[CAUT] Digest, Vol 1103, Issue 85 Moving Wippen Rail

[Richard Brekne]

Hi Keith

Ok... lets look away from where the lever is measured for the moment and 
just agree however we take it, it remains a third class lever.  And lets 
take a simple example lever and ratios for key and hammershank and do a 
quick calc on what happens with a 2 mm move that lengthens both arms of 
the whippen.

Say the input arm is 100 mm and the output is 150. Say also that the 
hammershank has a 7.0 ratio and the key ratio is 0.5 figured at 100 mm / 
200 mm

The sum ratio before the 2 mm move is then 7.*0.5*150/100 = 5.25
The sum ratio after the move is then 7*0.5*152/102=5.215

Altso... a net change of 0.035 in total ratio.  Not much there to go on.

Remembering  that taking down and up weight measurements is at best an 
iffy thing.... hardly in the ballpark of an exact science,  I am forced 
to wonder about all this.  True enough the changes in the arms dont 
exactly cancel each other out entirely, but you have to move the whippen 
rail quite a bit to force a significant change. So much so that the jack 
angle will be way out of kilter with its geometric requirements. I cant 
see any way you can really change the ratio much with a 2 mm move unless 
you either figure in (and explain) some other component, such as jack 
angle / force vectors (in which case our third class lever suddenly 
becomes a good deal more complex).

Thoughts ?

Cheers
RicB


    Any gain in touchweight is a product of a reduction of friction or a
    gain in
    leverage, Both of which can happen when aligning to the lines of
    convergence. (Did I miss any other things?) Friction is measurable
    and has
    been eliminated so that leaves one thing.

    I repeat, the load arm of the wippen is to the jack center pin. The
    jack is
    only a transitory post and is not a lever. Please define what the word
    "jack" means in this case if it is not what I say.

    Keith Roberts