From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Description of the Buckley Patent Adjustable Tappets, their components, and assembly process.
| Identifier | ExFiles\Box 147\1\ scan0030 | |
| Date | 18th March 1935 guessed | |
| THE BUCKLEY PATENT ADJUSTABLE TAPPETS. The tappets are illustrated in Drawing No.62 herewith attached. At the end of the valve stem is a cotter slot of sufficient length to accommodate two cotters with an interposed spiral spring washer in a state of compression. Over the end of the valve stem is placed a collar, hexagonally shaped externally, with a corresponding but slightly longer cotter slot. The part of the collar which overlaps the valve stem is bored to fit it while the other end is tapped to receive a tappet adjusting screw. Within the hexagon collar and compressed between the end of the adjusting screw and the valve tip is a second spiral spring washer. Immediately below the cotters the hexagon collar is encircled by a locking washer, as illustrated, stamped out of sheet iron or other suitable metal capable of being bent over the head of the tappet screw and centrally perforated with a hexagon hole to fit the hexagon collar. The diameter of the locking washer is somewhat greater than the outside diameter of the valve spring. Into the end of the hexagon collar is screwed a tappet adjusting screw which may conveniently have 24 threads to the inch or something of that order. The diameter of its head is equal to the outside diameter of the valve spring. The head is formed with flats as illustrated. In assembling the parts, the hexagon collar is coupled to the valve stem in the manner already described, the valve spring is then threaded over them and is itself retained by the locking washer which has in the meanwhile been threaded on to the hexagon collar. The tappet screw is now screwed well home into the hexagon collar thus compressing the inner spring washer against the valve tip and the valve spring against its own seating in the cylinder block. The valve and tappet screw are made of such a length that when coupled together with the intervening spring washer compressed to its utmost extent the overall length of the whole is such as to leave a clearance space of about 0.040 of an inch between the head of the tappet screw and the cam follower or rocker arm, as the case may be. As the exhaust valve has to open against a back pressure in the cylinder and as the inner spring washer has to transmit the thrust which causes it to open; the washer is made sufficiently strong to resist this pressure without yielding. The thrusts of the two spring washers oppose one another and the thrust of the outer washer is made about 10 per cent. greater than that of the other. During the opening stroke the thrust of the valve spring is entirely taken by the head of the tappet screw and not, as hitherto, by the valve stem; nevertheless during its closing stroke the | ||