A new sketch with Pro Engineer

Today I found a way to unroll (develop, expand, unfold, unwrap) the body in ProE (with the insert/advanced/Flatten quilt command). I did not find an exact description about what it really does. It does works on surfaces with single and compound curvature so I have to guarantee that the surfaces are of single curvature only. Modeling surfaces with the style feature in ProE is not that easy. I'm having a trouble with connecting the surfaces and making the connections tangent (smooth). Also I don't know how to guarantee a surface is developable in ProE. If you can help me with this please drop me a mail.

Add study in ProE of a velomobile with front wheels inside. The gap between
the grey top cover and the red plating is a modeling fault.

Red plating is developable. The nose is not and could be thermo formed. The grey top and tail have compound curvature and can be made of cloth. The sketch shows some ideas I'm thinking about: Wheels inside, a tail of textile, a nose with compound curvature. Wheels inside will reduce the aerodynamic drag but limit the steering angle. An even better alternative would be to have the wheels covered with doors that open at sharp turns. A textile tail is light, easily removed, makes no noise and can have a beautiful saddle like compound curvature.

I am very happy I have (almost) found a way to get total control about the design. The last proto was modeled in Autocad (R14). Developing the sheets was done manually...

Paddy makes his maiden ride

Paddy climbs into the velomobile. (The packing tape over the nose holes reduce the ventilation.
With open holes it gets to draughty when its cold)

Today Paddy Milford paid a visit. He made a short one hour trip. When he returned a fillet at the mount of the seat was failed. I have to strengthen this place. Exhilarating was the decent of the Moerlaken bridge : 50 km/h without much pedalling ! We discussed the project and hope to build at least 3 body's this summer. If you would like to join us this summer drop me a mail.

Wind and speed

Today I went for a short (10 km) test trip again. I improved the chain guidance with a long polyethylene (plastic shopping bag) tunnel under the floor of the body. Works great. No friction, no noise. At least until the packing tape fails... Than the chain springs of the rear chain wheel easily.

But what fun it is in a T-shirt only on a cold windy day driving on a dike. Catching the wind, sailing.The feeling that you are pushed aside. It was really drifting ! I have to get a speedometer.

I saw the nose flexing due to the load of the crank axle. I think this can be eliminated by closing or stiffening the little nose holes. Lots of other little nuisances: The brake cable is not mounted right, in a sharp right turn it brakes. The soft top comes of because the velcro is not strong enough. The Rohloff hub sometimes fails. The front suspension is too stiff.

But all in all I should be very happy with the results so far.

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.