kiwirex
|
 posted on 12/3/03 at 09:01 AM |
|
|
Whats a spring rate & why would I want one?
I've seen lots of talk about spring rates, and how to calculate them for a given spring, but can't figure out what I'd do with them once I know
what they are.
It'll be something to do with weight on the axle, vs... travel? pre-load?
Seems to me I should figure out what spring rate I want, then get springs made to suit. But how do I figure out what I want?
Thanks...
|
|
|
|
|
dozracing
|
| posted on 12/3/03 at 08:28 PM |
|
|
Springs are holding the car up. So the first thing is to know the weight of the car and the front/rear weight bias.
The wheel have a mechanical leverage over the springs so the "wheel rate" is lower than the spring rate by a square of the leverage ratio. So you
need to know this as well.
At ride height your selected springs stored load will be equal to the load the corner of the exerts on it. So you have one known point of interest.
The cars ride ehight should be known and the displacement of the shock should be calculated at full bump. At full bump your spring should provide
enough load to withstand a 5g bump ie hitting a kerb the chassis won't bottom out. So your corner weight becomes 5 times the staic weight and your
fully compressed spring should exert a load at the wheel equal to the bump load.
With this you should be able to calculate the required spring.
Or do it the easy way and a book Locost needs 275 lb per inch front spring and 175 rears. Look at the shock dimensions on my website and you'll have
enough information to back calculate what you require for a similar car with a different suspension layout.
www.gtscougar.freeserve.co.uk
Kind regards,
Darren
|
PLEASE NOTE: This user is a trader who has not signed up for the LocostBuilders registration scheme. If this post is advertising a commercial product or service, please report it by clicking here.
|
kiwirex
|
| posted on 17/3/03 at 09:08 PM |
|
|
Thanks Darren,
Using a 5g bump helps it all make sense.
Cheers,
Greg H
|
|
|
David Jenkins
|
| posted on 18/3/03 at 08:45 AM |
|
|
Darren,
As a matter of interest, what engine did you use in the chassis that had those spring rates?
The reason for asking is that I bought springs early on, to the book values. I believe these were 200 front, 180 rear. The rears seem OK and
everything sits nicely, but I already have 1.5" preload on the fronts and it's still not up to the proper height! I'm using a X-flow, which isn't
a heavy car engine.
My shocks are slightly more upright than in the book because the top mounts are on the side of the tube, rather than underneath (braced, I hasten to
add). This means that the springs don't need to be quite so strong, but I suspect that I'm going to need at least 250 lbs/ft.
Any guidance appreciated...
David
|
|
|
dozracing
|
| posted on 18/3/03 at 01:47 PM |
|
|
Those springs are for a X-flow engined book car.
Kind regards,
Darren
|
PLEASE NOTE: This user is a trader who has not signed up for the LocostBuilders registration scheme. If this post is advertising a commercial product or service, please report it by clicking here.
|
