Fork #2 done

The first adjustable-rake fork is done!  I haven’t put in tension screws yet since the track SS dropouts are narrower (7mm) than the sliders (9mm) which have the same 4mm bolt tapped into them that I was gonna try and put in the track drops.  If I try it, I’ll have to go with a smaller bolt to thread in there. Alternatively, I could just make sure i space the wheel right and crank on the quick-release so that it stays put.

I put an ISO disc tab on it just in case there’s enough room on the pads when the wheel goes back and forward a couple of cm’s.

I don’t see using this fork a ton, just for experimenting on myself.  The fork ended up being longer crown to axle than I had wanted but it’s a good length to have for the 29er (470mm). Everyone’s told me to NOT go over 470 since you make a bigger lever to work against the downtube and possible crimple the frame. In addition, the fork is just weaker with that much length. I’ve never seen a fork crimple a frame, or a rigid fork even crack (except for a Chinese Ti Spicer fork…), but I’ll take their word on it…they have many years of experience and I don’t need to fall on my face more than I already do.

The next fork I build will be more around the 435mm length and be more of the 5-piece or ‘segmented’ type. (Yo Eddy!).

The welds turned out OK, not great, but I feel like the 1st pass turned out better than last time. So, even though the 2nd pass isn’t really pretty, I think there’s better penetration overall and it’ll be a stronger fork. I am finding it hard to figure out the right amps to use on all the different combinations of tube thicknesses, especially when using the pulser.  I think that reason right there is why I may just plain stop using the pulser and either ‘self-pulse’ using the footpedal or not pulse at all even for a second pass.  For me, i feel like I’m giving up control when I turn the pulser on and letting it go on auto-pilot.  The bead looks better, but I can learn to do that without the machine’s help, and my practice welds today are looking up.

I TIG’d, then brazed the upper part of the crown race seat, just for fun.  Overkill, but it’s good practice. This was my 3rd brazing job using silver and flux from Henry James.  I finally got my little bottles (that I’ve had for over 4 years now) set up with a smaller torch (Victor J-28) and smaller/lighter hoses from Smith. It’s a sweet lightweight lil setup that feels really comfortable to use, at least for sliver brazing.  I’ve never brazed with brass so maybe i’ll need more power for that (?).  I did some practice runs before on 1″ tubing and some cable stops.  The ‘feel’ of brazing isn’t with me yet, i’m not even close to recognizing the heat indicators of when exactly to put in the brazing rod.  It’s easy to read in books and online that you add silver when the flux bubbles are about to pop and before the metal turns red, but there’s not much room in between those times to work with.  I’m sure more experience with the torch will have me laughing at this post and my early brazing jobs!  Now I just have to braze on the slotted dropouts on the frame before I get the tig torch out and the first frame.  I’m obviously stalling on welding the first frame together until my practice welds are looking better…

I have made a condition with myself that I must finish this first frame before I ride a mountain bike this season.  The snow is still covering most of the trails here at 8,400ft  in Colorado (but not all i hear), but I still can’t wait to build this thing up and give it a test drive!!

Safety notes:

(1) crack the garage door while brazing and wear a respirator!

(2) Don’t pick up your work piece right after welding it (duh!). After welding the disc tab on, I pulled off one of the stupidest maneuvers yet. I wanted to get to soaking the flux off so I picked up the fork right after finishing the bead, took my leather welding gloves off, and grabbed the fork leg with my left hand.  I got the fork a bit (too) hot while putting on the disc tab so it burned, pretty bad. First degree at most but it STUNG the entire night unless I put it in a bucket of cold water or held something cold.  I learned that a beer makes a great ice pack for your hand. For the rest of the night, I had to hold a cold beer to stop the stinging. After two beers (Lagunitas Lil Somethin & a TenFidy) I grabbed some advil and Neosporin and went to bed.

6 Responses

  1. nice!
    phrootah is 3 weeks away. you better weld that damned frame soon.

  2. Yes they could break if you go over 470mm . The Pine Mtn with ridgid forks got a 500mm axle to top crown & 470 under the little bridge.
    Go and look at :

    • Thanks for sharing that, i hadn’t heard! I’m wondering what they did to change the fork for the replacement. I don’t think it’s right to say the bending and breaking was due to the length alone but apparently something to do with the brake boss attachment point (stress riser on too thin fork blade tubing?). I can’t find any more info on what they did since they replaced the fork with another rigid of the same dimensions so it’s obviously not a length worry but something that was done wrong with the fabrication of the first version.
      I was under the impression when i was writing this blog post many years ago that the length of the fork limitation by some builders was due to worry about FRAME failure not fork failures since you can overbuild the fork to not break but it could put undue stress on the frame and there have been some frames that have split open when forks were installed that were not intended to be used on the frame.

  3. ” what they did since ” I just believe they took some heavier gauge steel everywhere . I say that cause I have just bought and dismantle a brand new XXL left over ’17 Pine-Mtn to put some frame saver in it and the fork alone weighs as much as the frame , not kidding . I think most suspension fork should weigh less than this rigid one . I find your blog cause I ‘m looking not necessarily for a lighter one but for adjustability . I want something who can handle my road 700cc wheel ( … or 29” ) . The distance between the 2 dropouts of this heavyweighs forks is 110 mm . Nobody seem to have experiment with adjustable width front drop -out ? But their 110 spacing seem close to road standard of 100mm . The Pine-Mtn got the weird QR 110mm front hub and rear 141×9 mm QR ” boost” , socal ” standard” . Also , I want some removable post for canti . Previously , I looking at Walty Ti for this kind of fork .. but I’m not sure with this chineese co to get what I want . Tks , Pierre …some indulgence with my bad english lol

  4. Hi Pierre,
    Glad they beefed up the fork blades! But yeah…that sounds heavy! 🙂
    At least it won’t break! lol.

    I am not aware of any adjustable front dropouts for forks but do know a couple companies that make swappable end caps for wheels to go from standard 100mm spacing to the new Boost spacing (110mm). I read about the weird Marin front Boost QR and not sure what to say about why they did that.

    MRP and Wolftooth both make the end caps to go between the two sizes for both front and rear wheels. But it’s not exactly what you were wanting since you have to swap the end caps on the wheels not the fork.

    Hope that helps…

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