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).
Modifications to a switch's recesses, bridge, and contact spring for endurance testing.
| Identifier | ExFiles\Box 168a\2\ img423 | |
| Date | 5th April 1939 | |
| 7c- KM/KC/MH.{M. Huckerby}5.4.39. OBSTRUCTION & SHAPE OF RECESS - Cont'd.{John DeLooze - Company Secretary} The gradient was reduced by countersinking and thus widening the top of the recess. This was done with a twist-drill ground to the shape of a shallow V.{VIENNA} It was eventually found desirable to widen the mouth of the recess to within about .015" to .020" of the edge of the segment face, and at the same time retain the .050" depth of the recess. This provided the easiest gradient within the size of the segment, free from all obstructions in the form of edges, and was obtained finally by a flat V-shaped drill, ground to an angle of about 135°. LENGTH OF BRIDGE BETWEEN RECESSES. To make the operation more decisive it was necessary to shorten the bridge or length of flat surface between recesses. This had the effect of reducing the time that the contacts remained poised, between leaving one position and dropping into the next. This was automatically done in widening the mouths of the recesses.. CONTACT SPRING PRESSURE. The pressure on the contacts, at rest, supplied by the original spring was about 5 lbs. This was thought to be sufficient but it was considered that a higher-rated spring giving a more rapid increase in pressure with movement of the contacts would result in a more snappy operation. A spring with a rating of 18 lbs. per inch, as compared with 6 lbs. per inch, was subsequently decided upon. When revised in the foregoing respects, together with corrected engraving and accurate location of the contact segments in the base, we anticipate that the switch will be sufficiently advanced for endurance testing. KM/KC. | ||