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).
Detailed review of the Bentley Mark V chassis, braking system, and specifications from 'The Motor' magazine.
| Identifier | ExFiles\Box 160\5\ scan0230 | |
| Date | 29th January 1941 | |
| January 29, 1941. 567 The Motor eliminate disturbance on the pedal caused by rear-axle movements. The means adopted to this end are the subject of a patent. The essentials are shown in a drawing and are as follow:— A tube is attached by a universal joint to a cross-member on the frame at one end and by means of flexible rubber connections to the rear axle at the other end. This tube carries the bell crank that converts the fore-and-aft motion of the brake rod from the brake pedal to the cross motion required on the transverse rods connecting the brake and drum. The longitudinal rod is arranged to swing round the same arc as the steady rod, in fact, they form one unit and move together. Twisting of the rear axle or departure from the radius of the brake unit is taken up in the flexible connection so that irregular motions cannot be transmitted to the brake connections. In consequence, incipient small judders do not build up and unusual steadiness of braking is obtained on rough roads and in conditions where the back wheels are nearly, or, in emergency conditions, entirely, locked. Stability and Comfort Yet another matter in which safety and stability as well as comfort have been studied is in the frame layout. Softly sprung cars with I.F.S. demand frames of great stiffness, particularly torsional stiffness. This is taken care of by an X-braced chassis in which light-gauge material of great depth of section is used, as can be seen from the chassis drawing. The X-member is of box-section, points of interest being the strength of the centre part of the X and the manner in which it is carried into the side members which are of box section at each end and further reinforced with X-members. It is not possible in this brief review to do more than summarize a few of the more outstanding features of this chassis which is a fine example of British engineering skill. We hope to refer to other technical refinements in subsequent articles and look forward to the advanced practice which it represents being incorporated in post-war models at a satisfactorily early date. TRADITIONAL PRACTICE: (left) Although the vast majority of the world's cars have right-hand gear change, the Bentley is one of the very few English makes to have this feature. In the Mark V it will be seen that the four-speed and reverse gate is mounted on the chassis frame, connections to the gearbox being made through an open shaft with universal joints. This ensures free movement of the lever in all circumstances. SIMPLIFIED SERVO: (above) The brake servo mechanism has been greatly simplified and, as shown above, consists solely of a friction face disc driven at 1/30th engine speed from the transmission. The servo member can be pressed into engagement by the brake pedal and thus applies the brakes; the corrugated spring-cum-cover forces the disc apart when pedal pressure is released. The lettering is referred to in the text. BENTLEY, Mark V Specification Engine: Six cylinders; 89 mm. by 114 mm., 4,257 c.c. 29.4 h.p. Detachable cylinder head and overhead valves operated by push rods. Two S.U. carbureetters; thermostatic starter; carburetter, inlet and exhaust manifolds on opposite sides, inlet water heated. Separate light alloy crank-case; seven-bearing crankshaft, white metal main bearings, R.{Sir Henry Royce}-R.{Sir Henry Royce} A.C.9 big-end bearings, hardened crankshaft. General oil filter. Transmission: Single-plate clutch with flexibly mounted flywheel; four-speed gearbox, ratios, 3.6 overdrive (4.3 direct), 6.15 and 10.3 to 1. Engine speed on overdrive: 30 m.p.h. per 1,000 r.p.m. Synchromesh on 2nd, 3rd and overdrive; right-hand gear lever. Divided propeller shaft with sealed flexibly mounted intermediate bearing. Rear axle, Hypoid gears with bevel differential fully floating axle shafts. Springing: Semi-elliptic rear spring with variable rate; independent front springing with open coil springs; damping by hydraulic piston-type shock absorbers with over-riding control to rear axle. Braking: By friction-servo driven from gearbox through rods in tension to Girling wedge and roller expander in brake shoes. Frame: Deep channel section side members with box section X-bracing. Chassis Lubrication: Positive lubrication by pedal-operated pump on toeboard. Wheels and Tyres: Wire wheels, 16-in. rims; 6.5 in. by 16-in. Avon tyres. Dimensions: Wheelbase, 10 ft. 4 ins.; track, front, 55.26 ins., rear, 58 ins.; length over bumpers, 15 ft. 11 ins.; overall width, 5 ft. 9 ins.; turning circle, approximately 42 ft. BENTLEY "CORNICHE" Designed for use with aerodynamic coach-work, this chassis is modified in the following points:— Gear ratios: 2.76, 3.73, 5.54 and 9.1 to 1. Engine Speed on Overdrive: 26.4 m.p.h. per 1,000 r.p.m. Rear Axle: Semi-floating half-shafts. Petrol Tank: 19 galls. (Mark V, 16 galls.). Wheels: Steel disc wheels with Avon "Speed" tyres. | ||