How droop works?
How droop works?
(OP)
Hi, I am not sure if this is a right place to post this question. But since this question is related to automotive engineering, I decided to give it a try.I have been playing RC car (radio control) for few months, there are many tips for tuning your car, one of them is droop setup. Droop is defined as how much down travel your suspension has. I thought it has very little influence on performance and more droop might be better because you want to keep all your tires on the ground when turning corners and on/off throttle. But actually it worked out opposite, I lessened the droop for quite a bit on both front and rear and the car ran much better than before (better turning ability). I asked some people on the track and also checked some articles on the internet, some of them mentioned about weight transfer. I don't think droop setting will have something to do with weight transfer. But how does it affect the performance? I may be wrong, droop setting does affect dynamic performance, but how? Can somebody explain the theory?





RE: How droop works?
Goran
RE: How droop works?
RE: How droop works?
Goran
RE: How droop works?
Norm
RE: How droop works?
RE: How droop works?
RE: How droop works?
The reason I ask about how the problem manifests itself depends on that the actual behavior of the car is important to draw conclusions about where the problem is. I would prefer to see and experience the problem in reality, to get a better vision of how things stand.
I have heard from others who work with racing cars that they experienced better braking performance by using the drop-stop on the back of the car, but I have made no self-tests that can confirm this. In dragraing it was popular to let the front drop out a lot, and we used the 90/10 damper for a slow return. Now days this appears to be used to a lesser degree, one simply let the front wheels leave the ground.
Drop stop or different hard suspension, etc. does not change the mass movement as such, but it changes the speed with which it occurs. When the drop-stop "taking in" so it works like a Panhard rods (one way). You could say that the car rolls around a center at the inner wheel, and therefore only the springs of the outer wheel will compress. It can give an initial addition to the outer wheel grip since the mass of the inner pair of wheels will (after a moment) add to sprung mass. Any such "additional" to the grip has a price in terms of lower grip later (or earlier if it is scheduled). How the overall situation manifests itself depends on the spring hardness and shock absorbers damping factor.
In any case, so far, I do not look at what I write as an explanation, only som sort of inlay.
Goran
RE: How droop works?
Thank you Goran. I didn't think about the leaving inner wheels will add to sprung mass, that is a good point to think about this problem. You said that the drop stop changes the speed of weight transfer with which it occurs, is it because later one end will add to sprung mass so the total weight that will be moved around will be heavier?
RE: How droop works?
On roadcars we use rebound springs in the shock absorbers to provide non linear roll stiffness, it is a quick and relatively easy way of adjusting limit handling under or over steer.
So, yes it is important, but there are no hard and fast rules.
It certainly breaks the simple rule of thumb that you want to maximise suspension travel and use all of it in one lap... but that rule is more of a fond hope based on theory than a proven path to success.
Cheers
Greg Locock
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