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Old 08-27-2014, 03:08 PM   #1 (permalink)
Sven7
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Join Date: Aug 2011
Location: Warren, MI
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Project Blue Bike (lowracer commuter bike)

I am building a recumbent lowracer bicycle for commuting and general transportation around the Detroit suburbs. My current commuter bicycle goes around 10mph average on a good day including stop lights, and I'd like to double that.

A friend and I collaborated on the design; he wanted to tinker with geometry and I wanted a fast bike without the uncomfortable seating position and inferior aerodynamics of an upright road bike. After a trip to an HPVA race in Ohio last year, we started in earnest.

We settled on a front wheel drive, moving bottom bracket (MBB) design built around a Sturmey Archer X-RD8(W) eight speed internal gear hub with integrated 70mm drum brake and 20 tooth cog. This hub was built into a 16" (305mm) steel rim (from Calhoun Cycle, MN) with a 1.95" Maxxis Hookworm BMX tire.

I am a short guy at 5'-2", so this configuration means that I can not only reach the pedals but run less of a chance of skinning my leg on the turned tire. It also allows the bike to be lower with a higher efficiency drivetrain than if we'd have gone RWD. All this essentially means that my entire drivetrain will be mounted to the front fork.

The Shimano rear hub is equipped with a Tektro 160mm disc brake, laced to a 20" (406mm) steel rim. My friend and I built both two-cross wheels in my living room; getting the spokes up and around each other on such big hubs and small rims was quite a challenge.

This bike will be equipped with chain guard, fenders and a rack to make it usable every day. I do not plan on racing it. It will feature remote under seat steering for comfort and control vs. a tiller. There will be a tall 'conning tower' of reflective tape and/or blinky lights to alert motorists of my presence, should I choose to ride on the roads; sidewalks can get bumpy or nonexistent around here and 20mph will be too fast to be passing pedestrians glued to their phones.

Bicycles are not legally considered vehicles in the state of Michigan and they are allowed on roads of 35mph or below. I'm not sure how this will all shake out in regards to practical riding, but seeing as this bike could be dangerous to pedestrians, I may have to bend some rules.

Below is the general blueprint of the bike with correct geometry.



It's borrowing a front fork and headset from a $25 Huffy step through I rode daily last winter, with a 65 tooth chainring sourced from a $10, 1970's-era Schwinn Exerciser on a ~$5 Stingray one-piece crank.

The 'bent's 65 tooth chainring with tiny cranks sitting next to the stock 46 tooth from my 1963 Schwinn American. The 65 tooth will run to a 20 tooth cog and gearing is estimated to allow 30+mph speeds if my legs can take it.



The donor-



The wheels-



Right now I am in the process of drawing plans for the front fork and whatnot. Here is the dropout blueprint. Next is working out measurements for the BB stays.



Issues I am expecting to run into are:

- The 65t ring is too big to fit around the donor's chainstay, so the stay will have to be notched or zee'd.
- I have no idea how the chainline will look.
- Clipless pedals do not thread into old-style Schwinn cranks, so I will need to run adapters first and hopefully later get new pedal spindles machined to thread into the crank.
- I have still to work out the under seat steering mount, but am planning on using a severely shortened headset in line with the frame. Possibly with gussets (pictured in blueprint) to strengthen.

Also, I would like to build this in a way conducive to disassembly for transport. I could very well want to take this on a plane or train where carrying an assembled bicycle would be expensive or prohibited, respectively. I am planning on doing this by incorporating a large 6-bolt flange somewhere in the frame. I would then unhook the (likely) rear brake, remove the seat and stack the frame parts in a suitcase.

Last, I am trying to keep an eye on everything I spend on this project, so once I find and count all my current receipts I will try to keep a running tab in this thread. I'm trying my best, but the bike isn't going to be cheap.

Cheers!

PS- It's Project Blue Bike as a pun on Project Blue Book. The bike will be powder coated the same bright blue as my 1974 Schwinn Varsity.

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Last edited by Sven7; 08-28-2014 at 09:00 AM..
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