Rear suspension design

[260DET]

I've been thinking of this topic for several weeks.......... What I came up with is that the front needs alot more help than the rear.

......................................

I decided that I will modify the front suspension rather than the rear. I may do the rear later after I have improved the front.

 

What I am trying to decide is how much KPI to design around. I can run a longer upper control arm by using a smaller KPI (5 to 8 degrees)' date=' and I feel that a longer UCA is better because the roll center will move around less. I am also trying to decide how tall to make the upright. I am currently leaning towards going with the tallest upright height that will allow the ball joint to fit inside the wheel.[/quote']

 

Yes, I'm going to start with the tallest upright that will fit inside the wheel too and then proceed to get the roll center right, near ground level but always above dynamically, never below.

 

Next priority will be to control camber in turns, particularly the inside wheel, the worst feature of a pure strut suspension.

 

Then look also at castor, at the moment maybe ~8 degrees, more research needed though.

 

Oops, this is a rear suspension topic

[Guest Zuma]

If you want to do some reading on suspenion design -it is very imoortant were you put the pickup points if you want to go around corners at more than reasonable speeds

Chasiss Engr.-Hreb Adams(simple)

Design to Win,Build to Win,Engineer to Win -Caroll Smith more advanced but understantable

Race Car Vehicle Dynamics -Wm.Milliken&Douglas Milliken -a textbook type book that came out of GM research in 60's & 70's

[tube80z]

Then look also at castor, at the moment maybe ~8 degrees, more research needed though.

 

A good rule of thumb is to run about twice the castor angle of the KPI. For roll centers try to keep it below 3 inches.

 

Cary

[tube80z]

Chasiss Engr.-Hreb Adams(simple)

Design to Win' date='Build to Win,Engineer to Win -Caroll Smith more advanced but understantable

Race Car Vehicle Dynamics -Wm.Milliken&Douglas Milliken -a textbook type book that came out of GM research in 60's & 70's[/quote']

 

My favorite is probably The Race and Rally car sourcebook. It has a good mix of theory and practical examples. As I've learned more the Adam's book seems to have some errors and the Smith books, while good, are getting a little long in the tooth. Some of what we wrote isn't really accepted anymore no that we have data loggers and can see what is happenning.

 

Cary

[260DET]

Staniforth's Competition Car Suspension is useful, where you can cut through the British waffle. The Racing and High Performance Tire by Paul Haney, although more a setup book, contains a lot of practical informantion.

 

Another aspect about using a strut as the basis for a double A arm suspension is that Z 'bumpsteer spacers' could be very useful in repositioning the lower outer pivot point.

[Guest Zuma]

Tubez---- data loggers only tell you if you made a wize choice not where to put the pick up points

The pic you posted looks familiar is that from a B210 that was @ Rd Atl ronoffs fron late 80's?

[tube80z]

Tubez---- data loggers only tell you if you made a wize choice not where to put the pick up points

The pic you posted looks familiar is that from a B210 that was @ Rd Atl ronoffs fron late 80's?

 

You're right but it's almost impossible to do any real suspension work without them. You can do simple things like log the suspension travel and then look at it as you go through a corner. Then see where the all those points are that you worked so hard to design and understand what to change. Even as a lowly autoxer I don't run the car without collecting some data anymore. I'm hoping to add a number of channels this year and share the data. I'm saving to eventually be able to reach my holy grail, real time tire temps.

 

The pic is Steve Epperly's 200SX GT4/5 car. Steve is a long time NASPORT racer and did run a B210 in the 80s. It was built very similar so that's why the pic may look familiar.

 

Cary