why is pushrod suspension better than normal suspension?

[frankyknuckles]

what makes it so good and how woud it compare to fully adjustable normal dampers?

 

www.R300.net

[Gambo]

Main advantages are: -

1 aero more efficient to have pushrod in air stream not damper unit

2:- reduces unsprung mass

3:- if designed properly then you can eliminate all falling rates and you can set the wheel travel to damper travel more acurately and it will remain constant.

4:- you can adjust ride height by increasing /decreasing pushrod length, thus not changing preload on spring.

5:- you can keep all anti roll bars inboard and much smaller and lighter as they can act directely onto the rocker, not onto the suspension wishbone, or hub.

 

 

Oh no I'm coming down with another bout of upgradeitus!

[knowley]

... and you can brag about it

[Joe 90]

Like a lot of things, a good conventional suspension will be better than a poor pushrod suspension. Pushrods are now common on high performance open wheel cars because they are aerodynamically superior, and aero considerations dominate F1 and similar formula. Pushrod suspension interposes a crank between the suspension movement and the damper/spring movement, which can be used to good effect to get a rising suspension rate, which is so much more desirable than a falling rate suspension.

 

SEP field working, not spotted in 102,700 miles. Some photos on webshots, updated 21 Sept

[RESOLVIWOLF]

aerodynamic advantages are minimal i would say

on a seven type car, pretty much non-existent

[Graham Perry]

Moving weight of dampers/springs inboard towards the centreline probably doesn't do any harm either

[Tony C]

If I remember correctly what Len Unwin (Freestyle) told me - its major advantage is improved damper movement, thus improving their efficiency. As previously mentioned, the more efficient spring set-up is another advantage.

 

BRG Brooklands SV 😬 It seems that perfection is achieved not when there is nothing more to add, but when there is nothing more to take away. (Antoine de Saint-Exupery)

[Bare]

Shox and springs work V much better when Vertical rather than lying down.. the greater the Angle off of Vertical the worse the problem.. (horizontal is a different animal as it's usually also rocker activated. and purpose designed) . Study the earlier 7 designs.. and note how over the years the shock/spring units have gotten to be lower and lower.. exactly the wrong direction IF performance was the intent.

Makes one wonder about the claimed advantages of 'wide track' at least without a rocker arm setup.

[Normans_Ghost]

Franky, Why not admit it, you keep asking these questions in order to justify a change of car. CSR next then?

 

norman verona, 1989 BDR 220bhp, Mem No 2166, the full story here

[Chelspeed]

Bare - I know what you are getting at but think you may confuse others by saying shocks don't work lying down.

 

As I'm sure you know a spring will work exactly the same in any orientation, it's just bending metal as you compress it and doesn't know which way up it is. Likewise a shock absorber, you're just forcing oil through an orifice, it doesn't know whether that oil is going up or down it just goes through the orifice when you close or open the shocker (ignoring things like mixed oil and gas shocks needing the gas at the top).

 

The important thing is the geometry of the shock absorber relative to the rest of the suspension. With short wishbones and a shock mounted from the outboard end of the lower wishbone to the body (as Caterham) the shock is compressed as the wishbones rise. With normal track this is roughly 2 to 1, ie 2 inch of suspension compression (wheel goes up an inch) will move the shock roughly 1 inch. As you make the track wider the shock absorber becomes more horizontal. Whats important though is that the 2 to 1 becomes more like 2.5 to 1. So 2 inch of wheel travel now gives you more like 3/4 inch of shocker movement. So you need stiffer springs (easy) and stiffer shocks (expensive and more difficult to do efficiently as the shock must work over a smaller movement).

 

So the suspension with the shock laying down works less efficiently than one where the shock is more vertical but for geometry reasons rather than because the shock doesn't like lying down.

 

With inboard designs there's a rocker which can be chosen to amplify suspension movements, Freestyle's gives more like 2 inches of suspension travel for every inch of wheel travel. The shock therefore has more movement to work over so the control of the oil flow within the shock body is much easier to control more accurately.

[Petrolhead]

You see before you a very confused man 😬

 

R500 no 65 😬

 

Edited by - Petrolhead on 5 Dec 2007 09:20:09

[Ron_F]

Simple trigonometry

[frankyknuckles]

Franky, Why not admit it, you keep asking these questions in order to justify a change of car. CSR next then?

 

😬 no mate, trying to justify £1500 worth of freestyle suspension

 

www.R300.net

[Gambo]

Ah, what you need is a pre'96 car. freestyle's sytems doen't fit, so I did not have to justify that spend, I couldn't do it. ☹️

 

Oh no I'm coming down with another bout of upgradeitus!

[frankyknuckles]

even on the advantages listed above, I still can't see how the freestyle system justifies itself, let alone adds up to £1500 !!

 

www.R300.net

[julians]

fashion, same as majority of carbon stuff

[Petrolhead]

£1500 does seem a lot, I would agree. Does anyone here have a car he could try for comparison.

 

A lot of people seem to fit Nitrons. Are they a big step over the std suspension?

 

R500 no 65 😬

[Tony C]

Good grief

 

BRG Brooklands SV 😬 It seems that perfection is achieved not when there is nothing more to add, but when there is nothing more to take away. (Antoine de Saint-Exupery)

[John Howe]

Gambo, talking to Len Unwin last week... he mentioned that on pre '96 cars the answer is to take it back to Arch, who for around £300 will take off the unwanted bits and weld on the new to give you post '96 spec.

 

It can be done without removing the side panels...

 

JH

Deliveries by Saffron, the yellow 222bhp Sausage delivery machine

[Gambo]

Thanks Mate ❗ ❗ ❗ Now I got to find a whole other reason not to do it,or face severe bollocking from SWMBO. I thought I'd managed to put that one to bed in my head. 😬 😬 😬

 

Oh no I'm coming down with another bout of upgradeitus!

[rgrigsby]

John I think you may have missed a 0 of that figure from Arch for a new long front.... it's not a cheap thing to do ☹️

 

Rob G

www.SpeedySeven.com

[Xracer]

Along with the many advantages of inboard rocker arm suspension come some disadvantages, any wear in the linkage will give undamped movement, the way the Caterham suspension is mounted places the dampers in the hot airstream from the radiator making the damper oil hotter than normal therefore reducing viscosity & efficiency.

All in all the advantages probably outweigh the disadvantages but at a price.

Regds

Ian

[Jason Plato]

The air is ducted out of the nosecone on the CSR , so the effect will be reduced on the factory car .

 

 

[Alias]

So if you have a pre '96 car, you need to spend £300 on the chassis mods and £1500 on the suspension mods bringing it up to about £2000.

 

I guess the burning question is whether a current De-Dion car can be converted to IRS at the rear. That would be worth paying £2000 for 😬

 

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1400 Supersport with 6 gears and clamshell wings

[Lennie]

We are hoping to be at Silverstone at the club track day and will be giving rides, in the super wide track car with a 213 Minister Duratec, whilst setting the car up which will be interesting for the passengers.

We don't think that IRS is the answer, at Brands the Japanese car was we believe 230 bhp not sure of the weight of the driver but we beat that with a 750 car, well done Peter, BUT we could be wrong it would be nice to see the factory car at Silverstone so we could compare times.