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).
Testing and failure modes of six different fans, with handwritten notes on materials and design.
| Identifier | ExFiles\Box 135\1\ scan0246 | |
| Date | 8th November 1938 guessed | |
| - 7 - Report on Fan Failures. First Fan. Life 10 hrs. 27 mins. plus approximately 3 hours previous running time. As this burst was so unexpected no attempt was made to look for fractures etc. prior to this point having been reached. The burst differed from the subsequent fan breakages in that the blade separated from the rest of the structure through the base of one of the steel spider legs. At the break the metal had a slightly crystalline appearance and was split in such a manner that it appeared to be laminated. The point of fracture was on one of the bends placed in the spider leg to give the blade the required angle of attack. Handwritten note (next to First Fan): Original Cadillac 5 blade fan Second Fan. The life of this fan was 5 hrs. 36 mins. In this case fractures were looked for on the spider but the failure eventually appeared on one blade as a diagonal break through the rivet at the tip of one of the spider legs. The blade was completely separated from the body, the others showed fractures in various stages of development. Handwritten note (next to Second Fan): PHM 5 blade original D.O shape blades. on Red material Third Fan. The previous spider was rebladed and returned to us for temporary use. After 2 hrs. 24 mins. running this fan was returned on receipt of the fourth fan. Fourth Fan. This fan had a life of 8 hrs. 12 mins. After 2 hrs. 37 mins. the black enamel was seen to be scaling off the blades. Examination while running, by means of the stroboscope, disclosed that the blade vibration was seemingly no worse than usual. After 4 hrs. 12 mins. one of the fan blades was showing a small fracture extending about 1/4" either side the spider tip rivet. The previous fan examination was carried out 25 mins. before this when no fracture was visible. The decision was made to return the fan when it was noticed that cracks were running in from the blade edges to meet those around the rivet. Handwritten note (next to Fourth Fan): PHM 5 Blade fan D O shape blades, on Red material, flange insert for blades radial Fifth Fan. After 21 hrs. 10 mins. running a fracture about 5/8" long was noticed on one blade. This eventually led to the blade tip parting through the usual tip rivet after a total fan life of 24 hrs. 7 mins. Handwritten note (next to Fifth Fan): PHM 5 blade fan original shape + material (Pure AL) Sixth Fan. This was returned after 4 hrs. 53 mins. with all the blades showing incipient fractures. After 3 hrs. 25 mins. one blade showed a crack 3/8" long. 30 mins, later all the blades had developed like fractures. Handwritten note (next to Sixth Fan): Paint 5 blade fan original shape blades + car. rad material. At certain times, when conditions are dark and consequently the "Strobotac" light is most efficient, it is possible to see the position of these cracks while the fan is running, especially when the blades are polished or enamelled bright black. Due to the blade vibration the crack itself is not visible but a depression can be seen which is centred at the spider tip rivet and extends outwards following the line of fracture. It appears as though the fan blade is blown clear of the spider except in the area surrounding the rivet end cracks, which is depressed. - continued - | ||