Rebound Springs

[TravWood]

How do they work? I have a small understanding of them but would like some other feedback/info.

 

[harrisj]

I've never heard of rebound springs, although a rebound stop is ideally some sort of spring.

On heavy vehicles, the forces on suspension components can be large when the wheel is suddenly unloaded (ie when it hangs over a void - frequently happens on off-road applications). A rebound stop is often simply the damper running out of travel and providing some metal-to-metal stop internally - not nice. Sometimes there is a check strap (wire cable or suchlike) which goes taut when the rebound travel limit is reached. Alternatively, a rebound stop, like a bump (jounce) stop, can be a rubber spring, a disc spring or whatever. I believe some German vehicles used volute springs as rebound and bump stops.

So unless 'rebound spring' has another meaning I'm not familiar with, it's just a more sophisticated way of stopping the rebound travel when the suspension runs out of 'droop'

John

 

[GregLocock]

A rebound spring is used in the top of a shock absorber, and provides an action directly analagous to a jounce bumper, but in rebound, not jounce.

I'm not going to provide a tutorial on them, but if the initial poster asks more direct questions he'll get a more direct answer.



Cheers

Greg Locock

 

[TravWood]

Greg,

In Particular, sedan road going passenger vehicles with low roll stiffness from sway bars etc to keep good articulation and wheel independent-ness. I.e. it’s no point going to all the trouble of making 4 wheel independent suspension and then tying them together with thick sway bars to stop excess roll (and pitch if a front to rear sway bar were to exist). If a rebound spring de-rates the overall spring rate of that wheel as it goes into droop (unloads) it would be good to have less force there when it does encounter a single wheel bump. My question is I have heard they work very well particularly for heavy vehicles, how do they work in controlling roll?

Thanks

Travers

 

[GregLocock]

They give you a nice transition as the wheel starts to lift in the air, otherwise you get a discontinuity in the roll moment vs roll angle curve as the shock reaches the end of its travel. This will cause a sudden change in the weight transfer, laterally and end to end, which could upset the driver and/or the car.



Cheers

Greg Locock

 

[TravWood]

This seems to be the case for the more normal type setup where they only come into play towards the end of droop. What about set-ups where they are active 5-10mm from ride height? How do these not make the car feel travel limited or unstable like the old race engineers tool of zero droop?

Subaru Outback (Front only), Ford BA Falcons, some Jags, many BMWs are all users of these systems, there must be more to it than stopping the suspension topping out suddenly?

And as OSVALDO mentioned they tend to work very well on heavy vehicles but I am lead to believe you can make small vehicles handle exceptionally well with very little roll and no anti roll bars.

I am looking to use them on the Suspension I am designing for my Suabaru outback, Mainly a replacement of original shocks with custom made Bilsteins, with more progression in the overall spring rate (OE spring plus bounce rubbers, active close to ride height as mentioned in previous threads - they do work very well) and if I work them out rebound springs)

Look forward to any responses.

Thanks

Travers

 

[GregLocock]

The ones I've seen only have 20mm of travel, I'd be interested to see an example where they use more.

Cheers

Greg Locock

 

[LotusManiac]

Heavy truck leaf springs at one time had a "rebound leaf". This spring leaf helped hold up the axle when the tire was off the ground, reducing the possibility of damage to the main leaf of the spring. This practice was replaced with various types of retainers that combine the stiffness of all or some of the leaves during a rebound.

 

[SusTestEng]

Toyota Highlander(USDM) has them.