dougvv Wrote:
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> Hi Ron,
>
> The pivot point is just that, a pivot point, it
> transfers no load. The balls transfer all the body
> load evenly from the car bolster to the truck
> bolster evenly between the two triangular pivot
> point cut outs.
>
> The ball field would be the truck bolster from the
> front to the rear of the side frames and from side
> frame to side frame in width. The springs of a
> traditional truck would be the equalizer or they
> could be replaced or assisted by a true equalizer
> system.
>
> Rollers can not be used since the trick has to be
> able to move from side to side as well as front to
> back UNLESS you add another plate between the two
> bolsters. Rollers on one level would allow front
> to back motion and rollers on the other level
> should allow side motion (since the pivot point is
> not inside the truck side frames, two directions
> of freedom are needed. the side to side motion
> need to allow the pivot point to be at either end
> of the truck bolster to be the center of rotation.
>
>
> Rollers would need to be parallel to the rails on
> one level. Since it is a rotational shift due to
> either the front or rear pivot point, rollers
> aligned axially for one pivot point would not work
> for the other unless you want to add yet another
> level of rollers set axially to the other pivot
> point. Balls are much simpler.
>
> Once again, the pivot point is just a rotational
> center and a shear pin so when the car body moves
> forward, the pin (attached to the body bolster)
> moves to engage the forward pivot point of its
> triangular slot. When direction is reversed, the
> pivot #1 has nothing to push on in its slot and
> the body slides back to when pivot 2 engages the
> pivot frame.
>
> The basic idea is that the pivot points need to be
> beyond and in front of the axles to that the axle
> journals are always pulled by the truck side
> frame.
>
> Another possible issue is that the truck
> assemblies now have a minimum radius defined by
> the limitation of the pivot point freedom to move
> laterally.
>
> It is so simple in basic concept that it is almost
> a "why don't they use it now" first reaction.
>
> Doug vV
Doug,
I see exactly what you are saying. The roller bed is centered on the truck. And the roller bed has two groups of balls, with one group tracking in the X direction and the other tracking in the Y direction. With the X-Y tracking, the arc motion of the truck pivot can be accommodated.
What I was visualizing at first was the use of an arc layout of cylindrical rollers generally positioned on the center of the tuck. The arc of rollers would have its radius centered on the truck pivot point. So it would be like an arc segment of a roller thrust bearing.
However, this arc of rollers would have to be flipped when the car changes dirction. I can see that your X-Y bearing would work in either direction without needing to be flipped. It is an interesting concept.
