Unfortunately (and with respect) the reality is not yet under control. The total leverage ratio is a combination of three factors.
The ramp angle of the pin and follower in the gear box. (Not adjustable)
The length of the Steering arm at the box shafts. The shorter the easier it is too steer due to the drag link moving less distance per inch of steering wheel circumferential travel. Thus the shorter the less effort. The shorter the fewer degrees of spindle rotation per inch of steering wheel rim travel.
The length of the spindle arms. The longer the less effort. Again the leverage is increased, increasing the distance the rim of the steering wheel must travel for each degree of spindle rotation.
The limit of steering is determined in the spindle stops. They are designed to prevent the spindle from turning beyond a maximum point (either toward the tractor, or away). The stop is provided to mechanically limit the force applied to the drag links and gears in the steering box to prevent most breakage, and to limit turning to about a 3 or 4 foot "U" turn around one skidding rear tire.
The limits to any geometry change (of any arm length) must consider whether the gear, ramp, pin and linkages can travel far enough to reach the mechanical stops in the spindle, allowing full short radius turns.
On my 350U the steering box will turn the steering arms about 1 inch either direction farther than the spindle arms will allow.
If I decreased the length of the steering arms on the box such that they would be just that inch less, it would decrease the effort by about 5% (guess). It would also allow the steering box and gears to be able to jamb (If the axle was deflected high on one side and low on the other, and I was turning tight, there might not be that buffer to keep force from the box.)
If (as you were discussing in your response to my answer above) both the arms were lengthened, the effective ratio would not change. One giveth, one taketh away.
An added element is that the drag links would no longer be parallel with the action of their pivot points (basically the ground). This affects the steering in turns dramatically because they are now pushing and pulling differentially when the axle is deflected. When they are parallel (level) one pushes when the other pulls during a bump of one side. If non level, they would not be equal from side to side.
The only advantage to lengthening them both would be to reduce the force on the drag links, but because they would move farther the steering ratio would not be affected at all.
I hope this makes it clearer. A power steering unit from a 460U can be made to work pretty easily. A PS unit from a 350U will bolt in, but are rare and not particularly strong. Jackson Power Steering can supply aftermarket solutions. Sorry if my earlier post mislead you. Jim
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