TOPIC:

I'd like to suggest a spring database. This is inspired by my Monster Beetle. I love my MB and it is better now that I've installed the MiP ball diff, but there is still one big problem: the rear springs are too stiff. This means there is no compression at all on the level which makes the u-joint angle really large causing noise and inefficiency. I'd like the rear to sit lower, but there are no alternate shock locations so the only option is softer springs. But which springs are softer and which would fit?

I'd suggest a spring database which has the critical parameters for Tamiya springs. This means not only the physical parameters like length and diameter, but also the spring rate (k) so we can tell which are stiffer or softer. This is actually not that hard to do. I spent the morning working out the formula and doing some testing.


G=7.93e7 (shear modulus for steel)
d=wire diameter (mm)
OD=outer diameter (mm)
L=free length (mm)
P=space between coils (mm)

This will give you the spring rate in N/m assuming squared ends which all Tamiya springs have. The formula may seem ugly, but it is very easy to put into a spreadsheet and run it on the spring dimensions. I tried out a sample of springs using only a crude dial caliper and a postal scale and found that I got the right answer within 10% which is good enough for comparative purposes.



What do you think?

Good idea but a big work.
For your mb, try another time lunchbox stock springs

I'll be happy to add this kind of information to The DataBase, but there's two challenges as far as I see:

How to know, with some certainty, which spring you are testing?
To be sure you need to pull springs from nib kits/Spare Parts and lnk the info to the individual spring's partnumber.

How to ensure decent accuracy?
I would say that one guy must do the measurements, with the same equiment, to have comparable measurements.

-Lars

larbut wrote:

How to know, with some certainty, which spring you are testing?
To be sure you need to pull springs from nib kits/Spare Parts and lnk the info to the individual spring's partnumber.

How to ensure decent accuracy?
I would say that one guy must do the measurements, with the same equiment, to have comparable measurements.

Yes, those are both real concerns. Regarding the measurements, since the only things which need to measured are dimensions anyone with a digital caliper ought to be able to do a decent job of it.

You're right that new kits or new spare parts are best. That can be a challenge with older parts and sets of course, but we could have a system where a 2nd or 3rd party validate the numbers.

I realize that throwing up an idea is a whole lot easier than implementing it and this idea is not simple. Perhaps it is too difficult to reasonably accomplish. If it could be accomplished though, I think the result would have real utility.