Reflections on the potential of human power for transportation

Tuesday, June 3, 2014

The Sinclair C5 to the Organic Transit Elf: Pedalectric Identity Crisis

The Sinclair C5

The Organic Transit Elf

One would think if George Georgeiv’s Varna Tempest could cover a distance of over 56miles in one hour, that it would be a straight forward process to design a commuter vehicle that could travel at half that speed, a vehicle that could keep up with urban traffic while only requiring about 200Watts of mechanical power. To date, this has proven to be more difficult than I would have expected, partly due to the increased requirements that go along with comfortable and safe commuting.

The first decision that designers must address is predominately where the vehicle will be ridden.
If it is mostly on bike paths, the vehicle can be considered an all-weather electric bicycle, or AWEB. (I use the term bicycle to embrace the most common embodiment of a pedaled vehicle. It will more likely be a tricycle.)

It takes more than adding a third wheel, a motor and a body to produce a fully functional AWEB.

 The main criteria is to keep the vehicle narrow enough to fit within bike lanes and keep it high enough to be visible to other cyclists and autos when it is ridden on shared roadways. For the bike lanes I use, the width needs to be less than about 33 inches.  (The width of a motorcycle is considered to be about 33 inches). If the vehicle is to be stable on slippery road surfaces it will require three wheels and if it is to have reasonable corning speeds without tipping over, it must be a leaning tricycle.

Most locations have speed limits for electric bicycles which limit their effectiveness in challenging cars for commuting purposes. In the US, the electric bicycle speed limit is 20mph.
If it is to be ridden where it shares the traffic lanes with autos it can be considered a pedal-electric car or PEC.  A PEC needs to be visible and able to keep up with traffic to not cause congestion. Where I live that means that it needs a top speed of 40mph.

In addition, for adequate traction on slippery road surfaces, more then 50% of the vehicle weight should be on the driving wheels.

The Drymer discussed in the post listed above comes very close to meeting all the requirements of an AWEB. The Cyclodyne discussed later came very close to meeting all the requirements of a PEC without an electric assist
In 1985 the British electronics industrialist Sir Clive Sinclair decided to mass produce one of the first pedalectric vehicles. More than just an electric bicycle, it had three wheels and a partial faring.  The pedals drove one rear wheel and an electric motor drove the other. Lotus Cars developed a flexible chassis in lieu of a suspension and Polymotor of Italy developed a motor with an integrated gear-reduction. To take advantage of riding the C5 without a license, the top speed was limited to 15mph.

 Automotive Engineering titled its May 1985 article “Motor Assisted Trike Presages Electric Cars.” For all the media hype and large financial investment in the project, 12million pounds, the result was an abysmal failure.

 Here is a list of the more obvious failings:
   1.        It had only one pedal speed.
   2.       The pedal cranks were much shorter than normal.
   3.       The pedal-seat distance couldn’t be adjusted.
   4.       It was too low to be visible in traffic.
   5.       It had poor weather protection.
   6.       It didn’t have enough electric power to get uphills.
   7.       The front wheel was too small.

Below is a picture of a tall rider, Automotive Engineering’s European Editor Scott, wedged into the vehicle.

Clearly there was no input from cyclists on the pedal drive or there would have been multiple gears and an adjustable seat-to-pedal distance. The pedal portion of the vehicle was merely window dressing.
The height issue was addressed by adding a tubular loop in the rear that could hold flags or reflectors.

The inadequate weather protection was addressed by adding a rain suit and waterproof side covers. (Anyone that has ridden a recumbent in the rain will see that this rider will develop a puddle in his lap!)

There were a few features that were to be commended. The overall design had an attractive, streamlined esthetic, in some part due to the delta configuration (one-front wheel, two rear wheels), which allowed the steered front wheel to comfortably enclosed by the nose of the vehicle. And having the handlebars beneath the seat proved a comfortable location.

In the end there were 17000 vehicles sold, but many owners abandoned the pedals and used electric power only. Although it aspired to be an AWEB, the C5 ended up being little more than a recumbent electric scooter.

Skip ahead 19 years to the Elf from Organic Transit of Durham, N.C. The Elf is a semi-enclosed electric tricycle using the tadpole configuration (two front wheels, one rear wheel). The pedals and the electric motor drive the rear wheel. It is a noticeable improvement over the C5. It has much better weather protection. The seat-to-pedal distance can be adjusted and it has multiple speeds. Below is a picture of an Elf chassis being assembled. The seat slides on the two-horizontal rails between the front and rear wheels.

Everything looks promising until we check the vehicle width, which at 48 inches is too wide to fit within most bike lanes. In addition, the rear wheel appears to support less than 1/3rd of the vehicle’s weight, so traction in snow will be a problem. (The Organic Transit site shows a pretty picture of an Elf in on a snowy road.) So the vehicle width prevents it from being a viable candidate for an AWEB. On the other hand, since the speed is limited to 20mph, it is not a candidate for a PEC either.

The people at Organic Transit are working on the next generation of the Elf. So one suggestion for a simple improvement is to go from the 26 inch dia. wheels to the more standard (for human-powered vehicles) 20 inch dia. wheels. These are more electric-motor friendly since they rotate faster. They also take up less space, so volumes for turning and fenders can be smaller, leading to a more streamlined design. Another simple improvement is to have only one door (like the Pedicar). This provides for a more continuous structure for the body and better weather protection.

If they are interested in adding leaning to their design, it would benefit them to take a closer look at how the Drymer people incorporated leaning into their trike design.

Because the Drymer leans, the c.g. of the vehicle can be shifted toward the rear wheel without concern for tipping during cornering. As a result, traction for the driving wheel is improved and suspension on only the rear wheel is very effective.

The Organic Transit people also have a utility trike on the drawing board called the Truckit. The Truckit uses a delta configuration for the wheel locations with pedals driving the front wheel.

 A more compact and streamlined concept for a delta-configuration velo truck, based on the EcoVia leaning-trike, is shown below.

The pedals drive a central driveshaft and the two leaning wheels are chain driven off that shaft.

The truck is 108 inches long, 33 inches wide, 57 inches high and has a cargo capacity of over 25 cubic feet. The leaning can be locked up for loading and low speed operation. The pedals drive both rear wheels and the motor drives both rear wheels through twin ratchets that act like a posi-traction differential. This produces excellent performance on slippery surfaces.
Had the Cyclodyne from the 1980’s incorporated an electric drive to supplement the pedal drive, it would have been the first successful PEC.

Even though it had a pedal-powered cruise speed of 30mph, it wasn’t quite fast enough to keep up with traffic, which it needed to do because it was almost as wide as an Elf. The addition of electric assist could have easily increased its top speed to over 40mph.

The Cyclodyne drove and steered both front wheels providing excellent all-weather traction. It would have been straightforward to integrate an electric motor into that drive.

So in conclusion, I believe that AWEBs, operating on most bikeways will have to use the leaning-trike configuration.

Bridgestone seems to reinforce this point by joining  the ranks of the AWEB's with their own version of a Drymer-like leaning trike.

For the less common PECs, leaning is not a requirement, since they will be able to keep up with cars and can therefore be wider. That being said, being able to lean makes the vehicle narrower and more aerodynamic. And this makes it more efficient. 

Automakers are again looking at tandem-seating two-passenger vehicles for fuel economy and they are also incorporating leaning to reduce the vehicle width. More on these man-wide vehicles in the next post.



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