Springs test results
 

A while ago i tested the Xray black springs to work out what the "C" meant, recently i tested some other springs and below are the measured results. I've put them all in Xray "C" values which are N/mm. To convert to lb/in multiply by 5.71.

Xray springs are very accurate to their advertised value.

I tested two of each spring type.

Measured Results

new style HPI springs (black)
Blue - 2.50
Silver - 2.79
Pink - 2.93
Gold - 3.31

Schumacher
white - 2.48
blue - 2.86

Yokomo
Black - 2.20
Blue - 2.24
Yellow - 2.44
Pink - 2.43

Conclusions:
- all springs tested are linear
- HPI Blue (advertised 2.68) is really 2.5
- HPI Silver (advertised 2.96) is the same as an Xray 2.8
- HPI Pink (advertised 3.15) is the same as an Xray 3.0
- HPI blue, silver and pink measured softer than their advertised rate
- Yokomo springs are junk

Hope this clears up a few myths out there :)

Attached is the full spreadsheet.

Chris...

You mention their advertised rates, but what were the actual rates?

the actual rates are the numbers shown, the measured results.

Attachment doesnt work??

ok i think i got it working now, forum doesn't seem to like Excel files.

Springy
 

So how did you calculate the actuals?

Interesting results, however have you tried to run 2.8 and HPI silver back to back on a car? For me the feel is significantly different.

i think the issue is in the consistency of the springs. The spec of the HPI silver should make it the same as a 3.0 Xray spring. Maybe some HPI's are actually closer to the specs? You would definitely feel it in that case. I actually tested 3 HPI Silver springs i had and there were all pretty close to each other (within a few %).

Were the springs you tried the new style HPI's, the black one's with the paint mark or the solid colored older style ones?

To test i put a 1.5kg digital scale on my CNC milling machine, put the spring on it, put a shock body and collar into the chuck. I set the height so that the scale is just registering (like 1-2grams), then zero everything. Then i step the mill down in 0.5mm increments and record the weight measured on the scale.

Have you tried measuring Tamiya springs?

In particular White and blue, as these seem to be the two that keep cropping up.

Skiddins

Don't have any sorry.

[QUOTE=gameover;7259160]i think the issue is in the consistency of the springs. The spec of the HPI silver should make it the same as a 3.0 Xray spring. Maybe some HPI's are actually closer to the specs? You would definitely feel it in that case. I actually tested 3 HPI Silver springs i had and there were all pretty close to each other (within a few %).

Were the springs you tried the new style HPI's, the black one's with the paint mark or the solid colored older style ones?

QUOTE]

I have both old and new, from memory the new black with paint silvers are fractionally stiffer than the old chrome silvers.

For me, the xray spring proves very smooth and stable, where the HPI gives a much more agressive feel with more corner speed.

I think that is a serious source of errors. Your scale has an error of grams (at best) so I wouldn't rely on the values it reads.

The preload you apply also is another source of errors (when you say you zero the scale) as it creates a deflection however small of the spring. This means you're not measuring the actual load needed to deform the spring, but something a bit higher. The fact that the scale reads 1-2 grams does not mean the load is the same either, as explained above.

What you need to use is a dynamometer and a good one at that. Typically, if you want gram accuracy you need .01 accuracy as errors multiply. Similarly, if you quote .01 gram accuracy, you need .0001 accuracy in your measurements to make sure errors are not going to trickle down (actually up) to .01 figures.

Why are yokomo springs junk?

Because it's a yokohomo keefy

nah it's not a problem, the weight on the scale at 1mm compression is around 200-300g and to compress the spring to 5mm takes close to 1500g (in some cases more). 1-2 grams error doesn't matter in the slightest.

the absolute load on the spring is not critical, actually when i calculate the final rate i ignored the first reading at 0.5mm to remove the variation. It takes the same weight to compress the spring from 1.0mm - 1.5mm as it does from 4.5mm to 5.0mm, its only the relative difference that is important for these linear springs.