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Watermill Blog -  PTO Mystery
24th July 2008

We suspect that most readers of our watermill blog are mechanically inclined and we have a bit of a mechanical mystery to solve.

PTO joint

We have known for a long time that the universal joint in the middle of the PTO shaft was very crudely made.

Martyn, Dave and Colin decided to do a trial assembly today, using the old bearings and various bits of timber packing.

The result was interesting, to say the least. The universal joint works much better in one direction than the other. The slack that seems to have been designed in makes the joint work quite differently when rotated one way rather than the opposite.

We have tried every way of assembling the joint and it definitely wants to be turned anti-clockwise. Unfortunately this would mean turning the waterwheel backwards.

To test our understanding of what was happening we made a rough centre for the joint out of scrap oak and tried it. The result was so good that we had the confidence to drive the whole PTO shaft with water power.

We know that the PTO drive to the stable block was replaced by an electric motor, but we don't know when. The condition of the shaft before we carried out repairs suggests that it may well have tried to self destruct so we are left with the mystery.

Did the PTO shaft ever work properly? The parts that we found when we dug it up certainly suggest that the design fault must have caused a great deal of friction and noise and probably caused premature failure.

Another possibility is that the PTO shaft was originally installed when the waterwheel was still of the undershot type, turning in the opposite direction to the current wheel. However, all the evidence suggests that the PTO was installed at the same date as the iron waterwheel. We just don't know.

nearly there

Elsewhere on site, Dick worked on the final assembly of the chaff cutter, re-installing the straw conveyor and fitting the covers and guards. Richard carried on making parts for the new tun and Bob did yet more painting.

John D, John N and Max roughed out the last step in the path from the farmyard to the roadway, quite a warm job on one of the hottest days we have had so far this summer.

There is still a lot to do but lunch time discussion sometimes turns to subjects like visitor control as we begin to think about actually being able to show off a working watermill.

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