A-arm lengths and mounting points help

[Gene]

Good advice right there.

[nutz4sand]

The Book Evan suggest you read IS so worth it. The two days or less it should take to read it will be money and headache saved IF you are not buying good plans and following them to a "T". (Translated if your making your own design you need to understand whats what.) You will same more time in not redoing it just from whats learned.

Also this is the link Gene mentioned. Its RC and on road but it translates over. To be harsh if you cannot see it on this site and figure it across building your own suspension design should not be attempted. Not trying to be cold. Just honest.

RcTek - Radio Controlled Model Car Handling Main Section Page

[Duden89]

That site is great. Clears up alot of things. Is there a specific book you recommend or just anything by Carrol Smith?

[nutz4sand]

Originally Posted by evan

IMO...I strongly suggest that anybody serious about designing / building a buggy or kart buy a chassis dynamics book. The $18 you spend will be well worth the headache saved. Most include diagrams and explanations well above what anyone can post on here. I strongly recommend devoting a weekend to reading any book by Carroll Smith. I always find myself referring back to "engineer to win." Also "tune to win" explains chassis dynamics which is the topic here. They refer to formula style cars so camber curves and other value are not helpful to us, but the understanding of these concepts allow you to deside what compromises you feel comfortable with.

The "Engineer to win" and "Tune to win" are both great. (I have both here too!)

Engineer to win is more about the designing and building.

Tune to win is more on how to make what you have built (hopefully with engineering to win :] ) and tune it.

The books are geared more towards asphalt racing. But the understanding it gives you will be priceless compared to the buying of the books and the reading time.

[Duden89]

What do you mean by you have both here too?

[nutz4sand]

I mean I have both of those books by Carroll Smith here too. (I guessed (assumed) from the reading that Evan has them both too.)

The books being "Engineer to win" and "Tune to win". Both by Carroll Smith.

[MXman]

On my car I have about -2 deg at right height and it cycles to about -6 at full bump.

[atomicjoe23]

I also suggest the book "Chassis Engineering" by Herb Adams (an engineer with GM previously IIRC).

It is the only one of the three books that I have right now, but it was more than enough to get me through designing my first A-arm suspension. It works very well. . .I ended up with 17+" of travel in the front; I don't remember what the camber numbers were, but I know the caster was set at 6* which is a good all around figure to shoot for as far as caster is concerned. The only geometry that "Chassis Engineering" didn't really touch on was Ackerman which is very important so don't forget about that!

I plan on getting "Engineer to Win" shortly.

[Duden89]

So whats a good kingpin inclination to shoot for?

[nutz4sand]

What kingpin inclination? The right one! :]

Its determined by where the time and rim combo put the contact patch on the ground. Some like it to be JUST a TAD inside the contact patch to give them some feedback in the steering. Some like it right under the center of the tire. To the outside of the tires contact patch is usually considered bad. To far to the inside of the car and the tires will do more steering than you and wear out the driver and make yah miserable. Genrally at least.

Heres the catch. If you have a dualsport car for sand and desert chances are the tires are not gonna be just the same if you run pure sand tires in the dunes and some kind of treaded off road in the desert. Have to make a compromise there or favor the one you use the most.

Its why a lot of builders will tell you to choose the tire and rim you plan to run and build inward form the wheels/tires. Then you can make the spindles have the K.P.I. right where you want it in the build. Then the arms figure out and the frame just holds it all together.

If you buy a spindle and just slap a rim and tire on it you might get lucky and you might just live with it if its not right or if its "close". But one that IS right will make for a MUCH happier driver!

Check the image below to see KPI as it should be. A wider offset rim will be totaly different as it will be much farther out.