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).
Optimal air gap size in a jump spark battery ignition distributor.
| Identifier | ExFiles\Box 179\2\ img213 | |
| Date | 1st February 1932 | |
| ORIGINAL K.{Mr Kilner} From Hs{Lord Ernest Hives - Chair}/Wst. c. to Ry. Wcr. c. to Sg.{Arthur F. Sidgreaves - MD} Da.{Bernard Day - Chassis Design} Hs{Lord Ernest Hives - Chair}/Wst.6/MA.S. 2. 32. X6118 R.R. JUMP SPARK BATTERY IGNITION DISTRIBUTOR. We have observed that the gap between the H.T. rotor blade tip and the sparking points in the distributor head is made very small. These fine limits necessitate an accurate grinding operation performed on each distributor head and rotor. The view is commonly held that this air gap must be kept down to only a few thousands of and inch. This refinement is quite unnecessary and it is indeed advantageous to have the gap as large as possible owing to the increased ability of the ignition coil to deal with adverse plug conditions. Making the gap however larger than about 2 mm. would begin to interfere with the main spark but gaps of the order of .010" to .015" are quite permissible especially as the energy out put is low in comparison with a magneto where such gaps are common. Hs{Lord Ernest Hives - Chair}/Wst. | ||