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).
The features and benefits of the G. U. C. automatic infinitely variable choke carburettor.
| Identifier | ExFiles\Box 122\4\ scan0107 | |
| Date | 17th April 1936 guessed | |
| 8 ring is too weak and the centre too rich, the result being uneven and incomplete combustion resulting in engine vibration and petrol waste. Scientific research on carburation has been steadily building up data for many years, but carburettors fitted to petrol engines have advanced very little, for, whilst it has been known what is required from a perfect carburettor, until the production of the G.{Mr Griffiths - Chief Accountant / Mr Gnapp} U. C. no practical solutions had been discovered to overcome the defects. The G.{Mr Griffiths - Chief Accountant / Mr Gnapp} U. C. incorporates many special features to ensure even slow running and exceptionally economical idling, also compensating devices to give an absence of flat spots throughout the complete range. The result is a carburettor years in advance of any other on the market. The following graph shows the readings taken from tests run on an H.{Arthur M. Hanbury - Head Complaints} F.{Mr Friese} Car Tester and proves conclusively that the G.{Mr Griffiths - Chief Accountant / Mr Gnapp} U. C. does deliver a practically perfect mixture at all speeds, for the pints of petrol consumed per brake horse power is the ultimate proof of carburation. 5 EVERY OTHER CARBURETTOR has a choke tube of fixed dimension (See Fig. 1 āGā) which is, at best, a compromise between these essentials. THE G.{Mr Griffiths - Chief Accountant / Mr Gnapp} U. C. contains an automatic infinitely variable choke, and it will be seen from the detailed diagram (Fig. 2) that this has been obtained in a most ingenious and simple manner. The Patent Automatically Variable Choke Tube is housed in the main body of the G.{Mr Griffiths - Chief Accountant / Mr Gnapp} U. C., and is shaped, as regards its bore, as a venturi tube (A). Vertical grooves are formed in the walls of the tube (B), the axes of which taper outwards as they approach the large diameter of the choke tube. The grooves (B) carry steel balls (C) which are free to slide vertically, but are retained radially by three-quarters of their diameter. Thus, when the balls are at rest, the throat diameter of the choke is considerably restricted (D). As the throttle opens and the depression in the choke tube increases, the resulting rush of air lifts the balls so that they run up the grooves, thus progressively increasing the diameter of the choke. It will be appreciated that this action is entirely automatic, controlled by the demands of the engine. This variable choke tube | ||