I thought members may be interested to find out more about the Ferguson Combined Epicyclic Gearbox and Live PTO Unit.
The earliest reference to these units I can find is dated June 1955 and that is an article from the Farmer and Stockbreeder magazine. The parts book I have is FP572 with a copyright date of March 1957, while the instruction booklet is FP6 I 2 not dated.
Before proceeding with a description of the function and operation of this Ferguson accessory it may be appropriate to point out to readers that The Howard Rotavator Co. introduced a suitable sized Rotavator for the TE20 tractors. As first gear was not low enough to operate the implement successfully, they developed their own reduction gear system. This was fitted internally behind the main gearbox. Direct drive or reduced speed was selected by moving a short lever mounted on a special cover plate fitted to the right-hand side of the transmission case, replacing the original that carried the dipstick. Of course Howards ensured that their plate incorporated a dip stick facility. These Howard units did what they were designed to do, ie give a reduction of about 3: I, but they gave no protection to the unit itself. If the unit was engaged by the operator, and a low gear was selected with the intention of pulling a tree stump out, then the teeth of the reduction unit would be sheared off!
It is my understanding that the Howard unit predates the Ferguson unit which I will outline next.
The Ferguson unit is a ‘sandwich’ gearbox that is installed behind the main gearbox. This has the effect of extending the tractor’s wheelbase of 80″ by 4.75″, thus giving the driver a bit more legroom. It also means both brake rods have to be extended by that amount, so two screw-in
pieces were supplied with the kit. It also meant that 4 extra pints of oil were needed bringing the total capacity to 5.5 gallons.
This unit, being more sophisticated than the Howard unit. does offer some protection because the brake band that is applied to the perimeter of the epicyclic gear unit to bring it into operation is powered by its own dedicated pump that delivers oil to a preset maximum pressure so if the unit is overloaded the brake band slips so no drive is transmitted.
Apart from the usefulness of giving a reduction of 3:1 in all gear ratios, the Live PTO facility that is available in low ratio is of great benefit when using, for example, a hydraulic loader or a PTO driven baler when the tractor could be stopped but the baler continues to run thus enabling a heavy patch to be cleared through the machine. The characteristic of self wrapping of the brake band only operates in the forward gears, the torque output in reverse will therefore be less but this is rarely a problem.
I feel it appropriate here to reproduce, from the instruction book, the details of its operation so that I will not be responsible for any errors!
Published in Journal No.102 Autumn 2022
