Front axle

McPherson wheel suspension

This is the front axle. It was simplified to the maximum. The polyurethane foam element is spring, damper and bearing. The McPherson suspension is a well accepted design but is it the lightest alternative ?
In the first comment on this post Bob Stuart, the designer of The Car-Cycle X-4, 
argues that the McPherson is one of the lightest options. In our design of a micro electric car (Elite) we used an alternative construction. It is a sort of torsion beam suspension. Because the distance between the wheels is so little, this construction may be lighter than the McPherson. Another advantage is that it incorporates the anti-roll function.

This drawing shows the wheel suspension of the Elite micro electric car. It was mounted to the body via silent blocs

The McPherson construction distributes the wheel load over six distant points on the monocoque. Large torque loads will be transferred as small forces in these points (braking, cornering). This seems all very beneficial but the McPherson construction urges us to strengthen the monocoque at places where we really don't need it to be strong at all, would we not have this suspension. When we use a McPherson suspension we are forced to add material at the mounts of the longitudinal arms and vertical columns. We also have to increase the lateral rigidity, for instance with an u-frame between the front wheels. This may increase the body mass. The torsion beam axle connects to the monocoque at the front side of the seat. This is a place where we need it to be strong and stiff anyway...

Torsion beam suspension

About mass

Mass distribution of the first prototype. Total mass 27 kg.

13 years ago I determined the mass distribution of my first prototype (see here). Although it was larger and a 'head in' design it is still illustrative. The total mass of the first proto was 27 kg. The second proto is 23.3 kg. The mass reduction is due to leaving out the heavy polycarbonate window and the rear wheel suspension and also due to the smaller size and improved body construction.

Mike Burrows Windcheetah, the archetype of a tadpole trike, is 15 kg. Based on my figures this would mean that Mike uses 5,4 kg for frame and seat. In the first prototype 3,5 kg is used for wheel suspension which the Windcheetah doesn't have. We can conclude that a velomobile of 23,6 kg is still 23,6-15-3,5=5,1 kg too heavy. Although one might argue that the mass of a coat and two bags should be added to Mike's (beautiful) design...

On the road !

Until I've got a better picture this will do. The black cover is fixed temporarily.
Lots to be done but I can ride it !

The second prototype is (almost) ready. I improvised a seat and made a short trip. Very much fun! Although some details can be improved I think the general concept is proven: It is possible to build a very light velomobile with plywood.

I will sum up the main specs and add a better picture as soon as the weather allows me to take one: Two front wheels with McPherson suspension, one unsprung wheel with Rohloff 14 speed hub behind. Two side sticks for steering. Monocoque body (No frame inside!). Drum brakes in front wheels. Size: 2750x720x750 mm (LxWxH).  Cost estimation: 300 euro (body materials only). Total mass 23.6 kg.

23.6 kg is very competitive...

Who's going to take the development further? Come and see our machine. Learn from our mistakes and and build your own! Please send me a mail if you are interested in building my plywood velomobile design.

The kit

The first prototype is inspected just after the arrrival at Boulogne Sur Mer

When the design is finalized, I will describe the d.i.y. kit that may be available then. It will consist of laser cut plywood sheets an bent aluminum tubes. The rest is up to you.

The body

Paulus van Staveren build this
body of a rear steered velomobile.

A body of airplane plywood (1.5 mm) can be made without a mold. This is a big advantage for doing it yourself but a major constraint in the design of the body shape too. A plywood sheet can not be bent into a sphere. In mathematical terms: the shape has to be developable.

The aerodynamic drag of developable shape may not be as low as that of a free formed shape. This is the compromise that I make to simplify the building and reduce the body mass.

I developed the sheets of my first velomobile with both a 1:5 and finally a 1:1 model. I simply wrapped paper sheets around curved panels. But this job can be done with a computer model too (for instance with the 3d surface modeler Rhino). I even developed a computer program in Matlab to do this. There is specialized software for hull design: Pilot3D, Delftship.

Introduction

A velomobile is something to have. But it is manufactured in limited numbers and expensive (I will name some makes: velomobiel.nl, leitra.dk, go-one, leiba.de, aerorider.com, sunrider-cycles.com, alligt.nl, dutchbikes.nl). Building it yourself is a good alternative and very much fun. This blog is dedicated to the development of a do it yourself velomobile.

The Alleweder Velomobile (photo Flevobike)

I was involved in the development of the do it yourself Alleweder velomobile at the Flevobike company in 1992. It was my job to improve and adapt the design of Bart Verhees. Bart Verhees is a very practical engineer and an experienced airplane designer. His Alleweder velomobile is build like an airplane: riveted aluminum sheet. At that time I saw the beautiful shapes that are possible using bent sheet only. And this idea never left me.

The electric machine

Together with designer Ronald Meijs we developed an electric car. It was made of an aluminum-polypropylene sandwich sheet (0.2-2-0.2 mm). This was a new material of Hoogovens named Hylite. It was aimed at the automotive industry.

Me and my first plywood car on a trip to Boulonge sur Mer

But my true love is human power and a year later I travelled to France in my first plywood velomobile. It was a 'head in' design and on that trip a learned that the fun of cycling is to feel the air flow along your head. But the concept of a velomobile of airplane plywood was proven. I made a new head out design which was build by Paddy Milford. It is has been hanging in my garage for 10 years now but recently Sjaak Bloemberg is working to get it on the road.

The De Havilland Mosquito: a plywood construction build in 1940-1950, (© FlightGlobal)

Wood is a very interesting material for velomobiles because of its low density. In the construction of the velomobile body the sheet stiffness is more important than its strength. The stiffness of the sheet is very much determined by its thickness. On stiffness relative to mass only sandwiches of alternative materials like carbon-aramid-epoxy with foam can compete with birch plywood. But building sandwiches is laborious and expensive and it is only recently that velomobile manufacturers offer bodies with sandwich sheet. For your information I will list some densities (kg/dm^3): birch plywood 0.7, aluminum 2.7, glass fiber 2.55, carbon fiber 1.75-1.95, polyester 1-1.45, epoxy 1.1-1.3.  Look at the site of Jan Hermhart for an example of plywood in aeroplanes.

My aluminum Alleweder was over 30 kg, my first plywood velomobile 27 and the second will be around 23 kg ! As soon as the second prototype has travelled its first 100 km I will get back to you. Let me know if you would like to be involved !

P.S. I'm not the only one: mosquito-velomobiles , gigomobile , Friend Wood, coronn