Suspension question (I'm a beginner)

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Post Sun Jul 27, 2008 1:49 pm

Hi all,

playing a bit with my RC car I came across a probably amateurish question for which I can't find yet a proper explanation.

The suspension is build up by a coil spring and inside it there is a small cylinder with oil in it. The usual suspensio systems work like that: coil spring and cylinder inside. But what I don't understand is the function of both of them together.

Couldn't the suspensio system run with just a spring? Or just with a oil-cylinder?

Thx in advance
Tifoso
 
Joined: 11 Feb 2007

Post Sun Jul 27, 2008 3:24 pm

The spring absorbs the initial energy of riding over the bumps, but a spring on it's own would mean the car would continue to bounce up and down for a long time. The oil is used to 'damp' the bounces down.
MattF1
 
Joined: 22 Jul 2008

Post Sun Jul 27, 2008 5:24 pm

Thanks MattF1, pretty stupid question #-o
Tifoso
 
Joined: 11 Feb 2007

Post Sun Jul 27, 2008 6:19 pm

Tifoso wrote:Thanks MattF1, pretty stupid question #-o


Hehe.
Tifoso, in short the damper in used for compression and the spring for it to return to its original position. :wink:
Racing cars are neither beautiful nor ugly, they are beautiful only when you win races.
HKS
 
Joined: 5 Mar 2007

Post Sun Jul 27, 2008 8:22 pm

HKS wrote:
Tifoso wrote:Thanks MattF1, pretty stupid question #-o


Hehe.
Tifoso, in short the damper in used for compression and the spring for it to return to its original position. :wink:


I see, thanks too. Its good to have a forum where someone can anwser this questions.
Tifoso
 
Joined: 11 Feb 2007

Post Mon Jul 28, 2008 2:51 am

Well, I'm sure HKS understands how a suspension works, but I'm not sure he was clear enough.

The spring is the whole "structural" member, it supports the car in compression or tension. It would "work" (supporting the car) even without a damper.

What a spring does is to "dissipate", or to "blurr", the effects of the irregularities of the road on the wheels.

The damper is used to dampen (duh...) the movements of the chassis. If you don't have a damper, the spring would oscillate "too much".

How much is "too much"? Well, in racing cars the idea is that, together, spring and damper work to keep the wheel in contact with the road.

Normal cars also use suspensions to keep passengers comfy, but this is in conflict with the "wheel-in-contact" idea, so...

"Wheel-in contact" means that the wheel transmit some load (some weight) to the road, without any "rebounds" (hopefully).

This transmitted "weight" is what gives grip to the wheel. Is this "weight" what allows you to steer, brake or accelerate.

Imagine you have an R/C car without a suspension: with a "hard chassis", the car will jump as soon as it hits a significant bump in the road, won't it?

If this "suspension-less R/C car" is on a curve and it jumps in the air, the wheels will loose traction and the car will slide.

So, the idea of suspension is to avoid that kind of jumping to offer the driver a more or less constant grip.
Ciro
Ciro Pabón
 
Joined: 10 May 2005

Post Mon Jul 28, 2008 6:09 am

From physics standpoint spring is like a KERS. It recovers kinetic energy so it won't damage car structure. Damper dissipate that energy by transforming it into heat. Without dampers ideal spring would keep bouncing eternally. Without springs dampers are not able to dissipate energy efficiently, because it have to be done too fast.
timbo
 
Joined: 22 Oct 2007

Post Mon Jul 28, 2008 8:42 am

The difference is simple.

The spring controls how MUCH the suspension moves when a force is applied.

The DAMPER (oil cylinder) controls how QUICKLY that movement occurs.
MrT
 
Joined: 17 Jan 2006

Post Mon Jul 28, 2008 1:37 pm

Ciro Pabón wrote:Well, I'm sure HKS understands how a suspension works, but I'm not sure he was clear enough.



My idea to keep the things very simple and Non-technical. :wink:
Racing cars are neither beautiful nor ugly, they are beautiful only when you win races.
HKS
 
Joined: 5 Mar 2007

Post Mon Jul 28, 2008 4:23 pm

Thanks all again, I have a clear view of how it works: aided firstly by the simple idea HKS and MattF1 gave me and then with the deeper help.

Thanks all!!
Tifoso
 
Joined: 11 Feb 2007


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