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newbie question about mid-engine chassi
khaOs - 27/12/06 at 02:00 AM

Hey! I was thinking about making a car from scratch to install the 1.6 vtec turbo engine that i have at home. the problem is that i don't have any experience in this field and i don't know how to start designing the chassi. Does anyone know where i can learn about this? thanks

kb58 - 27/12/06 at 02:25 AM

You've come to the right place. My advice is to take a year (really) and read, read, read. Here's my list of books

My own book will be ready at the end of January, which will be very helpful in your case. I used a Prelude VTEC drivetrain and mounted it mid-engine in a tube-frame Mini. Click on link in sig.

/End of self-promo...

[Edited on 12/27/06 by kb58]

Doug68 - 27/12/06 at 07:53 AM

Hi KhaOs,

I'd second what kb58 said I'm a roughly a year into my project and expect to start cutting metal soon!
I'm glad I didn't rush to this stage as I'm sure I would not have been happy with the result.
Other people on the forum have taken much less time than this and that's good for them .
As you'll see anyone who engages in this sort of project is fairly individual person, so expect lots of differing opinions from people who are not afraid to speak their minds!

Good luck!

gttman - 27/12/06 at 10:03 AM

You could try to buy some plans for a midi you like.

goodall - 27/12/06 at 12:19 PM

do mid engined cars not understeer like theres no tomorrow with just a few bit of box iron loading the front wheels

suparuss - 27/12/06 at 01:36 PM

quote:
Originally posted by goodall
do mid engined cars not understeer like theres no tomorrow with just a few bit of box iron loading the front wheels


not if its designed properly. its obviously an inherent problem to think about but there are plenty of ways around it.
edit- another point is that when going round a corner the weight in the back will tend more to push teh back out causing oversteer. depends on many little things.

to answer the main question, ill second what kb says- get some books and familiarise yourself with chassis design and suspension design principles and then the best next step would be to learn a cad program so that you can start playing with different ideas a lot easier.
one main requirement will be to have the main parts you intend to use to either measure into cad to design around, or make a scale model etc.

[Edited on 27/12/06 by suparuss]

DIY Si - 27/12/06 at 01:37 PM

No more so than a locost weighing 500 kgs with 50-50 weight will. And since all the weight is in the boot, a mild prod of right foot will soon sort any understeer out!

russbost - 27/12/06 at 06:18 PM

My cars handling is very neutral despite having about 2/3's of the weight up the back end, when you push to the absolute limit it starts to understeer slightly, but a dab of throttle puts the back end out - can then be controlled on the throttle just like a kart

kb58 - 27/12/06 at 06:23 PM

quote:
Originally posted by goodall
do mid engined cars not understeer like theres no tomorrow with just a few bit of box iron loading the front wheels


Kind of like saying, "What type of personality do blondes have?" It's hard to make broad (sorry) generalizations

Some people feel that a mid-engine car will understeer due to <50% weight on the front tires. Yet others say it'll oversteer due to having >50% on the rear tires.

Personally, I don't believe there's anything magic about having 50% weight distribution. It's never that value unless sitting still or at constant speed. How long can a car remain at an unchanging speed in a turn? Plus, it's likely the rear tires on this perfectly balanced car are larger than the front tires - so much for perfectly balanced traction. With larger rears, it'll push (understeer) in a constant speed corner.

Check out my videos for how mine handles. In the latest is me spinning it, due to braking hard way too late into a turn; that will happen in any car. Mine is 41/59 F/R, and I'm very happy with it. The car is very easy to place in any attitude. If I take a corner at constant spend, it has slight understeer. But if I get on the gas, it transisions smoothly to oversteer, and it's very easy to modulate, to stay between the two extremes.

nitram38 - 27/12/06 at 06:43 PM

quote:
Originally posted by russbost
My cars handling is very neutral despite having about 2/3's of the weight up the back end, when you push to the absolute limit it starts to understeer slightly, but a dab of throttle puts the back end out - can then be controlled on the throttle just like a kart


I can second that......I was right behind you when you did it !

NDC790 - 27/12/06 at 10:26 PM

If you build it..............it will run!




We hope.

cloudy - 27/12/06 at 11:47 PM

actually the further the weight is to the rear, the higher the tendency for oversteer, it's not about the weight on the wheels, but rather the inertia they are having to deal with, when you turn the wheels it's actually having to move less mass than the rear wheels and the car will tend to oversteer (even without your foot planted)

J

[Edited on 27/12/06 by cloudy]

khaOs - 28/12/06 at 11:25 PM

kb what books do you recomend from that list? several of those i can't buy here and the ones i can buy are kind of expensive. The areas where i have more doubts are the chassis and suspension.

kb58 - 29/12/06 at 12:13 AM

Anything by Staniforth. He has a practical, easy to understand, way of explaining things. Worked for me.

Doug68 - 29/12/06 at 12:45 AM

Amazon.co.uk has the "Race & Rally Car Source Book" together with Herb Adams "Chassis Engineering" which is another very practical book for 22 pounds, I don't think the post to you would be too much.

http://www.amazon.co.uk/Race-Rally-Car-Source-Book/dp/1859608469/sr=1-1/qid=1167352750/ref=sr_1_1/026-8771094-8851606?ie=UTF8&s=books

khaOs - 20/2/07 at 05:02 AM

Chassis Engineering should be here this week. i'll read this one and after that i'll see what i should do..