Dual Spring Rate Coilovers

[JHarshbarger]

Has anyone ever heard of a coilover with dual spring rates? The purpose I have in mind is that you would be able to drive around town with a nice soft ride, but when you take the car autocrossing or whatnot, you can quickly adjust the coilover so that your wheel rate is increased. You could put a smaller spring inside the main spring that would normally be loose and not compressed, but when you want the higher wheel rate you could crank down the perch for the inside spring so it is compressing.

Has anyone ever considered this type of coilover or seen one already in production? It seems like it is a feasible design.

-Joel

 

[GregLocock]

That would lift the car /up/. Is that really what you want?

Much better would be to drop the perch on the low rate spring

Cheers

Greg Locock

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[Yawing]

I have heard that Porsche (on on of their many racing car series) have an adjustable spring rate system simply by locking out a certain number of coils on the spring.

 

[patprimmer]

Some off road racers used a torsion bar as a secondary spring that could be bought into action by rotating the fixed end a few deg. This was preloaded in compression by a droop stop and the droop stop was set to maintain the torsion bar lever or arm contact point to just above normal ride height, so it only came into play during bump or on the outboard side during roll

Regards

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[cibachrome]

Spring rubber(s). Perfect for weekend warriors.

Not an endorsement, just an example:

http://www.racerpartswholesale.com/long70.htm

 

[JHarshbarger]

Thanks for the input. These are all great options, all of which seem to be simpiler than my idea (probably why I haven't seen it yet).

Shenanigans, on the Porsches, is the "coil locker" an automatic adjustment that can be made from the driver's seat or is it something that someone would have to put on the coils or engage themselves?

Patprimmer, I really like this idea. It appears to be similar to the blade style anti-roll system. Do you know where I could find some pictures of this system?

Cibachrome, I had forgotten about the spring rubber. This is probably the easiest way to effectively change the spring rate. Thanks for the input.

-Joel

 

[nobog]

Snowmobilers have had this set-up for years. One method as you described (coil inside coil) is used but mainly for making up the shortcommings of a falling rate suspensions. Dual or triple rate springs - stacked on top of each other is common. "tuning rings" are used to control the transfer point of one rate to another so you can set the point at which the next spring "takes over". We (

http://www.deycore.com)

have found the dual and triple rate springs mostly are more trouble than they are worth yet some suspension tuners love 'em. Jim

 

[patprimmer]

I am sure you will see examples in any old book on building and racing VW based Dune Buggies and Baja Bugs.

Regards

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[Yawing]

The porsche system was the spring perch would wind down and past some coils to "deactivate" them. buts its not from the drivers seat, you have to do it manually

 

[AlbertHung]

I have considered a setup like this. It could be as simple as putting a progressive rate spring on a coilover that has an adjustable spring perch. If the main coil is 600lbs/in, and the secondary coil is 200lbs/in, you could run the spring fully extended for daily driving, and it would obviously give you the benefits of a progressive rate spring. But if you decided you wanted a linear, high-rate spring for track use, you could simply "cancel out" the secondary coils by preloading the spring until all secondary springs are compressed to coil bind, in which case you're left with the main coil and a 600lbs/in spring.

I haven't tried it because we are limited by the design of our coilovers (short stroke, not enough room to fit >8" of spring) and our spring manufacturer. I hope this was what the OP was getting at though.

 

[GregLocock]

I think he was talking about springs in parallel, you are talking about springs in series, I think

Cheers

Greg Locock

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[EfiOz]

Yes, I've run a dual spring arrangement in F3 and GT cars for 3-4 years now. I usually make up an length adjustable collar so you can change the lockout point for the secondary spring.

There was an article in Racecar Engineering some time ago about it.

 

[bentwings1]

We have actually a triple rate on our sand buggy. Each spring has a spacer/stop that you can replace for various loads. The shocks are totally adjustable for rate and valving. To see this suspension working at 100 mph on a trail that it is nearly impossible to drive a off road truck on at all is interesting. The normal ride is very soft but controlled. As you pick up the pace it get a bit rolly then at about 35 mph it starts to smooth out. At high speed it more or less follows the blended roll of the terrain. I suppose you could call it an averaging of the bumps and rebounds. It is smooth for the speed.

99 Dodge CTD dually.

 

[MarkLo]

patprimmer do you have any pictures of the 'variable' spring torsion bar set-up ?

Regards

"Some off road racers used a torsion bar as a secondary spring that could be bought into action by rotating the fixed end a few deg. This was preloaded in compression by a droop stop and the droop stop was set to maintain the torsion bar lever or arm contact point to just above normal ride height, so it only came into play during bump or on the outboard side during roll"

 

[patprimmer]

I have not done off road for 20 years, but I know there are pics in a book called "How to Build Off Road Buggies and Baja Bugs" or something like that, by HP books or SA design books.

Regards

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