Elevation of semi-monocoque velomobile

Here is an elevation showing the position and size of the semi-monocoque chassis. Attached to the monocoque will be the rear swingarm, and the front a subframe to locate pedals and front suspension pickups. Again using a semi-monocoque will hopefully make for a lighter velomobile. The semi-monocoque will have to be stiff enough to take loads from the subframes without excessive bending or twisting. I have decided that a good quality plywood would be best for the monocoque for cost for performance.

Semi-monocoque

Electric assist on velomobiles

After about six months of no progress due to building a new home I have finally got my workshop back and will be starting work on Veloci-velomobile once again.

In this time of limbo I have thought about having electric assist on  a velomobile and came to the conclusion that it would be advantages to have such a system.
Advantages would be...

• Faster acceleration from standstill and rolling acceleration
• Easier climbing of hills

From reading reviews of various systems including hub motors, mid-drive and direct drive I believe that a mid-drive system would be best due to the fact it will use the gearing already in the bike. I really like the 8fun system which can be configured with different power outputs to suit regulations. Most common is 250W (Australia & Europe) 300W (New Zealand) and 750W (USA).

Even with 250W the acceleration would be quite impressive and with the aerodynamic advantage of Veloci-velo top speeds would/could  be..

• 250W = 75 km/hr (46 mph)
• 300W = 82 km/hr (50 mph)
• 750W = 120km/hr  (74 mph)

When designing Veloci-velo the design brief was to have a vehicle that could maintain 40km/hr for the average rider so the electric assist needs to be no more than 300W and geared to provide the best acceleration up to the 40 km/hr limit.

See table below...

Safety capsule/monocoque

One of my design criteria is to make this velomobile as safe as possible. If a velomobile is too be used on the same roads as automobiles some degree of crash protection has to designed into the vehicle. My plan is to have a monocoque seat/safety capsule. I have been designing a few different types and so far this is what I have come up with...

Veloci-velo safety capsule ©2014

The integrated seat will save on weight. I will construct a few test models out of card to check for strength etc. With the rest of the bodyshell, front frame and rear swingarm attached to this monocoque construction.

Aero tests continued

Last post I had a result that provided a cdA of 0.027. Unfortunately this result was wrong and after more testing I would have to put that result down to a glitch in the system.
Anyway I really liked the look of that particular shape which also allows more shoulder room for the rider. I ran the new tests after calibrating the software against a shape with a known Cd ( a sphere = 0.5). The new shape came back of a best of Cd=0.18 and with a slightly smaller frontal area of 0.44m2 with calculates to a CdA of 0.792 which is pretty good for a shape that can be produced using corflute/coroplast.

Veloci velomobile CdA=0.792

Veloci velomobile in virtual windtunnel

I am very happy with this shape now and the chassis design is going very well. I considered buying a KMX kart to use as a chassis but there were three things that I didn't like about these trikes...

1. Quite heavy at 19kg
2. Wheelbase not quite long enough
3. No suspension

KMX Karts are great value however and a fine product and would be suitable for a low cost velomobile. I will be building my own chassis this winter and hope to have Veloci-velo ready for Spring.

The Start

I want a human powered vehicle! Simple as that. It needs to be fast, comfortable and be able to be used 365 days of the year.
So whats wrong with a conventional bicycle? Nothing really - conventional bikes are great and I have owned rode/raced various bikes all my life but as I have got older my needs have changed and I want to 'push the envelope'.
I have designed and built some machines of my own in the last 10 years. The great thing about tinkering and building is that you find out pretty fast what works and what does not early attempts were often 'does not' but by trying again I have come up with what I believe to be a good design.
Design criteria for my perfect human powered vehicle-

• 365 days of the year use.
• Safe - able to withstand minor crashes
• Fast (esp. head winds)
• Full suspension
• Light as possible
• Simple but elegant

My previous attempts included a recumbent tadpole trike which won me a competition in 2006 which was to design, build and race a human powered vehicle capable of carrying cargo around a urban criterium circuit, a high speed  flying 200m and a roll down speed test. I won two of the three tests and was runner up on the other.

The trike chassis used was rather conventional (in recumbent terms) for a tadpole trike but I developed a coroplast bodyshell which had cargo carrying capacity and made it more aerodynamic than a diamond framed bike.

This vehicle was pretty good but I found it to be hard on tyres and not as fast as a bicycle in corners. With front suspension of the right geometry both of these problems can be fixed. Of course I want it to be faster than  the above and aerodynamics are one of my passions and I want to be able to produce a coroplast/corflute body design which is lightweight (why drag around more weight than neccessary), rugged enough for everyday use and as aerodynamic as I can make it.