New Renderings - Detail changes

Since my last design renderings I have further developed the design to improve the aerodynamics and the interior packaging. This has made it a little harder to construct but I think the overall look of of veloci-velo is quite unique to the velomobile world.

Unwrap that body!

I have been busy with finalising the body and chassis details and construction methods. Using 3D software allows me to 'unwrap' my veloci-velo model so I can cut it out into its various parts. Rendering below is a of the 5 parts that make up the bodyshell. Minimising the part count leads to savings in weight and cost so I am very conscious of keeping the design of this velomobile very simple.

Veloci-velomobile, showing major bodyparts

Velomobile aerodynamics final design

After re-drawing the bodyshell to fit the exact dimensions required I have found that the CdA figure has dropped to 0.081 Here is a few images of latest and final renderings before I make a full size working prototype.

This is a great result as I had thought that anything 0.10 or less would be adequate. My goals for the design have been reached with the low drag co-efficient, the low weight due to the construction in coroplast/corflute and I think I have achieved a a good looking design which is important for consumer acceptance.

I have been reading a lot about vehicle & chassis design and one thing really stood out to me was the way the automobile industry goes about designing a new vehicle as they take a very different approach.
Their most important criteria is asthetics. This is a basic overview of the design process...

1. Draw-up concepts
2. Choose a concept
3. Refine the concept
4. Larger scale concept produced concept adjusted to fit people and parts
5. Adjustments made to fit chassis platform and suspension
6. Body changes for aerodynamics
7. Prototypes built andtested, changes made
8. Production readying

Again the auto industry starts by defining the design by its appearance, designing a velomobile in such a way would lead to a vehicle that would not perform as expected. The design process for a velomobile and indeed Veloci-velomobile has been...

1. Application definition - lightweight, aerodynamic, single occupant, human powered vehicle
2. Chassis and suspension design - lightweight, stiff, independent suspension
3. Aerodynamically designed to envelop rider and chassis - again lightweight
4. Development of the entire design to make it user friendly and asthetically pleasing

So the design process is quite the opposite to the auto industry approach, I think I have achieved my goals in this design. Please feel free to comment.

Measurements

Using the 'mule' I have been fine-tuning the dimensions of Veloci Velomobile. I have changed the design of the frame to have a perimeter upper frame to provide extra impact protection and added torsional strength. At the moment I have been setting up the 'mule' to check seating position and clearances for wheels, steering bits and of course the rider to bodyshell interferences. I have found by doing this that I can make the Veloci-velo even a little bit smaller than I had planned with the entire bodyshell being able to envelop me the rider as close as possible.

The 'mule' test rig for Veloci-velo

This was one of my goals in building this velomobile and that was for it to be a scalable design instead of a "one size fits all" policy. In a production version the rider would supply the essential measurements and the bodyshell would be custom designed to fit his body / seating position. The chassis would be basically the same for every rider but the shell would specific to the rider.

Velomobile Frame Design

I have been coming up with different ideas on the design of the velomobile frame. I have decided that including some sort of impact protection would be a good idea so the above idea has 'side impact bars' which also double as handles to aid getting in and out of the velomobile.
I also want this frame to be stiff in torsion as well as bending forces as a stiff chassis makes for a better handling vehicle. I have chosen aluminium as the material for the frame as it is a material that when used with large diameter and thin walls both stiff and lightweight.
The seat is formed from plywood and will have a little adjustment fore and aft with the bottom bracket providing most of the adjustment for different size riders

Velomobile tyres

There is lots of debate about the pros & cons of various wheel sizes. I do not wish to add to this discussion but speak from my experiences.

I have used both 406 ERTO & 349 ERTO size wheels/tyres for my early velomobiles. I have found there is no noticeable difference between the two sizes in everyday riding.

Being a smaller rider I prefer the 349 size as it makes for a more compact trike/velomobile as well as being slightly lighter. I have noticed that tyre pressure has more influence on the ride & speed of the tyre than anything else.
A lot of the roads in my area are coarse chip and I have found that running tyres at a lower pressure is better on these surfaces. High pressures lead to more 'road buzz' and a very hard ride. Lower pressures (50-60psi) reduced the road buzz and made the ride and handing much nicer. However on smooth asphalt roads higher pressures are the best. It is all about finding what works for the particular vehicle and the rider.

Here is a little movie I made of the virtual wind tunnel with Veloci Velo in it. This is a slightly different body with more of a "swoop" in the side on profile. Part of the reason is purely cosmetic and also helps bring down the drag co-efficient.

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.

Velomobile Kit? or Retro-fit?

With the Veloci Velomobile method of body construction it will possible to scale it to fit a wide range of different recumbent trike chassis.

This is already been done by other manufacturers with the Borealis velomobile as well as the Ocean Challenger .These are both fine examples of fitting bodyshells to existing recumbent trikes. The drawback is that they are quite heavy (32-36kg) and still relatively expensive.

Veloci Velomobile would weigh in at 20-23kg depending on the trike used as the chassis. This would be a great option for someone who already owns a trike and wants to have a cost effective way of converting their recumbent trike to a velomobile. The estimated cost for a retrofit to an existing trike chassis would be $US = 1000 or Euro = 780.

This is only one option as a custom designed chassis would have less compromises and maybe even be lighter! I have built three recumbent trikes - two with rear suspension, with the lightest being 13.5kg and the others 15-17kg so in theory Veloci Velomobile could be as light as 18-20kg complete!

Velomobile safety and drag co-efficient

There has been a few cases of late of cyclist being hit by cars with major injuries or death being the result. I still think it prudent that some sort of passive safety is designed into Veloci Velomobile. I really like the construction method used on the eco-car TREV It is lightweight, reasonably easy to construct but very strong and with the foam as a core would have some energy absorbing capacity.
For Veloci Velomobile I will design a semi-monocoque with the monocoque being where the rider sits while the suspensions and crank boom are attached to the monocoque. I believe this would be the best approach to keeping it lightweight and having some crash/impact protection.

In addition to the crash protection of Veloci Velomobile I have been redesigning the bodyshell to make it a little more slippery and make the forward vision for the rider a lot better. I now have the Cd figure down to 0.20 thus the CdA= 0.45 x 0.20 = 0.09 which is really good and better than the Quest velomobile now. 

Veloci Velomobile drag co-efficient now 0.20

June 2013 Veloci Velomobile latest shape rendering

Velomobile excellence!

"Any intelligent fool can make things bigger and more complex... It takes a touch of genius --- and a lot of courage to move in the opposite direction."

 - Albert Einstein

A great quote from a great mind.

My goal for Veloci Velomobile is to make a velomobile which is practical, functional but yet elegant in it's design. Having ridden a couple of other 'hard shell' monocoque velomobiles (AeroRider & a home build fully enclosed similar to the AeroRider) I found both these machines too heavy and being fully enclosed too claustraphobic. To keep thing lightweight I will be using a space-framed chassis with suspension on all wheels and mounting a non-load bearing lightweight shell made of coroplast/corflute.

I really like John Tetz's work with velomobiles and he has produced a one-off velomobile that is lightweight, fast & practical.

Velo-Excellence! - John Tetz Foamshell Velomobile

CdA Calculations & Visualisations

Using the virtual windtunnel it was calculated that the shape of veloci velomobile has a drag co-efficient of 0.27 using this information to calculate the cdA which is cd x A (frontal area) = cdA.
Knowing that the frontal area is 0.45m2 X 0.27 = 0.1215 cdA which I believe to be pretty slippery. The Quest velomobile has a cdA of 0.09 but this is not confirmed as accurate or in what configuration. So for a velombile that will cost a quarter of what a Quest will be nearly as aerodynamically efficient. It was also interesting to note that a lowracer such as the M5 has a cdA of 0.14 which is  very good and is due to the very small frontal area and the tailbox, the great thing with these bikes is that they are so light (claimed 8.5kg) . This has made me think about the suitability/practicality of velomobiles as a lowracer can get pretty close aerodynamically and weigh a lot less than a velomobile. This is why I believe a lightweight velomobile (under 20kg) would be very effective as long as its cdA is low (0.10-0.08 would be optimal).

CFD that velomobile - virtual windtunnel

Veloci velomobile in the virtual windtunnel

After getting the basic shape and dimensions it was time to see if the body shell was aerodynamic! After all what is the point of putting a body shell on a human powered vehicle if it does not make it more efficient? The added weight of a body shell needs to be offset by the improved aerodynamics to make it worthwhile.The information gathered from using  a virtual wind tunnel has already led to me 'tweaking' the design to let it slip through the atmosphere with ease.

Velo Chassis / Test Mule

Now that I have finalised the body shape/dimensions I need to build a chassis for everything to attach to! I thought about using an commercially available tadpole trike but there are too many compromises. So I designed my own!As this is experimental I wanted to design it so changes can be made easily. I decided to make it out of 9mm ply as a semi-monocoque design with the seat being part of the load bearing structure. I like working with wood so this construction technique suits me. The pictured design is the chassis backbone and seat which still needs the boom, front suspension arms and rear swingarm. Pictured chassis weighs 3kg. I estimate the rolling chassis will weigh 15kg plus another 6-7 for the body shell giving my target weight for this velomobile of 20-22kg.

Modelling in 3D - Velomobile Crash protection?

Modelling in the 3D environment is quite easy. The basic steps are to create polygons, lay out basic dimensions and then modify the polygons to get a rough shape. From this rough shape filters can be applied to smooth the shape.

Another consideration when designing this velomobile is the matter of crash protection! Unfortunately there are drivers of automobiles who are not attentive enough when it comes to their driving. I have seen a few collisions (and been involved in two myself) while on a bicycle. All these collisions involved the car driver not being carefull or considerate to the rider.

So how do we make bicycling safer? There is no easy answer. How do we make velomobiles safer? Well my thoughts are to have some sort of roll over protection and in the case of Veloci velo to have side intrusion bars fitted to the chassis. These would only have to be strong enough to not bend when hit by a force equal to the mass of the velomobile and it's rider.

I really like Trisleds Rotovelo which is a rotary moulded monocoque which is strong (but a little heavy). Maybe the answer is not to get hit by becoming more visable eg. bright colours for the bodyshell and using flashing LED's even when riding in daylight. Some riders use flags, I like the idea of a aero mast which would be painted in a fluro safety colour and also have a flashing LED's on top for 360 degree visability.

3D CAD Velo design

One of the design consideration is to be scalable. How to achieve this has not been easy. Using 3D software has made it a lot easier however. By designing a base shape which can then be manipulated to change dimensions has been a great way for me to work. After final shape and dimensions have been finalised the shape is then unfolded in the programme to get a 'flat' version which can then be cut out onto the coroplast. I intend to mock-up a 1/2 size model just to check that everything will fit and work with the coroplast. It is also a chance to "tweak" the design.

Scalable Velo Design

Scalable design? Well at the moment it is a case of "one size fits all" or in the case of the Quest velomobile two sizes fit all. Using a design that is scaleable to the size of rider has two advantanges...

1. Sized to fit the rider, a snug fit for the rider in the fairing. Makes the velomobile size appropriate for the rider - why pedal more mass than needed?
2. Smaller - tighter fit fairing allows smaller frontal area  making velomobile more aerodynamic - again size appropriate to the rider.

Current velomobile practice is monocoque hard fairing designs, while very well built and great looking vehicles they have a number of compromises to allow to suit to a wide range of riders. My design will be made from Coroplast/coreflute to allow a 'custom fit' using a master template which will be able to be scaled to fit different riders.I have already got the base shape finalised, this shape was arrived at after two prototypes were built and lessons learn't from these ...

This velomobile was the second of the two I have built. The shape was sleeker and faster than the first. The chassis had rear suspension but nothing on the front wheels. All up weight was 20.5kg. Unfortunately this velo was rolled at 50 km/hr at a local soapbox trolley derby, the rider walked away with only a small scratch on his forehead. A  great testament to the toughness of coroplast/corflute. The body was knackered but the chassis was fine with the flexible body being able absorb a lot of the energy of the crash. Even so with a bit of Duct Tape and zip ties it finished the day with the second fastest time down the hill. (no pedalling).

Velomobile Design Considerations

Quest Velomobile. The ultimate velomobile?

Part of the design process is considering what and how a product will be used. Like all good designs a set of criteria is needed. My criteria for a human powered vehicle are as follows...

LOW MASS - Must be under 22kg, more mass means more power to accelerate and push up hills. Ideally I would like to get the weight down below 20kg. This will be achieved by building Veloci with a separate chassis/body shell. The body shell will be made of coroplast/coreflute - a flexible but lightweight material while the chassis will be large diameter aluminium tubing.
AERODYNAMIC - What is the use of having a bodyshell (mass) if it is not aerodynamic! The Quest Velomobileis seen as the ultimate in this respect but again the Quest weighs in at 30+kg. The design of Veloci will have a small frontal area as well as an aerodynamic shape, maybe not as slick as a Quest but again it won't be as heavy and will have a smaller frontal area which should counteract this fact.
FULL SUSPENSION - Suspension is a must on velomobiles. Suspension must allow maximum grip for the narrow bicycle type tyres and absorb power robbing "road buzz".
LOWER COST - Current Velomobiles are expensive. One of my aims is to lower the cost of buying such a machine. Simple elegant design will help achieve this goal.
I have already made up a prototype chassis which will test dimensions and suspension geometry. The bodyshell is still under development but on the website you can see 3D renderings I have done which is very close to the final shape and proportions.

Aerodynamics

To make a bicycle go faster you either have to become super strong & fit or somehow decrease the amount of energy required to move the bike and yourself. Of course as speed rises on a bicycle the energy needed to accelerate and hold a higher speed increases also.
The best way to go faster is to improve the aerodynamics and the percentage of energy required to push a rider and their bicycle through the atmosphere is far greater than all the other factors such as vehicle weight, mechanical losses etc.
My goals include being able to ride a human powered vehicle 365 days of the year so a body shell serves two purposes for me -

1. Keeps the rider (me) from the elements such as rain, cold, sun.
2. Makes the vehicle more aerodynamic (or more efficient).

I can't see the point of putting a body shell on a human powered vehicle if it is not in some way raising the efficiency of the vehicle because the other killer in human powered vehicles is weight.
More weight = slower. So to make the most efficient vehicle it will have to be -

• Lightweight (under 22kg)
• Aerodynamic with a CdA close to or under 0.10

concept of possible bodyshell

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.