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amidesign 10-21-2008 02:45 PM


I am from Switzerland.

When I was young I wanted to build my own airplane.

In 1996, I decided to build only a car.

I like drawing and building.
Ami-trike. 2007.

You can visit my Web Site: amidesign

Now I am working on a velomobile. It is a pedal car with an aerodynamic body : velo-mobile

Best regards.

truckncycle 10-21-2008 03:23 PM

Welcome to ecomodder.

The trike is very cool.

trebuchet03 10-21-2008 04:30 PM

mmm velomobiles :)

You might be interested in some of the stuff I've worked on :D

UCF Human Powered Vehicle Team

amidesign 10-22-2008 04:26 AM

Yes, I read rapidly your work.

If I good understand, you have a Cd of 0,09 . :eek:
How is it possible with a so shorter body ?

I will hope have a Cd of 0.1 with my project :

I respect this rule for top view :
Length of the tail = 10/3 of the cross section.

groar 10-22-2008 07:10 AM

amidesign, bienvenue sur

I bookmarked your site, it seams its content is great :)
I love the E-Push.

trebuchet03, also bookmarked your site to be visited later.


trebuchet03 10-22-2008 12:54 PM

Ami - the .09 was a nominal value based on CFD analysis and a scale tunnel test which had a perfect surface (I personally think the scale was too small).... In reality, the cD is probably double that if not more ;)

The key thing to remember with velomobiles is that at the relative low speeds these thins travel at (less than 40mph - realistically cruising in the 20mph range) ... Designing for laminar flow isn't the most ideal as environmental forces have a rather large effect. Incoming flow is, for the most part, already turbulent. Of course, over a long distance - every watt saved is good thing... But for short trips, it's a compromise.

That said, even the current speed record holder has a relatively short tail end. The widest part of the diablo 2 is right at the shoulder area (and he's crammed in there :D).

amidesign 10-22-2008 03:07 PM

As you see the tail of the most efficient vehicle of the world is a bit quite longer :

ETH - PAC-Car II - PAC-Car II Miscellaneous

The speed is only of 18 mph. The lateral wind is considered.

The first rule for aerodynamics is wrote in a stone.
Aerodynamics rule 1 .

As exemple the NACA series at 20% thikness:

NACA 4 Digits Series

But people speak of laminar airfoils. Better for Human Powered Vehicles. But it is extremly difficult to achive those technics. A big precision is need to respect the ideal shape. Sailplanes factories use this technic. But for how much money. A good old WWII propelled airplane achive a Mach 1 top speed in dive.

I have also a project of an electric car :

But it is for later. Maybe for half 2009 or end 2009.

trebuchet03 10-22-2008 04:23 PM


Originally Posted by amidesign (Post 68738)
As you see the tail of the most efficient vehicle of the world is a bit quite longer :

ETH - PAC-Car II - PAC-Car II Miscellaneous

The PAC2 is a very beautifully constructed vehicle... But, it's design goals (even the goals for the diablo2) are different than the design goals for a car replacement type velo.

A very supine position, very long body doesn't lend itself to be practical for daily use.

My long bike is occasionally too long to lock up everywhere - it's not a big problem at it's current length, but if it were any longer, it would be almost completely impractical for daily use.
Homemade Sport Utility Bike (SUB)

This vehicle, for example, is a very gentle taper... But it came at a very hefty compromise.... The pilot is laid back traveling head first and pointing backwards (the pilot navigates by looking through a mirror) - allowing your widest body part (hopefully your shoulders) to lead the vehicle. Aerodynamically efficient (for speed) - not practical for someone like me that would use the vehicle to commute, get groceries, etc :/

And remember, cD changes drag linearly... As does frontal area ;) Blimps tend to have incredibly low cD values - but have a huge frontal area. If you start at a respectable .20 cD with a cross sectional area of 5000cm^2 - you'll probably find it much easier to reduce 50000 than it is to reduce .2 :thumbup: (reducing both would be even better - but it's important not to forget one for the other).

In short, I'm saying that on the velo scale, what's efficient for aerodynamics is not necessarily efficient for daily use. And that's where compromise fits in...

amidesign 10-22-2008 08:27 PM

Ten years ago, I imagined a solution for my car :
Retractable Car bag tail.

The tail is made like a paragliding.

trebuchet03 10-22-2008 10:16 PM


Originally Posted by amidesign (Post 68779)
Ten years ago, I imagined a solution for my car :
Retractable Car bag tail.

The tail is made like a paragliding.

Every now and then someone brings up the idea of an inflatable boat tail. I totally like the idea of using ram wind principles (as long as it's not acting too much like a parachute :p). :thumbup:

I think it would be sweet to have a retractable/inflatable that uses inflatable kite bladders :)

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