Reflections on the potential of human power for transportation

Saturday, March 14, 2015

Transcending the Pedicar: The EcoVia, Part 3

Let us review the human powered commuter vehicle criteria that were the requirements for the design of the EcoVia.

1.       Weather Protection

2.       Statically Stable

3.       Reasonable Cruise Speed

4.       Cargo Carrying Capacity

5.       No Wider than a Bicycle

6.       Same Height as an Auto

7.       Comfortable posture and ease of entry

8.       Two-wheel drive

9.       Car-type Wheels

The completion of the faring essentially brings the EcoVia Mk1 project to a close. In this post, I will discuss the construction of the faring and reflect on how well the design criteria were met, comparing the EcoVia to the yardstick for commuter vehicles, the Pedicar.


The foundation of the faring was a lozenge shaped rectangle of ½” dia. cro-mo tubing. This rectangle is orientated parallel to the ground. The front of the rectangle screwed on both sides to a framework that attached to the trike chassis. Pivoting around the axis formed by the two screws allowed the faring to tilt forward for rider access. Attached at the front of the cro-mo rectangle was a smaller vertical rectangle of 3/8” dia. cro-mo tubing. This is where the nose cone attached
The nose cone was made from EPS insulation foam, five 2” sheets glued together and formed to the correct shape. The final shape was coated with Styrocoat to form a hard-protective shell. The back surface of the nose cone was glued to a 1/16” thick sheet of polycarb and the polycarb was in turn screwed the vertical portion of the cro-mo frame.
The skeleton of the faring was made from ½”x 1/8” soft aluminum strips screwed to the cro-mo frame and pop-riveted to each other. ¼” x 1/8” aluminum strips were used between the larger strips.


The two sagittal strips along the top of the framework are spaced about 10” apart. With the nose cone removed, a rectangle of double-stretch fabric wrapped around the cro-mo frame tube at its bottom and the aluminum strips at the front, back and top. The fabric was sewn in place with Kevlar thread. The fabric was Spandura, which in addition to being double-stretch that could be made water repellant with a spray like ScotchGuard.

Screwed to the framework along the faring top between the fabric strips and behind the nose cone was a polycarb strip. Behind the nose cone the strip was left clear. Around the rider’s head the strip stopped to allow for a polycarb windscreen. A second polycarb strip continued behind the riders head. A third polycarb strip enclosed the back of the faring and was hinged at the top to allow opening and access to the luggage compartment. This hatch was held closed by a magnet screwed to the framework.


Wireless turn signals were mounted behind the front window facing forward and at the top behind the rider’s head facing backward.


The front turn signal is shown above.
A wireless speedometer was attached to the inside of the windscreen along with the turn-signal controls.


Rear view mirrors, which really didn’t work very well were bolted to the framework through the fabric.


A handle was attached to the framework just behind the nose cone to allow the vehicle to be lifted and moved around.


The weight of the entire vehicle was 83#. The weight of the faring, without the front mounting bracketry and rear faring support, was 16#.
Of course, the nagging question was how would the faring improve cruise speed of the EcoVia? In an attempt to assess that objectively, I spent two weekends doing four test rides over a 6 mile stretch of road that, except for one gradual downhill, was essentially flat. Three of the rides were without the faring to familiarize myself with riding behavior and the fourth was with the faring in place.

I must say up front that I no longer ride recumbents but instead ride an upright mountain bike. I never could go as fast on a recumbent as an upright, despite 21 years of riding an Avatar 2000.

I noted two speeds from each run. One was a speed past a traffic monitor set up to advice motorists of their speed that I encountered early in the ride. I had routine readings on an upright of between 17 and 19 mph. The second speed was the average for the entire six mile run.

Without the faring the speed past the speed monitor was 17mph and the average over the six miles was 14mph.

With the faring the corresponding speeds were 20 and 16mph respectively.

Needless to say, the speed increase with the faring was unexpectedly low, despite the faring appearing relatively streamlined.

Three reasons for the low improvement come to mind. One is the added drag from the flow under the faring, since its bottom is open. The second is that mechanical losses from all the drive components dominated the aerodynamic losses. The last is that a vehicle as high as the EcoVia has a large cross-sectional area than typical streamlined vehicles, even though its width approximates that of a bicyce.

The day I used the faring was a chilly 40deg F and the space within the faring was comfortably warmer that the outside with only my face and neck feeling the chill.

So against the original design criteria and compared to the Pedicar (below), how did the EcoVia fare?


1.       Weather Protection: Assuming the fabric was sprayed with ScotchGuard, only the riders head is exposed to moisture. Internally the wheels were covered with fenders. So like the Pedicar the EV provides weather protection.

2.       Statically Stable: The EV has a lean-lock to make it statically stable and the Pedicar is naturally so.

3.       Reasonable Cruise Speed: I feel the EV fall short here, at least with me riding it. The 16mph average should be closer to 20mph. The Pedicar had a 15mph cruise speed.

4.        Cargo Carrying Capacity: Currently the EV has about a 2cu.ft. cargo capacity which could easily be increased to 3cu.ft. The Pedicar easily has twice that.

5.       No Wider than a Bicycle: The EV has a width of 28” and the Pedicar 38”.

6.       Same Height as an Auto: Both the EV and the Pedicar meet this criterion.

7.       Comfortable Posture and Ease of Entry: Again both vehicles satisfy this criterion.

8.       Two-wheel Drive: Both vehicles satisfy this criterion.

9.       Car Type Wheels: The EVs wheels can be removed with one screw. They are all the same and it carries a spare. It is not clear how the one would remove the Pedicar’s wheels.

10.   Electric Assist on Hills: Attempts to add electric assist to the EV have been put on hold indefinitely because the electrical engineer assisting me had more important obligations. Two attempts to develop a motor controller were unsuccessful. Only a small fraction of the motor’s 600 Watt potential were delivered by the batteries. The Pedicar has no electric assist.

I would say the EcoVia met seven of the 10 criteria. Bumping up the cargo capacity to 4cu.ft. should be straight forward. Bringing the cruise speed up to 20mph appears to be a lot more difficult.

 Some final thoughts:

1.       Starting and the lean lock: The procedure for starting on a recumbent bicycle requires supporting the bike with one foot and keeping the other foot on the pedal. The pedal is thrust forward and the bike needs to be moving fast enough to maintain balance until the second foot can thrust on the pedal. With the EV starts in this fashion were usually successful. If a start failed due to lack of speed, one foot could be put down to maintain support.
With the addition of the faring it was difficult to get the support foot back to the ground after unsuccessful launches. The presence of structure and the narrow width of the faring inhibited getting a foot back on the ground. Several painful crashes ensued during unsuccessful launches. 
So successful launches with the faring required the use of the lean lock. Below, the disk brake that acted as the lean-lock for the EV.


When the lean lock is engaged the vehicle is like any other statically-stable tricycle. The level of static stability is therefore a function of the c.g. height, the track width and the load distribution of the wheels.

Engaging the lean lock also makes climbing slow-steep hills much easier. You don’t have to waste energy and concentration on trying to balance the vehicle at very low speeds, which is where balance is poorest.  

So for the EcoVia Mk2 I will be lowering the seat height from 24” to 20” and increasing the track from 20” to 24” to improve static stability when the lean-lock is engaged. The other improvement will be pivoting the faring at the back instead of the front to eliminate the weight and the foot interference produced by the faring-support structure around the front wheel.

Below is the EV with the seat height reduced about 4”. Compare this to the second picture in the post.


2.       Aerodynamics and the Delta Trike layout. Despite the poor performance of the faring, I am still bullish on the rear-drive delta-trike layout. The drive to the rear wheels does prevent clean streamlining of the wheels, but the overall package is very compact and that should keep the wetted surface of the faring at a minimum. The most logical addition to the faring design in a panel under the vehicle to enclose the faring. It is in this area that the rear-wheel drive and pivoting-wheel beams presents problems.
I do take hope in the success of the Velotilt design. While the Velotilt drives the front wheel instead of both rear wheels it is the design that is most similar to the EV.

 Granted, the Velotilt is much lower than the EV and the streamlining much more sophisticated, but the 6okph speeds the vehicle is capable of obtaining indicate there is hope for the EV to sustain 35kph.
3.       Future weight reductions: I feel that is should be possible to pull about 20# out of the current weight of 83# for the EV. Most of this will be in a significant simplification of the chassis.

a.        An 11 x 1 drive will replace the two-stage 7 x 3 system with it twin bottom brackets.

b.      The structure for front faring pivoting will be eliminated.

c.       The Soft-Ride-type seat suspension will be eliminated in favor of a mountain-bike shock connected to a link that holds the linkage that synchronizes the pivoting wheel beams. This will remove one large frame tube

d.      Hydraulic disk brakes will eliminate the brake synchronization linkage that allows one lever to activate both rear brakes.

e.      Tube size and gauge will be optimized and not overdesigned as is currently the case.

So I consider the EcoVia Mk1 to be a successful proof-of-concept of a two-wheel-drive tilting trike, but much must be improved in production prototype.


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