Friday, 23 February 2018

Noise inside a velomobile

From my experience in riding velomobiles I have found one of the most irritating aspects to be the amount of noise (rumbling) when inside a moving velomobile. All this noise adds up to rider fatigue and makes the velomobile annoying to use when compared to a diamond frame bicycle.

Commercial fiberglass or carbon fibre monocoques are hollow tubes that echo like a drum with all the drivetrain and road on tyre noise as well as the suspension noise being transmitted to the rider.

Quest Velomobile Fiberglass Monocoque 

Solutions? I really like the foam shells of John Tetz the only issue with this construction method is the labour involved and the shell only provides limited crash worthiness. But it is lightweight and noise would be minimal due to the sound absorbing properties of the foam.

John Tetz Foamshell Velomobile
John Tetz Foamshell

Another great design is this Softshell concept velomobile has been made by Czech designer Martin Miklica. This approach would mitigate noise but if the fabric is too tight it may cause a drum effect.

Martin Miklica Softshell

Of course there are other solutions such as used in the car industry such as acoustic soundproofing, rubber mounted sub chassis etc. etc. but this approach always adds weight which is undesirable in a velomobile. Maybe even an approach of using all three of the above for one design could be a way of making riding a velomobile a quieter experience?

Saturday, 27 January 2018

Open wheel Velomobile

On my previous post "F1 inspiration" I tested a open wheel design which surprised me with it's aero efficiency. I decided to model this up a bit more in detail with some of the renders below.

What I really like about this design is its simplicity, ease of construction and ingress and egress would be very much easier than a wheels in design.

I can see many benefits especially I think this type of velomobile design would be more accepted by the general public as still being a "bicycle".

Saturday, 20 January 2018

F1 inspiration

I have been looking at single seat race cars for inspiration and although F1 cars have really bad CdA figures that is in part due foe for the need to have huge downforce and air intakes to cool a high output power plant.
The F1 tub by itself has to protect the driver but also allow the smooth flow of air to the wings, foils and intakes. If we take away these downforce/cooling aids (by the way they are not aerodynamic aids!) we are left with the tub/driver pod.
I quickly modelled up a velomobile with similar design to a F1 tub and put it through the CFD. It made for some astonishing results.
The frontal area calculated out to be 0.32m2 and the Cd was 0.28! put these two together and I got a CdA of just 0.0896 !!!

Although this figure is higher than my older design which had a CdA of 0.07. It really is an interesting comparison and with this "Open Wheel" design it could be made a lot lighter and easier to produce and also have a smaller turning circle. This could be a great design for a practical everyday velomobile.

Friday, 3 November 2017

Simplify and add lightness

Colin Chapman's quote "Simplify and add lightness" should be the catch-cry of anyone designing a velomobile or human powered vehicle. One of my favourite designs which has been designed along this mantra is Bob Stuarts Car-Cycle X-4

This is a fine example of integration of parts to make a simpler vehicle. The use of different materials such as fibreglass for the chassis and coroplast for the body is using the correct material for the job. The fibreglass chassis incorporated the hinges for suspension so in fact the chassis IS the suspension. The coroplast body is tough and resilient to bumps and knocks as well as being lightweight.

Another consideration I see in this design is the cost factor with no real "exotic" materials used.
Too often Carbon fiber is seen as a miracle material and used inappropriately or used in a way that does not utilise its specific properties (i.e.. stiffness with low weight). Read about this wonderful vehicle from the link above.

Sunday, 10 September 2017

Full size mock-up of Velomobile chassis

Mockup of velomobile semi-monocoque to test size and entry/exit. Will have to tweak the design a little. Very easy to get into but a little tight around the shoulders. Will revise.

Velocivelo semi-monocoque ©2017