Re: JD 520 PTO problems

Posted by Janicholson on January 13, 2018 at 09:05:55 from (63.152.209.198):

In Reply to: JD 520 PTO problems posted by Hal Roberts on January 13, 2018 at 08:29:05:

The hammering when turning may have been directly attributed to the geometry of the front universal joint's relationship to the
hitch pin location, the phase relationship of the yolks in the PTO shaft, and angle of the turn.
1]If the Ujoint location (front to back) is at or close to the hitch pin, the front joint is angled much more, or has all the
angle compared to the rear joint in that shaft. This causes rotational accelerations and decelerations in the the shaft that are
not cancelled by the rear joint. If not canceled, the change in RPM 4 times per rotation (faster slower faster slower) is trying
to change the speed of the driven attachment, be it a mower, or baler. The inertia of the implement causes this to be a radical
vibration. The hitch point pivot needs to be rearward of the front joint So that the angle in a turn is far more equal between
the two joints.
2} If the two Ujoints are not in phase (on a piece of paper draw a backward capital C draw a line from this wrong facing C about
an inch long and draw a correct facing capital C. The yolks of the shaft must be oriented the same way as these "C"s. That is
they must be coplaner. If they ar not, the shaft will vibrate and make noticeable vibration at nearly any angle. Each joint
accelerates out of phase with the other accentuating the issue.
3} All simple Ujoints create the acceleration deceleration issue. The shaft between them is supposed to be the only thing that
is subject to this velocity change if the angle is greater than about 25 to 30 degrees per joint the vibration will shake things
apart.
I am not aware of the construction of the JD PTO drive, so others will need to fill this in, but the Knocking caused it. Jim

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