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).
Page from 'Automotive Industries' magazine describing the Ansted engine and the Lexington model T chassis.
| Identifier | ExFiles\Box 50\3\ Scan050 | |
| Date | 6th January 1921 | |
| January 6, 1921 AUTOMOTIVE INDUSTRIES THE AUTOMOBILE 5 The Ansted engine used in Lexington model T cars, showing belt drive for fan, generator and water pump The crankshaft is unusually stiff and is very carefully balanced on a Carwen balancing machine before it is sent to the assembling department. The shaft is drop forged and has three main bearings. These are stepped so as to make the boring and reaming more economical and accurate. The bearings are assembled with a 0.006-in. shim between the case and the caps. They are reamed to size before the engine is run and do not have to be scraped or burned in. The front and rear bearings are provided with annular oil supply grooves, but aside from these there are no grooves in any of the main or connecting rod bearings. The crankpins all have 0.4375-in. holes through their centers and the connecting holes from the main bearings to the pins and between the adjacent pins are all 11/32 in. in diameter. The crank cheeks are unusually heavy in section. Care has been taken to prevent oil leakage at both the front and rear ends of the crankshaft. At the front end there is a thrower ring on the side of the crankcase, and a series of thin cork washers in the timing gear cover. At the rear end of the shaft there is an oil thrower ring turned integral with the shaft. Supplementing this there is a return thread on the shaft. At the rear end of the main bearing there is a small drain groove to prevent the oil under pressure from working out around the oil thrower ring. The valve gear is unique in that the valve rocker arms are so mounted that their fulcrum points provide a variable rocker arm ratio from 1.265 to 3.047 to 1, which causes the valve to start and stop slowly, but to obtain greater and more rapid lift than would be possible with a constant ratio rocker arm. This prevents valve clatter at high engine speeds. Double valve springs are used to prevent synchronism between the valves and the rest of the mechanism from causing floating. The valve tappets are easily accessible, as the tappet guides are held in place merely by the push rod inclosing tube. The tubes which inclose the push rods and through which the engine breathes are not fixed in place, but are pushed up into a counterbore in the bottom of the cylinder head and have a nut at the bottom end which presses down against the valve tappet guide. The latter is thereby held in place by the tube and the push rod completely inclosed. The valve tappet guides are grouped in pairs and have between them a small fillister head screw which prevents their turning in the cylinder casting. The valve mechanism, including the rocker arms, is Plan view of the series T Lexington chassis | ||