Toymods Car Club Inc: Tech & Conversions => How to understand "The value of damping force"

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gold28
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Madrid - Spain
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August 2002

Re: How to understand "The value of damping force"	Fri, 23 April 2004 04:13

There seems to be a lot of misunderstanding around of what a shock absorber actually does. Firstly it doesn't technically make your suspension stiffer. It's primary function is to prevent your wheels from bouncing, that is to help keep the tyres firmly planted on the ground. Which is why they are better referred to as "dampers". Because the springs should be absorbing the driving shocks and the damper controls the springs. You do not install a damper with a high damping force to make your ride stiffer. You put stiffer prings in for that and then follow it up with uprated dampers to control the bigger springs. A damper cannot support a static load, all it can do is slow down motion. If you look at the damping specs in the TRD page you posted, one of the units given is for kgf (kilograms force) Don't get this confused with weight as it is a force. As oldcorollas pointed out earlier, at the bottom of the page it qualify's the specification by saying that it is the damping force for a piston speed of 0.3m/s. in otherwords, if you had a damper with a compressive rating of 100kgf and stood it with 100kg on top, it would sink at 0.3m/s. If it had a stroke length of 0.3m, then it would take 1 second to travel the whole stroke length. Bare with me, there is a point in all of my dribble. We have established that the purpose a damper is to control the spring movement and keep the tyre firmly planted on the ground. To do this it will need to resist movement that is trying to push it into the guard but still let the wheel drop back onto the ground quickly. That is the fundamental reason why there is a different rating for bump and rebound. You can see this happening on race bred dune buggies. Unfortunatly as you are driving along, the harsher the bump, the faster the spring will want to compress and you will end up with an apparent increase in spring stiffness. This is a good reason why you wouldn't want really "stiff shockies" They need to be sized correctly so that they can maintian control of the wheels without increasing the natural frequency of the cars suspension. The next you ask will be how do you know what rating to use. Thats a hard one because it depends on the effective spring rate of each wheel/suspension assembly, and the ratio of sprund to unsprung weight at each wheel location. You could spend a lot of time calculating these values and at best you might come close to good. Realistically the best you can do is to get an adjustable set up that is close to the manufacturers recommendations, maybe a little stiffer if you are using uprated springs and fine tune it from there. I haven't really helped you have I, sorry. If it was easy they wouldn't pay F1 suspension engineers lots of money would they. [Report message to a moderator]

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