Introduction to the electric bicycle and tandem recumbent design website.

I haven't built any electric bikes yet, but I have built numerous recumbent bicycles, including commuter recumbents, terraquatic bicycles, mountain recumbents and fairing race recumbent bicycles. I sift through many concepts to select those I find will work in my theoretical framework. While I have not yet built full suspension recumbents, tandem recumbents or other hybrid power recumbents, I currently have a tandem full suspension prototype in process. ( 3/11/01 the tandem progresses, the main frame and seats are done, the disc brake tandem hubs and rims are at the wheel builders, hydraulic disc brakes and the suspension fork are here)

I have researched the electric bicycle arena since 1991. This is a small niche in the EV field. Most research is done for cars, or electric bicycles with a small assist. Consequently most equipment is either too heavy and powerful, or too light and weak. This website solicits input on theory, design, componentry, and sourcing.

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My electric bicycle dreamachine

A pollution free vehicle that can go far, fast, with a full load for almost free, while giving me a great workout. Ha! I define these as follows:

Pollution free vehicle: No pollution by the vehicle. Heat pollution, electric power generation, and materials manufacturing processes aren't currently included. Perhaps "low-fat pollution vehicle" is a better definition!

Far is a range of 80 miles

Fast means 30 MPH.

Full load means two people (300 lbs), the electric bicycle (100 -150 lbs) and all gear (80 - 120 lbs) or up to 570 lbs.

Almost free means significantly less than motorcycle maintenance, but more than bicycle maintenance.

Below are my optimal range values for flat terrain without a wind factor.

Daily Range on one charge with pedaling: 120 miles (30MPH)
Daily Range on two charges with pedaling: 200 miles (25MPH, weaker rider)
Daily Range on one charge without pedaling (to determine the electrical system requirements) 80 miles (20MPH)
Daily Range on two charges (1 full, 1 boost) without pedaling 120 miles (20MPH)

Top Burst Speed: 45 MPH
Cruise Speed: 30 MPH

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Comparisons with existing electric bicycles

Anyone who has a Citybike, an EV warrior, a Zap power assist, or another electric bicycle and can give accurate personal data (not promotional statistics) please send the range, top speed, average speed, duration of charge, total recharge time, significant boost (50%) recharge time, bicycle weight, and it will be posted! Comparisons:

Loaded recumbent average speed 10-13 MPH

Citybike Promotional statistics: (unknown)

Citybike Actual statistics: (unknown)

EV Warrior Promotional statistics:
Top hypothetical hybrid speed 30 MPH
Max. hypothetical electric only range 20 miles @10 MPH
Max. hypothetical electric only range 10 miles @ 20 MPH

EV Warrior Actual statistics: Unknown

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Using a Modular Concept in electric bicycle design

I am designing the electric bicycle in modules. If one system has problems, it can be replaced or redesigned without completely redesigning the bicycle. This facilitates systematically addressing challenges, overcoming obstacles and performing upgrades (when higher power density batteries emerge, the range may increased or the weight could decrease, for example). The basic modules are: Vehicle frame and safety, Energy charging and storage, Electric Motor and controls, Power transfer, Load placement and support, and Safety systems.

The heart of this modular system is a recumbent design frame. After riding many types I still favor short wheelbase (SWB), under seat steering (USS). My past designs used a 20" front wheel 24", 27", or 700cc rear wheels. .

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Wheels for the electric bicycle

Wheel selection addresses type (motorcycle, moped, bicycle), size, safety, weight, efficiency, availability, cost, and special features. Wheel type:

Motorcycle Wheels: Motorcycle wheels are heavy, increasing rotating weight and they have a greater road contact area, increasing rolling resistance. They seem to have more bearing resistance than bicycle wheels. They require heavier forks and frame adding considerably to the overall electric bicycle weight. Advantages include that disc brakes and front and rear suspension are readily available. A motorcycle wheel system is overbuilt, adding some safety.

Moped wheels: Moped wheels are ruled out. They are not readily available, generally have significant bearing resistance and use drum brakes. .

Bicycle Wheels: Bicycle wheels are efficient and readily available. While this electric bicycle uses many bicycling components and concepts, it is not a standard bicycle. The vehicle alone may weigh more than 150 lbs. It will travel at 30+ MPH. The wheels will be subjected to severe strains on stopping. Standard bicycle wheels were not made for such conditions.

Mountain Bicycle Wheels are built for greater loads and tougher conditions, but they are too big. A SWB recumbent design limits the height of the front wheel as fits below the rider. Bumps can distort larger wheel easier. After distorting many rear recumbents wheels, I favor 20inch tall, 1.5 - 2.2inch wide wheels. One advantage to same size front and rear wheels is carrying spares (tire, tube, spokes, even rim)

20inch BMX wheels have these advantages: They fit under the rider. They are big enough to handle rough roads and reduce road vibrations at high speeds (40+ MPH). Some are strong enough to handle the weight. Some can handle abuse without distorting. Maintenance (tires, tubes, spokes,) and repair (hubs, bearings, axles, rims) parts are generally available at a reasonable cost.

While some BMX wheels meet my strength and size criteria, they do not meet other requirements (disc brake availability, multiple sprocket freehub for gear range, suspension). Disc brakes are not made for 20" wheels. Suspension forks are rare (and under built when available) disc brake forks are not available. A disadvantage of 20inch BMX wheels is that ideal Mountain Bike componentry has to be customized for the smaller wheel. A cross between a BMX wheel and a Mountain Bike wheel is needed. Most MTB hubs do not come stock drilled for more than 36 spokes possibly requiring custom drilling through an accommodating manufacturer (ergo problematic replacement). A 40 or even 48 spoke pattern may very well be advantageous given the tremendous loads this vehicle will be subjected to.

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Brakes for the electric bicycle

Significant factors include: High Speeds; great weight. Brake types include rim, drum, and disc.

Rim Brakes: A 20inch wheel has a significantly shorter rim circumference which increases the heat generated as the brake shoe applies pressure to the rim. Because of the electric bicycle weight and speed, stopping distance is increased dramatically. This increases the heat factor and the likelihood of a heat blowout. Rim brakes alone are inadequate for an electric bicycle.

Drum Brakes: Drum brakes are few and far between. I have not solicited feedback from drum brake users to ascertain their adequacy or availability.

Disc Brakes: Disc Brakes also used to be rare, although their introduction to the MTB market has increased availability and enhanced performance. After considerable feedback I am working with Maguras, which are well known for brake modulation, controlling the braking applied.

In an electric bicycle, braking should disengages the electric power and light a brake lamp, before applying braking forces at the wheel. When power regeneration is available it can be used as a slowing force prior activating braking forces. Although power regeneration is not now feasible, it eventually will be.

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Suspension for the electric bicycle Some suspension is a desirable feature on any electric bicycle of this size. The disadvantages of suspension (weight, cost, design) are small compared to the advantages (safety, lower vehicle and rider maintenance). Front and rear suspension present different challenges. Front Suspension: Front suspension forks are rare for 20 inch wheels. When available they are often under built. This electric bicycle needs extra heavy duty suspension. Some options are: building custom forks; modifying mountain bike suspension forks; or using steerer tube suspension. A disadvantage to steerer tube suspension is that the head tube must be oversized and is limited to certain forks. A disadvantage to fork suspension is the need to accommodate travel, if completely separate (different wheels) human and electric drives are designed.

Rear Suspension: Limited travel is needed weight requirements may be a problem.

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Power Controls for the electric bicycle

With a dual power electric bicycle, dual controls are needed. Brake levers should also disengage the electric power. Power controls need to be immediately accessible. Grip shifters and thumb shifters may work. Electric control should offer: regeneration (if available) then no output (which should use no power either) then a range of power from low to high. Naturally a smooth power range is preferable to one with large differences

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Componentry for the electric bicycle

Most other componentry (crankset, chain, bottom brackets, pedals, gearing, derailleurs, freehubs, etc.) will initially use high tech maximum strength Mountain Bike componentry. When weak links are discovered (which will happen!) the issues will be addressed.

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Safety equipment for the electric bicycle The ideal electric bicycle should: be noticeable; have impact protection features including a rider retention harness; offer whiplash protection; have a loud horn; and have headlight, taillights, brake lights, blinkers and helmet lights. Mirrors (vehicle or helmet) should always be used.

The seat needs a headrest which meets vehicle standards against whiplash. A retention safety harness should be incorporated, tested and used.

Fairings should have front and rear bumpers, and side impact protection. I understand that motorcycle airbags are just now emerging, however they are not in use yet.

The helmet should be full face since the electric bicycle is expected to exceed bicycle speeds, a bicycle helmet is inadequate.

Cargo Racks: aerodynamic, with a low center of gravity. Racks and mounts are needed for the batteries, panniers, motor and charging equipment, fairings, lights, horn, etc.

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Electric System for the electric bicycle

Theoretical Electrical System Weight:

When I first designed this system I used a guess that I wanted about 80 lbs. of power storage, and 35 lbs. of motor, charger, controllers, racks, power cord and everything else related to the electrical system. I am guessing that I want:

(1/3-1 HP) (permanent magnet?)DC motor 10 lbs.
rack for mounting: 2 lbs.
Controller 1 lb.
Display 1 lb.
Charger 5 lbs.
Electric Cord 2 lbs.
Batteries 80 lbs.
Battery racks 4 lbs.
other 10 lbs.

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Theoretical electrical system output of the electric bicycle:

80 lbs. of lead acid batteries (Optima 850/6) yield the following data:
4 batteries at 6 volts x 56 amp hours, 20 lbs. each

Using the following formula
Power (w) = Volts (v) x Amp (A)
therefore over time:
Power (w) x hours (H) = Volts (v) x Amp (A) x hours (H)

results in the following equation for the batteries listed above:
wH= 4 x 6v x 56Ah = 1344vAH
wH= 1344 H

Knowing that 746 w = 1 horsepower (HP)
we can determine the batteries have 1344wH / 746 HP = 1.8 H

This means that we get 1.8 hours of power at 1 horsepower. This could also be calculated at 1 hour at 1.8 horsepower, or 5.4 hours at 1/3 horsepower.

All of this of course is theoretical and does not account for motor inefficiency, internal battery resistance, controller use and inefficiency, display use, or wire resistance.

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