default ReStackor needle geometry is a simple conical needle with a blunt
tip. d.bleed defines the needle seat diameter and flow
area at the wide open clicker position. MAX.clks defines the number of
clicks from closed to wide open. For more precise modeling of the bleed
circuit you can use a needle geometry table. The needle geometry table
lists the needle diameter as a function of clicker position allowing any
needle geometry to be entered into ReStackor. Input format of the needle geometry table
is defined here.
[=] Bleed port diameter at the needle seat in [mm].
[=] The number of adjuster clicks from closed to full open.
File [=] Setting both d.bleed and
MAX.clks to zero triggers the calculations look for a needle geometry table at the path given by the Geom.File parameter. In the example
needle geometry table is in a file located at D:\Needles\Showa50.in. The format
of entries in the geometry table are given here.
Speed Compression Adjuster and Mid-Valve Springs
HSC parameters define the stiffness of springs used to preload the stack
on both shock compression adjusters and fork mid-valve check springs. Setting
all inputs to zero means there is no spring.
[=] Spring preload in [mm]. For an HSC system the preload includes
static preload plus any additional preload from cranking down the
compression adjuster. The compression adjuster generally preloads the
HSC spring 1 mm per turn of the adjuster.
[=] Shim diameter where the HSC spring force is applied to the stack.
For the example with D.hsc= 10 mm the spring force is applied to the first shim from the
top of the stack that was an outside diameter greater than or equal to
draws a small box on the shim where the HSC spring force is
applied. The indicator is there as a reminder
spring force is being applied to the stack and to verify the contact
location is at the position you intended.
[=] HSC or mid-valve spring stiffness in [kg/mm]. Little information
is available on the actual stiffness of springs used in HSC systems, after market
springs or the springs used in mid-valve checks. Your options are: take the spring to a dyno tuner to get the
stiffness measured or estimate the stiffness using the spring design equations.
spring preload applied at the shim diameter specified by D.hsc
are capable of accurate measurements. Unfortunately other parameters creep into test resulting in identical
shock absorbers producing different damping force values. ReStackor uses
four parameters to help compensate for test-to-test variations in dyno
[=] Friction between shims makes a stack stiffer during
deflection and softer while closing. Friction has been measured in Belleville spring
stacks to increase stack stiffness by 30%. Values vary through the first couple of hours of
operation while the friction surfaces mate. That causes problems in
dyno testing where shim stacks are only run for a couple
of minutes resulting in identical stacks producing different
damping force values.
recommended value of cf.stk is one. Zero turns the shim friction model
off and a value of two doubles friction. The typical range is: 0.85 <
cf.stk < 1.15.
[=] Ostwald coefficient defined as the volume fraction of dissolved
gas. Suspension oils contain 12% by volume
dissolved air. The dissolved gas is in one of two states:
< xL.sat < 0.12: For positive values of xL.sat the gas
is dissolved in the liquid and the oil starts out as a clear liquid.
Pressure drops created byfrom flow accelerations through the shocks
circuits release the dissolved gas. The released gas causes a cavitation like
event, further accelerating the fluid driving damping
< xL.sat < 0: For negative values of xL.sat the
dissolved gas is released causing the oil to foam. The
lower density of foamed oil causes damping forces to go down.
un-opened bottle of factory sealed suspension fluid contains 12%
by volume dissolved air. When installed in a shock and
pressurized to 150 psi the 10:1 pressure increase compresses the
dissolved air volume to 1.2%. Let the shock sit for a
couple of months and nitrogen will diffuse through the reservoir
bladder into the the fluid re-saturating the oil to something in the 10% by volume
value: xL.sat= -0.015
[=] Dyno oil temperature increase between shaft velocities of 0.0 and
dyno test obtain all data in a single shock stroke. In that case
there is no oil temperature change between zero and 50 in/sec.
dyno tests (PVP testing) start at a slow cycle speed to get more
accurate low speed data and sequentially advance to higher speeds.
Through that test sequence oil temperatures continuously increase. The
temperature increase is an entirely computable value. However, unknowns
of the initial shock body temperature and efficiency of heat
transfer from the oil to the shock body make the true oil
temperature at each shaft velocity unknown. The ReStackor dToil
input is the estimated oil temperature increase between the start
of test and 50 in/sec.
value: dToil= 0.0