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).
Continued testing and comparison of different fan designs, including modifications and results.
| Identifier | ExFiles\Box 75\3\ scan0209 | |
| Date | 1st February 1925 | |
| Contd. -2- EFCl/T9.2.25. Curves similar to groups F and G of our last report are not given this time. Instead, there is however, sheet II of curves for three of the fans, in which the thrust produced and power required are given on a fan-speed base. The method of working still continues, and will continue to be exactly as described in the last report, as this is found to be very satisfactory. In each case the speed is taken up to the possible limit, but that possible limit may be determined by one of three things :- (1) Excessive belt slip in the case of a fan with a large ratio of power required to pulley size. (2) Excessive vibration due to slight unbalance, this being a little more possible on our arrangement than on the chassis mounting. (3) Available power output of driving motor, though this does not apply in the case of the 20 HP. fans, there being sufficient in all circumstances. The curves show a comparison between the results obtained on seven different fans. Fans arranged with other minor variations have been tested, but the curves given represent the more important results. On No.21 we started with a wide bladed fan. This was altered to No.22 by cutting off 1" of the leading edge, with some improvement in efficiency. Then by rounding off the leading edges and so producing No.23, a loss of efficiency occurred. No.24 was an attempt to make a fan somewhat similar to the Hispano, but this one did not come out so well | ||