Friday, August 29, 2008

I'm hungry for some bike...anyone got a fork?

On a whim, I decided to work on Eric's fork today. I'm building a Ho down box crown fork with hooded dropouts, disc tab, and removable canti posts for Eric. I've got a few other forks in the mix in the near future so I thought I'd make the most of my time and push out some extra tid bits for 6 other forks and make a few other folks happy at the same time.

The crown on the Ho fork is a bit complex, in that it not only needs some exacting mitering for the legs but also a through cut at an angle for the steerer tube that also sets the overall offset for the straight bladed design.

The crown begins it's life as a piece of 2x1 rectangular tubing cut to length. For manipulation, I start off by slitting in the top of the crown for the section that will mate with the fork legs, capping of the top.
Next, I use a hole saw to open up the crown to accept 1/2 of the fork leg, giving superior surface area contact at the point of connection...that gives me a super strong crown that will hold a line well under harsh conditions, allowing the lower legs to absorb the trail chatter.

After the leg slots are filed and cleaned up, I mill off the ends into a circular shape to match the outer diameter of the leg tubing, giving a seamless line when assembled.

The mill is reset with some angle, the piece is centered, and the steerer miter is made.

Once she's all cleaned up, I've got a crown made for a king...that's Eric in this case ;)

Now that the crown is fabbed up, I get to work on the crown race. All races come with a welded seam that prohibits the race from sliding onto the steerer tube, so the inner diameter must be opened and smoothed to a perfect fit. Here's a little delicate work on the lathe...a quick pass, a bit of scotchbrite and it's ready to go...

Once the race is ready, everything is cleaned super duper like, and it is welded together. I fusion weld the race, pulling a bit of material from the inside bottom edge and joining it to the surface of the steerer tube. This is a clean way to install the race, but you MUST be very careful not to undercut the actual steerer, a process that takes experience and precision to accomplish.
Flashing forward, I've cut the fork legs, turned them down in the lathe, mitered them at the dropout end for the splay angle, and fit it all together in the fixture...ready to tack and check.
Once I'm happy with the fit, it's back in the fixture for welding...and wha-la!

I made a similar fork for Carlos earlier in the week , coated it in gloss black, and it looks BADASS!

This is a positive omen for the build...everything is moving ahead nicely.

I'm going to hit the shop early in the morning, then I'm going to take the afternoon off to take Kalten rock climbing...really looking forward to it!




Chauncey Matthews said...

Beauty work as always- I love this blog!
Are those the Paragon "Wright" dropouts on that fork?


Rody said...


You got it...the Paragons were a long time coming but I'm glad Mark finally got these babies out.

They are a standard steel piece, so you could even braze them if you please.



Walt said...

Hey Rody -

The Paragon crown races don't require any lathe-love to fit up. Check 'em out.

Great blog, btw. I learned a ton reading through all your old posts! Can you believe I don't have a slitting saw setup for my BP? I use tiny end mills because... well, because I never thought about it. Damn I break a lot of those little bastards! But not anymore...slitting saw time for me.