Tube Frame Design

[anybody15]

Tango Charlie,

If you don't know where to start, buy, beg, borrow or steal "build your own sports cars for 250 pounds" and build that one. It should take you about 2-3 years. This is coming from a guy who has built one (not for high mileage but for brutal performance on a budget - total cash outlay $7500) Mine's the one on the top of the wikipedia page! It's since been painted.
David grey50 is correct about "Racing and sportscar chassis design" by Costin and Phipps. It is a fantastic book and highly recommended - but unless your math is strong enough to crunch the numbers, build the seven replica first. I can't stress highly enough how much you will learn.
Then make a slippery body for it. Mine turned out a bit heavy at 650kg.
Coyote X is also correct in stating "It is a lot easier to build a car than most people think, it just takes a huge amount of time." There is lots of information
on the locost forums particularly if you ignore anyone "still in the planning stages" . Chromoly is unnecessary, expensive and your first car should be conservative enough in design to not require it. You can use it however, but I wouldn't on the first one, 1020 is much more forgiving. Chromoly will crack if the wrong filler material is used and/or allowed to cool too quickly. Right now I'm building a tandem seat with a 500cc engine, it was for the x-prize, but we aren't far enough along to be sure we'll be done by the date, and besides the $7500 entrance fee is half the budget for the car. If you can hold out till July I should be able to sell you a set of plans for $50.00.

best of luck

Stephen Flood

[order99]

That's some car you've got there!

What's your MPG?

[anybody15]

No idea, every time I drive it the accelerator seems to end up on the floor.
;-) (4age twin cam 1600cc stock internals)

[anybody15]

Forget the oxy, ( unless you are using Chromoly, then it's a good idea) buy a mig.
(Miller, Hobart, Liquid air, lincoln.) it's easy to learn and about 10 times faster.

[Tango Charlie]

anybody15, welcome to ecomodder! You've done an awesome job with your Locost! What kind of engine did you use? I always thought a Locost with a Honda S2000 drivetrain would be fun around some twisty roads...
Actually, I do own Ron Champion's book. It's a great book if you want to build a Locost, but doesn't have any info on how to work out your own design, as that just isn't the point of the book. I'm wanting to build something I can commute to work in and get insane mileage; I've got some ideas that are begging to be proven.

[order99]

Now a Locost Trike would be awesome-use the front end of the car, A Diesel like the one featured on the MAX design...the Max is getting over 70MPG as is, wonder what would happen minus another, say, 300lbs on the frame?

[anybody15]

Tango Charlie,
The locost has a 4age corolla twin cam drivetrain (they were rear drive until 1987)
If you have a look at the X-prize pages there is a bloke entering a locost with a kotuba diesel engine, 60 odd mpg with aerodynamics of a brick. I am absolutely serious about
"build a locost first and drop a slippery body over it". With a small diesel you should be pushing 70mpg. Design your own is a great idea, but it is a STAGGERING amount of work. Don't get caught up it the idea rather than the task. You could spend 4 years designing something before you build anything - Don't. Hit the GO button. Make a light car ( and the locost is about as light as one can really go without moving to expensive composites), with lightness in mind you should be pushing 500kg. put a small/light engine in it (lupo diesel from europe?)

BTW the seven is for sale

Cheers

Stephen

[jamesqf]

For anyone that does want to get into design & doing finite element analysis and that sort of thing, there's this: OpenFEM for free. (I've never used it, just remembered it popping up in some other search, so caveat downloader :-))

[some_other_dave]

Originally Posted by anybody15

... "build your own sports cars for 250 pounds" ...

Thanks, that's the title I was trying to think of!

-soD

[MechEngVT]

I've heard lots of good things about Herb Adams' book Chassis Engineering. It's primarily oriented toward suspension theory and design but there is a frame design and construction section. I haven't read it but when I was in college on a FormulaSAE team the chassis/suspension guys pored over it for months (I was in the engine group).

The Formula SAE cars that use tube frames all use "chromoly" tubing of various mostly prescribed alloys (roll hoops have to be a certain alloy per the rules). They welded it using TIG with alloy-specific filler rod and used both pre- and post-heating. That's really the only way to avoid stress cracking long-term. Those cars were "thrown away" after 1 year of build/race and another year of test/train, but only the ones that were wrecked showed any frame damage. You can probably MIG chromoly but you would have to pre- and post-heat to get decent welds.