Look at the design page for info on the plywood velomobile construction.

Thursday, 29 December 2011

Hydraulic drive

check valves allow pedaling and free wheeling
Why not choose a hydrostatic transmission for the velomobile?

When I see a drum brake I think: In the same volume a hydromotor fits with about the same mass. With that motor one could drive and brake the velomobile. While braking energy may stored in a nitrogen volume to be used for starting again. A small electric motor could easily be added to the system.

Hydrostatic transmissions are used when high torques, power and control are needed. The efficiency of these drives use to be smaller compared to gears or chains. But the efficiency can be improved a lot. Innas has developed machines with pump efficiencies up to 97%. I think a hydrostatic transmission developed for the velomobile may compete with the derailleur en planetary gear systems.

Imagine two pedal cranks that are swinging about 120ยบ. Each connected to a hydraulic cylinder. Both front wheels of the velomoble are fitted with a small hydro motor. The scheme shows the basic system. Questions left: How to make it a variable transmission? How to realize a rear driving option?

Sunday, 23 October 2011

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...

Sunday, 9 January 2011

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.

Saturday, 8 January 2011

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.