NO. 3 LANGLEY MEMOIB ON MECHANICAL FLIGHT 2 I 1 



cular manifold pipe on the port side, through two connections to tlie radiating 

 tubes at the front and rear, respectively, of the cross-frame. These radiating 

 tubes, which were provided with thin radiating ribs soldered to them, finally led 

 the cooled water to the tank situated in the extreme rear of the aviator's car, 

 a suitable pipe from the bottom of this tank being connected to the inlet side of 

 the centrifugal pump. The centrifugal pump was driven by means of a verti 

 cal shaft connected to the crank shaft through a set of bevel gears which drove 

 it at three times the speed of the engine. The bearings through which these 

 gears were connected were mounted on the port bed plate, and in order to al- 

 low for a certain amount of vibration between the engine and the pump this 

 vertical connecting shaft had a telescoping section connected through suitable 

 splines. 



The sparking apparatus comprised, first, a primary sparker similar to the 

 simplest form of such devices which have since come into common use, where a 

 cam driven by the engine co-acts with a pawl on the end of a spring, but in 

 this case, as this sparker was used for all five cylinders, the cam was driven at 

 a speed of two and one-half times that of the engine shaft, thus making and 

 breaking the primary circuit five times in each two revolutions of the engine. 

 Second, a spark coil, the primary terminals of which were connected to the pri- 

 mary sparker and to a set of dry batteries. Third, a secondary distributor con- 

 sisting of a disc carrying a contact brush and driven at a speed one-half that 

 of the engine, this brush being constantly connected through a contact ring to 

 one of the terminals of the high-tension side of the spark coil and running over 

 the face of a five-section commutator, each of the sections of which was con- 

 nected to a spark plug, the other high-tension terminal of the spark coil being, 

 of course, grounded on the engine frame. This sparking apparatus was first 

 constructed by using blocks of red fibre for insulation. After the engine was 

 completed and was being tested difficulties were met with in the sparking appa- 

 ratus which at that time appeared- inexplicable. After a great deal of annoy- 

 ance and loss of time it was finally discovered that the red fibre was not as good 

 an insulating medium as it was supposed to be, owing to the zinc oxide used 

 iu making it. In damp weather the sparking apparatus absolutely refused to 

 work, and it was found that the moisture in the air caused the zinc oxide in 

 the fibre to nullify its insulating qualities. This trouble, after being located, 

 was cured by substituting hard rubber for the red fibre. 



At the time when this engine was built, as well as earlier when the experi- 

 mental engine was built, it was impossible to procure any wire which had been 

 properly insulated to withstand the high voltages necessary for the connections 

 between the hi?h-tonsion side of the spark coil and the secondary distributor, 

 and from the secondary distributor to the spark plu.2-s in the cylinders. While 

 at this time this appears a very simple matter, yet the trouble experienced and 



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