http://img513.imageshack.us/img513/4250/tempom7.png [Broken] This description is WRT the the image above. A force applies on the geared plank on the fulcrum...actually the fulcrum is attached with 100% rigidity. This geared plank has a grip on it corresponding to the geared sprocket; as a result when pressure falls on the fulcrum, it rotates the Geared sprocket; which in turn has coils of chains on it corresponding to the grip on the teeth so as to hold on to it firmly; cause of this rotation, tension on these chains tighten and they pull the hydraulic arms which are attached to the body. Now the direction at which the pull is generated is not same for both the arms, its opposite actually, this can be achieved by altering the way by which the chain coils upon the geared sprocket, that is for the same motion of the plank, one coils from above and one from below the geared sprocket. Since both the hydraulic arms are grounded to the body, the normal reaction by the fulcrum will be given by the rigidity of the body, that is the stress on the body. The 'body' here is the thing on which the whole arrangement is kept and hydraulic arms derive normal reaction from it. Ok by this analogy if we put the weight of the truck on the fulcrum, all the weight will not fall downwards, in fact none of the weight will fall down.......................and this seems impossible!...all the normal reaction will be derived from the body!