Three shock designs

[*J*]

Hi, im very interested in implementing a three shock design front suspension system on a light, small engined, formula style car. Im finding it very hard to find much technical information about such setups. Has anybody got any good info, links or experience of such things?

Many thanks

J.

[shiny side up!]

Why are you interested in a system utilizing 3 shocks? (I admit that is a bit of a leading question... )

[*J*]

Hi, in order to have a nice soft bump set up, for each wheel, with indipendent control of dive and squat.

[Lukin]

For a small non aero formula style car, is the added complexity of setup, construction and the added weight worth the gain from decoupling the different vertical modes?

Good for F1, but anything other than bragging rights for a small car?

[maddogf3]

Originally Posted by *J*

Hi, im very interested in implementing a three shock design front suspension system on a light, small engined, formula style car. Im finding it very hard to find much technical information about such setups. Has anybody got any good info, links or experience of such things?

Many thanks

J.

Dear J advise go and read some books on design ,visit websites i.e. Koni etc and then see if you would gain a benefit from Hi tech adjustments and if it will make your car faster or not .If you are not getting max out of your set up now. have you the knowledge to set up your car with added complication of high tech shocks. If you have a light softly sprung car with a 25mm travel then shocks can have a massive influence on how car handles on entry and exit of corner i.e weight transfer and of course over bumps. You can set the car to perform how you want . Please . Balance cost against complexity and then choose

[nitrous]

J

What you are looking for is what's called a third spring. Basically you run softer main springs and with the aero and braking the third spring holds the car off the ground. Now it sounds like you are not worried about aero so there are two ways to incorporate softer springs.
First you can utilize packers with silesto rubbers of different progression. If you don't have any data system you will need to do a trail and error by using ty-wraps on the damper shafts to see how much travel you have. Next you would engage the rubber to support the car under braking and hard cornering without sending the rates into infinity. Be very careful not to make your car too soft and create problems you originally thought were from being too stiff. Use a valve spring tester to measure the different silestos so you can manage your testing. Packers are small plastic discs that have a cut-out on one side so you can insert and remove them freely from the damper shaft to "pack" it to the desired engagement.

Next is the third spring which requires more linkage and is anchored to the chassis and the other typically to a T-bar style ARB (anti-roll bar). When the chassis moves up and down it moves the shaft in or out. You can utilize a bushing type set-up with bump rubbers or an actual small damper that is purpose built. It can be used on the front or rear or both of the race car. It was used wide spread in Champ car and mostly on the rear to aid in traction. Let me know if you would like to know more about it.
Using a shaft that goes into a small bushing is a very cost effective way of doing it just to experiment with.
Good luck.

[Lukin]

Further to what Nitrous said; The best way (ie most simplistic) I've heard to describe it's function was from another forum. When the car rolls (ie one wheel moves up, the other one down) the third spring/damper does nothing; it feels no displacement/velocity. When the car hits a bump, brakes, accelerates or is affected by an extra aero load, both wheels are pushed down (or up) and the third spring 'pushes' against it to resist this motion.

If you have linear pots, you can use the data to estimate what stiffness and damping from the third spring/damper. From the four pots you can find the contribution of each vertical mode (roll, pitch, warp and heave) to work out your effective 'pitch gradient' (I use that term loosely as I don't know the proper term). When working with roll bars you apportion a certain amount of roll stiffness to the bars and a certain amount to the springs, the same approach can be made with the third spring setup.

Apparently, this is how Williams did their active suspension. However, this method doesn't work with droop limited cars.

The UWA SAE car implemented a similar system (it had extra functionality) and you could bounce each corner up and down without too much effort, but pushing on the anti roll car (in pitch or roll direction) would get you absolutely nowhere.

[*J*]

Originally Posted by nitrous

J


Next is the third spring which requires more linkage and is anchored to the chassis and the other typically to a T-bar style ARB (anti-roll bar). When the chassis moves up and down it moves the shaft in or out. You can utilize a bushing type set-up with bump rubbers or an actual small damper that is purpose built. It can be used on the front or rear or both of the race car. It was used wide spread in Champ car and mostly on the rear to aid in traction. Let me know if you would like to know more about it.
Using a shaft that goes into a small bushing is a very cost effective way of doing it just to experiment with.
Good luck.

Hey nitrous and Lukin, cheers for the advice, however its a tad late now! cheers all the same.

I was undertaking a dissertation project for my MEng degree when i asked the question, i spent an academic year working on it and ended up doing more or less what Nitrous has described here. I designed the system and proved it within ADAMS/Car.

Its a complicated subject, but very interesting, and one where plenty of gains can be made.

Cheers
J