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).
Letter discussing design flaws and potential solutions for a crane's cross-shaft, brakes, and motor system.
| Identifier | Morton\M6\ img006 | |
| Date | 29th November 1929 | |
| Reg. TELEGRAPHIC ADDRESS: "ROYCE, WEST WITTERINGHenry Royce's home town." } TWO WORDS ONLY. TELEPHONE: CHICHESTER 210. STATION—PASSENGER & GOODS : CHICHESTER—7 MILES. SOUTHERN RLY. "ELMSTEADHenry Royce's home in West Wittering," WEST WITTERINGHenry Royce's home town, NR. CHICHESTER. 29th. Nov. 1929. Mr. J.C. Bentley. ROYCE LTD. MANCHESTER. Dear Mr. Bentley, CROSS-SHAFT IN CRANES. & long. brakes. These have not been fitted correctly; owing to their slow speed and small dia. their torsional deflection allows one end of the crane to accelerate more quickly than the other, and it is possible that because there is no damping [with roller bearings] surging may take place that would be very bad. Your 2 motors should, one agrees, have their fields in series, and I think their armatures in parallel, and under all conditions have the same volts between the brushes. [brushes] [CIRCUIT DIAGRAM] RETURN WIRE Low resistance VERY LOW RESISTANCE I have not shewn reversing connections. My impression is that for real safety you want a cross-shaft as well as the 2 motors, and this should run at maximum revs. that is safe from whirling. The brakes for longitudinal work should be mild and kind, not fierce enough to risk being dangerously unequal, or set up unnecessary stresses. I am definitely ashamed of the design shewn. There seems no reason why we cannot make them thus - [BRAKE MECHANISM DIAGRAM] pull rod nearly horizontal The oil dashpots fail when they are too small in dia. so that the lift of the solenoid can form a vacuum under the piston. Supposing the solenoid could lift 40 lbs. and only had 10 lbs. to lift, it would have 30 to lift against the oil, and would require at least 2 sq. ins. or would cavitate and lift up the oil. Or again there was insufficient oil in the pot the falling weight might send the oil upward at great speed. The cure is a big dia. deep pot of rough dimensions - i.e. might be a piece of drawn tube sweated on to a base with cover and hood, and keep in oil and outwater. Yours faithfully, [Signature] (SHEET 2. ATTACHED) | ||