Build an efficient SUV from scratch

[arcosine]

1 percent inspiration, 99 percent perspiration

[mort]

Originally Posted by wilcorp70

If electric must go at least 60 miles and have possibility of range extending.
Maximum speed of at least 70 mph (I think 65 would be ok)

Hi wilcorp,
I picked this line out just as an example of how much "tail wagging the dog" you have going on. You have a body design, but no power plant yet. Choose electric or not first. Do you have the possible funding for the speed and range of battery storage required? $5,000 in nimh D cells: bulky and a few hundred lbs. Motor and controller - you'll need at least 100 hp for getting on the freeway and that might weigh 1000 lbs and cost about $2000 new... Regen braking? Chassis design will follow from the power source. The tires should be chosen based on required load range which you can't really guess until you have a power plant...

I'm not trying to be rude, but this looks like a unicorn corral posting so far. There is no reality showing. There are real technical issues to building a car and you haven't touched any yet.

-mort

[wilcorp70]

First off, I appreciate the occasional healthy dose of skepticism. So while you made it clear that you are not trying to be rude, let me be just as clear in saying that I'm not just trying to bounce back with an argument. I carefully considered whether I have started this as you said "tail wagging the dog," but I think you may have limited your view of how a car is designed to be too narrow. Car manufacturers design cars in lots of different ways: some are built around an idea, such as maximum mpg; some are built around an established chassis or drivetrain; many are started from the artist's rendering and all sorts of combinations in between. Where I spend most of my time with cars is in the street rod world (My current car is a 49 Plymouth) and in this world generally the frame and body are your starting point and whatever you decide to keep until you can afford better. As an aerospace engineer most of my projects begin with a set of performance parameters. This is in no way intended to be a build log, it is the design stage; as I mentioned in my first post I want to design as much as possible while I have certain tools available. It is also not intended to be a unicorn coral as you put it.
I also didn't put all of the things I'm thinking about as its easy to lose focus that way. Mostly, I want to start with the body design, making it as efficient as possible. I want to make a car that requires as little to move it as possible. As for the drivetrain I want to either make it a series hybrid or full electric; most likely full electric. That being said I want the chassis to be versatile and able to accept a few different drivetrain choices ie strong enough to handle the batteries. This is not unusual as many cars come in hybrid or gas versions. I am going to use a fairly unmodified version of the spaceframe used in the GM Skateboard concept which was designed to support more than I would put into it. As for your last point, improving the aerodynamics of the body design are a technical issue and one that I've heard one particular aerodynamicist from GM complain that more designers dont do. But, if it makes it more real, I can move onto some chassis and drivetrain stuff while I work on the body sketchup model.

[SentraSE-R]

I'm with Mort in thinking you have set far too few specifications for your project, and are letting the tail wag the dog. In order for you to wag the tail, you need to have a budget, a frame with available powerplants and drivetrains, and some concrete design parameters for starters. Your budget will tell you whether battery power is practical. Your frame will tell you whether diesel power and 4 wheel drive are possible. If you want to use a Ford Falcon frame, you need to know if one is available without major front or rear end damage within a six state radius. It will simplify your choices of powerplants, too.

After you firm up your specs, where's your timeframe for completion? Powerplant and drivetrain functional by Feb 2012. Completed project by May. Lots of detail to keep you focused, and to let you know whether your project is feasible.

Right now, you're just dreaming. You can papier mache a cutesy body on anything, but if you're going to build a 6 passenger SUV, your wheelbase and drivetrain specs are already out there. So why don't you have a 116" wheelbase, 4WD, 4 doors, 175 hp, etc. (or something similar) in your specs?

Right now, your project seems much too ambitious. IIWY, I'd get a platform, be it a CR-V, RAV-4, Samurai, Explorer, whatever - then limit your project to building an aerodynamic body on it.