Sir Squirrel,

This statement describes the error in the mental image some seem to have
about the force required by the lift mechanism.  Because the lift bar
'goes up', intuitively it seems that an upward force of some kind is
required.  In reality there is *no* upward force required for the
lifting mechanism, and thus most of the upward force while not wasted,
precisely, it's expended with little, if not negative mechanical
advantage (pop the latch, stand under the top and raise it a couple feet
by directly pushing on the top, then do the same with the lift
mechanism, you'll quickly see what I mean).  The lift mechanism is a
'translational' device, that's the whole purpose, to translate
horizontal force into vertical force.  Think about what would happen if
you pushed *only* forward on the bar...all the energy expended would be
translated into vertical movement of the mechanism (and the top, of
course).  This is the mental model you need to keep in mind when
evaluating different lift assist systems; you don't want to add extra
translational losses to the system.  Just like the hydraulic/pneumatic
assists that Kim installed, they would be much more efficient installed
in a totally vertical orientation, unfortunately, they'd be a tad
inconvenient :-)

Keith Hughes
'86 Westy Tiico (Marvin)

>Date:    Thu, 8 Feb 2007 11:51:26 -0800
>From:    "Mike \"Rocket J Squirrel\" Elliott" <camping.elliott@GMAIL.COM>
>Subject: Re: Poptop Raise Assists (Fryeday content)
>
><snipped for brevity>
>
>*Actually, when the poptop starts its journey upward, I reckon that the
>liftbar initially needs to be pushed forward more than upward, and the
>direction of force wants to be more and more upward as it raises. So
>maybe the top needs to get started with a folded pole thing between the
>front edge of the upper bunk and the liftbar. Pull down to extend. Hang
>"S" from it. Then use the 6-foot floor bar take over.
>
>
>