omega 24 v6
|
| posted on 29/7/08 at 09:29 PM |
|
|
The old spring rate cherry again
Ok so the car is a 442 with an xe and an atlas live axle. I scaled the car last night (very roughly and on an uneven surface with solid rods in where
the shocks will be) and the followin pics are the results
Car with no passengers and no fuel front axle load
 
Description
Car with no passenger and no fuel rearaxle load.
 
Description
Car with no passengers and 17 litres (tank of 35 litres) fuel
 
Description
So what should I need for spring rates?? Also I cannot for the life of me get my head round whether to use longer or shorter springs. i.e. say an
8inch free length or a 6 inch free length (just examples plucked from nowhere) on a shock with adjustable spring seat platforms (protech). My logic
says to me longer so not so likely to bcome spring bound.
Car will be for mainly road use some track Say 80/20.
As usual many thanks in advance and I forgot to add i do know I'll need to work out the incle angle etc on the front coilover before selecting
the final rate.
If it looks wrong it probably is wrong.
|
|
|
|
|
mr henderson
|
| posted on 30/7/08 at 07:14 AM |
|
|
I can't tell you whatthe spring rates should be, but I can tell you how to work it out for yourself.
In order to avoid attracting the attention of certain snipers I will U2U it to you later
John
|
|
|
SeaBass
|
| posted on 30/7/08 at 10:11 AM |
|
|
quote:
Originally posted by mr henderson
In order to avoid attracting the attention of certain snipers I will U2U it to you later.
I think that's where it gets sad. Don't worry about the detractors. Just let us know what you've done in the past and how that has
worked for you...
JC
|
|
|
MikeCapon
|
| posted on 30/7/08 at 11:21 AM |
|
|
quote:
Originally posted by SeaBass
quote:
Originally posted by mr henderson
In order to avoid attracting the attention of certain snipers I will U2U it to you later.
I think that's where it gets sad. Don't worry about the detractors. Just let us know what you've done in the past and how that has
worked for you...
JC
Agreed. This forum should be about sharing information with everyone else and constructive discussion. Keeping stuff to yourself is not really in the
spirit of LCB is it?
If you have an answer you don't want to share just PM it. Posting to say you are doing that is of little constructive help to the others.
Here's a previous constructive discussion
|
|
|
mr henderson
|
| posted on 30/7/08 at 11:32 AM |
|
|
quote:
Originally posted by MikeCapon
quote:
Originally posted by SeaBass
quote:
Originally posted by mr henderson
In order to avoid attracting the attention of certain snipers I will U2U it to you later.
I think that's where it gets sad. Don't worry about the detractors. Just let us know what you've done in the past and how that has
worked for you...
JC
Agreed. This forum should be about sharing information with everyone else and constructive discussion. Keeping stuff to yourself is not really in the
spirit of LCB is it?
If you have an answer you don't want to share just PM it. Posting to say you are doing that is of little constructive help to the others.
Here's a previous constructive discussion
I've not made myself clear. What I was going to write to the OP in a U2U was pretty similar to what you had written in the post you linked to.
Had I been aware of what you had written then I would have provided a link to it and not spent the last couple of hours writing out a short treatise
on spring selection.
What I was trying to avoid was a situation where what I posted was picked apart by others. Now that I have read what you said (sorry I missed it the
first time round) I can see that I was very much on the right track with my treatise but should not have referred to it on the forum.
So it's a shame that you've not understood my intention but that was my fault. If a similar question crops up in the future and I see it
first them I will link to your excellent explanation
John
|
|
|
MikeCapon
|
| posted on 30/7/08 at 12:18 PM |
|
|
Hello Mr H,
I understand you reluctance to post stuff when there are a few people about who are not as constructive as they might be. However, if LCB is allowed
to be stifled by these few people then it's not going to continue to be the excellent source of information and food for thought that it is
today.
You will always get people sniping when you are discussing subjects that are either poorly understood or with differing approaches to how they are
understood.
If you do get hit by a sniper on here,
1 It doesn't hurt
2 If the sniper provides an alternative, at least that can be constructively discussed
3 If the sniper is just being a k**b for the sake of it then don't worry. Everyone else will draw their own conclusions
Very little progress is ever made without discussion.
Edited to add: All that aside Mr Omega, have you worked out what springs you need?
[Edited on 30/7/08 by MikeCapon]
|
|
|
Dangle_kt
|
| posted on 30/7/08 at 12:24 PM |
|
|
Can I suggest a group hug?
ALL FOR ONE AND ONE FOR ALL!
|
|
|
omega 24 v6
|
| posted on 30/7/08 at 03:32 PM |
|
|
quote:
Edited to add: All that aside Mr Omega, have you worked out what springs you need?
No not yet
If it looks wrong it probably is wrong.
|
|
|
pbura
|
| posted on 30/7/08 at 04:33 PM |
|
|
Mike's spreadsheet is very cool, as it solves the question of what spring rate is necessary to support the car properly.
Mike, I have a question for you. In cell B13 of your sheet [=B8+(B7/100*B5)], do you mean [=B8+(B7/B6*B5)]?
The sample values in the spreadsheet provide a frequency of 122 cycles per minute. This is considered a good rate for a light, sporty car, though
racers may want more.
The calculation for frequency is:
WR = wheel rate 530/(1.5^2)=236 lbs/in
SW = sprung weight (275-20)*2.2=561 lbs
Wheel Frequency = 187.8*SQRT(WR/SW)
= 187.8*SQRT(236/561) = 121.8
If Mike added a frequency calculation to his sheet, the user could juggle preload to achieve a frequency target.  IMO, his sheet is a great
solution for getting on the road and sorting out other refinements later.
Attention, geeks!
This spreadsheet is the absolute BOMB, IMO:
http://www.fromsteve.net/carstuff/suspension/SuspensionCalc.htm
You can open it as a file in Excel, insert your own data, and save on your HD in .xls format. It's best viewed in Excel.
It calls for a lot of data, but geeks won't mind.
Pete
|
|
|
Syd Bridge
|
| posted on 30/7/08 at 06:21 PM |
|
|
I'd say the 122 frequency may be a bit high, from experience. I'd be putting it nearer100~105
Most cars today are in the 70~80 range for comfort, and some go a little either side.
|
|
|
D Beddows
|
| posted on 31/7/08 at 07:34 AM |
|
|
How do you get the spreadsheet as a spreadsheet then anyone? The link just takes me to an html page in which you can't seem to change any of the
values and the links in the linked thread just seem to lead you to files which wont open in excel......
|
|
|
MikeCapon
|
| posted on 31/7/08 at 09:20 AM |
|
|
Spring rate calculator now with CPMs
Good morning and thanks for the feedback.
First off to pbura and the maths question. The value in B13 is the number of millimetres that the spring is compressed with the car at ride height.
First of all there is the spring preload B8 (number of mm the spring is already compressed when the shock is full open). When the car is at ride
height the shock will be compressed by the same percentage that the wheel has risen (or the chassis has dropped if you prefer) so B7 (shock stroke)
divided by 100 and multiplied by B5 (%age sag). I hope that clears that one up. Note that this spreadsheet assumes a linear wheel/shock movement.
I've added the frequency calc to the spreadsheet as requested. Here's the modifed version. As you will see for an existing chassis all you
can do is to play around with the spring preload to acheive the desired frequency.
Edited to add:- See 2 posts later for renamed (and apparently easier to download) file.
[Edited on 31/7/08 by MikeCapon]
|
|
|
pbura
|
| posted on 31/7/08 at 11:51 AM |
|
|
Syd:
Your comment made me realize that neither the spreadsheet nor my endorsement of a 120cpm wheel frequency recognize the contribution of the anti-roll
bar towards wheel rate. Tire compliance could well be upset when the bar is in use if the ride rate is set too high.
Syd, if you or anyone else could provide the formula for the wheel rate of an anti-roll bar. I'd be appreciative. Yes, I'm too dumb to
figure it out for myself. 
D Beddows:
To open the page in Excel, do File>Open in Excel and paste the URL in the 'file name' box. I tried this in desperation and was amazed
when it worked.
MikeCapon:
OK, I see it. I thought you were making a proportion of shock movement to total wheel movement, but now see that the % in D5 needs to be divided by
100. Duh!
Windows wants to save your file link as 'spring' with no extension. It needs '_' for spaces in the file name. I saved with
an .xls suffix and it works fine, thanks.
I hope your spreadsheet catches on, because it's vastly superior to buying springs based on what a vendor says or what somebody else uses
(unless their car is identical in all respects).
omega 24 v6:
How are you doing? You need to weigh again with a normal payload including you. I personally would chuck in 100# to represent a partial passenger,
but that's your call. You also need front and rear unsprung weights.
You're also going to need figures for wheel and shock travel between full droop and full bump. While you're at it, to have the wheel and
shock travel between full droop and ride height would be helpful as a check on your '% of wheel travel as sag'.
Please post your figures here, and we'll play devil's advocates on your setup. 
[Edited on 31/7/08 by pbura]
Pete
|
|
|
MikeCapon
|
| posted on 31/7/08 at 12:20 PM |
|
|
Spring rate calculator now with CPMs (2)
Hi, I tried to edit the attached file but apparently you can't do that.
Here's the file with amended name as requested
|
|
|
D Beddows
|
| posted on 31/7/08 at 12:22 PM |
|
|
Thanks for that pbura - amazed is right! I'd never have thought that would have worked (or of even trying it if I'm honest!) but
you're right it does!!
|
|
|
