Spring preload
#1
Posted 06 February 2010 - 15:12
I have a perhaps quite simpel question I am thinking about, it is concerning spring preload.
This attached picture is from a Seat Leon Supercopa with koni shocks without any normal options of adding preload.
But my question is:
As you can see on the picture i have attached that the helper spring is fully compressed, and the spring it self is also a bit compressed by the spring perch. This is in "static" mode when it not even is mounted on the car, and I can't figure out wether this will add a bit of preload on the spring. I of course now that it raises the rideheight, but what happens when the weight is being put on that spring. I have never seen an application where the helping spring is fully compressed without any load from car.
Thanks in advance
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#2
Posted 06 February 2010 - 16:14
It is common for tin tops to use compound springs (main & helper), but (now) to run with the helpers well coil bound. The helpers are used as "fillers" to stop the main spring load falling to zero & to help push the wheels out of the wheel arches for changing tyres quickly. I don't recall seeing the configuration you described & can't think why it should be that way, unless it is desired to limit droop travel for some reason.As you can see on the picture i have attached that the helper spring is fully compressed, and the spring it self is also a bit compressed by the spring perch. This is in "static" mode when it not even is mounted on the car, and I can't figure out wether this will add a bit of preload on the spring. I of course now that it raises the rideheight, but what happens when the weight is being put on that spring. I have never seen an application where the helping spring is fully compressed without any load from car.
#3
Posted 06 February 2010 - 16:35
I'm also guessing that they had to do this to get the correct ride height with that rate spring, they could only get the spring in that set length and at full droop the spring was dangerous close to being fully extended.
#4
Posted 06 February 2010 - 19:18
#5
Posted 06 February 2010 - 23:51
Normally, the wheels of a racing tin top are buried in the wheel arches, & an excess of rebound travel is required to change wheels/tyres without releasing the top mounts. That is the usual reason for including helpers in a spring assembly. Your example appears to negate that function.
#6
Posted 07 February 2010 - 05:16
Normally, the wheels of a racing tin top are buried in the wheel arches, & an excess of rebound travel is required to change wheels/tyres without releasing the top mounts. That is the usual reason for including helpers in a spring assembly. Your example appears to negate that function.
Point 1: correct
Point 2: correct.
The only reason I can see to have those tender springs on like that is for ballast.
#7
Posted 07 February 2010 - 09:12
#8
Posted 07 February 2010 - 09:15
Greg could you or somebody else please describe some of the good reasons for restricting wheel travel at fwd racecars?
Thank you all in advance, it is fantastic with a forum with lots of qualified people to pass on their knowlegde
#9
Posted 07 February 2010 - 09:21
Greg could you or somebody else please describe some of the good reasons for restricting wheel travel at fwd racecars?
Not what i said.
#10
Posted 07 February 2010 - 10:41
The Koni struts I have seen on a Leon have rebound controls that are not "detented", making precise setting of rebound damping something of an art form. It is also possible, I suppose, that the rebound control might occasionally self-adjust in use. If that happens, and the change is to reduce damping, then the vehicle will tend to "jack up". A droop stop would then control how far the vehicle can get "out of shape". Pure speculation, of course, but something to look out for, perhaps.
Edited by DaveW, 07 February 2010 - 10:43.
#11
Posted 07 February 2010 - 14:18
I wonder if either the length of the damper shaft has been reduced, or an internal droop limiter has been installed, as a "quick fix" following damper failures?
Or an internal droop spring and they use the small outside one to set the rate.