Quote:
Originally Posted by rotorwrench
While the individual right and left sides may be that long, the triangular shape changes the distance from the center of a line intersecting the two perch pins to the center of the radius ball to somewhat less than 4-inches. The 1st Gen Mercury with 99A front radius rod assembly may be 4-inches longer from front to rear but it will take an intact part from each car to verify that.
The measurement that was posted by rockfla seems to differ but the front axle does have caster angle built in so I guess it depends on which end of the perch mount is used for the measurement of center perch to center ball. Each individual part number of radius rod assembly would need to be measured the same way to at least be able to ID them by dimension. Measurement procedures should be the same and best done off the car. I wouldn't ask someone to dismantle their car for that.
Model A, 1932, and 1933/34 as well as later Ford car radius rods have been measured this way and these figures can be found but the Mercury changes things a good bit so this is the only reason for the question.
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Don't allow yourself to believe that these front, I-beam axles have the caster angle "built-in", 'cuz they don't! Such a statement would imply that these axles also have a front and a rear....they DON'T, dimensionally. The king pin bores as well as the perch pin bores in these axles are dead-straight vertically aligned with the upright axle as a whole when viewed from either end. As an aside, the king pin lock-bolt bores are NOT tapered from front to rear as some folks would have you believe, either. Hence, the prescribed CASTER angle for the vehicle's front axle is determined by the angle created by the perch pin positioning holes in the wishbone's two front "fork" forgings which are welded into the front of the two tubes, working in conjunction with the up/down angle of the wishbone's rear end, pre-determined by the wishbone ball's captive location.
My whole reason for interest in any of this has come to light by this loosely-thrown-around 4" figure we keep hearing reference to. I had earlier made reference to the fact that I had discovered by accident that a '41 FORD wishbone is a one-year-only piece when I stood one up against a wall, next to a '40 wishbone also standing against the wall. As I remember, there was ABOUT a 3" or 4" difference in height of the two balls. MOST folks don't realize this. '41 FORD front suspensions have some odd, and unique things going-on! We know that '42-'48 'bones are different because of the slight "goose-neck" toward the front of each leg. After hearing that the 99A-3405 Mercury wishbone is 'SOMETHING LIKE' 4-inches
longer than a '37-'40 FORD wishbone, I'm wondering if FORD didn't use the same 99A- Mercury wishbone on the '41 FORDS. I'm not close to any parts books at the moment, but can someone look-up the part number for a '41 FORD wishbone? If it's unique unto itself, the prefix should be "11A-". If it's the '39 Merc wishbone being re-purposed, it'll have that "99A-" prefix. Anyone? DD