Grime's Spec Koni Shock Dyno Plots - Q's and C's
04-15-2010, 09:19 AM
#81
Former Moderator
Originally Posted by captain_pants,Apr 15 2010, 06:11 AM
He also mentions multiple times that 'critical damping' is the damping rate at which the suspension will not move at all when a bump is struck. That's flat wrong.
I agree he's definitely proud of his design.
04-15-2010, 09:31 AM
#82
I got the book too, and thougt he wrote that 60% was when the shock would make 1.6 cycles, so that would mean that 100% would be one cycle, or bump then rebound and back to center.
04-15-2010, 09:37 AM
#83
Originally Posted by captain_pants,Apr 15 2010, 10:57 AM
I'm speaking with James right now, he's able to dramatically soften the shocks from what I originally got. Right now my shocks generate around 700 lbs in rebound at 6 inches/second at 3/4 stiff. The curves I'm considering are closer to 350 lbs at the same speed and adjustment and stay at around 1/2 as stiff all the way up to 12 in/s. For comparison, the OEM shocks generate around 200 lbs at the same 6 in/s speed.
I'm going to finish Jan Z's book before I make a decision on my new valving.
I'm going to finish Jan Z's book before I make a decision on my new valving.
) - he's supposed to get me the specifics on the valves/shims he used so that I can alter this stuff in the offseason. I apparently gave up my "free" rebuild since I wanted it done my way and not Joe's way. Although I could probably talk Jamie into it if I pushed hard enough I guess.
04-15-2010, 09:43 AM
#84
Registered User
Join Date: Jun 2007
Location: Winnipeg, MB, Canada
Posts: 626
Likes: 0
Received 0 Likes
on
0 Posts
I don't have the book with me now, but the common definition of critical damping is on this page: http://en.wikipedia.org/wiki/Damping
Look for the graph near "system behavior" here: http://en.wikipedia.org/wiki/Damping#System_behavior
I'll have to re-read Jan's definition(s) of critical damping, it doesn't match from what I remember.
That's picking nits though, I in no way feel that this minor point invalidates anything else he says. He even mentions early on that he feels that all the calculations in the world are nearly useless and that he much preferred to just see how something works on the car and then change it.
Look for the graph near "system behavior" here: http://en.wikipedia.org/wiki/Damping#System_behavior
I'll have to re-read Jan's definition(s) of critical damping, it doesn't match from what I remember.
That's picking nits though, I in no way feel that this minor point invalidates anything else he says. He even mentions early on that he feels that all the calculations in the world are nearly useless and that he much preferred to just see how something works on the car and then change it.
04-15-2010, 10:37 AM
#85
Originally Posted by captain_pants,Apr 15 2010, 12:43 PM
He even mentions early on that he feels that all the calculations in the world are nearly useless and that he much preferred to just see how something works on the car and then change it.
04-15-2010, 07:30 PM
#87
Registered User
Thread Starter
Join Date: Jul 2008
Posts: 1,342
Likes: 0
Received 0 Likes
on
0 Posts
For what it's worth, the practical definitions for critical,over and under-damping are as follows:
under-damping: a damping force such that when there is a disturbance (bump or otherwise) an overshoot from your original "static" position is observed
critically damping: the damping force that gets you right back to your static position as fast as possible without overshoot
over-damping: any damping force that is greater than the force needed to achieve critical damping. I.e. you will get back to static position slower than if you critically damped
under-damping: a damping force such that when there is a disturbance (bump or otherwise) an overshoot from your original "static" position is observed
critically damping: the damping force that gets you right back to your static position as fast as possible without overshoot
over-damping: any damping force that is greater than the force needed to achieve critical damping. I.e. you will get back to static position slower than if you critically damped
04-15-2010, 07:58 PM
#88
Former Moderator
Originally Posted by Forcednduckshn,Apr 15 2010, 08:30 PM
critically damping: the damping force that gets you right back to your static position as fast as possible without overshoot
Criticaly damped? I guess I can see how it's right both ways unless my definition of critical is incorrect.
But would Criticaly Damped vs Critical Damping be different?
04-16-2010, 05:40 AM
#89
[QUOTE=Forcednduckshn,Apr 15 2010, 07:30 PM] For what it's worth, the practical definitions for critical,over and under-damping are as follows:
under-damping: a damping force such that when there is a disturbance (bump or otherwise) an overshoot from your original "static" position is observed
critically damping: the damping force that gets you right back to your static position as fast as possible without overshoot
over-damping: any damping force that is greater than the force needed to achieve critical damping.
under-damping: a damping force such that when there is a disturbance (bump or otherwise) an overshoot from your original "static" position is observed
critically damping: the damping force that gets you right back to your static position as fast as possible without overshoot
over-damping: any damping force that is greater than the force needed to achieve critical damping.
04-16-2010, 06:26 AM
#90
Its .67 actually - but .7 is close enough
Dennis Grant has been doing a bunch of updates to his site recently if you guys haven't checked it out in the past few weeks. There are some good discussion points regarding critical damping.
He valves his shocks right near critically damped, same with Marcus Meredith (who did Jason's Bilsteins) and then they use bars/alignment to tune the handling. I like this idea for rebound, but on the compression side I find that damping ratio's as high as 1.2-1.5 can be a great tool to tune to various surfaces - it can also allow you to use a smaller sway bar and not reduce grip on the inside tire.
Dennis Grant has been doing a bunch of updates to his site recently if you guys haven't checked it out in the past few weeks. There are some good discussion points regarding critical damping.
A suspension that cycles exactly once in response to a deflection is said to be critically damped. A suspension that cycles twice in response to a deflection (bounce, bounce, stop) is 50% critical, and a suspension that has more damping force than needed to be critical is said to be overdamped.
He valves his shocks right near critically damped, same with Marcus Meredith (who did Jason's Bilsteins) and then they use bars/alignment to tune the handling. I like this idea for rebound, but on the compression side I find that damping ratio's as high as 1.2-1.5 can be a great tool to tune to various surfaces - it can also allow you to use a smaller sway bar and not reduce grip on the inside tire.