measuring ratios, (was popsicle)

[RicB]

Hi All

As long as we all remember that the <<ratio>> defined this way (ala 
Spurlock)  is not the same ratio relationship as Stanwoods Strike Weight 
ratio we are ok here. Stanwoods ratio is about how much weight at the 
key front is needed to balance whatever radius weight the hammer has out 
there on the end of that shank.  More specifically we are talking about 
how much weight would be needed to bring the action into the half blow 
condition in a frictionless world.  That is not at all the same thing as 
how much distance the hammer moves for any given amount of key travel.  
In fact, if you were picky enough about your measurements you would find 
that if you measured for a 8 mm key travel compared to 4 mm key travel 
you'd end up with two different figures there too.

 There is an approximate translation that generally works fair enough... 
and in any case if you are shooting for some BW in an action re-do  you 
nearly always end up within a couple grams (nearly always heavier) if 
you've calculated with the distance ratio as your figure for R.  Its a 
good thing to gain a basic idea of your general leverage zone by doing 
the Spurlock thing.  But if you plug that value into Stanwoods formula 
to arrive at a FW figure for some targeted BW, you are going to have to 
go back and add some few grams of FW in the end.  On the other hand... 
the error created is consistent... so you can either live with it and 
still have an even result... or try and compensate a bit by 
approximating a translation from one R to the other.

Cheers
RicB



    Greetings,
      I have been using a 6 mm block attached to a weighted length of
    2X2 on the
    top of the key, and a dial caliper to measure how much the hammer
    rises.  This
    gives me a ratio in approx. 15 seconds, ie.  if the hammer rises 36
    mm, it is
    a 6:1 action.  If it rises 30 mm, it is a 5:1 action.  if it rises
    33 mm, it
    is a 5.5 action etc.  
       This system will also give me other info, as in progressively
    using two 3
    mm blocks, which will tell me if an action has a higher ratio at the
    beginning
    of a hammerstroke (bad progression), or if the beginning ratio is
    lower than
    the final, (good progression).  
    Regards,

    Ed Foote RPT