Its uses, function and overhaul: Mike Thorne
I acquired a rather dilapidated Ferguson TE20 fitted with an early Perkins P3 conversion from a local smallholder. About 18 months later I purchased from John Popplewell an even more decrepit Ferguson TE20 also with a P3 conversion but this one had the added attraction to me of having been fitted with a Ferguson Reduction Gearbox.
The purpose of this article is to relate the story of the building into one nice interesting tractor: as well as to outline in more detail the principals and overhaul of this unit.
The unit became available in 1954 (I think) and this particular gearbox No.196 is a fairly early example. This gearbox which extended the tractor length by about 5″ enabled the TE20 series tractors to operate the Ferguson Rotavater attachment that was marketed at the time. Being made by Rotavater Ltd of Essex and painted Ferguson Grey and coming with a Ferguson Identification Plate. At this time both Howard and Reekie of Forfar in Scotland made very neat built-in reduction gearboxes for TE20s. These consisted of a set of reduction gears and a dog-clutch inter disposed between the output shaft of the existing gearbox and the pinion drive shaft to the rear axle crown wheel, giving of course 8 forward and 2 reverse speeds. The control lever for the reduction box being neatly incorporated into the inspection plate on the RH side of the transmission housing where the dipstick is located.
It is my guess that HF engineers wanted to improve on this. not only as a sales point to better what outside manufacturers had on offer but possibly because they had in mind the development of the build-on combine harvesters which would need a slow travel speed and of course live P.T.O. This unit bolted between the rear of the gearbox and the front of the final drive housing as I said extends the tractor by about 5″: makes it more comfortable to drive and probably helps traction. I have noticed that the tractors used in Antarctica are fitted with this device. I observed this by wondering how the engineers were able to fit 600 x 19 wheels to the front of these tractors: investigating Artic Sue at Banner Lane I found the answer. Let us look at the operating principles involved in this gearbox from the output shaft of the gearbox drive is taken into the epicyclic reduction unit, it can be either braked, to give low range or direct drive taken through the unit. LPTO is only available in low range. The PTO lever is engaged in the normal way and is then running as soon as the engine is fired up and is stopped by depressing the clutch pedal. Drive is transferred to the rear wheels by pulling gently upwards on lever A. Having already engaged operating lever B. Lever B brings the epicyclic unit into mesh with rear drive shaft and by operating lever A the Annulus brake band around the epicyclic unit is applied – allowing the six and planet gear wheels inside to do either reduction job. The power to apply the annulus brake is supplied by a small single cylinder pump which is designed and regulated to slip if the torque transmitted to the rear axle exceeds the specified limits ensuring safety to the drive main components.
[A precursor to the Multi-Power?] This must have been quite an advanced [and expensive] feature in the early 50s and one up on Reekie and Howard of course!
Published in Journal No.44 Summer 2003