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Cargo Bike Design Documentation Updated 2-12-06 by Aaron Goss
   
Requirements  
Gross Vehicle Weight 800lbs max
Cargo Room 2' wide, 3' long behind rider's heels
Overall Length not important
Standover Height 699mm  We need to allow for the lowest seat height (BB center to top of saddle) to be 700mm as a minimum (Gypsie's seat height). 
Rider Size Range 5'6" to 6''8"
Accessory Accommodations Fenders (with 2.35 tires), StokeMonkey (3/4" tube), front rack on downtube extension
Ground Clearance Ability to climb/descend 6" or higher square curb
Maximum Lean Angle TBD (width and height of cargo area frame rails are design variables)
Standard Cargo Loads Unloaded; Hay; Chicken Feed; Couch; Toolbox; Drill Press; Passengers; Loose Dirt
   
Specifications Decided Upon  
Two Wheels Because we don't want to build a Trike
20" Wheels 21" actual wheel size with large tire.
Clearance for 2.7" actual tire width with fenders West Coast Chopper fenders?
Integrated Center-Stand with handlebar brake lever actuation (like Val's bike) Val to design.
Side kickstand Why not have both?   Will need special bracket on boom tube and a custom tube extension for a Greenfield 305mm stand.
Plastic rails on cargo area frame rails To prevent hanging-up on curbs and driveways (Skate Board type, Nylatron?)
Tube Dimensons DT 2"    Seat Tube 1-1/4"    TT 1-1/4"    SS 3/4"    2-1/2" Boom   Rack 3/4"  Tandem Chainstays   HT 1-1/2 x .083 machined to  external butt. Steerer 1-1/8"
Albatross Handlebars  
Vertical Drop-outs Will need to cut our own, solid. Rohloff specific with dearilleur hanger
Mid-chain double wheel tensioner Double pully type, location and design to be determined. Singulator style mounted to a 10x 1mm hole could be easy.
Frame Material: 4130 Steel  
American BB Shell  
Rohloff Hub 40 x 16 Gear (actual tire diameter is 21" for gear calculations) OTHER OPTIONS?
Bed Deck Lenghtwise Spruce slats coated with water-proof clear coat, mounted to bed supports with "J"-brackets and carridge bolts with nylok nuts. Brackets could be made out of L-Alumunim.
Design of Bed Framework Welded-on cross members. Square corners. Front "fence" framework to support top rails.  Also perhaps wood (spuce?) slats should be installed as well and design side pannels to be able to carry loose loads like sand/dirt/yard waste.  Perhaps we should use marine grade plywood instead of slats?
Rear Rack design See new drawing
Removable bed upper rails Aluminum tubes or square stock with M8 x 1.25 stainless bolts (same as a standard seatpost bolt!)  Rails should bolt-on (stash) to the bottom of the deck when not in use. Stainless nuts could be brazed on to the bed supports.  Deck side grind rails should be thicker than the stashed rails.
Chain Routing and Tensioning Top run of chain is straight with a 2-pully style tensioner on bottom run.
Boom Tube 2 1/2" boom tube STAINLESS (because it is available in the diameter and wall thickness we need)  DENNY- do we need that large?
Brake Hayes Hydraulic with 8" rotors.  Someone is making a 9" rotor, need to find who. As the front fork drop-outs are drawn, hydraulic hose routing should NOT be a problem with a Hayes brake!
Fork Existing fork dimesions are agreed.  No prototype.  First fork will have Maxle.  Chalo to machine fork ends.
Basket mount Large tube stub welded to head tube.  Basket frame support to slide over telescopically with a clamp like a seat collar.
   
Stoke Monkey Rear triangle to be built with room for motor and plate welded on for motor mount.  Mount should be inline with BB and motor axle to eliminate tension cable system. KMC PT710-NP Half Link (Pintle) Chain 1/8" would be a good choice for the chain to allow small chain length adjustments. 1/8" freewheel and chainwheel would increase durability. BMX Left Side Drive crankarm makes it easy, except the larges chainring is only 48 teeth. Maybe Chalo can find larger? Todd recommended 60T with the more powerful motor. Remember 1/8" thick is nice, but not absolutly necessary.The "dry zone" just in front of the rear wheel would be a good place for the SM battery and controller.  Will require much longer wires.
   
Performance Targets  
Descending Queen Anne Counterbalance, without brake fading / failure, fully loaded on a hot day
Climbing TBD (400watts fully loaded, minimum Rohloff gearing, minimum balance speed)
Frame Stiffness TBD (bounce mode, torsion mode, lateral mode)
Safety Factors TBD (yield and fatigue)
   
Progress  
Drawing is now metric!   1mm = .03937"  
Aaron has built the front wheel with Schwalbe Big Apple 20 x 2.35" tire, 48 spoke Diatech "Swinger" hub (convertible from 20mm Thru-axle or standard QR) and Alex Supra E rim (according to Chalo, the strongest rim of any size made!). The hub will allow us to make a prototype fork with long horizontal dropouts to experiment with trail, then build a thru-axle fork once determined and use the same wheel. The hub comes with different end caps.
Next Meeting: Monday, February, 27th, 2006 @ 7:30 PM (Meet at David's Shop then move to Stellar)
Stellar Pizza , Ale & Cocktails 5513 Airport Way S, Seattle, WA 98108 (206) 763-1660
Chalo to update existing drawing and create top view.  Denny to report on boom tube size required, even if he cannot attend? Please!  Order tubing!  David will need some money.  So far we have paid around $250  David?  Also from David, can we get an estimate for building the frameset (unpainted with minimal braze-ons at this point)? Aaron will work on a parts package price.  Val, price of kickstand?
Misc. Notes:  
Denny can do 3D modeling. Chalo can print life size drawings