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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.
Printed out unfolded 3D file and cut up and stuck it together with tape. Scale was 1/8th and it worked really well and the resulting model looks good and was easy to put together. At full scale the velomobile shell will only require 2-3 sheets of coroplast / coreflute, the estimated weight of the shell would be about 2.5kg, so if the rolling chassis weighs less than 17.5kg I will have a velomobile that weighs less than 20kg . The next step is to make a 1/4 scale using 2mm coroplast / coreflute and maybe tweak the design from there. The beauty of this design is that it is totally scalable and able to be customised to individual needs / size / dimensions as required.
After a bit of playing around finally got the model to unfold to flat the way I wanted it to. Just have to print to a 1/5th scale and fold it all up to see if it works. The model below is not symmetrical that is because I wanted to try a different nose style for each side.
Great article about velomobiles...
These are renderings of the improved shape with the velomobile now having enclosed wheels for a slippery shape. This shape is now slighly more aero than a Quest velomobile. The estimated weight for this velo is 22kg which makes it 6-8kg lighter than the Quest. Next step here is to unfold this shape and make a 1/4 scale to see if it all goes together
This is the final virtual wind tunnel test for Veloci Velomobile. After tweaking the shape I have managed to get the CdA to 0.0945 which is just short of the Quest velomobile (If anyone has a 3d file of the Quest velomobile I would like to test it using my settings) This means for an input of 200W from the rider Veloci should be capable of 47 km/hr which is about 30% faster than a UCI racing bicycle. Of course in bicycle racing the bunch rules and riding in a bunch sees an improvement of about 30% over riding solo. Elite riders can maintain 47 km/hr by having a power ouput of 500W + but this velomobile can maintain the same speed for much less power output.
Using the virtual windtunnel it was calculated that the shape of veloci velomobile has a drag co-efficient of 0.27 using this information to calculate the cdA which is cd X A (frontal area) = cdA.
Knowing that the frontal area is 0.45m2 X 0.27 = 0.1215 cdA which I believe to be pretty slippery. The Quest velomobile has a cdA of 0.09 but this is not confirmed as accurate or in what configuration. So for a velombile that will cost a quarter of what a Quest will be nearly as aerodynamically efficient. It was also interesting to note that a lowracer such as the M5 has a cdA of 0.14 which is very good and is due to the very small frontal area and the tailbox, the great thing with these bikes is that they are so light (claimed 8.5kg) . This has made me think about the suitability/practicality of velomobiles as a lowracer can get pretty close aerodynamically and weigh a lot less than a velomobile. This is why I believe a lightweight velomobile (under 20kg) would be very effective as long as its cdA is low (0.10-0.08 would be optim).
Veloci velomobile in the virtual windtunnel
After getting the basic shape and dimensions it was time to see if the body shell was aerodynamic! After all what is the point of putting a body shell on a human powered vehicle if it does not make it more efficient? The added weight of a body shell needs to be offset by the improved aerodynamics to make it worthwhile.
The information gathered from using a virtual wind tunnel has already led to me 'tweaking' the design to let it slip through the atmosphere with ease.
Now that I have finalised the body shape/dimensions I need to build a chassis for everything to attach to! I thought about using an commercially available tadpole trike but there are too many compromises. So I designed my own!
As this is experimental I wanted to design it so changes can be made easily. I decided to make it out of 9mm ply as a semi-monocoque design with the seat being part of the load bearing structure. I like working with wood so this construction technique suits me. The pictured design is the chassis backbone and seat which still needs the boom, front suspension arms and rear swingarm. Pictured chassis weighs 3kg. I estimate the rolling chassis will weigh 15kg plus another 6-7 for the body shell giving my target weight for this velomobile of 20-22kg.