muzchap
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 posted on 1/4/08 at 02:45 PM |
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Spring Rates...
Hi Guys,
I've trawled through the search and couldn't find anything to help...
How do I calculate spring rates? Since I've dropped the heavier S2000 lump/gearbox into my car, it sits a bit lower and now I think the springs
might be a bit weedy.
I can measure the axle weight at a friends MOT station, but was trying to figure out what the best way of calculating my spring requirements would
be.
Ideally, I'd like an excel sheet, where I plumb in the numbers, but if somebody has the manual equasion, I'll do it manually 
Cheers,
Murray
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If you believe you're not crazy, whilst everybody is telling you, you are - then they are definitely wrong!
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fesycresy
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| posted on 1/4/08 at 02:58 PM |
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I'd ring Procomp and let Matt figure it out 
He'll then sort you some springs out.
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The sooner you fall behind, the more time you'll have to catch up.
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Mr Whippy
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| posted on 1/4/08 at 02:59 PM |
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Mind that the spring rate required will be quite a bit more than the axle weight since the angle the shockers are at will reduce their effectiveness.
Fame is when your old car is plastered all over the internet
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MikeCapon
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| posted on 1/4/08 at 02:59 PM |
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Have a look here. This is how I proceed to get an idea for first testing.
http://www.locostbuilders.co.uk/viewthread.php?tid=84991&page=2
www.shock-factory.co.uk
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Mr Whippy
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| posted on 1/4/08 at 03:01 PM |
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quote:
Originally posted by MikeCapon
Have a look here. This is how I proceed to get an idea for first testing.
http://www.locostbuilders.co.uk/viewthread.php?tid=84991&page=2
what on earth is that? I can't seem to open anything on it
Fame is when your old car is plastered all over the internet
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worX
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| posted on 1/4/08 at 03:01 PM |
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try this then
http://www.locostbuilders.co.uk/viewthread.php?tid=84991
steve
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MikeCapon
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| posted on 1/4/08 at 03:06 PM |
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Is that any help Murray? Or should I knock up an Excel spreadsheet?
www.shock-factory.co.uk
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worX
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| posted on 1/4/08 at 03:10 PM |
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I'd be very VERY interested in an excel spreadsheet Mike! I am considering building a Locost next and would love to do some research into how to
make it handle as best it possibly could and therefore make better informed decisions!
Have sent you U2U!
Steve
quote:
Originally posted by MikeCapon
Is that any help Murray? Or should I knock up an Excel spreadsheet?
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muzchap
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| posted on 1/4/08 at 03:26 PM |
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Thanks - I'll take a look
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If you believe you're not crazy, whilst everybody is telling you, you are - then they are definitely wrong!
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omega 24 v6
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| posted on 1/4/08 at 03:55 PM |
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What about this little baby of a site
Springs and things
If it looks wrong it probably is wrong.
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MikeCapon
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| posted on 1/4/08 at 04:12 PM |
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How do I post an Excel spreadsheet then?
www.shock-factory.co.uk
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indykid
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| posted on 1/4/08 at 04:30 PM |
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add another post and at the bottom, there should be an attachment section.
browse for the file and add it.
post it
we'll then be able to download it.
tom
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worX
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| posted on 1/4/08 at 04:35 PM |
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Posted for Mike!
Thanks very much!!!
Steve
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MikeCapon
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| posted on 1/4/08 at 04:35 PM |
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Thanks Tom,
Has that worked?
www.shock-factory.co.uk
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muzchap
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| posted on 1/4/08 at 06:34 PM |
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Mike,
You're a diamond! If at stoneleigh, let me know and I'll buy you a beer
M
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If you believe you're not crazy, whilst everybody is telling you, you are - then they are definitely wrong!
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Syd Bridge
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| posted on 1/4/08 at 08:38 PM |
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Do wheel frequencies not count in the equations these days?
THE single biggest factor in comfort and handling. Or used to be in the good old days!
Cheers,
Syd.
[Edited on 1/4/08 by Syd Bridge]
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Kaspa
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| posted on 2/4/08 at 07:44 AM |
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I use what i beleive to be a much simpler and more accurate method and all you need is a couple of measurements ,the angle of the shock, and the
weights that the wheel will see
you will need meas, 1 the distance from bottom A arm chassis pickup to bottom shock mount= meas A
the bottom A arm chassis mount to center of tyre =Meas B
to get the Motion ratio at the tyre [A/B]2
example if A = 14 and B=18 then the formula will be
[14/18]2 =.61
.61 is the motion ratio at the wheel so divide .61 into the weight at the wheel to detirmine the amount the spring is holding up.
the other little thing you need is the angle of the shock to get an accurate correction factor, and they are
shock angle correction factor
10 deg .96
15 deg .93
20 deg .88
25 deg .82
30 deg .75
35 deg .66
40 deg .59
45 deg .50
the greater the angle the heavier the spring needed, so if for a verticaly mounted shock you need a 200lb spring.
if you lay the shock at 30deg you will need a 266lb spring
ie, 200/.75 =266lb
a reasonably good guide for spring rates for a road track car are
spring 250lb= 800-1200lbs
spring 350lb= 200-1500lbs
spring 450lb= 1500-2000 lbs
spring 550lb= 2000-2400lbs
spring 650lb= 2400lbs pluss
the second figure being the total load on the front wheels
so for a road going clubby with around 350kg on the front with a shock angle of 35deg i'd run some where between 200-300lb springs depending on
wether road or track
I am no Einstein or math genious, but i have used this method for many years and have found it both simple and accurate
hope it helps in some way
cheers Kaspa
[Edited on 2/4/08 by Kaspa]
understeer= when you hit the wall front first
oversteer=when you hit the wall back first
HP= how fast you hit the wall
Torque= how far the wall moves when you hit it
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Fred W B
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| posted on 2/4/08 at 08:17 AM |
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Good thread! - pity its stuck in bobywork?
quote:
Do wheel frequencies not count in the equations these days?
a clue - he has static droop as an input.
My attempt -
Cheers
Fred W B
 
rates
[Edited on 2/4/08 by Fred W B]
You can do it quickly. You can do it cheap. You can do it right. – Pick any two.
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MikeCapon
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| posted on 2/4/08 at 09:15 AM |
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Hi Syd,
Yes, you're right. The classic method does involve the wheel frequency calculation and I have used this in the past, although, I have to add,
without much success.
The point is that you need to choose the frequency and hence spring rate. Using supposed "correct" frequencies often gave me ridiculous
results.
Any method will have its weaknesses and proper testing is the real solution. In having to develop shocks for many different vehicles as rapidly as
possible, I came up with "my" solution to find a starting point for testing.
For the case in question it seemed to me to be the most appropriate method.
Mike
www.shock-factory.co.uk
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Syd Bridge
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| posted on 2/4/08 at 10:38 AM |
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In my work, the only definitive reference is frequencies, and they are really the only way to see which direction you are going. Then driver
'feel' comes into play.
Maybe bikes are that much different. I s'pose the much lighter weight must negate a lot of what car technology relies on.
Cheers,
Syd.
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Kaspa
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| posted on 4/4/08 at 06:23 AM |
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The trouble with trying to sort out a wheel frequency is, has anybody tried to bounce a clubby with coil overs with the shock removed, Mmmmmmm
Kaspa
understeer= when you hit the wall front first
oversteer=when you hit the wall back first
HP= how fast you hit the wall
Torque= how far the wall moves when you hit it
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