Technical COILER Spring Question

[Hybrid_From_Hell]

Ok,

Trev (LR90) and I have been PMming each other a lot (oooeeer) recently about springs (see)

Trev has built his superb calculator program, which measures spring length when compressed by the LR weight etc, which I have then allowed unsprung weight (ie axles) out of the equation.

All seems ok, cept I have come across some spring data which is "Odd" to say the least.

Basically every spring chart I have come across shows.

Number of Coils, sometimes thickness of each, then the free klength etc, THEN the POUNDAGE (ie 170 LBs) and colours (say Red & White).

This then I have shoved through the program, tweaked for unsprung weight etc etc

Now I have ONE Chart which is from a main dealer, its a service bulletin, and talks about exactly the commnet above PLUS one extra column....

LOADAGE.

This shows that whilst a LR Spring may have a poundage, you can have 2 spring with differing LOADGAE ratings...

Ie

NRC 4304 RED & WHITE 170 LBs 17.71 Length 7.00 coils vs

NRC 4234 Green & Yellow 170 LBs 16.2 Length 7.00 coils

RED & WHITE - LOADAGE 1106.06 vs Green and Yellow 978.84

So, I have done some research (also 90 rear springs are 225 LBs and 585...low LOADAGE but high Rating) and think I have some idea, ie the 1st is the amount of force needed to move springing, the second is the amount of weight it can carry without exceeding loading ?.

Ie for the red and whites they both will move at 170 lbs force, but the red and white can carry more weight without exceeding their carrying capacity.

Intersting here is I now have springs some 2+ inches longer on the 90, with 55LBs less Poundage but higher carrying capacity, result is a 20mm lift and better off and on road handling....

Anyone care to expand how the POUNDAGE vs LOADAGE works, and more importantly how can this be calculated into a linear calculation as to final length when fitted to a known weighted LR ?

Nige

[Les Brock]

[02GF74]

isn't poundage the weight that when applied results in a given change in length i.e. the spring rate?

I can't remember what this is but 1 inch springs to mind and seem reasonable from the figures (I've recently read an article about spring but took no real interest as I have leafs).

Unless you have funky springs where the coils are unevenly spaced, the compression will be linear so this mysterious calculator that you speak of is simply multiplying two numbers then taking that from the free length?

loadage from the figure implies the maximum load the spring can carry. obvioulsy if you exceed that, it will become coil bound so no longer act as a spring. my guess this figure is chosen so that the spring is not fully compressed so will still act as a spring.

disclaimer - ^^^^ this is all conjecture and is my best guess at an answer.

[Tonk]

i can understand the concept but not the need

[FridgeFreezer]

Oi Tonk - he said you can't apply! so I'd better do it: 3 Leaf Fronts, 4 Leaf rears Nige!

Coat, hat, and boots on and running like a waxoyled cat...

[Bush65]

The correct term for what you are calling poundage is spring rate. It is the force to compress (or extend) the spring one unit distance. In imperial units the rate is normally given in lbs per inch.

Then if the spring rate is 170 lbs per inch, and a load of 680 lbs is applied, the spring deflection is 680 lbs / 170 lbs/in = 4 inches.

Also, if the spring is compressed 6 inches, then the load is 170 lbs/in x 6 in = 1020 lbs.

As the load is increased, the spring deflects more and the wire of the spring is twisted and the torsional stress in the wire increases.

There is a maximum allowable working stress limit, which depends upon the wire material and the heat treatment. My guess is that the loadage that you have refered to is the load that will not exceed the maximum allowable working stress limit.

[Diff]

Hi Nige,

There is a different loadage rating because the springs are different lengths.

In you first example, both springs are 170lbs/inch. This means that each spring will be compressed by 1 inch if a 170lb load is applied to it, 2 inches if 340lbs is applied, etc etc.

However, the longer spring will have a higher 'loadage' because it will support a heavier load at 'standard ride height' than the shorter spring, and will consequently support a higher total load before the bump stops are hit. So, you would use the longer same rated 170lb spring to achieve similar spring performance characteristics if you had a heavier engine for example.

To put it another way, the longer spring will take more weight to load it down to the same length as a shorter spring of the same rating. BUT, both springs will be similar in performance and ride.

Hope this makes things a bit less confusing!

Regards,

Diff

[Hybrid_From_Hell]

Hmmmmm

Interesting thinking but unsure if thats it..

for example from the chart :

Pink & Purple 16.47 long 178 lbs rated vs

green n yellow 16.2 length 170 lbs rated

1st has poundage of a lowly 449 lbs, 2nd 978 ??

surely this huie difference in carry capaciuty is not just 8lbs and 0.27 inch ?

esp when you look at the other end of the scale.....

red red length 16.02 330 lbs rating but only 643 poundage ??

Nige

[Diff]

Hi Nige, without looking at all the specs of all the springs, I can't be sure, but many landrover springs are progressive. ie they have several coils closer together than the rest, which once closed up, alter the overall spring rate. So a progressive spring that is the same 'overall' rate and length as a standard spring will also have a different loadage rating.

Regards, Diff

Edited to say, also, I think that some of the data on the charts is not entirely accurate - which of course makes things harder to sort out!

Edited November 16, 2005 by Diff

[Hybrid_From_Hell]

True,

This is a factor, but I am trying to work out a formula for say a std spring to take into account the differences...

ie 7.00 - 7.5 coils ?...and coil thicknesses ....and this apprenet poundage thing...progressives are another issue all round !

Without taking the poundage into account the spring length was out but over 1 inch...ie I expected a drop, of say 5-10mm it went up by nearly 20mm, this was not just axle weights, I worked it all ways, if I left the axles out completely it was .25 inch drop !...

Thinking..................................

Nige

[BogMonster]

Loadage by the sound of the above discussion is almost a measure of "rubbishness" (the amount that a spring can support without being in danger of permanent deformation)

So the "loadage" of a certain brand of orange springs everybody loves, is probably about 50lb

It would be a v complex calculation though, to try and work out the max load on any individual spring under cross axle conditions on a steep uphill/downhill slope where quite possibly a large proportion of the vehicle weight is effectively being supported by the spring on one corner

Also does loadage refer to the "average load" at rest or "peak load" e.g. if you hit a trench at 50mph and bottom the suspension out against all the bump stops

With leaf springs if you do that you tend to break them (especially on things like Suzuki SJs) but I don't recall ever hearing of a coil spring breaking under those conditions....?

[Bush65]

Spring rate = (d^4 x G) / (8 x n x D^3)

where d = wire dia in inches (mm)

G = modulus of rigidity in psi (MPa) for most steels (ex Austenitic stainless) = 11,500,000 to 12,000,000 psi (79,300 to 82,700 GPa)

n = number of active coils

D = mean dia of spring in inches (mm) = outside dia - wire dia

d^4 = d x d x d x d

D^3 = D x D x D

for approximate number of active coils, count the number of coils then subtract 1.75 when both ends are squared and ground.

Note spring rate will change as some of the coils touch when the spring is compressed.

[simonr]

I was under the impression that the loadage is just the load on that corner which will result in the vehicle sitting at the manufacturers design height.

Makes it easier for the people in the workshop - just stick a wheel on a load cell and pick a spring with that loadage (less a bit for the axle, but that is only going to be about 10%.

You can thus be fairly certain that the vehicle will sit level.

This is also why loadage is only quoted by motor manufacturers as it will be different on different vehicles or desired ride heights.

Si

[MarkieB]

I'd say it's to do with progressive springs too. When you think of it, 'poundage' refers effectively to a 'model spring', while real springs behave a bit differently. Once you add the progressive springs into the equation, the only fully accurate way of describing a spring's behaviour is in several graphs, static/dynamic etcetera.

[Ex Member]

I think Land Rover is making up words. "Loadage" is not a word used for coil springs. Like stated, it must refer to the maximum load acceptable on the spring. Bush65 has it all correct.

[LR90]

I think Land Rover is making up words. "Loadage" is not a word used for coil springs. Like stated, it must refer to the maximum load acceptable on the spring. Bush65 has it all correct.

Thanks Red90.

Must admit I've searched to find info on LOADAGE and drawn a blank so thought it was time to call in an expert

90 spring NRC9449 - Poundage : 225, length 14.8 LOADING 585 lbs,

versus NRC 4234 - Poundage : 170, length 16.2 LOADING 978 lbs,

Not sure its max load acceptable though, my 90 on the light side but still near 1000lbs a corner unladen. Also for the springs above the 9449 would still be some 12" long (well above stock ride height) and the 4234 about 9" (an inch or so below stock)

So you recon we're ok to just ignore it (have done till now and been happy with the results).

[Ex Member]

Sure, ignore it.

[Inglishg]

Ok,

Trev (LR90) and I have been PMming each other a lot (oooeeer) recently about springs (see)

Trev has built his superb calculator program, which measures spring length when compressed by the LR weight etc, which I have then allowed unsprung weight (ie axles) out of the equation.

All seems ok, cept I have come across some spring data which is "Odd" to say the least.

Basically every spring chart I have come across shows.

Number of Coils, sometimes thickness of each, then the free klength etc, THEN the POUNDAGE (ie 170 LBs) and colours (say Red & White).

This then I have shoved through the program, tweaked for unsprung weight etc etc

Now I have ONE Chart which is from a main dealer, its a service bulletin, and talks about exactly the commnet above PLUS one extra column....

LOADAGE.

This shows that whilst a LR Spring may have a poundage, you can have 2 spring with differing LOADGAE ratings...

Ie

NRC 4304 RED & WHITE 170 LBs 17.71 Length 7.00 coils vs

NRC 4234 Green & Yellow 170 LBs 16.2 Length 7.00 coils

RED & WHITE - LOADAGE 1106.06 vs Green and Yellow 978.84

So, I have done some research (also 90 rear springs are 225 LBs and 585...low LOADAGE but high Rating) and think I have some idea, ie the 1st is the amount of force needed to move springing, the second is the amount of weight it can carry without exceeding loading ?.

Ie for the red and whites they both will move at 170 lbs force, but the red and white can carry more weight without exceeding their carrying capacity.

Intersting here is I now have springs some 2+ inches longer on the 90, with 55LBs less Poundage but higher carrying capacity, result is a 20mm lift and better off and on road handling....

Anyone care to expand how the POUNDAGE vs LOADAGE works, and more importantly how can this be calculated into a linear calculation as to final length when fitted to a known weighted LR ?

Nige