Shock Histogram
#16
Rennlist
Basic Site Sponsor
Basic Site Sponsor
Joined: Jun 2008
Posts: 19,273
Likes: 3,473
From: Durham, NC and Virginia International Raceway
This is true, Roger. Will do that before the end of the month.
__________________
-Peter Krause
www.peterkrause.net
www.gofasternow.com
"Combining the Art and Science of Driving Fast!"
Specializing in Professional, Private Driver Performance Evaluation and Optimization
Consultation Available Remotely and at VIRginia International Raceway
-Peter Krause
www.peterkrause.net
www.gofasternow.com
"Combining the Art and Science of Driving Fast!"
Specializing in Professional, Private Driver Performance Evaluation and Optimization
Consultation Available Remotely and at VIRginia International Raceway
#17
Also, on that note it is beneficial to understand how each adjustment actually affects damper response. Is it a orifice change, or preload, or bleed change? Then secondly, know how much each click changes the damper curves. I've seen 3 and 4 way dampers where the low speed adjustment is essentially useless and the high speed circuit has more authority of the low speed events.
#19
Also, on that note it is beneficial to understand how each adjustment actually affects damper response. Is it a orifice change, or preload, or bleed change? Then secondly, know how much each click changes the damper curves. I've seen 3 and 4 way dampers where the low speed adjustment is essentially useless and the high speed circuit has more authority of the low speed events.
#22
Rennlist Hoonigan
which cost no drachmas
Lifetime Rennlist
Member
Rennlist
Site Sponsor
which cost no drachmas
Lifetime Rennlist
Member
Rennlist
Site Sponsor
Joined: Dec 2001
Posts: 12,741
Likes: 1,037
From: Manchester, NH
I think the best way to help decide logger speeds is to look at the ground covered at a speed and see what you think. At 120 mph, 100 Hz is one sample every 1.8 feet. Your shocks do a lot of movement in that time that won't be captures. At 200 Hz, it's one sample every 11 inches. Still a lot of ground covered.
#23
I think the best way to help decide logger speeds is to look at the ground covered at a speed and see what you think. At 120 mph, 100 Hz is one sample every 1.8 feet. Your shocks do a lot of movement in that time that won't be captures. At 200 Hz, it's one sample every 11 inches. Still a lot of ground covered.
#24
Rennlist
Basic Site Sponsor
Basic Site Sponsor
Joined: Jun 2008
Posts: 19,273
Likes: 3,473
From: Durham, NC and Virginia International Raceway
Due to a hardware limitation I've been limited to 100hz on my logger for shock data. So far it has been adequate. The velocity data appears to cover the bulk of the events that occur on my local track. It is a very bumpy surface that has a lot of content (vertical motion) and even at 100hz it has been able to capture nearly all of it. I'll see events up to and over 15 in/s and have no issue capturing everything below that. And from a tuning perspective anything over about 10 in/s is of little use to me as that is all super high speed events of which I can't manage to tune out anyway with the available damper adjustments.
A caveat to that is the body motions at that speed take longer than 1.8 ft to occur. You may miss small surface content at that logging rate, but the gross vehicle motions that you really need to fine tune should still be visible in the data. Pitch, roll, heave, warp motions should be useful. But I do agree that any surface imperfections or inputs that you may be struggling with could very well be undersized or mostly hidden.
A caveat to that is the body motions at that speed take longer than 1.8 ft to occur. You may miss small surface content at that logging rate, but the gross vehicle motions that you really need to fine tune should still be visible in the data. Pitch, roll, heave, warp motions should be useful. But I do agree that any surface imperfections or inputs that you may be struggling with could very well be undersized or mostly hidden.
#25
In a nutshell.
If you are seeing velocities in the 15-20's that's bad. Would not be a very good car to drive on the bumps.
Turn in, braking, pitch and roll is .25-2" sec. Mid speed is 2-5" sec (mid corner in the middle of the set when the car is hunting for grip) 5-10' sec are bumps.
On a three way or four way you need a decent amount of high speed to see or feel the low speed working.
Its impossible to cover this on a thread. Just remember all the math in the world only applies to the mathematical moment, of which the car is never in . Get your damper velocities in the workable ranges and tune from there. If bump and rebound are working together not against each other one click is a huge difference.
Dampening is one of the simplest things in a car. You are just controlling how fast the spring is compressing. But many make the mistake of over complicating it.
-T.O.
If you are seeing velocities in the 15-20's that's bad. Would not be a very good car to drive on the bumps.
Turn in, braking, pitch and roll is .25-2" sec. Mid speed is 2-5" sec (mid corner in the middle of the set when the car is hunting for grip) 5-10' sec are bumps.
On a three way or four way you need a decent amount of high speed to see or feel the low speed working.
Its impossible to cover this on a thread. Just remember all the math in the world only applies to the mathematical moment, of which the car is never in . Get your damper velocities in the workable ranges and tune from there. If bump and rebound are working together not against each other one click is a huge difference.
Dampening is one of the simplest things in a car. You are just controlling how fast the spring is compressing. But many make the mistake of over complicating it.
-T.O.
#26
Rennlist
Basic Site Sponsor
Basic Site Sponsor
Joined: Jun 2008
Posts: 19,273
Likes: 3,473
From: Durham, NC and Virginia International Raceway
In a nutshell.
If you are seeing velocities in the 15-20's that's bad. Would not be a very good car to drive on the bumps.
Turn in, braking, pitch and roll is .25-2" sec. Mid speed is 2-5" sec (mid corner in the middle of the set when the car is hunting for grip) 5-10' sec are bumps.
On a three way or four way you need a decent amount of high speed to see or feel the low speed working.
Its impossible to cover this on a thread. Just remember all the math in the world only applies to the mathematical moment, of which the car is never in . Get your damper velocities in the workable ranges and tune from there. If bump and rebound are working together not against each other one click is a huge difference.
Dampening is one of the simplest things in a car. You are just controlling how fast the spring is compressing. But many make the mistake of over complicating it.
-T.O.
If you are seeing velocities in the 15-20's that's bad. Would not be a very good car to drive on the bumps.
Turn in, braking, pitch and roll is .25-2" sec. Mid speed is 2-5" sec (mid corner in the middle of the set when the car is hunting for grip) 5-10' sec are bumps.
On a three way or four way you need a decent amount of high speed to see or feel the low speed working.
Its impossible to cover this on a thread. Just remember all the math in the world only applies to the mathematical moment, of which the car is never in . Get your damper velocities in the workable ranges and tune from there. If bump and rebound are working together not against each other one click is a huge difference.
Dampening is one of the simplest things in a car. You are just controlling how fast the spring is compressing. But many make the mistake of over complicating it.
-T.O.
#27
Typical shock velocities
I am a little confused about typical shock travel. In my car (SCCA SRF 3) it has a relatively short typical shock travel compared to others (I think), it is in the range of 1” by spec because of the spec springs. When we talk about shock velocities, are the norms for a car with 1” typical travel twice that of what the norms are for a car with a typical shock travel of 2”. Or do you expect to see the same velocity’s for cars with 1” and 2” of travel? Can we make generalizations about velocities when different cars have 1, 2 and 3” of travel?
My car is the only one I have experience with so I am not sure what is typical for shock travel in other cars and when we make statements about typical velocities how does that relates to a car that has twice the travel I have or ½ the travel. The books I have read don’t seem to make a distinction or if they did I missed it. Are velocities expected to be in the same range for different length shocks? Do we design to keep velocities in a typical range or if we have a shock with 2” of travel do we design velocities to be in a different range than a shock with 1“ travel. What is the correlation, do you expect the same shock velocities in a 911 and a SCCA SRF 3?
Bill Parenteau
My car is the only one I have experience with so I am not sure what is typical for shock travel in other cars and when we make statements about typical velocities how does that relates to a car that has twice the travel I have or ½ the travel. The books I have read don’t seem to make a distinction or if they did I missed it. Are velocities expected to be in the same range for different length shocks? Do we design to keep velocities in a typical range or if we have a shock with 2” of travel do we design velocities to be in a different range than a shock with 1“ travel. What is the correlation, do you expect the same shock velocities in a 911 and a SCCA SRF 3?
Bill Parenteau
Last edited by wparente; 06-24-2015 at 01:16 PM.
#29
Exactly.
Travel is many things, how much leverage you have over the roll axis and spring rate, and of course the grip of the tire.
Too soft and you have 2"+ of travel and that means three tires on the ground instead of four Too stiff less than 1" of travel and all that energy that the spring doesn't absorb has to go somewhere, and that is straight into the sidewall of the tire, folding it over.
Lets say 35mm of travel and damper velocities no higher then 10 and that's a good starting point to tweak on, of course this assumes the rest of the alignment (ride heights, castor's, cambers, toes, corner weights) are all kosher
-T.O.