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...

High Quality Veloci-velo renders

In a moment of spare time while designing the chassis and suspension, I decided to render a few high quality images of Veloci-velo in it's final format. Design changes include a larger entry/exit hole and wider at the riders shoulders. I hope to have some more info on the chassis soon and get building!!!

LHS

RHS

Safety capsule/monocoque

One of my design criteria is to make this velomobile as safe as possible. If a velomobile is too be used on the same roads as automobiles some degree of crash protection has to designed into the vehicle. My plan is to have a monocoque seat/safety capsule. I have been designing a few different types and so far this is what I have come up with...

Veloci-velo safety capsule ©2014

The integrated seat will save on weight. I will construct a few test models out of card to check for strength etc. With the rest of the bodyshell, front frame and rear swingarm attached to this monocoque construction.

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!

Continued Development update

Its has been a while since my last post. Chassis design still in progress. I really want to incorporate crash protection into the velomobile. Semi-monocoque with the seat being part of the load bearing structure seems logical. Other velomobiles (apart from the Rotovelo) have separate seats which offer no strength to the structure but are only used for the rider to sit on. When you consider that the seat weighs about 1kg it makes perfect sense for the seat to be integrated into the chassis or in fact become the chassis with suspension members hanging off it. There will be a rendering/picture to follow in the next few days.

Trisled RotoVelo

Crash Protection

There have been quite a few cyclists lately been run over and killed or seriously injured over the Christmas break. This was after the cyclists had gone to great length to make themselves visible and they were all experienced riders. Cyclists are vulnerable and it seems some drivers are not being careful enough.

How can we make bicycles safer? I don't think bikes are unsafe - it is more that other road users are careless and not considerate enough. Still it has made me think again about how to make Veloci-velo safer to use and I am exploring ways to make this velomobile a safe transport option. This could include crumple zones and / or airbags to help protect the rider.