Saturday 31 August 2013

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.

Thursday 29 August 2013

Measurements

Using the 'mule' I have been fine-tuning the dimensions of Veloci Velomobile. I have changed the design of the frame to have a perimeter upper frame to provide extra impact protection and added torsional strength. At the moment I have been setting up the 'mule' to check seating position and clearances for wheels, steering bits and of course the rider to bodyshell interferences. I have found by doing this that I can make the Veloci-velo even a little bit smaller than I had planned with the entire bodyshell being able to envelop me the rider as close as possible.

The 'mule' test rig for Veloci-velo

This was one of my goals in building this velomobile and that was for it to be a scalable design instead of a "one size fits all" policy. In a production version the rider would supply the essential measurements and the bodyshell would be custom designed to fit his body / seating position. The chassis would be basically the same for every rider but the shell would specific to the rider.