Wheels out velomobile

Here is a render with exposed wheels on Veloci Velomobile. Advantages of this design is the ability of  a tighter turning circle and ease of changing a tyre. I like the look of such velomobiles with the only downside being loss of aerodynamic efficiency (this would be quite small).

Velomobile in Virtual Wind tunnel

Since I have established the final shape which now has a larger opening and is wider at the shoulders to accomodate the rider. I thought I better re-run the final shape in the virtual windtunnel to get an idea on how aerodynamic the shape is.

The results surprised me a little with the figures coming back at a Cd factor of 0.20 at a velocity of 11.2 m/s or 40kph. This was excellent as I was expecting the Cd figure to be a little higher with these changes. Now with a frontal area of 0.35m2 the CdA is now 0.07!

This final design is the result of appox. 200 hours testing and tweaking in the virtual windtunnel. I am confident that the figures are pretty close as I have calibrated the results against shapes of a known Cd figure.

Veloci-velo Velomobile 2014©

Power required to have a velocity of 40kph is a very achievable (for the majority of people) 122 watts.

see below...

Velomobile Frontal area

I finally have measured the frontal area of the new shape and the result has been good as the frontal area for this new shape is 0.36m2.

Calculating the CdA is now 0.36 x 0.21 (Cd) = 0.0756 CdA.
I can calculate using this excellent calculator power outputs and speeds for Veloci-velomobile. The graph below shows that for a modest 150W of power  a speed of  approx. 46 km/hr can be attained. I used 150W because this is what a untrained but fit cyclist could acheive for any length of time.

I also found that smoothing my final shape did not make any real difference to the Cd factor, at the most  it would have changed it by 0.1 so it is best to leave it as is. Now to build the models and then the real thing!

Rendering and Unfolding of the bodyshell

I am happy with the final shape and the Cd factor of this shape. Have unfolded it now to cut out to make 1/10th size model and then I will make a 1/4 size to sort out any small problems.

Aero tests continued

Last post I had a result that provided a cdA of 0.027. Unfortunately this result was wrong and after more testing I would have to put that result down to a glitch in the system.
Anyway I really liked the look of that particular shape which also allows more shoulder room for the rider. I ran the new tests after calibrating the software against a shape with a known Cd ( a sphere = 0.5). The new shape came back of a best of Cd=0.18 and with a slightly smaller frontal area of 0.44m2 with calculates to a CdA of 0.792 which is pretty good for a shape that can be produced using corflute/coroplast.

Veloci velomobile CdA=0.792

Veloci velomobile in virtual windtunnel

I am very happy with this shape now and the chassis design is going very well. I considered buying a KMX kart to use as a chassis but there were three things that I didn't like about these trikes...

1. Quite heavy at 19kg
2. Wheelbase not quite long enough
3. No suspension

KMX Karts are great value however and a fine product and would be suitable for a low cost velomobile. I will be building my own chassis this winter and hope to have Veloci-velo ready for Spring.

Aero Revelations

I have recently read an article on Mercedes-Benz modelling a car on a animal called the Box Fish. This fish has a remarkable ability to swim in very turbulent currents. Mercedes-Benz then took the basic shape of a Box Fish and built a car which then has a Cd of 0.19 which is very impressive for such a boxy looking vehicle.

I thought I would give this a try on the model on Veloci-velo with startling results.

The previous best cDA figure I achieved was 0.081

Re-modelled "Box Fish" shape cDA= 0.027 !!!

I could not believe it so I ran three separate tests and all tests came back with the same result!

This is quite a reduction in drag and would make Veloci-Velo and very fast velomobile.

I am conducting more tests and calibrating with objects of known Cd factors, More to come on this!

Velomobile aerodynamics final design

After re-drawing the bodyshell to fit the exact dimensions required I have found that the CdA figure has dropped to 0.081 Here is a few images of latest and final renderings before I make a full size working prototype.

This is a great result as I had thought that anything 0.10 or less would be adequate. My goals for the design have been reached with the low drag co-efficient, the low weight due to the construction in coroplast/corflute and I think I have achieved a a good looking design which is important for consumer acceptance.

I have been reading a lot about vehicle & chassis design and one thing really stood out to me was the way the automobile industry goes about designing a new vehicle as they take a very different approach.
Their most important criteria is asthetics. This is a basic overview of the design process...

1. Draw-up concepts
2. Choose a concept
3. Refine the concept
4. Larger scale concept produced concept adjusted to fit people and parts
5. Adjustments made to fit chassis platform and suspension
6. Body changes for aerodynamics
7. Prototypes built andtested, changes made
8. Production readying

Again the auto industry starts by defining the design by its appearance, designing a velomobile in such a way would lead to a vehicle that would not perform as expected. The design process for a velomobile and indeed Veloci-velomobile has been...

1. Application definition - lightweight, aerodynamic, single occupant, human powered vehicle
2. Chassis and suspension design - lightweight, stiff, independent suspension
3. Aerodynamically designed to envelop rider and chassis - again lightweight
4. Development of the entire design to make it user friendly and asthetically pleasing

So the design process is quite the opposite to the auto industry approach, I think I have achieved my goals in this design. Please feel free to comment.

Velomobile safety and drag co-efficient

There has been a few cases of late of cyclist being hit by cars with major injuries or death being the result. I still think it prudent that some sort of passive safety is designed into Veloci Velomobile. I really like the construction method used on the eco-car TREV It is lightweight, reasonably easy to construct but very strong and with the foam as a core would have some energy absorbing capacity.
For Veloci Velomobile I will design a semi-monocoque with the monocoque being where the rider sits while the suspensions and crank boom are attached to the monocoque. I believe this would be the best approach to keeping it lightweight and having some crash/impact protection.

In addition to the crash protection of Veloci Velomobile I have been redesigning the bodyshell to make it a little more slippery and make the forward vision for the rider a lot better. I now have the Cd figure down to 0.20 thus the CdA= 0.45 x 0.20 = 0.09 which is really good and better than the Quest velomobile now. 

Veloci Velomobile drag co-efficient now 0.20

June 2013 Veloci Velomobile latest shape rendering