The Left-handed Cyclist
Monday, March 4, 2024
A Full-body Exercise Recumbent: The Omnidyne 3P
Sunday, September 4, 2022
Transcending the Pedicar: The EcoVia Mk3
The EcoVia Mk2.4, the best packaged, most aerodynamic version.
For those of you new to the blog or those of you that haven't followed it in a while, the EcoVia project was intended to design and build an all-weather ped-electric commuter tricycle. To reconcile having a narrow width and rider height that was visible to motorists, it would incorporate leaning to improve roll-over-resistance, ROR.
The initial concept was a tadpole configuration with pedal-drive to the two front wheels and a steered- motor driven rear wheel. ( I refer to this as the Dymaxion layout in reference to Bucky Fuller's famous Dymaxion Car)
https://www.blogger.com/blog/post/edit/7497191769424400596/839528612731061124
Now there are two ways to control the leaning of a tricycle. The first is free-leaning, where you balance like a bicycle. The second is to control the lean manually in addition to controlling the steering. Rear-steering bicycles are, at best, difficult to ride. A free-leaning rear-steering tricycle has similar issues, so the initial design intent was to control both steering and leaning with the same motion. Since the amount of lean is a function of steering angle and vehicle speed, this approach can only be approximate at best.Below is the control mechanism for the EV1.4
Unfortunately, combining leaning and steering can lead to the undesirable phenomenon of bump-steer where, when a steered wheel hits an obstacle, the steering is perturbed unexpectedly. This occurred during a medium speed test run. I was upside down in the road before I knew what hit me. I pushed the trike back home and never road the EV1.4 again.After a period of reflection I realized the only thing to do was flip the wheel arrangement around into a delta configuration. With the rear steering gone, the delta trike leaned and balanced like a bicycle. I had my design. Several design iterations followed to drop the bottom bracket height and use a large Q bottom bracket to maximize pedal-wheel clearance. EV2.3 resulted.
I had no problems starting and stopping with the EV2.3 until I added a faring.
As often as not, I would tip over before getting started of trying to stop. I had a lever that would lock up the leaning, but the trike was not always upright by the time I activated it. So I came up with a no-lean lock lever. If I was only partially leaned over, pulling the lever did two things. It pushed the trike upright and it locked it in that position.
Given the no-lean-lock lever and it's reduction in crashes, I was confident enough to do some speed tests. I was able to comfortably cruise at about 25mph on the flats. This confirmed the validity of the design concept.The initial faring in the picture below is 4" higher at the riders head than the final design.
The EV3 is a delta e-trike with the ability to be statically tilted using a long lever on the riders left side.
The seat height is 20" and with a bottom-bracket height of 14.4", the riding position is very comfortable. The rider's head at car level. Cranks are 165mm.
Vehicle weight without the faring is 99 lb. The faring weighs 23 lb.
The battery is 36V which gives a top speed of 15mph. The motor is a geared-hub motor that stops contributing to propulsion at its max speed. The design intent was to have plenty of torque for hill climbing. So much torque, that the front wheel brakes loose if too much throttle is applied when starting.
For comparison the EV3 has a width of 33"(838mm) and a riders head height of 49"(1245mm)
The EV4 is currently in the design phase. Because free leaning has been eliminated, I can return to the EV1 tadpole configuration with a Dymaxion layout. The foot-front-wheel interference is removed. The intermediary bottom bracket and its associated chain will be gone. The beam suspension will be replaced by springs in the lean linkage, in addition to adding suspension to the rear wheel. These, and other integrations will significantly simplify construction and reduce weight.
Wheel pants will streamline the front wheels which will be outboard of the fuselage. In addition the rear-motor wheel will use dual tires to improve traction and insure steering control is maintained in the event that one of the tires goes flat.
Thursday, August 25, 2022
Dave Wilson and the Improved Safety Bicycle Part 2: Outriggers
Sunday, August 21, 2022
Dave Wilson and the Improved Safety Bicycle Part 1
We can consider the late Prof. David Gordon Wilson, emeritus professor of mechanical engineer at MIT and author of four editions of Bicycle Science, the technical bible for all-things bicycle, as the father of the modern recumbent bicycle.
Wilson was a life long bike commuter and environmentalist and rode a small-wheeled Moulton to work. When Wilson launched his bicycle redesign competition in 1967, his goal was to encourage the development of a safer bicycle.
http://lefthandedcyclist.blogspot.com/2019/10/david-gordon-wilson-father-of-modern.html
With Fredrick Willkie, Wilson developed the Wilson-Willkie recumbent.
The Wilson-Willkie received national exposure when it was featured in a Mobil Oil commercial in 1976.Sunday, March 28, 2021
The Podbike and the Quadracycle Quandary Part 2
From the previous post, we concluded that the Podbike, with a few refinements, was an environmentally responsible vehicle for a single individual to take short trips using pedal and battery power. The problem was that having four wheels, if did not constitute an e-bike in the US and Canada.
If we were to convert the design to static three wheeler and maintain the roll-over resistance, ROR, the width would have to increase by 50%, making the trike too wide to share the road with autos of share a bikeway with other cyclists. And converting the design to a leaning trike would increase the cost and complexity.
So, can we eliminate the electric assist and match the top speed of a Class 3 e-bike, 28mph? Since extremely streamlines recumbent bikes have covered a flying 200m at over 90mph and were ridden over 57 miles on a track in an hour, this should be very doable.
Let's take another look at my all-time favorite all-weather, pedal-powered commuter vehicle, the Pedicar. It was designed by two aerospace engineers, Robert Bundshuh and Lionel Martin and produced in 1973. The Pedicar is discussed in detail in "Pedicar Technology" in a previous post.
https://www.youtube.com/watch?v=zvh44wzhw9c
Several factors prevented the Pedicar from becoming popular. Only 20 vehicles were produced. At $550, it was expensive compared to an average bicycle and had a top speed of only about 18mph.
How would one make the Pedicar more efficient so your average cyclist could pedal comfortably at 28mph?
The main speed limiter was the drivetrain followed by the aerodynamics.
The Pedicar had a linear-motion constant-treadle pedal drive (see " Lure of the Linear Pedal Drive" in a previous post) connected to a 5-speed transmission. Bundshuh incorrectly assumed that the constant treadle would produce a 50% power increase over circular pedaling. It could produce a 50% torque increase, but the deadspots at the extremes of the pedal stroke prevented even rotary-pedaling power levels from being realized. The pedals were not coupled together and that prevented a smooth pedaling stroke. One benefit of the linear pedal stroke was the nose of the Pedicar was lower than it would have been with circular pedaling. This resulted in a very unobstructed view of the road ahead of the vehicle.
Possibly an even bigger problem was the transmission. It had five speeds and allowed a range of 1:6.8, but the step size was 60%. The size of the steps never allowed the rider to get in a comfortable gear. A derailleur system has significantly smaller steps and combined with a rotary crank was considerably lighter. The weight of the Pedicar as 125lb. So some weight reduction is in order.
So we could replace the Pedicar transmission with a 1x12 mountain-bike drive that has a ratio of 1:5.6 and a step size of 17%. To minimize the swept pedal volume at the nose of the vehicle we could use 160 to 165mm cranks with a bottom bracket having a low "Q" factor.
The other area for improvement is the aerodynamics.
The exposed wheels are the biggest problem. The top of the tire is entering the airstream at twice the speed of the vehicle. So the airdrag of that tire is 4X the drag of a tire that is not rotating. The solution is to enclose each wheel in what the aviation world calls a wheel pant.
A place to look for ideas for streamlining a single-person, four-wheel vehicle is Extreme Gravity Racing.
Many of the racers use a bod-pod + wheel-pod approach for their layouts. Even though the drag coefficient, Cd, is larger than if the driver and wheels were enclosed in a single body, the cross-sectional area is significantly lower and the product of Cd*A is low enough to produce a noticeably more streamlined vehicle.
The picture at the beginning of the post is a corporate entry gravity racer from General Motors. Now the picture is deceptive because the GM car is very low and the wheels are only 12" in diameter.
In the end you might wind up with something that looks like the doodle below.