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The Alpha Cycle
Code Name: The "Little King Alpha" Project
09 December 2002, by Jon Sharratt - Web Page by Mark Stonich
jon.sharratt@mts.com
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Frame and Fork Features
- Started as a way to build a curved frame using straight pieces
- 4130 CrMo throughout
- 1.75" x .049 main tubes
- 2" x .049 cross tubes
- Silver brazed
- Segment frame construction features design flexibility and ease of assembly
- Cross tubes and segments can easily be changed to any angle during design or construction (12 & 37 degrees in this example)
- Laying the frame on a flat surface to tack weld results in a straight frame
- Frame gussets double as cable guides
- CNC'd rear dropouts with the help of Alpha Engineering & Manufacturing
- Started 27 December 1999!
- Modified Waterford fork
- Reynolds 531 blades, Henry James fork crown
- Sleeved construction
- Raked by Ray Brick
- Reinforced fender mounts
- Integral brake reaction arm mount
- Rear fork
- Made from Trek mountain bike fork blades
- Brass brazed
- Rear suspension
- Simple design uses 3/8" automotive fuel line hose as an elastomer
- Telescoping struts made from 3/8 x .035 and 7/16 x .028
- Elastomer stops made from common washers
- Aircraft clevis from Aircraft Spruce & Specialty provides pivot
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Seat Details
- Earth Cycles frame and mesh
- Tig welded 5/8 x .035 CrMo
- Pylon mount
- Slides fore and aft on main frame
- Offset to prevent interference with frame joint
- Anti-rotate provided by 1/8” stainless rod brazed to side of frame
- Lateral location by small pins brazed into seat frame
- Breakaway design held in place by heavy duty zip ties
- Both mounts pivot to accommodate suspension movement
- Seat angle adjusted by changing length of fuel line hose
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Drivetrain Features
- 68 tooth TA chainring
- 155mm TA crankarms
- Boone Technologies “Helixx” titanium BB
- 125mm Q-factor
- Be-Bop pedals
- Chain tensioner
- 12 tooth Shimano derailleur pulley
- Internal spring anchored by tiny spoke and nipple
- Anti-rotate peg
- Star Trek communicator shape
- Provides cable guides and computer mount
- Mid-drive
- Positioning the largest cog to the outside provides better chainline
- 3 self-aligning bushings mate the cassette to the frame and provide a mount for the front derailleur hanger
- 3/8” crosstube inside the frame for strength
- Standard 7-speed cassette body modified so cogs can be reversed for correct chain ramp orientation
- 4 front cogs expandable to 5 (possibly 6) with wider cassette body
- Backwards front derailleur for “pre-selector” shifting
- Mover the lever then shift the front by pedaling backwards ¼ turn
- Shifting possible while sitting still
- 2 short cage derailleurs for better ground clearance and plenty of chain wrap
- 7-speed Sachs rear freewheel
- 28 speeds total, expandable to 35
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Brakes
- Sturmey-Archer drum brakes with nutted axles
- No trouble with clearance at the fork crown, no cantilever posts, great bearings
- Modified aero-bar brake levers
- Brazed torque reaction mounts front and rear
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Biplane Rack (lower section only at this time)
- Made from 3/8 x .028 and ¼ x .028 CroMo, silver brazed
- Joining lugs and dropout bosses made from stainless steel
- Drive chain passes through it
- Comes apart in 5 pieces
- Hanging bottle mount
- Breakaway design held in place with zip ties
- Proper width for tail box attachment
- Upper level (not completed) tapered for tail box and positioned flush with rear tire for standing on end
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Handlebars and Stem
- Handlebars adjustable for width, made from old aluminum crutches
- Hand carved stem with Internal clamps
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Other Details
- Steering lock for storing bike on end (see rack description)
- Plastic mudguards from Luke at Calhoun Cycles
- Custom stainless steel mudguard mounts
- Bottle Opener
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Specifications
Weight 34 lbs
Length 70 in
Wheelbase 45 in
Width 15 in
Height 36 in
Seat height 17 in
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Head angle 72 deg.
Trail .25 in
Gear range 24 – 130"
Cost guess $1200
Time to completion: 3 years (but the biplane rack isn't done yet)
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