The le Rhone Motor
The Le Rhone motor is a radial revolving cylinder engine that has many of the principles which are incorporated in the Gnome but which are considered to be an improvement by many foreign aviators. Instead of having but one valve in the cylinder head, as the latest type “monosoupape” Gnome has, the Le Rhone has two valves, one for intake and one for exhaust in each cylinder. By an ingenious rocker arm and tappet rod arrangement it is possible to operate both valves with a single push rod. Inlet pipes communicate with the crank-case at one end and direct the fresh gas to the inlet valve cage at the other. Another peculiarity in the design is the method of holding the cylinders in place. Instead of having a vertically divided crank-case as the Gnome engine has and clamping both halves of the case around the cylinders, the crank-case of the Le Rhone engine is in the form of a cylinder having nine bosses provided with threaded openings into which the cylinders are screwed. A thread is provided at the base of each cylinder and when the cylinder has been screwed down the proper amount it is prevented from further rotation about its own axis by a substantial lock nut which screws down against the threaded boss on the crank-case. The external appearance of the Le Rhone type motor is clearly shown at Fig. 215, while the general features of construction are clearly outlined in the sectional views given at Figs. 216 and 217.
The two main peculiarities of this motor are the method of valve actuation by two large cams and the distinctive crank-shaft and connecting rod big end construction. The connecting rods are provided with “feet” or shoes on the end which fit into grooves lined with bearing metal which are machined into crank discs revolving on ball bearings and which are held together so that the connecting rod big ends are sandwiched between them by clamping screws. This construction is a modification of that used on the Anzani six-cylinder radial engine. There are three grooves machined in each crank disc and three connecting rod big ends run in each pair of grooves. The details of this construction can be readily ascertained by reference to explanatory diagrams at Figs. 218 and 219, A. Three of the rods which work in the groove nearest the crank-pin are provided with short shoes as shown at Fig. 219, B. The short shoes are used on the rods employed in cylinders number 1, 4, and 7. The set of connecting rods that work in the central grooves are provided with medium-length shoes and actuate the pistons in cylinders numbers 3, 6, and 9. The three rods that work in the outside grooves have still longer shoes and are employed in cylinders numbers 2, 5, and 8. The peculiar profile of the inlet and exhaust cam plates are shown at C, Fig. 219, while the construction of the wrist-pin, wrist-pin bushing and piston are clearly outlined at the sectional view at E. The method of valve actuation is clearly outlined at Fig. 220, which shows an end section through the cam case and also a partial side elevation showing one of the valve operating levers which is fulcrumed at a central point and which has a roller at one end bearing on one cam while the roller or cam follower at the other end bears on the other cam. The valve rocker arm actuating rod is, of course, operated by this simple lever and is attached to it in such a way that it can be pulled down to depress the inlet valve and pushed up to open the exhaust valve.
A carburetor of peculiar construction is employed in the Le Rhone engine, this being a very simple type as outlined at Fig. 221. It is attached to the threaded end of the hollow crank-shaft by a right and left coupling. The fuel is pumped to the spray nozzle, the opening in which is controlled by a fuel regulating needle having a long taper which is lifted out of the jet opening when the air-regulating slide is moved. The amount of fuel supplied the carburetor is controlled by a special needle valve fitting which combines a filter screen and which is shown at B. In regulating the speed of the Le Rhone engine, there are two possible means of controlling the mixture, one by altering the position of the air-regulating slide, which also works the metering needle in the jet, and the other by controlling the amount of fuel supplied to the spray nozzle through the special fitting provided for that purpose.
In considering the action of this engine one can refer to Fig. 222. The crank O. M. is fixed, while the cylinders can turn about the crank-shaft center O and the piston turns around the crank-pin M, because of the eccentricity of the centers of rotation the piston will reciprocate in the cylinders. This distance is at its maximum when the cylinder is above O and at a minimum when it is above M, and the difference between these two positions is equal to the stroke, which is twice the distance of the crank-throw O, M. The explosion pressure resolves itself into the force F exerted along the line of the connecting rod A, M, and also into a force N, which tends to make the cylinders rotate around point O in the direction of the arrow. An odd number of cylinders acting on one crank-pin is desirable to secure equally spaced explosions, as the basic action is the same as the Gnome engine.
The magneto is driven by a gear having 36 teeth attached to crank-case which meshes with 16-tooth pinion on armature. The magneto turns at 2.25 times crank-case speed. Two cams, one for inlet, one for exhaust, are mounted on a carrying member and act on nine rocker arms which are capable of giving a push-and-pull motion to the valve-actuating rocker-operating rods. A gear driven by the crank-case meshes with a larger member having internal teeth carried by the cam carrier. Each cam has five profiles and is mounted in staggered relation to the other. These give the nine fulcrumed levers the proper motion to open the inlet and exhaust valves at the proper time. The cams are driven at 45⁄50 or 9⁄10 of the motor speed. The cylinder dimensions and timing follows; the weight can be approximated by figuring 3 pounds per horse-power.
| 80 | H.P. | 105 | M/M bore | 4.20′′ | bore. |
| 140 | M/M stroke | 5.60′′ | stroke. | ||
| 110 | H.P. | 112 | M/M bore | 4.48′′ | bore. |
| 170 | M/M stroke | 6.80′′ | stroke. | ||
| Timing— | Intake valve opening, lag | 18° | ⎫ | 110 H.P. | 18° | ⎫ | 80 H.P. |
| Intake valve closing, lag | 35° | ⎮ | 35° | ⎮ | |||
| Exhaust valve opening, lead | 55° | ⎬ | 45° | ⎬ | |||
| Exhaust valve closing, lag | 5° | ⎮ | 5° | ⎮ | |||
| Ignition time advance | 26° | ⎭ | 26° | ⎭ |