Velomobile front beam suspension design

Most commercially availible velomobiles feature Macpherson Strut independent front suspension. A popular choice for full monocoque designs.

Tadpole design three wheeelers require roll stiffness at the front because the single rear does not have anti-roll stiffness so suspensions have to be correspondingly stiff to reduce body roll.
I intend to have a very simple beam front suspension with the advantages being...

• Simplicity
• No track variance when bumps encountered (zero scrub)
• Can be made lightweight (for velomobile applications)
• Great roll stiffness

The beam axle can be mounted to the monocoque section using four elastomers which will be the spring and damper all in one. The benefit of this is that the elastomer will provide vibration isolation and reduce the "road buzz" to the occupant. This isolation reduces the fatigue on the occupant.

Go to this link to see a an arguement for a beam axle front Vs Macpherson Strut.

Suspension for Velomobiles

Because Velomobiles are capable of higher average speed than conventional bicycles the need for suspension on all three wheels is a requirement. Suspension is not just needed for rider comfort but also to allow the wheels to keep in contact with the road surface and allow the tyres maximum grip when changing direction. Because Velomobiles are low mass vehicles there are some  considerations when designing suspension -

1. Keep unsprung weight to a minimum.
2. A torsionally rigid frame/chassis.
3. Keep the center of gravity as low as possible.
4. Use of a fully independent suspension.
5. The roll centre should be as low as possible for a low mass vehicle.
6. Roll stiffness is essential for a low mass vehicles especially so with a three wheeler as the single rear wheels provides no roll resistance.

There are many different geometries for suspension and the design of suspension systems is a complicated process AutoSpeed has this excellent article on the basics of geometry of different suspensions. My design for Velocivelo will follow the above 6 steps to arrive at the design.

The suspension I think that is suitable for velomobiles is the swing axle as it has a low unsprung weight, is fully independent and can be arranged to have a low roll centre. Disadvantages are "jacking" and lack of roll stiffness, but theses are negated to a certain extent because of the low mass of a velomobile.

One design of front suspension that is already out there is the ICE - Road Response Suspension. If there was a trike chassis to base a lightweight velomobile on it would be the ICE SPRINT with Road Response Suspension.