Reflections on the potential of human power for transportation

Sunday, May 10, 2020

Velomobiles, E-trikes and the Transportation Infrastructure

It has been forty years since the Reader's Digest Magazine published this digest of a New York Times article from August of 1980. That summer, at the International Human Powered Speed Championships, a streamlined tandem tricycle, the Vector, was the first human-powered vehicle to break the 60mph barrier for a flying 200m speed run. But what captured the media's attention was that same tandem trike was pedaled from Stockton to Sacramento California on Highway 5 covering 41.8 miles at an average speed of 50.5 mph. Finally, it seemed that streamlined human-powered vehicles could provide a  viable, healthy alternatives to the automobile. 

In this vein, the magazine article described a hypothetical future commute to work by "Joe Wheeler", pedaling a single-person, Vector-like velomobile, the Shooting Star. Joe, riding along dedicated human-powered-vehicle lanes, covers 25 miles at an average speed of 60mph.

The article goes on to show a schematic of the single-person Vector.

And I have added a close-up photo of the Vector's interior. Note that the width of the Vector is 25in. and the height is 32in.

So 40 years has passed and why aren't people zipping to work in bullet shaped tricycles? One answer is transportation infrastructure. There are no limited-access high-speed bike paths for vehicles like the Vector. I do occasionally see a bright-yellow Quest velomobile on the local bike way, but I have never seen it 1n the bike lanes adjacent to local roads.

Now the progression in HPV speeds has continued in the ensuing 40 years. The longest distance covered in an hour is 58 miles and the flying 200m record is almost 90mph. The current trend has been to use a two-wheel layout since the aerodynamics are significantly better than three and four wheel design.

The Vector trikes, like the dragsters of the automotive world, were limited-use vehicles. The same small cross-section that made them so aerodynamic also made them very difficult to see from the perspective of an automotive driver. During its record setting 42 mile highway run, the Vector tandem was bracketed, front and back, by guard vehicles to protect it from autos merging into the space it occupied. The limited wheel lock for the steered front wheels made only large radius turns possible. The lightweight high-pressure tires required a clean road surface to prevent punctures. And the rider in the Vector had a limited field of view. Not to mention that a light 51 lb. vehicle provides woefully inadequate crash protection for a vehicle traveling at 60mph. Finally, these low-narrow layouts require the assistance of at least another person for the rider to get in and out of the vehicle 

Now, after the Vector speed records, Alan Carpenter, a designer from Colorado, build a production vehicle that he felt would be a practical human-powered vehicle. The Cyclodyne was a very well thought out and well-engineered vehicle.

The Cyclodyne was a tadpole trike, like the Vector. It was, however higher at 40in. for better visibility and wider at 38in. to provide the necessary roll-over resistance. It even incorporated driven front wheels to double the drive traction over the typical tadpole trike. A fit cyclist could pedal the Cyclodyne at over 30mph.

One owner related a critical problem with the Cyclodyne. Even being pedaled at 35mph, it was not fast enough to prevent traffic backups behind it  when ridden in automobile lanes. The motorists didn't know what to make of the vehicle. In frustration, he finally removed the faring so the drivers could see he was operating only on pedal power. His speed fell drastically, but the cars lost their reluctance to  pass him and the backups were eliminated.

Since the Cyclodyne was only 38in. wide, it would comfortably fit within most bike lanes located adjacent to many roadways but it was not fast enough to be interleaved with automobiles. The appropriate traffic infrastructure wasn't available for the above owner.

The Cyclodyne demonstrates that, with a bit more attention paid to aerodynamics, an enclosed all-weather trike could reasonably be expected to have a top speed of over 40mph.

So back to transportation infrastructure. Where could such a vehicle be ridden? Do legal vehicle speeds preclude the use of such vehicles? 

A catalog of the places and speed limits for use in the Seattle, Washington reads something like this:

Sidewalks, no speed limits
Residential streets, 25mph
Local roads, 35 to 40mph. Most of these roads have adjacent bike lanes.
Interstate highways. 60mph in the city and 70mph outside the city. Many of the highways outside the city have wide shoulders that allow cyclists to safely use them.

So residential streets and any other roads with adjacent bike lanes would be acceptable. For safety reasons there are the two requirements that the vehicle should be clearly visible to motorists and narrow enough to not obstruct traffic. A Cyclodyne-like vehicle satisfies these requirements.

Carpenter made one bad decision that limited the sales of the Cyclodyne. Its price tag of $4000 in 1980's dollars. He justification was that Early Winters, an outdoor outfitter in Seattle, was selling a used Vector trike for $10,000. Now the the Vector cost was not representative of a production vehicle. There was only one of them and it never sold. It ultimately was donated to a Seattle human-powered vehicle club.

Let us assume that a Cyclodyne-like tadpole trike, with some aerodynamic improvements would allow a reasonably fit rider to reach 40mph without sprinting. So the technology predicted in the Reader's Digest article exists, albeit at a 40mph level instead of a 60mph level.

(In fact, since the Cyclodyne already had front-wheel drive, one big improvement would be to allow the rear wheel to do the steering. The front wheels would present less frontal area. The main faring could just enclose the rider and the rear-steered wheel. The front wheels could be mounted outside the faring with individual wheel pants to streamline them. Joy-stick steering could be substituted for the under-seat steering to further reduce the faring width. While the drag coefficient for this layout might be greater that the original design, the cross-sectional area would be significantly reduced and the product of drag coefficient and cross-sectional area would make the vehicle more aerodynamic.This would be at the expense of some cargo capacity. In addition, having two front wheels that do not steer is much more stable when going over obstacles when compared to two steered wheels which can be deflected causing unwanted steering inputs.)

The continued development or an all-weather commuter vehicle that could be safely integrated with traffic has also been largely curtailed by pedal-electric technology.

But is the electrification of bicycles and tricycles a bad thing for the development of human-powered commuter vehicles?

Let's look at the electric bicycle regulations for Washington state to get more specific on answering that question. Keeping in mind that tricycles and velomobiles fall under these requirements. 

The above regulation lost part of a sentence, one that is as important as the categories. The second sentence should read "The electric bike must have two or three wheels and fully functioning pedals" .
The eliminates vehicles like the Pod Bike (strange name for a four-wheel vehicle) and the Quattro Velo if it includes electrification. Now this is a bad requirement if one is designing an all-weather commuter vehicle, since for a given track and weight distribution, a quad had 50% more rollover resistance than a trike. On the other hand, a four-wheel motorized vehicle falls into the category of a micro car with all of its extra regulations.

Another electric bike regulation says that the vehicle must have a bicycle seat and for trikes, one of the wheels must be at least 20" in diameter. Now requiring a bike seat would eliminate all recumbents. And I, like the Cyclodyne designer, prefer three 16" wheels because they allow a smaller vehicle volume.

Class 3 is a recent and welcome addition to what is considered an pedal-electric vehicle.

Now a fit cyclist can generate 200+ Watts of mechanical power. So with more than three times the available power, aerodynamic and weight considerations can essentially be ignored. One problem that this surplus power can't solve is vehicle width.

For visibility in traffic, it is desirable that the rider's head height is no lower that that of a driver in a sports car. For static tricycles, roll-over-resistance is developed by making the vehicle width approximately on the order of twice the height of the vehicles center-of-gravity, c.g. If the designer is not diligent in keeping the c.g. low, the vehicle width can get excessive.  It is my opinion that electric velomobiles like the Elf, with a 48" width, are too wide to share dedicated bike lanes with other vehicles.
I think that electric velomobiles should have a width restriction of 1m (39") for access to dedicated and roadway adjacent bike lanes.

An electrified version of the Cyclodyne, at a 38" width, could easily manage the 28mph speed limit for a Class 3 electric tricycle and be a very beneficial all-weather pedal-electric commuter vehicle.


Friday, October 25, 2019

David Gordon Wilson: The Father of the Modern Human-powered-vehicle Movement

Prof. David Gordon Wilson died on May 2nd 2019 at the age of 91. He began the modern human-powered-vehicle movement when he sponsored a design competition for an improved version of human-powered land transport in 1967.

Wilson received his PhD in mechanical engineering from the University of Nottingham in 1953. Between that time and 1966 when he joined the faculty of MIT in 1966, he engaged in multiple pursuits.

 He received a Commonwealth Fund Fellowship to conduct research in the USA with MIT an Harvard concluding with work for the Boeing Commercial Airplane Company as a gas turbine engineer.

Wilson did a two-year stint in Africa, teaching at he University of Ibadan in Ziria. Nigeria.

After doing two years of Voluntary Service in Cameroon, Wilson contracted malaria and was forced to more back to England.

In 1960, he was invited to be the technical director of the Northern Research and Engineering Corp to form a London branch specializing in turbo-power machinery and heat transfer.

Invited to MIT for a permanent position in 1966, Wilson taught thermodynamics and mechanical engineer. Students he advised conducted research in turbo-machinery, fluid mechanics and other design topics.

Wilson retired from MIT in 1994 after 28 years. He acted as professor emeritus until his death.

Outside of the university he pursued issues as an environmental activist particularly in regard to transportation. Wilson was appointed to a commission of the Massachusetts Bay Transportation Authority.   He served on the Center for Transportation Studies.  He joined the Massachusetts chapter of Common Cause and was the co-founder of the Massachusetts Action on Smoking and Health which advocated for the rights of non-smokers.

In later years Wilson invented a heat-exchanger and a micro-turbine which are fundamental to non-photo voltaic solar power production. The company, Wilson Turbo-power was formed to commercialize the inventions.

And in 1974, Wilson came up with the idea of the Carbon Tax.

Of course, when it comes to the environment and responsible transportation, Wilson will be most remembered as a life-long commuter cyclist who used a bicycle instead of an automobile. Wilson was not deterred from using bicycle by the most severe weather.

Up until the mid 70's, Wilson rode a Moulton. Now at the time the Moulton design was quite sophisticated. It used 17" narrow high-pressure tires and had front and rear suspension. The small wheels made room for carrying quite a bit of cargo over the front and rear wheels. (I knew a college physics professor, an all season cycle commuter like Wilson, who carried a 55 lb. filing cabinet on the back of his Moulton.) The Moulton could also be folded in half for storage and transport.

So, even though he was riding the best engineered commuter bicycle, he still felt there was a lot of room for improvement.

As Wilson was about to leave the UK for the USA and his job at MIT, he found out he would not be able to take his savings with him.So in 1967 he took his savings and organized an international competition for man-powered land transport. There were 73 entrants before the judging in 1969.

A summary of the results can be found in the magazine:

Engineering (London) vol. 2071, no 5372, 11 April 1969, pp. 567-573

The winning design was from W. D. Lydiard, a British aerospace engineer. Not only did he submit a paper design he build an actual prototype of his Mk.3 version. He called this version the Bicar.

Shown below is a  schematic of the Mk. 3 version top and the Mk. 4 bottom.

The Bicar was an enclosed recumbent bicycle that used 16" wheels. Lydiard invariably encountered what I call "the recumbent bicycle problem", that being, for a front steered recumbent bicycle, the pedals want to be in the same location as the front wheel for an ideal weight distribution. He solution was to use an non-circular, elongated pedal path located above the front wheel. the pedals moved in near linear tracks and  were attached to connecting rods that pulled on a conventional crank. This mechanism is what I refer to as a "oscillating treadle".

The post listed below discusses linear pedal motion in some depth.;postID=5532337496842064005;onPublishedMenu=template;onClosedMenu=template;postNum=9;src=postname

Lydiard encountered interference with the pull rods when he put his feet on the ground through the flaps in the body, so he also presented a Mk. 4 version that used what I refer to as a constant-torque treadle.

Wilson was quite taken with the use of an elongated pedal path to minimize foot-front-wheel interference and came up with over a dozen sketches of different concepts, eventually detailing the design show below.

In 1973 Wilson was approached by Frank Rowland Whitt, a chemical engineer and a writer of technical articles for cycling publications. Whitt had gathered material for a book about Bicycling Science and he approached Wilson in hopes that he could help him get it published. Wilson in turn approached MIT Press and they agreed to publish it if Wilson would be a co-author.

The first edition was published in 1974. It was the first technical treatment of bicycle technology since Archibald Sharp's Bicycles and Tricycles published in 1896 and republished by MIT press in 1977. At last, human-power vehicle enthusiasts had a technical reference to aid in their research and designing. The technical bible had arrived and has only gotten more comprehensive with each edition.

Soon to be in it's forth edition, it is MIT Press's best selling publication.

In the mid 70's Wilson was contacted by a California bicycle mechanic named Frederick Willkie regarding the design of a recumbent bicycle and Wilson sent him several sketches. What resulted in what Willkie call the Green Planet Special 1 shown below.

The GPS1 was very similar to the Ravat recumbent of the 1930's.

Willkie found the GPS1 uncomfortable to ride and asked for some modification suggestions. Wilson told him to lower the pedals in front of the front wheel, locate the handlebars below the legs directly on top of the fork and lean the seat back. The GPS2 was born.

For reasons not revealed, Wilson purchased the GPS2 form Willkie. He made subsequent modifications and the Wilson-Willkie recumbent bicycle was created. Wilson added a number of creative features to the WW. Loops attached to the pedals that allowed one to ride with dress shoes, a large luggage box behind the seat and a hammock style seat.

By 1976, Wilson riding the Wilson-Willkie recumbent became the poster child for a better bicycle, at least in the USA. He was featured in newspapers, magazines and a commercial for creativity by the Mobile Oil Company

I sure the irony of a man riding an alternative to the automobile being showcased by an oil company was not lost on Wilson.

Wilson teamed up with Harold Maciejewski and Richard Forrestal to investigate making commercial recumbents.

The Avatar 1000 thus followed the WW.

And the Avatar 2000 followed that.

The Avatar 2000 went on sale in 1980 and was the first commercial recumbent since the Second World War. ( The Hypercycle, being a knock-off of the Wilson-Willkie quickly followed.)

I have ridden s.n.85 Avatar 2000 for 35 years and I must say it is the most comfortable bicycle and recumbent that has ever been manufactured. The only negatives I have encountered are the difficulty in transporting a bicycle with a 63" wheelbase and a lightly loaded front wheel which can wash out on slippery surfaces.

Wilson generated a chart comparing the weight distributions of various upright and recumbent designs.

The ideal appears to be having between 36 & 40% of the vehicle and rider weight on the front wheel.

It is interesting to note that if one used a 16" and was to allowed an intermediary bottom bracket with sprockets on both sides, ( as the GPS1 and GPS2 had) then the wheelbase could be made 8" shorter than the Avatar 2000 and the front-wheel weight distribution could be increased the 35.5%, getting very close to the idea.

In later years Wilson did not commute on an Avatar 2000. When he rode to the campus  at MIT he had to carry his bike up quite few flights of stairs to his office. The Avatar 2000 was much too cumbersome for that task so he rode more compact recumbents of his own design.

The second picture was probably Dave's last recumbent and is of interest because it uses a timing belt to connect the pedals to the intermediary bottom bracket.

I was first introduced to Wilson in 1972 reading his 1968 article "Where Are We Going In Bicycle Design?" reprinted in Harley M. Leete's "Best of Bicycling" book.

I bought the first edition of "Bicycling Science Ergonomics and Mechanics" in 1974.(I subsequently bought the second and third editions and will buy the fourth edition when it is published next year).

  I started communicating with him in 1976 while in grad school requesting more information about his recumbent designs.

 In 1989 he edited my article on rear-steering recumbent bicycles published in "Human Power", the magazine of the International Human-powered Vehicle Association (IHPVA).

He sent me over a dozen of his designs for linear pedaling recumbents.

I met Prof. Wilson at the 1990 IHPVA speed championships held in Portland Oregon. I believe he was the president of the IHPVA at that time.

 And he endorsed the Lefthandedcyclist blog and his friend and publisher Richard Ballantine expressed interest in publishing a collection of my posts.

Prof. Wilson, the bicyclist and human-powered vehicle builders of the world are greatly in you debt.

Dr. Recumbent, we solute you!


Thursday, November 29, 2018

Aerion: An Optimized All-weather Ped-electric Trycicle

Those of you that have followed my blog at all know my opinion on what constitutes an optimal ped-electric commuter vehicle.

1. The vehicle should have three wheels for stability on slippery surfaces.
2. It should place the rider's head at the height of a typical automobile.
3. It should be narrow enough to comfortably fit in a bike lane. I can be more specific on this. It should fit between barriers spaced 36" apart, so assume a maximal width of 34".
4. It should not overturn when cornering. Assume a tipping resistance of 1 gee.
4. It should be enclosed to protect the rider from the elements.
5. And for traction on slippery surfaces, it should drive two wheels.

Now if the vehicle is a static tricycle point 2 and 3 are at odds with each other. High enough rider and wide enough to not tip over in turns results in a vehicle that has a width of about 48".

The solution to this contradiction is a leaning tricycle.

When correctly designed, leaning trikes can be balanced just like bicycles. Like bicycles, the most difficult task is getting started from a stop. One has to develop balancing speed often with one pedal thrust to avoid tipping over or having to put a foot down and start again.

Problems appear when the leaning trike is enclose in a body that interferes with the action of starting.
To remedy this potential problem the vehicle need a mechanism to lock-up the leaning for starting, and stopping. The locked-up mode could also be used in slippery conditions when balancing is not practical. You now have two modes of operation, balancing and being stable. The rider has to switch modes and decide when to do so.
Refer to the Velotilt design where the leaning needs to be locked up when the rider gets into the vehicle and starts moving or when the vehicle is stopping.

I discussed the problems I had starting and stopping my EcoVia trike in the post below.

When a fellow HPV-er tried to ride the EcoVia he pointed out the average rider would have trouble mentally switching from one mode to the other. I could not disagree, having once forgotten that I was in the balancing mode and thinking I was in the static mode. This resulted in a swerve that may have ended my HPV career had there been any other cars near me at the time.

So how to address this problem?

I believe you must have the static mode for starting, stopping and slippery conditions. The balancing mode is the most problematic so eliminate that. Since you still need to lean the trike to prevent tipping over in corners, make it controlled by the rider by means other than balancing. 

Now since accelerometers, controllers and stepper motors are inexpensive, the logical approach for controlling lean for an electric vehicle is computer control, with it being transparent to the rider. Since lean angle is a function of radial acceleration, which in turn is a function of steering angle and vehicle speed, the necessary calculations are relatively simple.

Lean control for non-electric vehicles is more problematic.

GM's Lean Machine from the 1980's used foot pedals, since the vehicle as gas-powered.

A human-powered vehicle more likely than not uses foot pedals for propulsion, so that is not an option.

One could combine lean control and steering into one action. I tried that with the first version of the EcoVia, but the approach introduced bump-steer with disastrous consequences.

Or one could use dual-control that used two hand motions, one for steering and one for leaning. The Tripendo uses this approach with apparent success. It employs two long levers. One does the steering and one does the leaning. The rider continually adjusts both to keep the trike stable.

Dual control could be used without requiring continuous lean adjustment. For example, the MK3 version of my EcoVia has a c.g. height of approx. 23 in. an a track of 30". This allows for a .43 gee turn without needing to lean.


One can calculate the required geometry for a fixed lean that can resist one gee just at the limit of tipping over.

For a vehicle that leans by having its wheels move essentially vertically, staying parallel to the vehicle, like the Toyota iRoad above, the relations below apply:

The first equation calculates the relation between width, height and lean angle at the limit of tipping. The second equation calculates the relation between the width, height and lean angle that will resist one gee laterally without tipping.

Interestingly, the lean angle for this condition is not a function of w (track) or h (cg height). It ends up being 26.6deg. Not surprisingly,  The lean angle of the iRoad is about 26deg. And the iRoad width is about 34"

The cg. height for the above conditions is a function of the lean angle and the effective track, w. If the actual track is 30", the effective track is approx 2/3 of that for an equal-wheel-load configuration or 20". For a 20 track the required c.g. height is 25".

 Let us compare the gee limits for several configurations with this geometry.

1. Statically, without any lean, it would take .4 gees to tip over.
2. For balanced leaning, it could withstand .5 gees. The vehicle would have to lean 45deg to resist 1 gee.
3. If the vehicle had four wheels where the front and back track was equal, it could withstand .6 gees. The track would have to be 50" to resist 1 gee statically.
4. And with the lean locked at its 26.6 deg limit, it could withstand 1 gee.

Clearly, for a given track width, a tricycle with controlled leaning gives the greatest resistance to tipping.

So our optimal all-weather ped-electric trike will have controlled leaning where the leaning is determined by computer.

What about the wheel layout? Should it be a delta trike or a tadpole trike. Due to drive-train complexity I will eliminate the tadpole configuration where the front wheels drive and steer. That means that if the two front wheels drive, the single rear-wheel steers. (Like the iRoad).

Below is the EcoVia Mk3. The long lever controls the leaning while steering is located below the seat.

The biggest advantage of the delta configuration is the pedals can overlapped with the front wheel to produce a very short vehicle. The vehicle can be lighter weight because the structure supporting the front wheel can also support the pedals. Along with these advantages comes three disadvantages. The steering lock is limited. Not enough to be a problem for normal turns but enough to prevent tight turns. Only one wheel is available up front for braking where the load is transferred to during hard braking. Lastly, the steered wheel is the first wheel to encounter obstacles like railroad tracks. The obstacles can perturb the steering and unexpectedly change vehicle direction.

Below is the EcoVia Mk1

The biggest advantage of the tadpole configuration is it doesn't suffer from the three issues plaguing the delta configuration. On the other hand, the package is longer that the delta configuration because the pedals are on one end and the steered wheel is on the other. The space between the seat and the rear wheel could be used as a trunk. And there is the issue with rear-wheel steering. Since the controlled leaning approach does not involve balancing, this should not be a show-stopper. After several communications with Jim Kor of Urbee fame, he described his approach to make his rear steering stable. The Urbee without body is shown below.

I believe despite its problems, the tadpole configuration wins out.

Below is a drawing and photo of the Cyclodyne, a tadpole trike from the early 1980s that was capable of cruising at over 30mph. The Cyclodyne, of all the commercial human powered vehicles, came the closest to harnessing the potential of human power as a transportation alternative.

To resist tipping rider's head height was about 39" and the vehicle width was about 48". Roll-over resistance as at least 1gee. While the rider's head height was acceptable, being comparable to a sports car, the width was too wide to fit comfortably on a road shoulder.

Had it been made a quad by adding a fourth wheel, the width could have been reduced to the target 34" and speed would have been increased as well, making it a very practical commuter vehicle. But the fourth wheel would prevent it from being considered an electric bike if a motor was added.
Adding controlled leaning could have reduced the vehicle width, increased visibility by raising the rider's head height and allowed it to be electrified. An optimal all-weather tricycle configuration.

Even though it only exists as a few equations and a few crude sketches, I have a need to give a name to this all-weather, ped-electric, fixed-leaning, front-driving, rear-steering tricycle. I will call it the Aerion. (Aerion is also the name of an aviation company developing a supersonic business jet).

I have a bias for the Toyota iRoad. My first configuration in 1990 for the EcoVia was a front-driven, rear-steered leaning configuration. I was not using controlled leaning but was balancing the vehicle and I could not make the rear-steering stable. More than two decades later, electronic controls allow the iRoad to do what I couldn't and reap the benefits of an optimal configuration.


Wednesday, December 23, 2015

The Velotilt: a Pedal-Powered Commuter Trike for a Bike-Friendly World

In 1980, after the Vector trikes shattered the Human Powered Vehicle Championship speed records, people began to believe that human-powered vehicles could travel fast enough to be viable transportation vehicles. The ultimate nod to HPV recognition was an illustration of a Vector trike on the cover of Scientific American magazine. The age of pedal-power had arrived.

Well, not really. Vehicles like the Vector were low to the ground, and, as a result, not very visible in traffic. Their extreme streamlining kept the wheel-track narrow so high-gee turns were not possible.
One vehicle, the Cyclodyne did come close to being a practical commuter vehicle. A tadpole-layout trike with front-wheel drive and steering, the Cyclodyne could be pedaled over 30mph by a fit rider. Its practicality was compromised, however, by its width. It was too wide to fit in a 36” bike lane next to a car lane, but not fast enough to keep up with 35mph traffic in the car lane. A noble effort, but a dead-end.

Now to some extent, the lack of a fast commuter vehicle may be as much a problem with a lack of suitable places to ride them as the vehicles themselves. The really fast vehicles (>30mph) are low to the ground for minimal aerodynamic drag. Such vehicles are difficult to see in traffic. On the other hand, dedicated bike paths, where vehicle visibility may not be an issue, have 15mph speed limits that prohibit high-speed vehicles. (Riders on the Burke-Gillman trail in Seattle have received tickets for exceeding 15mph.)

If there was a bike-commuter infrastructure that separated bicycles from car traffic and allowed for very-fast pedaled vehicles, Wim Schermer’s Velotilt would be the vehicle to ride.


The Velotilt is a delta trike where the front wheel is driven and the rear wheels are attached to beams that can pivot. The act of pivoting allows the Velotilt to lean into corners like a bicycle.


 The degree of leaning is limited so the vehicle cannot tip over statically. The beams are interconnected by a mechanism that causes one beam to move down while the other moves up. The middle link in the mechanism is composed of a sector of an arc. As the mechanism moves the sector rotates. This sector can be clamped in any portion of its extremes of travel and thereby lock the leaning.


In addition the entire mechanism can translate, allowing both beams to pivot together. This motion is resisted by a mountain-bike shock and provides suspension for the rear wheels.
The rider’s legs wrap around the front-steered wheel. The cranks are located in front of that wheel and the wheel is driven through a very pricey Rolloff 14 speed internal-geared hub.

All three wheels have disc brakes but in all the photos, the rear disc are lacking calipers and actuation cables.

Commercial vehicle weight is expected to be 55lb. The vehicle height is approx. 40”.

The Velotilt body and the rear-wheel pants make the vehicle extremely aerodynamic. Schermer calculates that it will take 150W to do 40mph. Bicycling Science 3rd Ed (D.W. Wilson) estimates that an ultimate HPV would require 200W to do 40mph, so the efficiency of the Velotilt is indeed impressive.
An optional 750W motor could help propel the Velotilt to 60mph for a duration of over 2.5 hours, but where would you ride it? Too low to mingle with car traffic and too fast to mingle with regular bicycles.

Possibly, one could transform the high efficiency into something other than raw speed.
For example, the Velotilt might be able to sustain a constant 15mph on solar power alone. Or the vehicle could be made higher than its current 40"to be more visible in traffic. As it stands, I believe some evolution remains in the Velotilt’s future.


Some of the pictures in this post came from Adam Ruggiero’s article, “The Future of Human-Powered Transport is a Trike” in the March 18 issue of GearJunkie.

Monday, December 21, 2015

The Sinclair C5: The Worlds Worst Invention or the Template for an All-weather E-bike

I confess to being overly fascinated by the Pedicar. Maybe because it became available when I was discovering recumbents and realizing there were more utilitarian human-powered vehicles than the safety bicycle. It made a significant public relations splash because it was aimed at replacing the automobile for short trips. And at least one auto maker, Chrysler, took enough notice to lampoon the vehicle.

Now if available today, the Pedicar would make a worthy commuter vehicle. Placing the rider’s head at the same height as an auto driver, it had good visibility on the road, a feature I feel is a must if you are going to ride next to 35mph traffic in a 36” wide bike lane. Add wheel pants and a more aerodynamic body along with rotary pedals and a derailleur shifting system and you would have a faster, lighter and less expensive vehicle. (It probably would not climb hills as well.)
Drive the wheel (wheels) with an electric motor and you would have a very functional all-weather E-bike. (I use the word bike in this sense to refer to a pedal-powered vehicle that can have more than two wheels.)

But not so fast! In the US and other countries, and E-bike can have no more than three wheels. Add a fourth wheel and you become a moped, losing the legal status that lets you use bike lanes and bikeways.

And removing that fourth wheel causes problems with the vehicles ability to corner without overturning. The Pedicar, with a 36” track had a rollover resistance of in excess on one gee. If you went to a three-wheel layout and located the center of gravity (c.g.) such that each wheel was equally loaded, (1/3 of the wheelbase from the paired wheels,) the rollover resistance would be reduced to 66% that of a four-wheel vehicle.

Let’s look at some contemporary all-weather E-bikes.
The ELF is manufactured by Organic Transit and uses the tadpole wheel configuration (two front steered wheels and one rear driven wheel). I would consider it a laudable effort at producing an all-weather E-bike, (AWEB) but it has some issues that would prevent me from using in in my commute to work, namely it has a 48” width. 

The width is necessary to prevent rollovers when cornering. I will assume the track is 44” and there is 2/3rds of the weight on the front wheels. Even with the added width, compared to the Pedicar the ELF’s roll over resistance is only 80%.

In addition to the 48” with causing the ELF to hang out into the auto traffic lane on some bike lanes, it results in poor aerodynamics. This may not be an issue because E-bikes in the US are limited to 20mph, in some cases with pedal assist and in others without.

 The ELF uses a 750W electric motor to achieve its 20mph, which is the maximum power for the E-bike regulations the Organic Transit people are citing. With respect to the power a human can generate, 750W is a lot of power. World-class cyclists can sustain half that amount for about an hour. A racing cyclist requires about 155W to go 20mph (Bicycling Science 3ed-D.G.Wilson). This source states that a commuter-human-powered vehicle should require on the order of 75W to go 20mph. (The Organic Transit site states that the ELF has the same drag coefficient, Cd as a bike rider. We know that air drag is proportional to the product of Cd and cross-sectional area, so we can extrapolate that the ELF has about four times the frontal area of a bike rider.)

Vehicle weight is between 170 and 190lb
So as a pedal-powered-only vehicle, the ELF is not very efficient. As long as the battery is at full charge, this is probably not an issue. Run the battery down, however, and you will be working very hard to hit 15mph and with a topped off battery it will require a lot of effort to reach 25mph.

The prototype Velocar from VeloMetro has a layout similar to the ELF and, as a result will be subject to the same issues.
Now the 33% loss of rollover resistance when going from a quad to a trike is based on locating the c.g. so all the wheels are equally loaded. There is no requirement to do this. If the c.g. were located near the paired wheels the rollover resistance of a trike would be minimally compromised. With a typical tadpole layout, this would result in a lightly loaded drive wheel and potential tire slippage. Unless, of course you are driving and steering the front wheels (which, while technically interesting is more complex an approach than driven the rear wheel only).

The alternative trike layout is the delta, with one wheel forward and two wheels back. Biasing the weight toward the rear wheels aids traction but results in the front tire being lightly loaded and more prone to lateral slippage in slippery conditions. A delta trike, with an enclosing body, is inherently more streamlined than the tadpole trike, because the steered-front wheel is easily enclosed within the body.

The Sinclair C5 was a delta trike. A sectioned view is shown below.


The C5, the brainchild of the British industrialist Sir Clive Sinclair, had been called one of the world’s worst inventions. Even so, until the sale of the Nissan Lear, It held the record for number of electric vehicles sold at over 7500 units. The separation between genius and madness is often small.
The C5 used a 250W motor to reach 15mph, the legal limit for vehicles of the type in Great Britain. IMO the vehicle was quite attractive and relatively aerodynamic. Bicycling Science gives a racing cyclist’s power to travel at 15mph as approx. 80W, but unlike the ELF the C5’s inefficiencies were a result of rolling resistance and mechanical losses.

The front tire was 12” in diameter, the rear tires were 16” in diameter. There was only one pedal speed and no provision to adjust the distance between the seat and pedals. The crank length was about 130mm (normal is closer to 170mm) and the gear was about 44”.

Wheelbase was 51” (not too long for a recumbent bicycle), width was 29” and the seat height appeared to be on the order of 12 to 14”. Vehicle weight with a battery was about 99lb.
A custom geared motor drove the left-rear wheel through a belt drive and the pedals drove the right-rear wheel through a freewheel on the axle.

An attempt was made to allow the wheel-support outriggers on the rear chassis to flex and result in some suspension. (Photos of used vehicles show that the chassis developed cracks between the outriggers, suggesting that the chassis designer, Lotus Sports Cars, underestimated the stresses the flexing would cause.)

The video below is quite lengthy. If nothing else, skip to the end to the C5 on the road. It doesn’t seem to roll very smoothly. I don’t know if it is due to wheel size or lack of rear suspension. The original front wheel rims were plastic with caliper brakes acting on them. The brakes resulted in the rims melting so restorers often used pram wheels in the front. These could be as small as 8” in diameter.

From a human-powered assist perspective, the biggest design flaw was that the pedals seemed to be added after fact as opposed to being integrated into the design. Restorers often insert a 3-speed hub ahead of the rear axle to get the extra speeds. Making the seat to pedal distance adjustable is not something that could be easily retrofit-able because of one-piece chassis and one-piece lower body pan.

Besides the pedal-ergonomic issues, other concerns were that the rider sat too low for good visibility in traffic and inadequate weather protection. The former concern was addressed by adding a framework behind and above the rider that held reflectors. The latter was addressed by optional side curtains and a rain suit for the rider.

Three factors probably resulted in adequate rollover resistance. The seat height was relatively low compared to the track of the trike. The c.g. was biased strongly over the rear wheels and the maximum vehicle speed was only 15mph.

In 2010 Sinclair was working on resurrecting the concept of an all-weather E-bike in the form of the X1, which is a true bicycle, having only two wheels.

The latter part of the video below deals with the X1.

As the comparison illustration states, the X1 had better weather protection and a higher rider height Than the C5. The top of the vehicle is 55”, which in the photo next to an auto, looks like it should be even higher for good visibility. On the other hand, the roof of my Honda Civic is about that height. The width at 27” is 2” narrower than the C5. Both wheels are now 16” in diameter. Although it is not stated, the fact that, at 83”, the X1 is approx. 12” longer than the C5 may indicate that the seat to pedal distance may be adjustable by sliding the seat. There is no indication that the vehicle had more than one pedal speed. The electric motor drives the rear wheel and produces 190W and the overall vehicle weight with battery is a light 66lb. Like the C5, the design of the body is quite attractive. The vehicle seems to roll with less vibration than the C5. Partly because of the longer wheelbase, (about 73” vs the 51” for the C5) but mostly because both wheels appear to be suspended.
The fact that five years have passed and there is still no commercial X1 may indicate that the design had issues that prevented it from being commercially viable. I can speculate about what one major issue might have been.

Going from a tricycle to a bicycle, one loses the static stability necessary to get into a semi-enclosed vehicle. The body can interfere with lifting the support foot up when starting and putting a foot down when stopping. Even though there are cutouts in the lower body so the feet can touch the ground, the cutouts prevent the feet being paced laterally very far from the vehicle. So one must put their foot down before the vehicle has tipped very far. In the video above, we see the rider stopping but not restarting, the more difficult of the operations. See below.

So the Sinclair team apparently went from three to two wheels as a weight saving and lost the static stability in the process.

So as is my want, l would like to speculate about the changes required to the C5 to make is a viable all-weather E-bike for the US market where the top speed could be 20mph. 
I would use larger wheels, 16” in front for better rolling resistance and 20” in the rear for the ability to obtain higher gears.

I would make the seat to pedal distance adjustable by making the structural frame in two parts. The rear part would hold the rear wheels, the seat, batteries and any cargo. The front part would hold the front wheel and the pedals. The front part could be slid into the rear part to adjust seat to pedal distance. A similar approach is used in the Kettwiesel tricycle below.

I would have the seat height about 18”, placing the riders head about 48” off the ground wearing a helmet. I would keep the bottom bracket at about 15”, as low as I could get it without having the rider’s heals scrape the ground.

I would use a single chainring in front and attach a cassette to the rear axle. I would connect both rear wheels to that axle through freewheels, thus insuring a posi-traction-type drive.
I would use a hub-motor in the front wheel for the electric drive.

I would suspend the rear wheels and load the front wheel lightly enough so it didn’t need suspension, say 25% of the vehicle weight.

I would divide the body into two parts. The front cowl would completely enclose the front wheel and cover the rider up over the legs. This cowl would move with the crank and front wheel when adjusting the seat-to-bottom-bracket distance. The rear portion of the body would cover the riders head and the rest of the body. The rear portion would rotate upward about a pivot in the back of the vehicle to allow the rider to enter and exit.

I call the vehicle below the Avacar because it has a similar rider layout to the Avatar recumbent. The rider’s head height with helmet is 48”. The wheelbase is 53” and the vehicle track is 26”.

To this point I haven’t discussed turn-induced rollover issues with my redesigned C5. One advantage of making the Sinclair X1 a bicycle is that it has dynamic stability and can lean into the turns.
Let us assume that the original C5 had no rollover issues. I have made two changes that will reduce its rollover resistance, (ROR). I have raised the c.g. of the vehicle and I have increased its top speed. The 4” increase in seat height reduces the ROR by about 10%, assuming a c.g. height of about 17” for the original C5. The 5mph increase in speed reduces the ROR by about 44%. Together I have reduced the ROR by about 50%
The track of the old C5 was about 27”. To maintain the ROR of the original, the track would have to increase to 40.5” and the width to almost 43”. The width of the redesign is no better than the ELF or the Velocar.

That brings me to the question,” Should the AWEB be a leaning tricycle?” There is an all-weather E-bike on the market, the Drymer. It utilizes the tadpole layout.

Now I have discussed the design of leaning trikes ad nauseam. However, I have two new observations about the design of leaners when they have bodies that prevent riders from easily putting their feet on the ground to support the vehicle.

The first observation is related to the lean-lock mechanism that prevents leaning at very low speeds and when entering and exiting the vehicle. The default state for the lean-lock should be engaged and the rider should actively disengage it. For electric vehicles, engagement could occur when power is shut off or when vehicle speed falls below a predetermined low level. Engagement must be quick and positive, where the engagement force is not provided by the rider but inherent in the mechanism. The rider merely overcomes the engagement. This approach insures that there is always enough engagement force for complete prevention of leaning. Engagement mechanisms that are position dependent as opposed to force dependent are preferred.

The second observation is that, under no circumstances, should the vehicle be allowed to lean far enough to tip over statically. Now, an observant reader might point out that under these circumstances, the dynamic ROR is only slightly better than the static ROR. But that is not true if the lean-lock is engaged when the vehicle is completely leaned over. (The vehicle is leaned into the turn and locked in that position.) With the leaning locked in that position, the acceleration is acting against the full track of the vehicle instead of just one-half the track as in the static case.

Now I decided I wanted my design to be able to resist one gee acceleration when locked fully leaned over at the same time it was at its static tipping limit. It turns out the lean angle for this condition is 24.5deg. For a given c.g. height the vehicle track at the c.g. location is .829 times the c.g. height. The actual track is the c.g. track divided by the % of the weight on the rear wheels.

For example, if my CG height is 20.5”, the c.g. track is 17”. If 71% of the weight is on the rear wheels, the actual track would be 24”.

The Avacar drawing above is based on these numbers with 2” added to the track for a little safety margin. The vehicle width is 4” wider than this or 30”.