2 degrees on each side, as the possibility420 of over-lubrication of the bottom cylinders was feared if a regular radial construction were adopted. In order to overcome the unequal balance of this type, balance weights were fitted inside the crank 鏉窞淇濆仴鎸夋懇涓婇棬 case.
The final development of this three-cylinder radial was the 鈥榊鈥?type of engine, in which the cylinders were regularly disposed at 120 degrees apart; the bore was 4?1, stroke 4?7 inches, and the power developed was 30 brake horse-power at 1,300 revolutions per minute.
Critchley鈥檚 list of aero engines being constructed in 1910 shows twelve of the radial type, with powers of between 14 and 100 horse-power, and with from three to ten cylinders鈥攖his last is probably the greatest number of cylinders that can be successfully arranged 鏉窞鍊惧煄浼氭墍 in circular form. Of the twelve types of 1910, only two were water-cooled, and it is to be noted that these two ran at the slowest speeds
and had the lowest weight per horse-power of any.
The Anzani radial was considerably developed, special attention being paid to this type by its makers, and by 1914 the Anzani list comprised seven different sizes of air-cooled radials. Of these the largest had twenty cylinders, developing 200 brake horse-power鈥攊t was virtually a double radial鈥攁nd the smallest was the original 30 horse-power three-cylinder design. A six-cylinder model was formed by a combination of two groups of three cylinders each, acting upon a double-throw crankshaft; the two crank pins were set at 180 degrees to each other, and the cylinder groups were staggered by an amount equal to the distance between the centres of the crank 鏉窞榫欏嚖浜ゅ弸 pins. Ten-cylinder radial engines are made with two groups of five cylinders acting upon two crank pins set at 180 degrees to each421 other; the largest Anzani 鈥榯en鈥?developed 125 horse-power at 1,200 revolutions per minute, the ten cylinders being each 4?5 inches in bore with stroke of 5?9 inches, and the weight of the engine being 3?7 lbs. per horse-power. In the 200 horse-power Anzani radial the cylinders are arranged in four groups of five each, acting on two crank pins. The bore of the cylinders in this engine is the same as in the 鏉窞鍝佽尪鏈嶅姟 three-cylinder, but the stroke is increased to 5?5 inches. The rated power is developed at 1,300 revolutions per minute, and the engine complete weighs 3?4 lbs. per horse-power.
With this 200 horse-power Anzani, a petrol consumption of as low as 0?49 lbs. of fuel per brake horse-power per hour has 鏉窞娲楁荡鎸夋懇濂抽儙 been obtained, but the consumption of lubricating oil is compensatingly high, being up to one-fifth of the fuel used. The cylinders are set desax茅 with the crank shaft, and are of cast-iron, provided with radiating ribs for air-cooling; they are attached to the crank case by long bolts passing through bosses at the top of the cylinders, and connected to other bolts at right angles through the crank case. The tops of the cylinders are formed flat, and seats for the inlet and exhaust valves are formed on them. The pistons are cast-iron, 鏉窞姘寸（鏈嶅姟 fitted with ordinary cast-iron spring rings. An aluminiu