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).
Two telegrams sent regarding issues and solutions for 'jaggering' four-wheel brakes.
| Identifier | WestWitteringFiles\K\November1923\ Scan108 | |
| Date | 11th November 1923 | |
| TO no. FROM R.{Sir Henry Royce} HS.{Lord Ernest Hives - Chair} c. to SJ. BJ. c. to PN.{Mr Northey} HA. re. FOUR WHEEL BRAKES. X1557 x9940 (1) We wired you today as below - "QUITE CONVENIENT FOR YOU TO COME ON TUESDAY. JAGGERING BRAKES MANIFESTLY NOT DUE TO AXLE MOUNTING OR OPERATING PULL BUT DUE TO FLEXIBLE OVERHANG OF BRAKE DRUM OR SHOE CARRIER CAUSING OR PERMITTING LAPPING BRAKE SHOE TO JAM. SUGGEST UNTIL OTHER IMPROVEMENTS READY DEFINITELY EASING OPERATING END AND INCREASING LEVERAGE OF OPERATION BY MR. DAY'S LEVERS OR OTHER CONVENIENT MEANS. LONG MEMO BY POST TONIGHT." ROYCE. (2) We also wired you this afternoon - "DEFINITE CAUSE OF JAGGERING IS FERODO EXTENDS ROUND TOO FAR FROM ANCHOR PIN ON ALL OUR BRAKES. CUT OFF THREE OR FOUR INCHES ON BOTH SHOES UNTIL IT DOES NOT REACH MORE THAN 120 DEGREES. YOU WILL THEN GET CONSISTENT AND SMOOTH ACTION BOTH WAYS. DRUMS MAY REQUIRE STIFFENING RINGS AS SUGGESTED. INCREASE OPERATING PULL. TRY EACH SHOE JOINTED TO FORM SERVO. TREAT FLOATING FULCRUM TYPE SAME. ALSO SERVO SHOES MAY BE TOO LONG AND THEREFORE GRABBING." ROYCE. (3) Experiments so far do not conclusively shew cause of jaggers. We know you see the result but that is not the cause. (4) We believe it has always been within the brake and is due to (a) flexibility of the drum or the diaphragm which carries it, or the carrier for the shoes, (b) this flexibility probably overhanging enabling the lapping shoe to alter its bedding so as to jam. (5) We think this is manifest by the fact that easing off the end of the lapping strap cures the fault. We should never depend upon the excessive wrapping to give us our braking power, but should increase the leverage as you would have to on a railway type brake. (6) If you remove the flexibility of any of the mountings naturally you considerably alter the conditions. (7) The standard springs should carry a proportionate braking effort smoothly, because they are (1) | ||