tall)



    And some highlights of the build:
    Fork: Fox 34 Factory, 130mm travel
    Groupset: SRAM GX Eagle, 32t by 10-50t, 175mm cranks
    Brakes: Shimano XT M8000
    Rotors: 180mm F/R (Custom 140mm flat mount to 180mm post mount adapter for rear)
    Dropper: Brand-X XL 170 x 30.9mm



    I had it powder coated at Premium Powdercoating in Longmont, CO with a Prismatic Powders Illusion Green Ice (PMB 7025) base coat and Clear Vision (PPB 2974) top coat. The color came out really well. Itís a very vibrant metallic green that completely changes in different lighting conditions. In darker, indirect lighting itís almost a dark emerald green but in the direct sunlight itís a much lighter, metallic green. The photos definitely donít do it justice.


    Iíve hardly had a chance to ride this bike yet (just a few dozen miles commuting through the snow to work over the last couple of weeks), but Iím already planning/scheming/designing a full suspension trail bike (think 150/140mm 29er or so) that Iíd like to build over the winter.


    Please feel free to post any comments, questions, or critiques that you have.












  2. #2
    mbtr member
    Reputation: scottzg's Avatar
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    Things i like-

    THE COLOR
    long XC bike geo
    aesthetics of internal cable routing
    smart build kit


    Things i'm curious about-

    weird internal routing; rust?
    detail shot of DS chainstay
    looks like a ton of saddle-bar drop
    dropper routing
    how was working with through axle dropouts

    You got some long legs. Thanks for sharing!
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

  3. #3
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    The internal routing is continuous stainless steel tubing from end to end, silver brazed to the main tube at either end. So for example the rear derailleur cable enters the left side of the head tube, goes through the stainless liner tube until it pops out in front of the BB. It then enters another section of stainless through the chain stay and pops out by the derailleur. These tubes mean that any water running into a cable port stays within the stainless steel until it comes out the bottom. The exception to this is the dropper routing. This tube goes from the right side of the head tube down the length of the down tube, takes a bend up into the seat tube (my seat tube is offset 12 mm so it joins the down tube directly) and ends about 150mm later. This isn't a fully sealed tube, unfortunately, so water could run down along dropper cable and into the frame. I've coated the inside of the seat tube and down tube with frame saver (all the other tubes were sealed completely during welding) and there is a drain hole at the lowest point of the down tube, so I should be fairly safe rust wise. I figured that since the seat tube is never sealed anyways, I wasn't giving too much up with this technique. The other advantage of this internal routing technique is that it is incredibly easy to run the cables. You just stick them in one end and they come out the other! It's faster then zip tying to external guides and looks much cleaner. (I do have a pair of external guides around the chain stay yoke to ensure that the cables stay out of the tire. See the last photo attached below.)

    As for the saddle to bar drop, that what happens when you have long legs and arms. (I'm 6'2" with a +3" ape index and an 815mm saddle height.) My road bike (587mm stack, long -7˚ stem, no spacers) has a massive drop, this hardtail (649mm stack, 5mm spacer, riser bar) feels virtually upright by comparison.

    Working with the through axles was very easy for me, but I also did buy a set of dropouts with integral brake mounts (DR2085 - Steel Flat Mount Dropout Assembly 58 Degrees, No Eyelets, 12 mm Skewer). I turned down a dummy axle on a lathe that bolts to my frame jig and the dropouts bolt to that. I've attached a rather poor photo that hopefully makes it a little clearer how I did it.





    Dummy rear axle.


    Photo from my first frame (V1.0, blue, last summer) showing how the dummy axle works.


    Mostly completed (V2.0, green) frame in jig.


    The only halfway decent shot that I have on hand of the chainstays.
    Last edited by CallumRD1; 11-18-2018 at 04:14 PM. Reason: Added photos

  4. #4
    WIGGLER
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    Cool bike Nice fixture!!
    PAYASO 36er.....Live the Circus

    MR. 36er TROLL

    I'm sorry what part of "BIGLY" didn't you understand?

  5. #5
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    Dang. Nice work, that color is killer! Looks like a solid build, good job. I also like the fixture you came up with, it's a very rigid looking setup for how much material you used. Also, that wood drawer cabinet in the background of the last couple pics is beautiful!

    Nice work. What do you want to build next?
    Myth Cycles handbuilt bike frames
    Durango, CO
    http://www.mythcycles.com

  6. #6
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    How does it ride with that chainstay yoke? Does it make the ride noticeably harsher?
    _

  7. #7
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    ...Does it seem like this forum is more active and positive than usual?

    I'm not complaining! It just seems like people are kickin butt lately, and here's another one
    Disclaimer: I run Regular Cycles (officialy in 2016, functionally in 2020).

  8. #8
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    Quote Originally Posted by uphiller View Post
    How does it ride with that chainstay yoke? Does it make the ride noticeably harsher?
    I haven't ridden it much yet but I can't say that it feels any harsher. In fact it feels much more comfortable, likely because I went from a 2.1-2.2" rear tire to a 2.5" tire. And I feel that I can drop the pressure even more from where it is now. I'm fairly confident that any stiffness difference there would be dwarfed by the compliance contribution of the tires.



    Quote Originally Posted by Erichimedes View Post
    Dang. Nice work, that color is killer! Looks like a solid build, good job. I also like the fixture you came up with, it's a very rigid looking setup for how much material you used. Also, that wood drawer cabinet in the background of the last couple pics is beautiful!

    Nice work. What do you want to build next?
    Thanks! The wood tool chest I built last winter both in a desire to do a big woodworking project and because I really needed some proper tool storage! It's pretty much full at this point, though.

    The plan for this winter (although I haven't purchased anything yet, this is just stewing in the back of my brain at the moment) is to build a full suspension 29er trail bike. I threw together a quick mock-up of what I had in mind with Linkage and it doesn't look like it would perform too poorly. The design will take some tweaking, and then a bunch of time thinking about how to do the pivots properly, but it seems like it would be a great project. I've attached a couple of drawings below. (The top of the seat tube in the drawings is at my saddle height.)

    Any critique/input on this design would be more than welcome. I'm working quite a bit beyond my knowledge base designing a full suspension bike as I haven't spent very much time riding them.

    Current mock up geometry:

    Front travel: 160mm
    Fork axle-crown: 567mm (Fox 36, 160mm)
    Rear travel: 140mm
    Shock stroke: 61.4mm
    Stack: 641mm
    Reach: 480mm
    Head tube angle: 65.5˚
    Head tube length: 110mm (+20mm headset)
    Seat tube angle: 76˚(Effective, at my saddle height of 815mm)
    Chain stay length: 435mm
    BB height: 350mm
    BB drop: 25mm


    Unsagged, 160/140mm mockup


    Full droop, 160/140mm mockup

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