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).
Options for a fan drive and blower on the Bensport project, comparing a Powerplus blower with a new design.
| Identifier | ExFiles\Box 140\1\ scan0005 | |
| Date | 13th August 1932 | |
| V 209 To R.{Sir Henry Royce} from E.{Mr Elliott - Chief Engineer} E.7/HP.13.8.32. c. Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} Hs.{Lord Ernest Hives - Chair} Hy.{Tom Haldenby - Plant Engineer} Pa.{Mr Paterson} re Bensport - Fan Drive and Blower. RECEIVED 15 AUG 1932 We have been over the question of the fan drive on Bensport, and there is no doubt that driving it from the camshaft is what we should like to do from every point of view, but unfortunately there are certain limitations imposed by the presence of the blower. If we were to use the No.11. Powerplus blower of 2250 cc. capacity, which is of small diameter, and great length it would enable us to mount a pulley of about 4" external diameter on the end of the camshaft. Our original design of short type of blower on the front end would not permit of a practical size of pulley. Mr. Eyston was very much in favour of this shorter blower, because he says they realise that their No.11. blower is too long to be practical, and entirely reliable, and gives trouble due to the rotor and blades twisting. Since the blades have to cross each other in the rotor it means that each individual blade is cut away in the centre up to slightly over half its length, and that beyond a certain ratio of length to diameter the overhanging wings of the blades are liable to set up excessive twist. This ratio of length to diameter is considered by the Powerplus Co. to have an optimum value of 1.5. We have accordingly set out a new blower in which the rotor has a length of 1.5 diameters, and we find this will permit of a fan pulley on the end of the camshaft, of a maximum diameter of 3.75, as shown on blueprint LeC.3166, attached. This pulley is only slightly less than the minimum prescribed diameter for the size of fan pulle belt proposed, but as the speed is not excessive we think the slightly increased bending on the fan belt probably would not matter. The belt drive as shown would be capable of transmitting 2 1/2 HP. at 2500 revs. of the camshaft. This may be enough for the fan we wish to use, but two belts could be used in parallel if found necessary. The side elevation on LeC.3166 shows the proportions | ||