Jay's Bigwheel begins to take shape

Jay first hooked up as a Groovy customer when we resto'd his old Monster Fat, a rewarding project that started us down the path of making a new classic for his fun time. Jay lives in mountainous terrain, and pedals quite a bit of dirt road before he can dodge into the woods for some rocky/rooty adventure. So the goal is to design a big wheeled bike that can sit by the door, ready for whatever path he chooses to take.

Much like me, the younger years of being flexible as a sapling have passed on, so we are designing the bike with a little less saddle to bar drop than his current cockpit, to bring him more into the bike than on top of it, and give him a bit more of a heads up position.

The bike will accommodate everything from skinny shoes to 2.5 knobbies, run on a Rohloff internal 14 speed hub, stop with Magura Marta SL discs, and bling it out with a Phil/White Industries bb/crank combination...Sweet!

Let's get the fixture all set up!

Here's the selection of tubing that we're gonna use...the massive pipe on the left is EBB material, I'll tell ya why that big guy is here in a moment.

First order of business, though, is to roll out each tube and find the correct axis to place it in. Despite all the pains we take to insure tolerances, you gotta keep in mind that even the most expensive tubing is not straight. Here's a bit of an arc in this top tube...

Ok, it's time for a bit of a rant. If you spend any time at all reading through the various forums, you're sure to see the frequent threads stating "Why is my EBB creaking", or "Why won't my EBB loosen and turn", or "Why won't my EBB stay tight?". All of these questions are a direct result of consumer driven designs to make bikes lighter or technically different. The unfortunate truth is that almost all of these new EBB designs are superfluous, abound with their own new problems, and were never really required to begin with.

Maybe I'm just old and biased, but I think that function should take precedence over form anyday. The new heavily machined, quirky wedge/expansion/set screw units just don't do it for me. So, I build my own EBB's. I like a functional way to tension the chain for single speed /Rohloff use that is simple to use, provides for maximal surface contact area to reduce slippage and annoying noises, and is easily maintained.

I start off with my own 4130 shell material that is cut to rough width...

I then size the piece to the correct width, face, debur, and chamfer off the edges.

Next I bore out the inside of the shell to be a slip fit for my internal eccentric...

The finished shell and the machined insert that will reside within.

A tasty slip fit. Once on the bike, the shell will have two pinch clamps brazed in place and the shell will be slotted. This arrangement allows for maximal surface area to tighten around the eccentric so that it is firm and quiet. To adjust the chain tension, loosen the pinch bolts, place a trail side tool in the milled depression and use your crankarm against it to rotate the insert...simple and clean.

Ok, next up on the frame is preparing the head tube. The head tube is rough cut, faced on the lathe and then internally relieved to the proper spec to receive the headset cups. I work real hard to avoid hand held facer/reamers as they just are not as accurate as firmly fixtured tooling. Too many builders either under size the headtube causing expansion stress on the frame, or oversize the head tube from poor technique and have cups that just drop in and do not hold firmly. Proper machining and weld heat control for me, thank you very much. This bike will sport a King Headset. Chris King cups require an internal diameter of 33.9mm for perfect fit, I'm pretty darn close here so I'll leave it at that...

The finished piece, you can see the internal relief if you look close :)

Lastly, the final piece that sets up the frame's backbone is the seat tube, so I take time to prep it correctly before it enters the fixture. I use my pinch bolt to indicate off...this keeps my seat tube top miter and my bb miter in the correct plane.

Two small tacks to secure it in place...

The BB miter is cut exactly 90 degrees to the pinch bolt by using the face of the jig to align off of.

The seat tube in place...

Next up came the down and top tube, nice and tight...

The downtube receives another miter to fit around the seat tube. This has gotta be a tight fit, as any gap in this area will cause the edges to peal away as you try to weld it.

The front tri all fit up...

Next up I drilled out all the water bottle bosses and the Rohloff clamp bosses.
Vent holes are cut...
and the parts are ready for brazing...

I laid down some 56% silver for the bosses...

and some 45% for the binder bolt, gently caressing it around the piece so there will be no clean up or filing necessary.

My last chore for the day was to assemble my new bender. This is the newest model of the solid JD2 bender, called the model 32. I decided to upgrade to this model as it incorporates a new spring back retainer, which increases it's ability to provide wrinkle free bends in very thin wall tubing, just what I need for bicycles.

Overall, not a bad day of productivity for as terrible as I feel. Even worse, the rest of the family is now sharing it with me...what a sorry lot ;)

Til later,

rody