David Brown Steering Development

The standard steering available on the Selectamatic tractors was the re-circulating ball type manual steering which, over the years, had proved to be reliable and up to most jobs. However, in some jobs – when loading for instance – the steering effort was greatly increased. The late Tom Lazenby recalled that: ’Although there was nothing wrong with what we had on offer, economy-minded farmers avoided our extra costs for power steering, and so we had a job selling the Selectamatics to some customers.

This was especially so if they were converting from an earlier tractor on which power-assisted had been fitted. We, therefore, put a lot of pressure on the Design Department to come up with a form of manual steering that gave much easier operation, and eventually three models were produced for evaluation. Two were sent to farms owned by Browns, and I took one to a farm near Northallerton. We watched these tractors a great deal, and they performed well under every set of circumstances. We knew that if we could start offering these for sale, we’d have yet another popular seller!’

Power-assisted steering consisted of a hydraulic ram cylinder fitted to the tractor’s main frame at one end, and to the steering lever on the top of the kingpin at the other. The drag link attached to a valve on the ram and the manual steering box etc was retained.

The final type of steering used was hydrostatic steering, and David Brown was the first British tractor manufacturer to introduce this system on volume produced tractors. The company responsible for introducing hydrostatic steering in Europe was the Danish firm of Danfoss, but the concept was based on the American Orbitrol patents. A big advantage of hydrostatic steering was the elimination of mechanical linkage, and this gave greater space saving, which was then utilised with the introduction of Q cabs. The oil in the system could however get very hot, so a cooling coil was later introduced to control the temperature.

The positioning of the steering ram was initially down the side of the tractor, but this had a number of drawbacks. The entire steering load was on the near side kingpin that could wear more as a result, whilst the ram could hamper some side-mounted equipment. The side-mounted ram steering also resulted in unequal amount of turns on the steering wheel, but this problem was addressed by incorporating a regenerative valve in the ram, which could feed oil from one side of the ram piston to the other.

The transverse ram mounted behind the axle, first introduced on the 14 series tractors, overcame the above problems. It also was well protected from damage by trash, which could be a specific problem in forestry Work. After several years in service, problems are now being experienced with this type of ram, but most can be put down to a lack of maintenance ie grease. On the 1394 tractors a twin-ram arrangement behind the axle was introduced towards the end of production. The 4WD front axles were fitted with steering rams mounted out of harm’s way behind the axle. Some rams were bent in Scandinavia – probably on forestry work – and we encountered the same problem with one fitted to our Field Test 1690. This ram failed on particularly arduous loader work, involving the removal of tree stumps and general clearance after timber felling, in the Langsett area, near Stocksbridge.













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