Questions about Shock Rates and Responses

[Frank]

I'm starting to become interested in shocks, and I have a couple of questions perhaps some of you might be able to answer.

Question 1
Say our car is in "mythical steady state cornering"� at 1.3 g's...

Lets say the shock travel from rest is 10 mm at this point....

Where would you ideally like to see the transition from low-speed to high-speed response on a dyno plot?

10 mm.s^-1 ?
20 mm.s^-1 ?
(see point "x"� in graph attached)

Question 2
Are you looking for your (transient roll stiffness?) "turn-in"� (with a smooth driver) to be dominated by the "low-speed response"� of the shock?

Question 3
If "yes"� to question 2, is it ideal to have an equal "low speed response"� in both rebound and compression?

Question 4
Or are you wanting the "high-speed response"� to be dominate turn-in, and since rebound has typically a greater damping rate, you end up concentrating on rebound settings in transient lateral g's?

Question 3
If you are primarily tuning the transient lateral g's using rebound settings, does this mean the car will dive in transient lateral g's? (and get less roll on turn in / more roll on corner exit?)

Thx in advance to responses to this fairly confused questioning

http://www.uq.edu.au/fsae/dyno.jpg

Graph stolen without permission, and hacked in Photoshop http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Frank]

I'm starting to become interested in shocks, and I have a couple of questions perhaps some of you might be able to answer.

Question 1
Say our car is in "mythical steady state cornering"� at 1.3 g's...

Lets say the shock travel from rest is 10 mm at this point....

Where would you ideally like to see the transition from low-speed to high-speed response on a dyno plot?

10 mm.s^-1 ?
20 mm.s^-1 ?
(see point "x"� in graph attached)

Question 2
Are you looking for your (transient roll stiffness?) "turn-in"� (with a smooth driver) to be dominated by the "low-speed response"� of the shock?

Question 3
If "yes"� to question 2, is it ideal to have an equal "low speed response"� in both rebound and compression?

Question 4
Or are you wanting the "high-speed response"� to be dominate turn-in, and since rebound has typically a greater damping rate, you end up concentrating on rebound settings in transient lateral g's?

Question 3
If you are primarily tuning the transient lateral g's using rebound settings, does this mean the car will dive in transient lateral g's? (and get less roll on turn in / more roll on corner exit?)

Thx in advance to responses to this fairly confused questioning

http://www.uq.edu.au/fsae/dyno.jpg

Graph stolen without permission, and hacked in Photoshop http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Denny Trimble]

I was staring at that plot last night reading a certain shock manual. But, I can't answer your questions yet http://fsae.com/groupee_common/emoticons/icon_smile.gif Still learning myself.

[Frank]

http://www.uq.edu.au/fsae/slow_corner.jpg

I've been playing around with this data in the "motec sample"�.

Condition 1 = (Left Travel-Right Travel) /2 , and scaled to a "more typical FSAE value"�

Condition 2 = Condition 1 filtered (ie.. it follows lateral G's)

Condition 3 = Condition 2 differentiated

Condition 4 = squat(+ve) , again scaled to a typical FSAE value

Condition 5 = Condition 4 filtered (follows longitudinal G's).. I swear I can see it squat in transient lateral G's

Condition 6&7 = travel differentiated (L&R scaled to typical FSAE value)

[Frank]

ok,

Can anyone tell me if this simulink sheet is correct?

The assumptions are:

Rebound = Compression

SMCG equal heights front & rear

NSM at width of track, and equal on each corner.

Roll centre at ground, and in centre of car.

Usual small angle approximations

Mechanism movements neglected in force / moment balance calculations.

It is looking at a FSAE car going through corner entry in a fairly quick corner.(50km/ish)

There is only lateral acceleration, no longitudinal accelerations available.

The damper curve is put in a "lookup table"�. ((you must use rebound = compression .. or it wont work))

http://www.uq.edu.au/fsae/corner_entry.mdl

http://www.uq.edu.au/fsae/model2.jpg

oh, and im wondering, what sort of damping ratios are usual for cars like these?

(im calculating damping ratio using sprung mass acting on the shock / damper system)

[Frank]

a few more errors fixed now

oh there's a "switch" at the bottom to change to "steady state"

the "graphical output" sometimes gives strange outputs in "steady state mode"... but the numerical output is correct

[Juan Romero]

Hi Frank,

As you, i´m starting to become interested in shocks. I´ve been reading the shock absorbers handbook. But there are some terms you handle I don´t understand very well.

What literature would you recommend me so I can try to answer your questions?

Help from anyone is welcome.

Regards,