Linkage

[clarkie_49]

Hi,

First i would like to say what i great program linkage is. I have been using it during the last week to analyse the different shock pivot points on my dual suspension frame.

However, i think i have come across a problem with the wheel rate calculation (atleast when using the air shock): without knowing for sure the internal formula used to convert the shock rate to wheel rate, it would seem that the formula is simply:

x / y ; where x is "shock rate" at a given wheel travel and y is the leverage ratio at that given wheel travel.

If this is the case, i believe it is incorrect; the formula should be:

x / {y^2} ; divide once for the work done on the shock, and once more for the actual wheel travel.

When i use the program with my air shock data the wheel rate forces are huge. Infact the suspension would not compress with my weight on it. I had to use 36 psi as the initial posative pressure, and i see a lot of other people have been using approximately 50psi.

I did up a quick graph using x / {y^2} and the theoretical rider sag was within reason of the actual numbers.

I could be completely wrong, but i have read elsewhere (probably the Tony Fole book on motorcycle geometry) that the linkage ratio needs to be squared. On the other side, if i am right the we could start to get a database of real air shock parameters which work with the actual users initial pressures.

Anyway, feel free to correct me or take on board what i have said.