To give you the low down here is what we are shooting for...
Eric wants a sweet do it all bike that he can take anywhere in the world and if something goes wrong, be able to find parts or switch it up and keep moving. To accomplish this, we are setting up the bike to handle gears or single speed, discs or removable cantis studs, internal cable routing, braze ons galore and designing it to be used with a rigid fork but keeping the geometry balanced to run with the new 650b sussy forks or throw a 100mm 26er fork on the front without it feeling funky. Whew...gonna be a fun build!
So, based off of some good conversation with Eric and some detailed queries, I put together a tube set to keep him on the trail for a lifetime of smiles.
To accomplish the single speed duties, I gonna run the frame with an EBB. EBB's have been around for a long time and due to the single speed movement of late, have become very popular. Unfortunately, if you do much reading/research on them, you'll see a lot of threads from people complaining about how much noise they make, problems with them loosening, etc... The real problem is that the ever present drive to get lighter has crept into this area. Truth be told, many of the issues and new designs have created more problems than they have solved. Want a quiet EBB that won't loosen, the secret is exacting machining and reaming, proper surface area contact, and even tensioning of the shell. I've been spinning up my own shells and using custom machined inserts for years now without any of those issues. Yep, they weigh a few grams more than a Bushnell or the latest kid on the block, but mine will never make you frown ;)Most of the tubing I'll be using is on the "Just right" sizing for wall thickness and strength...8/5/8 dimensions. This will allow for plenty of material to support the internal cable routing and still give Eric a lively ride.
So, let's get started setting up the fixture!
The fixture setup begins with positioning the seat tube angle off of the bb. The st block runs on a slotted arc and allows for tube over bb position and angle.
Once in place, I set the bb drop and cs length for the build, in this case 44.45 drop and 425.45 length.
Once my drop is set, I throw in my straight edge and work out the front end positions based off of the wheel base; axel to crown length, top tube length, and head tube angle. I'll keep the geometry paper real close to insure I've got it all where it belongs. A quick double and triple check (you hate to find out you were off 1/2 inch once everything is welded) and everything is clamped tight and outlined in marker to be able to visually see if any fixture member moves.
With the fixture ready, lets start prepping the materials. The BB material is cut on the cold saw...
Then the faces are cut parallel, top edge filed, and inside edge deburred.
Here's a shot of the AL insert I use. Like I said, I could mill it out and make it lighter by a few grams, but the full surface area contact of the outer diameter lends great strength to the piece.
Next up I prep the head tube. I cut it to length, face both ends, file the outer edge over, debur the inside lip, then remove some material to allow a perfect press fit for the headset. The high end head set builders (King, Hope, Cane Creek) spin your piece to a numerical perfection, if your builder is not taking the time to bore out the head tube to provide a perfect fit, your going to have some mechanical deformity of all that pretty anodized aluminum, inconsistent surface contact pressure and eventually hear from your headset about it :)
With the main pieces prepped, I hit some Luv Handle work quick to get ready for the September delivery. Mitering on Eric's tubes and welding on some bars forth coming!
The build list is updated on the web site...if you SHOULD be on it and do not see your name, please contact me! For those of you with special time considerations (Mike and Alton), I've not forgotten you.
cheers,
rody
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