Aviation Engines Part 21

The following instructions are given in the Curtiss Instruction Book for installing the OX-2 engine and preparing it for flights, and taken in connection with the very clear ill.u.s.tration presented no difficulty should be experienced in understanding the proper installation, and mounting of this power plant. The bearers or beds should be 2 inches wide by 3 inches deep, preferably of laminated hard wood, and placed 11-5/8 inches apart. They must be well braced. The six arms of the base of the motor are drilled for 3/8-inch bolts, and none but this size should he used.

1. _Anchoring the Motor._ Put the bolts in from the bottom, with a large washer under the head of each so the head cannot cut into the wood. On every bolt use a castellated nut and a cotter pin, or an ordinary nut and a lock washer, so the bolt will not work loose. Always set motor in place and fasten before attaching any auxiliary apparatus, such as carburetor, etc.

2. _Inspecting the Ignition-Switch Wires._ The wires leading from the ignition switch must be properly connected--one end to the motor body for ground, and the other end to the post on the breaker box of the magneto.

3. _Filling the Radiator._ Be sure that the water from the radiator fills the cylinder jackets. Pockets of air may remain in the cylinder jackets even though the radiator may appear full. Turn the motor over a few times by hand after filling the radiator, and then add more water if the radiator will take it. The air pockets, if allowed to remain, may cause overheating and develop serious trouble when the motor is running.

4. _Filling the Oil Reservoir._ Oil is admitted into the crank-case through the breather tube at the rear. It is well to strain all oil put into the crank-case. In filling the oil reservoir be sure to turn the handle on the oil sight-gauge till it is at right angles with the gauge.

The oil sight-gauge is on the side of the lower half of the crank-case.

Put in about 3 gallons of the best obtainable oil, Mobile B recommended.

It is important to remember that the very best oil is none too good.

5. _Oiling Exposed Moving Parts._ Oil all rocker-arm bearings before each flight. A little oil should be applied where the push rods pa.s.s through the stirrup straps.

6. _Filling the Gasoline Tanks._ Be certain that all connections in the gasoline system are tight.

7. _Turning on the Gasoline._ Open the c.o.c.k leading from the gasoline tank to the carburetor.

8. _Charging the Cylinders._ With the ignition switch OFF, prime the motor by squirting a little gasoline in each exhaust port and then turn the propeller backward two revolutions. Never open the exhaust valve by operating the rocker-arm by hand, as the push-rod is liable to come out of its socket in the cam follower and bend the rocker-arm when the motor turns over.

9. _Starting the Motor by Hand._ Always r.e.t.a.r.d the spark part way, to prevent back-firing, by pulling forward the wire attached to the breaker box. Failure to so r.e.t.a.r.d the spark in starting may result in serious injury to the operator. Turn on the ignition switch with throttle partly open; give a quick, strong pull down and outward on the starting crank or propeller. As soon as the motor is started advance the spark by releasing the r.e.t.a.r.d wire.

10. _Oil Circulation._ Let the motor run at low speed for a few minutes in order to establish oil circulation in all bearings. With all parts functioning properly, the throttle may be opened gradually for warming up before flight.

STANDARD S.A.E. ENGINE BED DIMENSIONS

The Society of Automotive Engineers have made efforts to standardize dimensions of bed timbers for supporting power plant in an aeroplane.

Owing to the great difference in length no standardization is thought possible in this regard. The dimensions recommended are as follows:

Distance between timbers 12 in. 14 in. 16 in.

Width of bed timbers 1-1/2 in. 1-3/4 in. 2 in.

Distance between centers of bolts 13-1/2 in. 15-3/4 in. 18 in.

It will be evident that if any standard of this nature were adopted by engine builders that the designers of fuselage could easily arrange their bed timbers to conform to these dimensions, whereas it would be difficult to have them adhere to any standard longitudinal dimensions which are much more easily varied in fuselages than the transverse dimensions are. It, however, should be possible to standardize the longitudinal positions of the holding down bolts as the engine designer would still be able to allow himself considerable s.p.a.ce fore-and-aft of the bolts.

[Ill.u.s.tration: Fig. 148.--End Elevation of Hall-Scott A-7 Four-Cylinder Motor, with Installation Dimensions.]

HALL-SCOTT ENGINE INSTALLATION

[Ill.u.s.tration: Fig. 149.--Plan and Side Elevation of Hall-Scott A-7 Four-Cylinder Airplane Engine, with Installation Dimensions.]

The very thorough manner in which installation diagrams are prepared by the leading engine makers leaves nothing to the imagination. The dimensions of the Hall-Scott four-cylinder airplane engine are given clearly in our inch measurements with the metric equivalents at Figs.

148 and 149, the former showing a vertical elevation while the latter has a plan view and side elevation. The installation of this engine in airplanes is clearly shown at Figs. 150 and 151, the former having the radiator installed at the front of the motor and having all exhaust pipes joined to one common discharge funnel, which deflects the gas over the top plane while the latter has the radiator placed vertically above the motor at the back end and has a direct exhaust gas discharge to the air.

[Ill.u.s.tration: Fig. 150.

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[Ill.u.s.tration: Fig. 151.

CENSORED]

The dimensions of the six-cylinder Hall-Scott motor which is known as the type A-5 125 H. P. are given at Fig. 152, which is an end sectional elevation, and at Fig. 153, which is a plan view. The dimensions are given both in inch sizes and the metric equivalents. The appearance of a Hall-Scott six-cylinder engine installed in a fuselage is given at Fig. 154, while a diagram showing the location of the engine and the various pipes leading to the auxiliary groups is outlined at Fig. 155.

The following instructions for installing the Hall-Scott power plant are reproduced from the instruction book issued by the maker.

Operating instructions which are given should enable any good mechanic to make a proper installation and to keep the engine in good running condition.

[Ill.u.s.tration: Fig. 152.

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FUEL SYSTEM INSTALLATION

[Ill.u.s.tration: Fig. 153.--Plan View of Hall-Scott Type A-5 125 Horse-Power Airplane Engine, Showing Installation Dimensions.]

Gasoline giving the best results with this equipment is as follows: Gravity 58-62 deg. Baume A. Initial boiling point--Richmond method--102 Fahr. Sulphur .014. Calorimetric bomb test 20610 B. T. U. per pound. If the gasoline tank is placed in the fuselage below the level of the carburetor, a hand pump must be used to maintain air pressure in gas tank to force the gasoline to the carburetor. After starting the engine the small auxiliary air pump upon the engine will maintain sufficient pressure. A-7a and A-5a engines are furnished with a new type auxiliary air pump. This should be frequently oiled and care taken so no grit or sand will enter which might lodge between the valve and its seat, which would make it fail to operate properly. An air relief valve is furnished with each engine. It should be screwed into the gas tank and properly regulated to maintain the pressure required. This is done by s.c.r.e.w.i.n.g the ratchet on top either up or down. If two tanks are used in a plane one should be installed in each tank. All air pump lines should be carefully gone over quite frequently to ascertain if they are tight.

Check valves have to be placed in these lines. In some cases the gasoline tank is placed above the engine, allowing it to drain by gravity to the carburetor. When using this system there should be a drop of not less than two feet from the lowest portion of the gasoline tank to the upper part of the carburetor float chamber. Even this height might not be sufficient to maintain the proper volume of gasoline to the carburetor at high speeds. Air pressure is advised upon all tanks to insure the proper supply of gasoline. When using gravity feed without air pressure be sure to vent the tank to allow circulation of air. If gravity tank is used and the engine runs satisfactorily at low speeds but cuts out at high speeds the trouble is undoubtedly due to insufficient height of the tank above the carburetor. The tank should be raised or air pressure system used.

[Ill.u.s.tration: Fig. 154.--Three-Quarter View of Hall-Scott Type A-5 125 Horse-Power Six-Cylinder Engine, with One of the Side Radiators Removed to Show Installation in Standard Fuselage.]

[Ill.u.s.tration: Fig. 155.--Diagram Showing Proper Installation of Hall-Scott Type A-5 125 Horse-Power Engine with Pressure Feed Fuel Supply System.]

IGNITION SWITCHES

Two "DIXIE" switches are furnished with each engine. Both of these should be installed in the pilot's seat, one controlling the R. H., and the other the L. H. magneto. By shorting either one or the other it can be quickly determined if both magnetos, with their respective spark-plugs, are working correctly. Care should be taken not to use spark-plugs having _special extensions or long protruding points_. Plugs giving best results are extremely small with short points.

WATER SYSTEMS

A temperature gauge should be installed in the water pipe, coming directly from the cylinder nearest the propeller (note ill.u.s.tration above). This instrument installed in the radiator cap has not always given satisfactory results. This is especially noticeable when the water in the radiator becomes low, not allowing it to touch the bulb on the moto-meter. For ordinary running, it should not indicate over 150 degrees Fahr. In climbing tests, however, a temperature of 160 degrees Fahr. can be maintained without any ill effects upon the engine. In case the engine becomes overheated, the indicator will register above 180 degrees Fahr., in which case it should be stopped immediately.

Overheating is most generally caused by r.e.t.a.r.ded spark, excessive carbon in the cylinders, insufficient lubrication, improperly timed valves, lack of water, clogging of water system in any way which would obstruct the free circulation of the water.

Overheating will cause the engine to knock, with possible damaging results. Suction pipes should be made out of thin tubing, and run within a quarter or an eighth of an inch of each other, so that when a hose is placed over the two, it will not be possible to suck together. This is often the case when a long rubber hose is used, which causes overheating. Radiators should be flushed out and cleaned thoroughly quite often. A dirty radiator may cause overheating.

When filling the radiator it is very important to remove the plug on top of the water pump until water appears. This is to avoid air pockets being formed in the circulating system, which might not only heat up the engine, but cause considerable damage. All water pump hoses and connections should be tightly taped and sh.e.l.lacked after the engine is properly installed in the plane. The greatest care should be taken when making engine installation _not_ to use smaller inside diameter hose connection than water pump suction end casting. One inch and a quarter inside diameter should be used on A-7 and A-5 motors, while nothing less than one inch and a half inside diameter hose or tubing on all A-7a and A-5a engines. It is further important to have light spun tubing, void of any sharp turns, leads from pump to radiator and cylinder water outlet to radiator. In other words, the water circulation through the engine must be as little restricted as possible. Be sure no light hose is used, that will often suck together when engine is started. To thoroughly drain the water from the entire system, open the drain c.o.c.k at the lowest side of the water pump.

PREPARATIONS TO START ENGINE

Always replenish gasoline tanks through a strainer which is clean. This strainer must catch all water and other impurities in the gasoline. Pour at least three gallons of fresh oil into the lower crank-case. Oil all rocker arms through oilers upon rocker arm housing caps. Be sure radiators are filled within one inch of the top.

After all the parts are oiled, and the tanks filled, the following must be looked after before starting: See if crank-shaft f.l.a.n.g.e is tight on shaft. See if propeller bolts are tight and evenly drawn up. See if propeller bolts are wired. See if propeller is trued up to within 1/8".

Every four days the magnetos should be oiled if the engine is in daily use.

Every month all cylinder hold-down nuts should be gone over to ascertain if they are tight. (Be sure to recotter nuts.)