Build a car from scratch....

[Blue Bomber Man]

I am no engineer and I have no experience with Solidworks, but I plan to make all of my work available on a public website so that people can help with suggestions.

I can say that I am an intelligent individual with a lot of determination. Several years ago I developed a macro program for a game I used to play that involved over 6000 lines of code. I did that with no programming background. So I hope that I can learn this program as well.

As far as getting compensation for developing drawings I think I need to prove something first as a designer before I can entertain such ideas. However if it is something relatively simple I might be willing to try it for practice. If it comes out well we could figure something out.

[Bicycle Bob]

Originally Posted by Blue Bomber Man

Kevlar is a good composite to use with carbon fiber, but without it I do not think it has the right properties for a vehicle. Kevlar provides excellent resistance to punctures and tears but the carbon provides much more support

I probably will use both together for their combined properties.

I used all aramid and 'glass, no carbon for my all-composite frame and integrated suspension. Every fiber has its place. Do you have experience in composite construction? Half the potential weight savings can only be realized with advanced construction techniques. Carbon is not magic, just expensive. In the real world, toughness often counts for more than sheer strength, and stiffness works against that.

Something I found was that details such as turn signals and door seals are just as time-consuming and almost as essential to do right as the main systems. There's a lot to a car; many lifetimes of engineering have gone into the ones you see every day. For more typical products of small shops, see the post-war micro cars or current kit cars.

I am also dabbling at vehicle software. I found Rhino too limited, lacking parametrics and with some apparent bugs, but had good hopes for SketchUp pro. But I've been "away" for two years. Solidworks has a solid reputation.

[JQmile]

For a 15K budget, I'd have no problem building a car from scratch. If it's a cheap chassis you're after, then I would check out Everything you need to build your dream street rod A t-bucket? Yep, they are light, cheap, and you can build your own body however you want to. My 82 Chevette makes 35 hp to the wheels and weighs 2400 lb with me in it. I figure something that weighs 1200 lb and has a 15-20 hp electric motor should do about the same thing, and be fast enough for freeway use. Once upon a time, I was building a T for drag racing, and I can tell you that the chassis, suspension, steering, and front brakes weigh no more than about 300 lb. If it were me, I would build a three-wheel car, that way it would be classified as a motorcycle which means you could get by with fewer regs from the motor vehicles dept. As for a body, I'd design it as close as I could to 1/2 an airplane wing and call it good. Good luck!!

[Blue Bomber Man]

So initially the software I got for solidworks worked, but it was the version for xp and I have Vista. It meant that I could only launch the program from the installer after an install.

So this past week I was able to virtualize a copy of XP inside Vista and then reinstalled it in XP and my problems are gone, and currently it runs quite well without any performance issues.

I think I have decided to change my mind about building a car for now though and decided to design an electric motorcycle in it's place. The are many benefits over car for doing this.

Simpler design.
Lower overall weight
Lower CdA.
All of which contributes to much significant savings for construction and shortens the design time.


The first thing I need to do is spec out approximations for weight and CdA so that I can estimate the battery pack watt-hours.

I think for now I will use google's web designer since it also hosts for free. I can post designs and images there and hopefully get some feedback here. However if anyone would like to get more involved in this and perhaps help create a site to run this (and I would like to advertising on the site to help fund the project) it would be great.

[Blue Bomber Man]

So I just found this on a motorcycle, has some interesting things built into it's shape.

Ecosse Spirit: Frameless Motorcycle from Bikes in the Fast Lane - Daily Motorcycle News

It says it has a Cd of about .4 and weighs 265 pounds. I feel that I can probably beat the Cd fairly easily by creating a bit of a tail and enclosing the front feel design, but I like how it's contoured around the rider. I don't think that I could beat their weight though but who knows.

For now I am going to plan on a Cd of .35 (which I can probably beat that but I need to be pessimistic for my battery sizing) and maybe 330 for the weight.

I'm going to guess that frontal area will be around 10 square feet, though it is probably lower, which will give us a CdA of 3.5.

[Blue Bomber Man]

If anyone knows anything about motorcycle tires that would be quite useful to me. I cannot find any actual numbers regarding rolling resistance for them. I imagine the RR is quite a bit lower then a car tire given that they have a much lower contact patch with the road, but I don't know this for sure.

[Blue Bomber Man]

So here are the goal specs that I have tentatively:

Range: 100 miles
Max Speed: 85 mph
Cd: .35
Frontal Area: 10 sq feet
CdA: .35
Weight with driver: 500 pounds

With these specs PAMVEC tells me I will need about 5 kw hours of battery pack and can expect around 650 mpg equivalent for performance.

The biggest limiting factor is the CdA which is quite high at the moment and is limiting both the top speed and range.

A very rough guestimation for the cost is around 10 grand at the moment, figuring roughly $1000/kw-hour for the battery pack.

[hummingbird]

why would you have a Cd goal at par/worse than production cars...?

[NeilBlanchard]

Hi,

You might want to check out SpaceClaim 3D modeling software as well. It is as easy as using SketchUp, but it is a true solid modeler -- and the cost is much lower than some of the better known programs.

[Blue Bomber Man]

Thanks Neil, but I have access to SolidWorks now so I think I will stick with that =).

As far as the CD of .35 that is actually significantly lower then most motorcycles which range around .5-.6 based on what I could find. I posted a link to a site with a motorcycle that is considered to be very aerodynamic and it came in around .4 but there are some obvious spots for significant improvement.

I do not plan on making this vehicle fully enclosed to make it super aerodynamic, but however I will design it so that the body helps complete the air flow, and hopefully some sort of tail that helps keep the air flow attached. Additionally the front wheel will be enclosed. With all that I bet I can get it down to at least .25, but I want to be conservative for now.