Lugged fork crowns – take 2

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My first two lugged crown forks are done.  I finished the smaller cyclocross fork a week or so ago but just wasn’t too inspired to blog about it since it was…just OK.  Not sure what I expect for my first lugged fork but I’m just focused on fatbike stuff right now.  The first fork was built to use on a standard cross bike – 395mm axle to crown, 46mm rake, and uses a Nova crown without any built-in offset, so I had to bend the legs to get the 44mm of rake with my oak fork blade bender from Nicola Cycles.  It works great, but I ‘used’ a few blades getting used to it.  The hard part is not varying the bend from the vertical plane — not bending it out AND down while pulling on the fork blade.  The result – if you do end up not pulling straight down on the fork blade – is that you get a fork blade that can be set to the right rake but bows out or in after you braze it into the fork crown.  I got the 1st fork pretty straight with no noticeable ‘drift’ in the blades.

My 2nd lugged fork crown was built for my next frame, a monster-cross with disc brakes. It also didn’t have any offset built into the crown so I had to bend the legs as well.  I honestly have a preference for straight-blade forks for some reason, but there are very few fork crowns with offset built in.  I’m considering using an endmill to introduce some offset into the steerer tube slot but not sure how safe that is…anyone?  Anyways, I made the fork as long as possible but not as long as I want. There are not many options for fork blades that fit into lugged crowns. In fact, they only come in one length.  I used plate-style dropouts so to not cut any off the tips of the fork blades off for the beefier plug-style dropouts (although I could’ve cut the plug off and TIG’d them on i guess…).  There are some plug-style dropouts that fit into the smaller diameter tips of the fork blades, but not the dropouts I’d want to use for a MCX bike (small, light, and no eyelets for a rack or fenders).  Using these beefy double-eyelet Paragon dropouts, I was able to get 420mm axle to crown to help fit fat tires (2.25’s fit fine and I could probably fit 2.4’s even).  This fork crown is pretty huge, more of a MTB fork than a MCX fork but it was on sale and I gotta practice my lug brazing on cheaper lugs.  The hard part of lugs is not knowing (when you’re a novice) how much silver is getting to where it’s supposed to go.  I ended up over-heating the crown and having the silver pool at the bottom just because I was trying too hard to get enough in there to make it safe to ride.  So..i wasted silver and money but I know it’s well and good.  The shorelines of the lug (the margins of the lug where the fork blade and crown meet) are flooded but at least I learned why. The flame is like a paintbrush and the silver is your paint. There’s a fine line between adding too much paint and not enough, as well as adding too much heat or not enough.  It’ll just take more practice to get clean shorelines.

For the the MCX fork, I used the sweet Willit’s style Paragon disc mount.  With raked fork blades, there’s some ‘conversation’ on whether it’s a good idea to put disc brakes on or to just use cantilever brakes instead.  The fork blades are of similar wall-thickness as larger diameter straight-blade MTB fork legs, but because you’re bending the legs and they are such small diameter, some builders don’t think they are safe and in fact will ‘un-rake’ the fork over time! Yikes. But,  I’ve seen several respected builders do it though so I gave it a try. (check out this beautiful one.)  I had to bend the disc mount to fit the rake of the fork blade using the torch.  I loaded the disc mount in the Anvil Front Shui fixture and with the torch I heated up the top of the mount. When orange-hot, I slowly pulled the narrow upper part of the mount into the fork blade with pliers (one part of the jaw on the blade, one on the mount) until it was as close as it could get.  After cooling down, I filed the disc mount to a snug fit on the blade and finished with brazing the mount to the leg with brass. Turned out pretty ok!

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