Velomobile excellence!

"Any intelligent fool can make things bigger and more complex... It takes a touch of genius --- and a lot of courage to move in the opposite direction."

 - Albert Einstein

A great quote from a great mind.

My goal for Veloci Velomobile is to make a velomobile which is practical, functional but yet elegant in it's design. Having ridden a couple of other 'hard shell' monocoque velomobiles (AeroRider & a home build fully enclosed similar to the AeroRider) I found both these machines too heavy and being fully enclosed too claustraphobic. To keep thing lightweight I will be using a space-framed chassis with suspension on all wheels and mounting a non-load bearing lightweight shell made of coroplast/corflute.

I really like John Tetz's work with velomobiles and he has produced a one-off velomobile that is lightweight, fast & practical.

Velo-Excellence! - John Tetz Foamshell Velomobile

CdA Calculations & Visualisations

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 optimal).

CFD that velomobile - virtual windtunnel

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.

Velo Chassis / Test Mule

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.

Modelling in 3D - Velomobile Crash protection?

Modelling in the 3D environment is quite easy. The basic steps are to create polygons, lay out basic dimensions and then modify the polygons to get a rough shape. From this rough shape filters can be applied to smooth the shape.

Another consideration when designing this velomobile is the matter of crash protection! Unfortunately there are drivers of automobiles who are not attentive enough when it comes to their driving. I have seen a few collisions (and been involved in two myself) while on a bicycle. All these collisions involved the car driver not being carefull or considerate to the rider.

So how do we make bicycling safer? There is no easy answer. How do we make velomobiles safer? Well my thoughts are to have some sort of roll over protection and in the case of Veloci velo to have side intrusion bars fitted to the chassis. These would only have to be strong enough to not bend when hit by a force equal to the mass of the velomobile and it's rider.

I really like Trisleds Rotovelo which is a rotary moulded monocoque which is strong (but a little heavy). Maybe the answer is not to get hit by becoming more visable eg. bright colours for the bodyshell and using flashing LED's even when riding in daylight. Some riders use flags, I like the idea of a aero mast which would be painted in a fluro safety colour and also have a flashing LED's on top for 360 degree visability.

3D CAD Velo design

One of the design consideration is to be scalable. How to achieve this has not been easy. Using 3D software has made it a lot easier however. By designing a base shape which can then be manipulated to change dimensions has been a great way for me to work. After final shape and dimensions have been finalised the shape is then unfolded in the programme to get a 'flat' version which can then be cut out onto the coroplast. I intend to mock-up a 1/2 size model just to check that everything will fit and work with the coroplast. It is also a chance to "tweak" the design.

Scalable Velo Design

Scalable design? Well at the moment it is a case of "one size fits all" or in the case of the Quest velomobile two sizes fit all. Using a design that is scaleable to the size of rider has two advantanges...

1. Sized to fit the rider, a snug fit for the rider in the fairing. Makes the velomobile size appropriate for the rider - why pedal more mass than needed?
2. Smaller - tighter fit fairing allows smaller frontal area  making velomobile more aerodynamic - again size appropriate to the rider.

Current velomobile practice is monocoque hard fairing designs, while very well built and great looking vehicles they have a number of compromises to allow to suit to a wide range of riders. My design will be made from Coroplast/coreflute to allow a 'custom fit' using a master template which will be able to be scaled to fit different riders.I have already got the base shape finalised, this shape was arrived at after two prototypes were built and lessons learn't from these ...

This velomobile was the second of the two I have built. The shape was sleeker and faster than the first. The chassis had rear suspension but nothing on the front wheels. All up weight was 20.5kg. Unfortunately this velo was rolled at 50 km/hr at a local soapbox trolley derby, the rider walked away with only a small scratch on his forehead. A  great testament to the toughness of coroplast/corflute. The body was knackered but the chassis was fine with the flexible body being able absorb a lot of the energy of the crash. Even so with a bit of Duct Tape and zip ties it finished the day with the second fastest time down the hill. (no pedalling).

Velomobile Design Considerations

Quest Velomobile. The ultimate velomobile?

Part of the design process is considering what and how a product will be used. Like all good designs a set of criteria is needed. My criteria for a human powered vehicle are as follows...

LOW MASS - Must be under 22kg, more mass means more power to accelerate and push up hills. Ideally I would like to get the weight down below 20kg. This will be achieved by building Veloci with a separate chassis/body shell. The body shell will be made of coroplast/coreflute - a flexible but lightweight material while the chassis will be large diameter aluminium tubing.
AERODYNAMIC - What is the use of having a bodyshell (mass) if it is not aerodynamic! The Quest Velomobileis seen as the ultimate in this respect but again the Quest weighs in at 30+kg. The design of Veloci will have a small frontal area as well as an aerodynamic shape, maybe not as slick as a Quest but again it won't be as heavy and will have a smaller frontal area which should counteract this fact.
FULL SUSPENSION - Suspension is a must on velomobiles. Suspension must allow maximum grip for the narrow bicycle type tyres and absorb power robbing "road buzz".
LOWER COST - Current Velomobiles are expensive. One of my aims is to lower the cost of buying such a machine. Simple elegant design will help achieve this goal.
I have already made up a prototype chassis which will test dimensions and suspension geometry. The bodyshell is still under development but on the website you can see 3D renderings I have done which is very close to the final shape and proportions.