Kraig,
Regarding that drawing of the blade setup you posted over in the classifieds, I would expect IH to put those springs there for downforce as you stated, but if that drawing is accurate, that's not what it's doing. In the down position as shown, the spring passes very slightly above the pivot point, so it would be generating a very slight lift in the down position. As you raise the blade, the lift force would very quickly increase as the spring centerline gets further from the pivot. I don't know if the drawing is accurate, but IH usually seemed to be pretty good about keeping that stuff to scale in the manuals.
Jerry
Regarding that drawing of the blade setup you posted over in the classifieds, I would expect IH to put those springs there for downforce as you stated, but if that drawing is accurate, that's not what it's doing. In the down position as shown, the spring passes very slightly above the pivot point, so it would be generating a very slight lift in the down position. As you raise the blade, the lift force would very quickly increase as the spring centerline gets further from the pivot. I don't know if the drawing is accurate, but IH usually seemed to be pretty good about keeping that stuff to scale in the manuals.
Jerry