NO. 3 LANGLEY MEMOIR ON MECHANICAL FLIGHT 215 



For the preservation of the equilibrium of the aerodrome, though the avi- 

 ator might assist by such slight movements as he was able to make in the lim 

 ited space of the aviator's car, the main reliance was upon the Penaud tail. 

 But, in the absence of any data for determining the effeel produced in passing 

 from the model to the large machine, it could not be certain thai calculations 

 based upon the balancing of the model would accurately determine the proper 

 balancing of the large machine. It was therefore decided to provide such at- 

 tachment for the Penaud tail that, while it would always have elastic connec- 

 tion with the main frame, yet its angle could be appreciably changed without 

 affecting in any way the degree of elasticity of this connection. After many 

 changes in plans for securing this result, it was finally decided to arrange it 

 in the manner shown in the drawings. Referring to the general plans in Plates 

 53 and 54, and to the details in Fig. 1 of Plate 56, the main stem of the Penaud 

 tail is seen to be connected by a pin to the horn (17), which is brazed to the clamp- 

 ing thimble, by which it is mounted on the vertical tube (16), suitably connected 

 and braced to the rear end of the midrod, the horn (17) being larger than the 

 stem of the tail and set at an angle to the vortical tube (16), the pin connec- 

 tion permitting the tail to swing up and down. The bridle (40), connected to 

 the center of the tail on its upper side, passes upward where it is connected 

 to the spring (41), the other end of which is connected to a single wire rope 

 (42), which passes over the pulley moulded on the top of the post (4:5), which 

 is guyed to the upper guy-post by the wire (44). The wire rope (42), after 

 passing over the pulley, is connected to the spring (45), around the two ends 

 of which it forms a loop, and from there it passes down to the plane of the main 

 frame and through suitable pulley blocks to the aviator's control wheel (50), 

 which is mounted on the starboard side of the main frame, convenient to the 

 aviator's right hand when he is facing forward. From this point the wire 

 rope passes through the various pulley blocks towards the rear of the machine, 

 and through the pulley block (46) mounted on the side and near the bottom of 

 the rear lower guy-post. At a short distance beyond this pulley it is connected 

 to a weaker spring (47), the other end of which is connected by a second bridle 

 (48) to the under side of the Penaud tail at its center. In order to prevent the 

 springs (41), (45) and (47), which furnish the elasticity for the Penaud tail 

 connection, from being strained beyond their elastic limit, either by a sudden 

 gust of wind or by the aviator attempting to move so large an area of surface 

 too suddenly, the wire rope (42) was made continuous around the springs, the 

 portion between the points where it was joined to the two ends of the springs 

 being made of such a length as to take the entire strain should the strain on 

 the cord become greater than sufficient to stretch the springs 50 per cent of 

 their original length. 



