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).
Calculations analyzing rotor movement, volume swept, and pressure based on indicator card data.
| Identifier | ExFiles\Box 152\1\ scan0074 | |
| Date | 12th January 1933 guessed | |
| - 5 - of the cards is 2.78". The movement of the lever arm corresponding to .21" on the card is therefore 4" x .21" / 2.78" = .302" The corresponding movement of the centre of pressure of the rotor is therefore .302" x 1.031" / 8 = .039" The volume swept by the rotor during this movement is therefore .039" x .813" x 1.5" = .0475 cu.in. Since the pressure attained at this point is 600 lbs/sq.in. the volume swept by the indicator piston up to the same point is 6 x .009 = .054 cu.in. It will be seen that the volume displaced by the indicator piston is approximately equal to that swept by the rotor during the increase of pressure at the beginning of the stroke. If, therefore, the indicator were absent, the pressure line would rise almost vertically at the beginning of the s troke to the maximum pressure. The same argument clearly applies to the fall of pressure at the end, and it may therefore be definitely stated that in the absence of the indicator the card under conditions of No's 371 & 390 would be almost perfectly rectangular. In the case of the high speed short stroke cards, consider No's 391 & 410. The average card length equals 2.035". A pressure of 600 lbs/sq.in. is reached at .50", i.e. at .50" / 2.035" = .245 of the stroke. The corresponding movement of the centre of pressure of the rotor is 1 x .245 x 1.031 / 8 = .032" The volume swept by the rotor up to this point is therefore .032" x .813" x 1.5" = .039 cu.in. The volume swept by the indicator piston up to 600 lbs/sq.in. would be 6 x .009 = .054 cu.in. It is thus seen again that the slope of the rising pressure line on the indicator card is accounted for approximately by the displacement of the indicator piston, and it may again be stated | ||