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

[Richard Brekne]

Hi Keith

Yes.... well I see where we are getting mixed up with each other here.  
I has seemed to me that you were saying that the lever was indeed a 
simple 3rd class lever with the input arm being the whippen cushion to 
the whippen flange center and the output arm the whippen flange center 
to the jack center.  I think I said in my last reply that this 
perspective requires either a very large move to create a significant 
change in ratio or the perspective was wrong and you had to figure in 
another component which made the whole situation a bit more 
complicated.  I dont see that you've explained this other component. 
Grin... given your example I'm not even sure at this point you accept 
the whippen is a 3rd class lever to begin with.  Besides... you throw in 
a post (which I suppose is supposed to represent the jack itself) and 
dont take into consideration that the angle this post takes is supposed 
to change depending on the placement of the input and output loads.  
Please do not misunderstand... I mean no disrespect.  I am very sure the 
picture you are drawing with your words is very clear in your mind... 
but why dont you just use a simple drawing using MS Paint or something 
like that to illustrate what you are saying.

Strikes me that it makes no real difference whether you figure the 
whippen as 3rd class lever using the flange center to the jack top or 
the flange center to the jack center in this context.  Either way moving 
the whole whippen 2 mm moves both points 2 mm. Reseting the jack angle 
to meet the knuckle in the case you view the later creates essentially 
the same effect as if you simply took the view of the former.  Which may 
explain why most folks simply decide to figure the output arm from the 
jack top.  Nothing imaginary about this at all me thinks. 

Draw a pic and let me get a clearer look at what you are getting at :)

Cheers
RicB



    Excuse me, you are not accepting the fact that the resistance lever
    arm is
    to the jack center pin. This by definition of a lever. Show me the solid
    beam that translates the force from the capstan directly to the top
    of the
    jack. You have an imaginary RA. The force is transmitted through the
    lever
    arms to the jack center pin. The center pin then lifts the jack. If
    I change
    the EA of the wippen, the force at the jack center pin will change.
    Am I not
    correct on this? The premise you base everything on is that the RA
    changes
    with the rail move. It does not so a 2mm move is a lot and the input at
    center pin to the jack, even though it changes slightly with the
    rotation of
    the jack, is counter acted by the change in the alignment at the top
    of the
    jack. Therefore all of the resultant changes MUST be due to the
    change in
    the EA of the wippen.

    Picture this. A five story building. You have a motor that  lifts a
    whole
    bunch of weight 3" and lets it back down. You need work done on all the
    floors. You put the motor in the basement and stand a post up
    through the 5
    stories. On the 5th story you have machine that is the most
    important and
    needs to accelerate a part from the floor to the ceiling and you
    need more
    lift of the post to make it work. So you put in a 2nd class lever in the
    basement between the motor and the post. Now this post does this
    same work
    on every floor. Do I measure the RA of the lever in the basement to 5th
    floor, the 4th floor, the 1st floor? If I disconnect the equipment
    on the
    5th floor and move it to the 2nd, do I have to recalculate the RA
    and adjust
    the setup so the same work is then accomplished?

    Keith Roberts