Chapter V: E. Johnson steam driven hydroaëroplane Opp. 120 (2)

One of the most notable results of the National Model Aëroplane Competition of 1915 was the establishing of a new world’s record for flying boats. Considering that the model flying boat is a difficult type of model to construct and fly, the establishing of this new world record of 43 seconds is remarkable. Credit for this performance is due Mr. Robert La Tour of the Pacific Northwest Model Aëro Club, who designed, constructed and flew the model flying boat which is herewith described and illustrated. Diagram 13.

The frame is made of laminated spruce 40″ in length, made of two strips glued together. They are ³⁄₈″ × ¹⁄₈″ at the center tapering to ³⁄₁₆″ × ¹⁄₈″ at the ends. The cross braces are of split bamboo and are fastened to the frame side members by bringing them to a wedge at the ends and then inserting them into slots in the sides of the frame side members and are finally drilled and bound to the latter. The rear brace is of streamlined spruce ¹⁄₄″ × ¹⁄₈″; this butts against the frame side members and is bound to them. The propeller accommodations are made of brass.

The propellers are 10″ in diameter with a 19″ pitch. These are carved from a block of Alaska cedar 1¹⁄₄″ wide by ³⁄₄″ thick. Of course the propellers may also be made from white pine. To turn the propellers 15 strands of ¹⁄₈″ flat rubber are used.

Bamboo about ¹⁄₁₆″ square is used to obtain the outline of the wings. The main wing has a span of 33″ with a chord of 5¹⁄₂″. Split bamboo is used for the making of the 9 ribs. The wing spar or brace is of spruce ³⁄₁₆″ × ¹⁄₈″ and is fastened below the ribs as illustrated in diagram 13. The elevator is constructed in like manner but has a span of only 17″ × 4³⁄₄″ and has only 5 ribs. A block ³⁄₄″ high is used for elevation. Both wings have a camber of ¹⁄₂″ and are covered on the upper side with silk doped with a special varnish and a few coats of white shellac.

The boat is 20″ long, 3″ in width and shaped as shown. The slip is ¹⁄₂″ deep and is located 7″ from the bow. The rear end is brought down steeply to avoid the drag of the water on this point when the boat is leaving the surface of the water. Spruce ³⁄₆₄ths of an inch thick is used for the making of the sides, but the cross bracing is of slightly heavier material, there being six braces used throughout. The rear brace is much heavier in order to withstand the pull of the covering and to receive the ends of the wire connections. The outriggers or balancing pontoons are constructed of the same material as that of the boat and are held together by a spruce beam 18″ long, ¹⁄₂″ wide by ³⁄₁₆″ thick, streamlined. This beam is fastened to the boat by means of three brads to permit changing if necessary. The lower edges of the outriggers should clear the water about ¹⁄₈″ before the steps on the boat leave the water. The boat and outriggers are covered with silk, shrunk with a special solution and then coated several times with white shellac. It is a good plan to shellac the interior walls of the boat and pontoons before covering to prevent them from losing their form by becoming soft from the influence of water in the case of a puncture.

The boat is connected to the frame at its front by two steel wires, their ends being inserted into the cross members of the boat, and then brought up along the sides, crossed and then bound to the frame. A similar pair of connecting wires are used to connect the rear end of the boat to the rear end of the frame. A U-shaped wire is bound to the outrigger beam and frame. A single diagonal strip of bamboo is also fastened to the outrigger beam with a brad, its upper end being bound to the cross bracing of the frame, making a very solid connection.

Under ideal weather conditions this model will fly on 12 strands of rubber with the possibility of a better duration than has been made. But, however, with 15 strands the model will rise at every attempt. More rubber, however, causes the bow of the boat to nose under and to accommodate this increase of power the boat should be lengthened.

THE COOK NO. 42 WORLD
RECORD MODEL

(TWIN PROPELLER HYDROAËROPLANE, 100.6
SECONDS RISING FROM WATER)

During the National Model Aëroplane Competition of 1915 held under the auspices of the Aëro Club of America, a number of new world records were established, one of which was for twin propeller hydroaëroplanes. The credit for this record is due Mr. Ellis C. Cook of the Illinois Model Aëro Club, who succeeded in getting his model hydroaëroplane—which by the way is a rather difficult type of model to operate—to rise from the water and remain in the air for a duration of 100.6 seconds. This model is of the common A frame design with the floats or pontoons arranged in the familiar fashion, two forward and one aft. The model is fairly light, weighing, when complete, 3.33 ounces, ¹⁄₂ ounce of which is made up in rubber strands for motive power. Diagram 14.

The frame is made of two sticks of white pine for side members, each member measuring 38¹⁄₄″ in length, ⁵⁄₁₆″ in depth, by ¹⁄₈″ in width. These are cut to taper toward the ends where they are only ¹⁄₈″ in width by ³⁄₁₆″ in depth in the front and rear respectively. Three “X” strips of streamlined bamboo measuring ³⁄₁₆″ in width by ³⁄₆₄ths of an inch in depth, are used for bracing the frame between the front and rear and are arranged as shown in diagram 14. The propeller bearings are of small streamlined forgings of light weight, and are bound to the rear end of each side member first by gluing, then binding around with thread. The front hook is made of No. 16 piano wire and is bound to the frame as shown in diagram 14. The chassis which holds the floats or pontoons is made of ³⁄₃₂″ bamboo bent to shape and bound to the frame members. By the use of rubber strands the floats are attached to the chassis; the forward ones being attached so that angle may be adjusted.

The main wing has a span of 36″ and a chord of 5″ and is constructed of two white pine beams each 39″ long, with bamboo wing tips. The ribs, seven in number, are also made of bamboo and are spaced along the edges of the wing at a distance of 4¹⁄₂″ apart. The “elevator” or front wing has a span of 14″ and a chord of 3¹⁄₄″, the framework of which is made entirely of bamboo. The entering edge of this wing is given a slightly greater dihedral so that the angle of incidence at the tips is greater than at the center. By this method the added incidence in the front wing is obtained. By the use of rubber bands both wings are attached to the frame.

The two forward floats are spaced eight inches apart and are of the stepped type, the step being 3¹⁄₂″ from the front and has a depth of ¹⁄₈″. These two floats are separated by two bamboo strips as shown in the diagram, which are tied to the rounded portion of the under carriage by small rubber bands. By the sliding of these strips back and forth the necessary angle of the floats may be obtained to suit conditions. The floats are built up with two thin pieces of white pine for sides, separated by small pieces of wood about one-half the size of a match in cross section. Chiffon veiling which is used for the covering of the wings, is also used for the covering of the floats, after which it is covered with a special preparation to render both the wings and the floats air and water-tight.

The two ten-inch propellers with which the model is fitted have a theoretical pitch of twelve and one-half inches. The propellers are carved from blanks one-half inch thick, the blades of the completed propellers having a maximum width of one inch at a radius of three inches. The propeller shafts are made from No. 16 piano wire and have small washers for bearings. Each propeller is driven by three strands of ¹⁄₄″ strip elastic. The rubber is given 1700 to 1750 turns and revolves the propellers at 1150–1200 r.p.m., when the model is in flight.

The model usually runs over the surface of the water for a distance of from two to three feet before it rises, after which it climbs at a very steep angle to the necessary altitude. The model seems, when in flight, to be slightly overpowered but this is misleading. The rubbers usually unwind in from 85 to 90 seconds. On four out of six flights this model has made a duration of between 98 and 100 seconds which is rather unusual for a model of this type.

THE RUDY FUNK DURATION MODEL

Of the many different types of duration models that have made their appearance during the year of 1915 perhaps the model described herewith, constructed and flown by Mr. Rudolph Funk, of the Aëro Science Club, was one of the most successful. Unlike most models the propellers of this model are bent and not cut. This model made its appearance during the latter part of 1915, on several occasions having flown for over 100 seconds duration. Diagram 15.

While retaining the important characteristics of his standard model, slight changes have been made. Instead of the usual wire for the construction of the frame of the wings, bamboo is used in its place for lightness and strength. The wing frames are single surfaced, China silk being used for covering. The “dope” which is used to render the silk airtight is made by dissolving celluloid in banana oil. This in turn is applied to the silk with a soft brush.

The camber of the main wing is ³⁄₄″ at the center, with a slight reduction towards the negative tips; it also has a dihedral angle of 2 degrees. The main beam, which is secured to the under side of the frame for rigidness, is of spruce 1″ by ⁵⁄₆₄″, tapering to ³⁄₄″ × ⁵⁄₆₄″. The ribs for the main wing and small wing or “elevator” are cut from solid pieces of bamboo ³⁄₁₆″ thick by ¹⁄₄″ wide. These pieces of bamboo are first bent to the proper camber and are then cut into strips each ¹⁄₁₆″ wide. The ribs are next tapered to a V at the bottom, toward the trailing edge, as shown in diagram 15, and also toward the entering edge. To accommodate the entering and trailing edges of the frame, each rib is slit slightly at both ends. Both edges of the frame are then inserted in the slots at the ends of the ribs and bound around with silk thread.

The frame is composed of two sticks of silver spruce 38″ in length, ⁵⁄₁₆″ × ³⁄₁₆″, tapering to ¹⁄₄″ × ⁵⁄₃₂″, held apart by a streamline bamboo cross brace in the center. An additional brace of bamboo is securely fastened across the frame toward the front. The propeller brace consists of a streamline-cut piece of bamboo 12¹⁄₂″ in length by ³⁄₈″ in width at the center, tapering to ¹⁄₄″ toward the ends. The propeller brace is inserted in slots cut in the rear ends of the frame members, then bound and glued.

The propellers are bent from birch veneer, the bending being done over an alcohol flame as illustrated in diagram 15. But first of all the blades are cut to shape, sandpapered and finished before they are bent. As shown in the drawing a slot is filed in the hub of each blade to enable the propeller shaft to pass through when both have been glued together. The blades are then glued and bound together, first by placing a piece of wire in the slots to insure their being centered and also to prevent their being filled with glue. After this has been done each propeller is given three coats of the same dope as is used on the wings.

The propeller bearings are turned out of ¹⁄₃₂″ bronze tubing, the length of each bearing being ¹⁄₂″. Steel washers are slipped over the propeller shaft, between the bearing and propeller to insure smooth running. The propeller shafts are made from steel hatpins which are heated at both ends, one end of which is bent into a loop to receive the rubber strands, the other end being bent around the hub of the propeller to prevent the shaft from slipping during the unwinding of the rubbers. Two strips of brass, each ¹⁄₄″ × 2″, are bent around the one-half inch bearing and soldered. The brass strips are then glued and bound onto the ends of the propeller brace as shown in diagram 15.

THE ALSON H. WHEELER WORLD RECORD MODEL

(TWIN PUSHER BIPLANE 143 SEC. DURATION
RISING FROM THE GROUND)

Since the beginning of model flying very little attention has been paid to the model biplane. Practically all records are held by model aëroplanes of the monoplane type. With this fact in view, the record established by Mr. Wheeler with his Twin Pusher Biplane is extraordinary, in so far as it surpasses many of the monoplane records. This model is a very slow flyer, and has excellent gliding ability. At the time when this model flew and broke the world’s record, the greater portion of the flight consisted of a beautiful glide of 86 seconds’ duration, after the power gave out, making it possible for the model to remain in the air for a duration of 143 seconds.

The frame consists of two I-beams, each 48″ in length, running parallel, and spaced by cross pieces, each piece 11¹⁄₂″ long. The bearing blocks used made it possible for the propellers to clear by one-half inch. Two 12″ expanding pitch racing propellers are used and these are mounted on ball bearing shafts. The main upper plane has a span of 34″ with a chord of 5″, the lower plane being 26″ by 5″. The elevator consists of two planes, each measuring 14″ by 5″. Cork wheels are used, each being one inch in diameter. For motive power one-eighth inch flat rubber is used, this being coated with glycerine to prevent sticking.

A MODEL WARPLANE

The model shown in the accompanying photograph was constructed by Master R. O’Neill, of Montreal, Canada. The machine was designed after one of the leading warplanes now in active service abroad and in carrying out the entire features he did not fail to include the identification marks which are of utmost importance in the war zone.

The dimensions of the model are as follows: Length of fuselage, 23″; span of top wing, 33″; span of lower wing, 29″, both having a chord of 7″. Motive power is derived from two ¹⁄₈ inch square elastic strands which operate a multiple gear to which is attached a 10″ propeller.

In coloring the model a dull aluminum was selected. Complete the model weighs 12 ounces. Perhaps the most interesting feature of the model is the ability to change it to a monoplane by the removal of the upper wing after which the lower wing is raised to the sockets in the fuselage which were especially arranged for that particular purpose.

A SIMPLE COMPRESSED AIR ENGINE

During the past few years model flyers in America have shown a tendency toward the adoption of compressed air engines for use in connection with model aëroplanes. Hitherto, England has been the home of the compressed air engine, where a great deal of experimenting has been carried on, to a considerable degree of success. Flights of over 40 seconds have been made with models in which compressed air power plants were used. But, however, the desire on the part of a large majority of model flyers in America to build scientific models, that is, models more closely resembling large machines, has made it necessary to find a more suitable means of propulsion; rubber strands being unsatisfactory for such purposes. Many different types of compressed air engines have made their appearance during the past few years, among which the two cylinder opposed type is very favorably looked upon, because it is perhaps one of the easiest to construct.

To make a simple two cylinder opposed compressed air power plant, as illustrated in Figure 1 of diagram 16, it is not necessary that the builder be in possession of a machine shop. A file, drill, small gas blow torch and a small vise comprise the principal tools for the making of the engine.

The first things needed in the making of this engine are cylinders. For the making of the cylinders two fishing rod ferrules, known as female ferrules, are required. And for the heads of the cylinders, two male ferrules are required. Such ferrules can be secured at most any sporting goods store. The female ferrules should be filed down to a length of 2″, cut down on one side a distance of ³⁄₄ of the diameter, then cut in from the end as shown in Figure 7. When this has been done the two male ferrules should be cut off a distance of ¹⁄₈″ from the top as shown in Figure 7-a, to serve as heads for the cylinders.

A hole ¹⁄₈″ in diameter should be drilled in the center of each head so as to enable the connecting of the intake pipes. By the use of soft wire solder the heads should be soldered into the ends of the cylinders as shown in Figure 1-d.

The pistons should now be made; for this purpose two additional male ferrules are required. These should be made to operate freely within the cylinders by twisting them in a rag which has been saturated with oil and upon which has been shaken fine powdered emery. When they have been made to operate freely they should be cut down one-half inch from the closed end as shown in Figure 5-a. For the connecting rods, 2 pieces of brass tubing, each ¹⁄₈″ in diameter by 1¹⁄₄″ long, are required, and, as illustrated in Figure 6, should be flattened out at either end and through each end a hole ³⁄₃₂″ in diameter should be drilled. For the connecting of the piston rods to the pistons, studs are required, and these should be cut from a piece of brass rod ¹⁄₄″ in diameter by ¹⁄₂″ in length. As two studs are necessary, one for each piston, this piece should be cut in half, after which each piece should be filed in at one end deep enough to receive the end of the connecting rod. Before soldering the studs to the heads of the pistons, however, the connecting rods should be joined to the studs by the use of a steel pin which is passed through the stud and connecting rod, after which the ends of the pin are flattened, to keep it in position as shown in Figure 5-a.

For the outside valve mechanism and also to serve in the capacity as a bearing for the crankshaft, a piece of brass tubing ¹⁄₄″ in diameter by 1¹⁄₂″ long is required. Into this should be drilled three holes, each ¹⁄₈″ in diameter, and each ¹⁄₂″ apart as shown in Figure 4. Next, for the valve shaft and also propeller accommodation, secure a piece of ³⁄₁₆″ drill rod 2″ long. On the left hand side of the valve shaft, as shown in Figure 3, a cut ¹⁄₃₂″ deep by ¹⁄₂″ in length is made 1″ from the end. Another cut of the same dimensions is made on the right side only; this cut is made at a distance of ³⁄₈″ from the stud end.

As shown in Figure 1-f, the crank throw consists of a flat piece of steel, ³⁄₃₂″ thick, ³⁄₈″ in length by ¹⁄₄″ in width. At each end of the crank throw a hole ³⁄₁₆″ in diameter should be drilled, the holes to be one-half inch apart. Into one hole a piece of steel drill rod ³⁄₃₂″ in diameter by ¹⁄₄″ long is soldered, to which the connecting rods are mounted, as shown in Figure 1-f. Into the other hole the stud end of the crank throw is soldered.

Before making the tank it is most desirable to assemble the parts of the engine, and this may be done by first fitting the pistons into the cylinders as shown in Figure 1-b, after which the cylinders should be lapped one over the other and soldered as shown in Figure 1-a. When this has been done a hole one-fourth of an inch in diameter should be drilled half way between the ends of the cylinders, and into this hole should be soldered one end of the valve casing shown in Figure 4. For the inlet pipes as shown in Figure 1-c secure two pieces of ¹⁄₈″ brass tubing and after heating until soft, bend both to a shape similar to that shown in Figure 1-c. When this has been done solder one end to the end of the cylinder and the other in the second hole of the valve shaft casing. The valve shaft should now be inserted in the valve shaft casing and the connecting rods sprung onto the crank throw as shown in Figure 1-d. To loosen up the parts of the engine which have just been assembled it should be filled with oil and by tightly holding the crankshaft in the jaws of a drill the engine can be worked for a few minutes.

The tank is made from a sheet of brass or copper foil 15″ long by ¹⁄₁₀₀₀″ thick. This is made in the form of a cylinder, the edges of which are soldered together as shown in Figure 2. Sometimes this seam is riveted every one-half inch to increase its strength, but in most cases solder is all that is required to hold the edges together. For the caps, or ends, the tops of two small oil cans are used, each can measuring 2¹⁄₂″ in diameter. To complete the caps two discs of metal should be soldered over the ends of the cans where formerly the spouts were inserted, the bottoms of the cans having been removed. The bottom edges of the cans should be soldered to the ends of the tank as shown in Figure 2. Into one end of the completed tank a hole large enough to receive an ordinary bicycle air valve should be drilled. Figure 2. Another hole is drilled into the other end of the tank, into which is soldered a small gas cock to act as a valve. Figure 2. This should be filed down where necessary, to eliminate unnecessary weight. To connect the tank with the engine, a piece of ¹⁄₈″ brass tubing 3″ long is required, the ends of which are soldered into the holes in the valve shaft casing nearest the cylinders, as shown in Figure 1-ee. As shown in Figure 1-ee, a hole ¹⁄₈″ in diameter is drilled in one side of this piece, but not through, in the end nearest the tank. Another piece of brass tubing ¹⁄₈″ in diameter is required to connect the tank with the engine, one end of which is soldered to the cock in the tank, the other in the hole in the pipe which leads from the engine to the tank, illustrated in Figure 1-ee, thus completing the engine.

In conclusion it is suggested that the builder exercise careful judgment in both the making and assembling of the different parts of the engine in order to avoid unnecessary trouble and secure satisfactory results. After having constructed an engine as has just been described, the constructor may find it to his desire to construct a different type of engine for experimental purposes. The constructor therefore may find the descriptions of satisfactory compressed air engines in the following paragraphs of suggestive value.

COMPRESSED AIR DRIVEN MODELS

The development of the compressed air engine has given an added impetus to model making, necessitating more scientific experimenting and developing the art of model flying along lines of greater value to those who may eventually take up the work of building our future air fleets.

THE DART COMPRESSED AIR DRIVEN MODEL

In the accompanying illustration is shown a model aëroplane of monoplane type driven by a three-cylinder rotary engine which was constructed by Edward Willard Dart of South Norwalk, Connecticut.

The engine was constructed after several months of patient labor. Careful judgment was exercised in the drafting of the plane and likewise in the assembling of the engine for it is absolutely essential that all parts be properly fitted as to enable the engine to run smoothly. In designing the wings every detail was taken into consideration to insure good flying.

The main wing has a spread of 58″ and 7″ in chord. The elevator measures 23″ in spread and 6″ in chord. In the construction of both wings bamboo ribs are used, the frames being covered over with China silk and coated with celluloid solution. The main wing is made in two sections to facilitate quick adjustment to the fuselage.

THE MCMAHON COMPRESSED AIR DRIVEN MONOPLANE

One of the latest developments in the field of model flying is the McMahon compressed air driven monoplane. This model was built to be used as either a tractor or pusher, but in view of its ability to balance more easily as a pusher most of the experiments have been carried out on this machine as a pusher. The machine in itself is simple and inexpensive to construct, the chief portion of the expense being involved in the making of the engine. By using the machine as a pusher a great deal of protection is afforded both the propeller and engine, and this protection helps to avoid damaging the propeller or engine, which would mean an additional expenditure for repairs, thus minimizing the cost of flying the model.

The frame has been made to accommodate both the tank and engine, and this is done by using two 30″ strips of spruce, each ¹⁄₄″ wide by ³⁄₈″ deep, laid side by side, a distance of three inches apart, up to within 10″ of the front, as shown in the accompanying photograph. No braces are used on the frame, as the tank, when securely fastened between the frame, acts in that capacity.

The wings are made in two sections, each section measuring 24″ in span by 8″ in chord, consisting of two main spars, ³⁄₁₆″ in diameter, one for the entering edge and one for the trailing edge. To these edges, at a distance of three inches apart, are attached bamboo ribs, 18 in all, each measuring 8″ in length by ¹⁄₈″ in width by ¹⁄₁₆″ thick. The wings are round at the tips, and have a camber of approximately one-half inch, but they are not set at an angle of incidence. Light China silk is used for covering and after being glued over the top of the wing frame is given two coats of dope to shrink and fill the pores of the fabric. A good “dope” for the purpose can be made from celluloid dissolved in banana oil. The wing sections are attached to the frame and braced by light wire. The forward wing or “elevator” is made in the same manner as the main wing, but should measure only 18″ × 3″. Instead of being made in two sections as the main wing, the forward wing is made in one piece.

The chassis is made by forming two V struts from strong steel wire sufficiently large enough so that when they are attached to the frame of the model the forward part will be 9″ above the ground. One V strut is securely fastened to either side of the frame, at a distance of 8″ from the front. A 7″ axle is fastened to the ends of these struts. On the axle are mounted two light wheels, each about 2″ in diameter. The chassis is braced by light piano wire.

The rear skid is made in the same manner as the forward skid, only that the ends of the struts are brought together and a wheel 1 inch in diameter is mounted at the bottom ends by means of a short axle. The struts are not more than 7¹⁄₂″ long, thus allowing a slight angle to the machine when it is resting upon the ground.

The machine complete does not weigh over 7 ounces. The power plant used in connection with this model is of the two cylinder opposed engine type, with tank such as has just been described in the foregoing chapter.

The tank is mounted in the frame by drilling a ¹⁄₁₆″ hole through either end of the tank, through which a drill rod of this diameter can be inserted. About ³⁄₄ths of the drill rod should extend out on each side of the tank, to permit the fastening of the tank to the frame side members. This method of mounting the tank serves two purposes to a satisfactory degree. First, it permits secure fastening; second, as the rods are passed through the side and cap of the tank they help materially in preventing the caps from being blown off in the event of excessive pressure.

THE MCMAHON COMPRESSED AIR DRIVEN BIPLANE

In the McMahon model we find a very satisfactory type of compressed air driven model. On several occasions this model has made flights of over 200 feet with a duration of between 10 and 15 seconds, and the indications are that by the use of a more powerful engine the model can be made to fly a greater distance, with a corresponding increase of duration. The engine used in connection with the model is of the two cylinder opposed type, such as described in the foregoing paragraphs. The tank, however, is somewhat different in design from that just described, it having been made of 28 gauge sheet bronze, riveted every one-half inch. The two long bolts that hold the steel caps on either end of the tank also serve as attachments for the spars that hold the tank to the engine bed, as shown in diagram 17. The tank has been satisfactorily charged to a pressure of 200 lbs. per square inch, but only a pressure of 150 lbs. is necessary to operate the engine. The tank measures 10″ in length by 3″ in diameter and weighs 7 ounces.

The wings of this machine are single surfaced and covered with fiber paper. The top wing measures 42″ in span by 6″ in chord. The lower wing is 24″ by 6″. The wings have a total surface of 396 square inches and are built up of two ³⁄₁₆″ dowel sticks, flattened to streamline shape. Only two sets of uprights separate the wings, thus adding to the streamline appearance of the machine.

Both tail and rudder are double surfaced and are built entirely of bamboo for lightness, the tail being made in the form of a half circle measuring 12″ by 8″. Steel wire is used on the construction of the landing chassis, the chassis being so designed as to render it capable of withstanding the most violent shock that it may possibly receive in landing. The propeller used in connection with the model is 14″ in diameter and has an approximate pitch of 18″.

COMPRESSED AIR ENGINES

THE WISE COMPRESSED AIR ENGINE

Although of peculiar construction, the Wise rotary compressed air engine offers a very interesting design from a viewpoint of ingenuity. This engine embodies a number of novel features not hitherto employed in the construction of compressed air engines, and in view of the fact that the majority of compressed air engines are made on the principle of the opposed type, this engine suggests many possibilities for the rotary type engine.

The engine consists of five cylinders and weighs four ounces, including the propeller and mounting frame. On a pressure of 15 lbs. the engine will revolve at a speed of 1000 r.p.m. The connecting rods are fastened to the crankshaft by means of segments and are held by two rings, making it possible to remove any one piston without disturbing the others. This is done by simply removing a nut and one ring. The crank case is made from seamless brass tubing, into which the cylinders are brazed. The valve cage and cylinder heads are also turned separately and brazed. One ring only is used in connection with the pistons. The cylinders have a bore of ¹¹⁄₃₂″, with a piston stroke of ⁷⁄₁₆″. In view of the fact that pull rods show a greater tendency to overcome centrifugal force, they are used instead of push rods to operate the valves. The crankshaft has but one post, which is uncovered in turn by each inlet pipe as the engine revolves. The “overhang” method is used to mount this engine to the model. With the exception of the valve springs, the entire engine, including the mounting frame and tank, is made of brass.

THE SCHOBER-FUNK COMPRESSED AIR ENGINE

Two of the most enthusiastic advocates of the compressed air engine for use in model aëroplanes are Messrs. Frank Schober and Rudolph Funk, both members of the Aëro Science Club. For a number of months both these gentlemen have experimented with compressed air engines of various designs, until they finally produced what is perhaps one of the most satisfactory rotary engines now in use, from a standpoint of simplicity and results.

As can be seen from the accompanying illustration, this little engine is remarkably simple in appearance. The engine complete, with equipment, weighs at the most but 14 ounces. The cylinders, three in all, are stamped from brass shells for strength and lightness. The pistons are made from ebony fiber. The cylinders have a bore of ⁵⁄₈″, with a piston stroke of ¹⁄₂″. The crank case is built up from a small piece of brass tubing and is drilled out for lightness. The crankshaft is hollow, and is supported at the rear by a special bearing which acts as a rotary valve, admitting the intake through the crankshaft and permitting the exhaust to escape through a specially constructed bearing.

The tank is constructed of 30 gauge sheet bronze, wire wound, and fitted at the ends with spun brass caps. The actual weight of the engine alone is 2¹⁄₂ ounces, the tank and fittings weighing 11¹⁄₂ ounces, making the total weight of the complete power plant 14 ounces.

THE SCHOBER FOUR CYLINDER OPPOSED ENGINE

Another interesting type of compressed air engine that has been developed in America is the Schober four cylinder opposed engine. While this engine is different in appearance from most compressed air engines, it has been made to work satisfactorily and is consistent with the same high class construction that is displayed in most all of Mr. Schober’s engines. The accompanying diagram 18 illustrates the method of operation of the four cylinder engine.

The crank case is constructed from four pieces of 24 gauge spring brass, substantially connected in the form of a rectangle, the top and bottom being left open. The front and rear walls have flanges which engage the inside of the side walls and are secured thereto by four small screws on each side, thereby making it an easy matter to take the crank case apart.

The four cylinders are made from drawn brass shells and have a bore of ¹⁄₂″ and stroke of ¹⁄₂″. The pistons are made of solid red fiber. The two-throw crankshaft is built up of steel with brass webs. The bearings are of steel. The valves, being overhead, are driven by a gear mounted at the end of the crankshaft, the gear driving the valve shaft by means of a gear on that shaft, with which the crankshaft gear meshes. The valve arrangement, as shown in diagram 18, consists of four recesses cut into the valve shaft, two of which allow the air to pass from the inlet pipes, which lead into the valve chamber at the center of same, to two of the cylinders at once, while the other two recesses allow the exhaust to pass from openings in the sides of the valve chamber.

The cylinders are secured to the side plates of the crank case so that when those side plates are removed, the cylinders are removed with them. The pipes are detachable at their centers; small pipes running to the heads of the cylinders extending into the larger pipes which run to the valve chamber. This arrangement is shown in the end view of the engine. A 17″ propeller is used in connection with this engine.

GASOLINE ENGINES

THE JOPSON 1 H. P. GASOLINE ENGINE
FOR MODEL AËROPLANES

During the past few years several attempts have been made, both in this country and abroad, to produce a reliable gasoline engine for model aëroplane work, but mostly without any degree of success. The reason for this inability, no doubt, is due to the scarcity of small working parts sufficiently light and at the same time reliable. The engine described herewith, designed by Mr. W. G. Jopson, a member of the Manchester Aëro Club, England, is one of the few that have been made to work satisfactorily.

As the accompanying diagrams 19 and 20 and photograph show, the engine is of the four-cycle, horizontal opposed type, having two cast-iron cylinders of 1¹⁄₄″ bore and 1³⁄₈″ stroke. Each cylinder is cast in one piece, and as the engine is air cooled, they are cast with radiating fins. One h.p. is developed at 1500 r.p.m. The total weight of the engine, gasoline tank and propeller is 7¹⁄₂ lbs. In preparing the design of this engine, the designs of similar full-sized aëro engines were followed as far as possible. The pistons are similar to those used on large aëro engines and are fitted with two rings; the crankshaft is turned out of two inch special bar steel, and is carried in two phosphor-bronze bearings. There is no special feature about the connecting rods, these being of the standard type, but very strong and light. To enable the two cylinders to be exactly opposite one another, the connecting-rods are offset in the pistons and are connected to the latter by gudgeonpins. The aluminum crank case is extremely simple, being cylindrical and vertically divided. The inlet valves are automatic, the exhaust valves being mechanically operated; the camshaft is driven from the main shaft by two-to-one gearing.

Sectional elevation of the 1 h.p. Jopson gasoline engine for
models. The disposition of the gasoline tank and wick carburettor
is particularly noteworthy. It will be seen that metal journals are
provided for the crankshaft, which is turned out of 2-inch bar steel.
Courtesy _Flight_.]

To assist the exhaust, and also the cooling, small holes are drilled round the cylinder in such a position that when the piston is at the inner end of its stroke, these holes are uncovered, thus permitting the hot exhaust to escape, and so relieve the amount passing through the exhaust valves. The commutator is also driven off the camshaft, as shown in the drawing. No distributor is fitted to the commutator, as small ones are somewhat troublesome and very light coils are obtainable at a reasonable price.

The gasoline tank is made of copper in streamline form, and is usually fitted to the back of the crankcase, thus reducing the head resistance, but if desired it can be fitted in any other position. The action of the carburetor can be easily seen from the drawings; it is of the surface type and much simpler, lighter and quite as efficient as the spray type. Specially light and simple spark plugs are used, that give very little trouble. The propeller used in connection with this engine is somewhat out of the ordinary, having been specially designed for this engine, and patented. The propeller is made entirely of aluminum and has a variable pitch, this being easily obtainable, as the blades are graduated so that any desired pitch, within certain limits, may be given at once. The results of a series of tests on a 30 inch propeller are shown on the accompanying chart, and from it the thrust as certain speeds with a certain pitch can be obtained. Taking the engine running at 1540 r.p.m. with a pitch of 15″, the thrust comes out at 9¹⁄₂ lbs., or more than the weight of the engine and accessories.

Diagram of results obtained from tests of the 1 h.p. Jopson model
gasoline engine, showing the thrust in pounds at varying speeds with
propellers of different pitch. Courtesy _Flight_.]

THE MIDGET AËRO GASOLINE ENGINE

Although numerous model constructors in America are experimenting with model gasoline engines, the Midget Gasoline Engine, the product of the Aëro Engine Company, Boston, Massachusetts, is perhaps the most satisfactory up to the present time. An engine of this type was used by Mr. P. C. McCutchen of Philadelphia, Pennsylvania, in his 8 foot Voisin Type Biplane Model, for which he claims a number of satisfactory flights.

The engine is made from the best iron, steel, aluminum and bronze and the complete weight including a special carburetor, spark plug and spark coil is 2¹⁄₂ lbs. From the top of the cylinder head to the bottom of the crank case the engine measures 7″. It is possible to obtain from this engine various speeds from 400 to 2700 r.p.m., at which speed it develops ¹⁄₂ h.p. The propeller used in connection with this engine measures 18″ in diameter and has a 13″ pitch.

It might be of interest to know that one of the parties responsible for the development of this engine is Mr. H. W. Aitken, a former model maker and who is now connected with one of the largest aëro engine manufacturing companies in America.

STEAM POWER PLANTS

Aside from the compressed air engine there is the steam driven engine which has been used abroad to considerable degree of success. Owing to the difficulty in constructing and operating a steam driven engine, very few model flyers in America have devoted any attention to the development of this engine as a means of propulsion for model aëroplanes. But irrespective of the limitations of the steam engine a great deal of experimentation has been carried on in England, and without doubt it will soon be experimented with in America.

H. H. GROVES STEAM POWER PLANTS

Perhaps one of the most successful steam power plants to have been designed since the development of the Langley steam driven model, is the Groves type of steam power plant, designed by Mr. H. H. Groves, of England. On one occasion several flights were made with a model driven by a small steam engine of the Groves type weighing 3 lbs. The model proved itself capable of rising from the ground under its own power and when launched it flew a distance of 450 feet. This is not a long flight when compared with the flight made by Prof. Langley’s steam driven model on November 28, 1896, of three-quarters of a mile in 1 minute and 45 seconds, but the size of the models and also that Mr. Groves’ model only made a duration of 30 seconds, must be considered. The model was loaded 12 ounces to the square foot and had a soaring velocity of some 20 m.p.h. The total weight of the power plant was 1¹⁄₂ lbs. Propeller thrust 10 to 12 ounces. The total weight of the model was 48 ounces. The type of steam plant used in connection with this model was of the flash boiler, pressure fed type, with benzoline for fuel.

Mr. Groves has done considerable experimenting with the steam driven type power plant. Many of the designs used in the construction of steam plants for models are taken from his designs. A Groves steam power plant is employed in one of Mr. V. E. Johnson’s (Model Editor of _Flight_) model hydroaëroplanes, the first power-driven, or “mechanically driven” model hydroaëroplane (so far as can be learned) to rise from the surface of the water under its own power. This model has a total weight of 3 lbs. 4 ounces.

G. HARRIS’S STEAM ENGINE

Another advocate of the steam driven type model is Mr. G. Harris, also of England. Several good flights were made by Mr. Harris with his pusher type monoplane equipped with a steam driven engine. As a result of his experiments he concluded that mushroom valves with a lift of ¹⁄₆₄ part of an inch were best, used in connection with the pump, and at least 12 feet of steel tubing should be used for boiler coils. The first power plant constructed by Mr. Harris contained a boiler coil 8 feet long, but after he had replaced this coil with one 12 feet long, irrespective of the fact that the extra length of tube weighed a couple of ounces, the thrust was increased by nearly a half pound.

The principal parts used in Mr. Harris’s steam power plant was an engine of the H. H. Groves type, twin cylinder, ⁷⁄₈″ bore with a piston stroke of ¹⁄₂″. The boiler was made from 12″ of ³⁄₁₆″ × 20″ G. steel tubing, weighing 10.5 ounces. The blow lamp consisted of a steel tube, ⁵⁄₃₂″ × 22″ G. wound round a carbide carrier for a nozzle. The tank was made of brass ⁵⁄₁₀₀₀″ thick. The pump, ⁷⁄₃₂″ bore, stroke variable to ¹⁄₂″, fitted with two non-return valves (mushroom type) and was geared down from the engine 4.5 to 1.

PROFESSOR LANGLEY’S STEAM ENGINE

The Langley steam driven model, of which so much has been said, and which on one occasion flew a distance of one-half mile in 90 seconds, had a total weight of 30 lbs., the engine and generating plant constituting one-quarter of this weight. The weight of the complete plant worked out to 7 lbs. per h.p. The engine developed from 1 to 1¹⁄₂ h.p. A flash type boiler was used, with a steam pressure of from 150 to 200 lbs., the coils having been made of copper. A modified naphtha blow-torch, such as is used by plumbers, was used to eject a blast or flame about 2000 Fahrenheit through the center of this coil. A pump was used for circulation purposes. With the best mechanical assistance that could be obtained at that date, it took Professor Langley one year to construct the model.

FRENCH EXPERIMENTS WITH STEAM POWER PLANTS

About ten months after Langley’s results, some experiments were carried out by the French at Carquenez, near Toulon. The model used for the experiments weighed in total 70 lbs., the engine developing more than 1 h.p. As in the Langley case, twin propellers were used, but instead of being mounted side by side, they were mounted one in front and the other behind. The result of these experiments compared very poorly with Langley’s. A flight of only 462 feet was made, with a duration of a few seconds. The maximum velocity is stated to have been 40 m.p.h. The span of this model was a little more than 6 meters, or about 19 feet, with a surface of more than 8 square meters, or about 80 square feet.

CARBONIC GAS ENGINE

The six-cylinder carbonic gas engine described herewith is the product of Mr. Henry Rompel, Kansas City, Missouri.

This is perhaps one of the most interesting of its kind to have been developed during 1916, and its appearance in the model aëroplane field adds weight to the claim that mechanical engines will soon replace the rubber strand as motive power for model aëroplanes.

Mr. Rompel’s engine is of rotary, carbonic gas type, having six cylinders, a bore of ⁵⁄₈″ and a stroke of ³⁄₄″.

The intake is derived through a rotary valve which also acts as a crank shaft bearing, thereby saving weight.

The exhaust is accomplished by mechanically operated valves situated in the heads of the cylinders being opened by the aid of rocker arms and push rods, which gain their timing from a cam placed on the crankshaft.

To save weight in construction the crankshaft, connecting rods, pistons and cylinders were made of telescopic tubing with a side wall of one thirty-second of an inch or less in thickness.

The engine has a swing of 5¹⁄₂″ over all, weighs a little less than 8 ounces complete, and is operated on 1,500 pounds pressure (carbonic gas) and at a speed of 3,500 to 3,700 r.p.m. will develop about 1 horse power. While spinning a 17″ propeller with a pitch of 20 inches it will deliver a thrust of 21 ounces, and has a duration of 40 seconds. Two hundred and fifty-six pieces were embodied in its construction.

THE FORMATION OF MODEL CLUBS

To form a model aëroplane club at least six interested persons are necessary. As soon as a place in which to hold meetings has been decided upon the club should proceed to elect a director whose duty should be to manage the affairs of the club. One of the first things to be considered is the name under which the club will operate; the custom is usually to adopt the name of the town or city in which the club is located, viz.: Concord Model Aëro Club, Concord, Massachusetts, although it is the privilege of the majority of the members to choose a name such as they might feel will best benefit the purpose for which the club was organized. As in the case of the Aëro Science Club of America, this club was formed for the purpose of stimulating interest in model aëronautics and to help those who might become interested therein, not only in New York City but throughout the entire United States.

When the matter of name and place has been settled the club should decide upon the course it is to follow, first by electing OFFICERS and second by preparing a CONSTITUTION AND BY-LAWS. In the case of clubs whose membership does not comprise more than six members, it does not seem desirable to have more than one officer, namely, a DIRECTOR, who might perform the duties of a president, treasurer and secretary until the club has reached a larger membership. In this way the members are enabled to concentrate upon the construction and flying of models and to engage in such other activities as to carry out the purpose for which the club was organized. However, the foregoing is merely a suggestion on the part of the writer, who by the way is a member of the Aëro Science Club of America and formerly acted in the capacity of secretary to that club.

Clubs whose membership totals more than twelve, however, should proceed to elect a President, Treasurer and Secretary, all of whom must receive a vote of at least two-thirds of the membership. With clubs of this size a director is not needed as the affairs of the club are usually entrusted with the governing officers, the President, Treasurer and Secretary. In as much as the constitution and by-laws are an important factor in the affairs of any model club, the governing officers, before mentioned, should hold a private meeting at the earliest moment whereat to frame a constitution and set of by-laws embodying the purposes and policy of the club. When the proposed constitution and by-laws are completed they should be presented to the members for approval after which a copy should be given to every member.

The following is a specimen of constitution and by-laws that might be used by any person or persons desiring to form a Model Aëro Club:

CONSTITUTION AND BY-LAWS OF A MODEL
AËROPLANE CLUB

ARTICLE 1. NAME. The name of this club will be known as The .......... Model Aëro Club.

PURPOSE. The object of this club shall be to study and increase the interest in the science of aëronautics in every way possible and to realize this object, shall construct and fly model aëroplanes, gliders and man carrying machines.

FURTHER, Contests shall be held for model aëroplanes and prizes awarded to the winners thereof. And as a further step in the advancement of this art, meetings, lectures, discussions, debates and exhibitions will be held.

ARTICLE 2. MEMBERSHIP. Any person may become a member of this club provided his application receives the unanimous approval of the majority of members, or is passed upon by the membership committee. A member may resign his membership by written communication to the secretary who shall present it to the membership committee to be passed upon.