THE fundamental principles along which it is planned to develop a new business are of major importance. Details can be worked out to perfection, but if the foundations are unsound failure is sure to follow. Conversely, if the foundations have been correctly laid the business will prosper in spite of imperfect details.
THE coming spring days mean mud on the flying fields, and deep sticky mud on the fields mean that planes are apt to nose over. Nosing over may mean really serious damage to the plane and injury to the passengers. Nosing over is probably an even more frequent cause of damage to planes than running into obstacles.
AMERICAN air mail pilots are as fine a group of fliers as can be found anywhere in the world, but this does not necessarily mean that they can be transferred to passenger transport planes without a certain amount of training. The air mail pilot at the controls of a transport plane sometimes does not realize the feelings of the passengers inside the cabin, or he may even be inclined to take advantage of his situation and treat his passengers to a “ride.”
The Relation of Heat Characteristics to Operating Conditions
WHEN a spark plug performs unsatisfactorily it is often due to use of a plug intended for another type engine, or a different operating conditions. No matter how good a spark plug may be, it will not give satisfactory service if it is of the wrong type.
Four Place Cabin Craft Produced by Paramount Aircraft Corp. Is Designed Around the Warner “Scarab" Engine
THE “Cabinaire” biplane, which is now being produced by the Paramount Aircraft Corp., Saginaw, Mich., is one of the first airplanes to be designed around the Warner “Scarab” engine. This craft, which is intended for private use and operation over mail and express feeder lines, is a four-place, cabin biplane.
THROUGH three years of operation in the flying school business, the Embry-Riddle Co., Lunken Airport, Cincinnati, O., has realized the imperative need of a rigid system of instruction both in ground school and flying school. Without such a system the school easily slips into the haphazard, and the airport gathers a crowd of loafers, most of them unable to take training, but willing to sit for hours and watch planes fly.
WE have seen that the distribution of overhead through a blanket percentage, or burden on bare cost, may lead to large errors; that results are more correct when overheads on materials, labor, selling and administration are handled separately, and that a still closer approximation is reached when departmental divisions and distributions of overhead are made.
Wright Company Establishing Chain of 36 Service Depots
Manufacture, Sale and Servicing of Engines Also Arranged in Foreign Nations
PATERSON, N. J.—The establishment of 36 depots in all parts of the United States for the repair and servicing of Whirlwind and Cyclone engines is announced by the Wright Aeronautical Corp. This the company calls the most extensive arrangement yet made by any manufacturer in the aviation industry for the convenience of airplane owners.
LONG ISLAND CITY, N. Y. — A double working schedule has lately been followed by the Chance Vought Corp., this city, in order to quickly turn out a fleet of attack planes for the Federalists in Mexico now engaged in warfare with revolutionists. Col. Samuel C. Rojas, military attache of the Mexican embassy, Lieut.
WASHINGTON, D. C—In pursuance of Senate Joint Resolution 11, a joint committee of five Senators and five Representatives has been named to investigate the problem of control of aircraft for seacoast defense. The committee follows: Senators Bingham, Hale, Fletcher, Swanson, and Reed (of Pennsylvania), and Messrs.
WICHITA, KAN. —While in this city recently, J. E. Granger, Pacific Coast Swallow plane distributor operating at Santa Monica, Calif., placed an order for 50 Swallows costing in total approximately $175,000. All are to be delivered during 1929. Mr. Granger, who last year was the firm’s leading distributor, has a territory which includes Washington, Nevada, California, Oregon, New Mexico, Lower California, and the Hawaiian Islands.
WASHINGTON, D. C—New approved type certificates for planes are announced as follows: No. 111. Travel Air, SC 2000, three place open land biplane, Curtiss Challenger ; No. 112. Travel Air W 4000, three place open land biplane, Scarab ; No. 113. Mono-Aircraft Monocoupe, two place closed land monoplane, Velie 55.
PITTSBURGH, PA.—As AVIATION goes to press, the first local annual aircraft show, scheduled for March 9 to 16, is well under way. Crowds have been thronging the Motor Square Garden every day and the display has aroused considerable interest throughout the whole Pittsburgh district.
Leading Cities Named as Bases in Instructional Chain To Be Formed
CHICAGO, ILL.—Under the general activities of Universal Aviation Corp., which now extend into almost every branch of aviation activity, shortly will be listed a most comprehensive chain of schools, according to plans announced. The three school divisions—Robertson in St. Louis, Mid-Plane in Minneapolis and Egyptian in Marion, 111.—will be increased to 11.
OKLAHOMA CITY, OKLA.—Members of the local chamber of commerce aviation committee are making plans for the first annual Oklahoma City air exposition which will be held sometime in May. The committee, of which Thomas R. McHenry is chairman, includes Sherman Lohman, B. S. Graham, C. R. Anthon, Ray Dawson, W. A. Kitchen, Cy Fentris, J. R. Green, Burrell Tibbs, and Paul Braniff.
LANGLEY FIELD, VA.—The Fourth Annual Aircraft Engineering Research Conference of executives and engineers of the aircraft industry and N. A. C. A. representatives is scheduled to be held here May 14. The primary purpose of the meeting is to ascertain through discussion the various points of view regarding technical problems of aircraft design and construction.
NEW YORK, N. Y.—According to reports, holdings in the Stromberg Carbureter Co. have been acquired by Richard F. Hoyt, C. M. Keys, and Vincent Bendix. These men, it is said, have taken positions on the board. Carries Letters to Eaker WASHINGTON, D. C.—Capt. Ross G. Hoyt, Air Corps, recently completed a round trip flight between Bolling Field, here, and Kelly Field, San Antonio, Tex., in the fast time of 37 hr. 35 min. The actual flying time for the 3,100 mi. was but 25 hr. 45 min., it is reported. Captain Ross carried official correspondence to Capt. Ira C. Eaker to be transported in turn by the latter in his planned dawnto-dusk flight to the Canal Zone, which has, incidentally, been postponed indefinitely because of recent Mexican revolutionary disturbances.
WASHINGTON, D. C.—During the week, the fog surrounding the impending appointments and resignations in Government aviation positions has begun to clear. Edward P. Warner, it has been announced, will be succeeded as Assistant Secretary of the Navy for aviation by Davis S. Ingalls of Cleveland, O. ; F. Trubee Davison, on the other hand, is to be retained in his present position as Assistant Secretary of War for aviation.
WASHINGTON, D. C.—The Harmon Trophy for 1928 was awarded here March 9 to Carl Ben Eielson for his participation in the trans-Arctic flight with Capt. Sir George Hubert Wilkins. Medals of honor were awarded to four Americans and one foreigner, these being the late Charles B. D. Collyer, Wilmer L. Stultz Arthur Goebel, Thomas Carroll, N. A. A. test pilot, and Captain Wilkins.
<p>CHICAGO, ILL.—Report is issued by J. N. Janes, advertising manager of the Ta-Ho-Ma Airplane & Motor Corp. this city, that the firm’s three place biplane is going along nicely at the Elgin, 111., factory, and that it will be ready for display in the Buffalo Air Show. B. H. Vanderveld is president of the organization, while M. D. Gardner is general factory manager.</p>
Craft Designated as “R. S. V.” Is Unique Convertible "Bi-Monoplane"
NEW YORK, N. Y.—Plans have been completed for the manufacture in this country of the Belgian R. S. V. convertable biplane-monoplane, it was announced by Ivan R. Gates, president of the Gates Aircraft Corp., whose firm will immediately begin production of the small planes at a plant located in Long Island.
INDIANAPOLIS, IND. — A new record for a plane powered with a 60 hp. engine is claimed for the Davis monoplane, this craft having been flown on March 7 from Richmond, Ind., to Pittsburgh, Pa., in the fast time of 106.32 m.p.h. The distance is 280 mi.
Lehman and Harriman Interests Back “The Aviation Corporation"
NEW YORK, N. Y.—Called one of the largest projects of its kind yet launched, organization of The Aviation Corporation is announced here. The company, which will be primarily a holding and development corporation for the aviation industry, will have an authorized capitalization of 10,000,000 shares of common stock with no senior securities authorized.
OAKLAND, CALIF.—According to the claim of its inventors, an accurate record of a plane’s flying time may be kept with a new device they have developed here. The “Hourometer,” as it is called, is an electrically actuated clock apparatus which when properly attached to the landing gear automatically starts and stops when the wheels leave or touch the ground. Eugene P. Fraser and Malcolm C. Elrick, a former U. of C. student, designed the instrument.
<p>PITTSBURGH, PA. —Aircraft and Airways of America, Inc., eastern distributors for Ryan planes and owner of Bettis Field here, have taken the Western Pennsylvania agency for Command-Aire, according to an announcement by F. LeMoyne Page, president.</p>
WASHINGTON, D. C.—Double pension for disabilities suffered by Army fliers in line of duty is granted in a measure signed recently by the President. The double amount has previously been allowed to Marine and Navy aviators.
DETROIT, MICH.—A nation-wide model airplane exposition will be held in Detroit one week prior to opening of the second annual All-American Aircraft Show under the joint auspices of the Detroit Board of Commerce and the Detroit Board of Education, it was announced recently by Harvey J. Campbell, executive vice president and secretary of the Board of Commerce.
PATERSON, N. J.—The New Standard Aircraft Corp. here has placed an order for 50 American-built Cirrus Mark III engines with American Cirrus Engines, Inc., of Belleville, N. J. The first 50 engines turned out at the new Cirrus factory are to be delivered on this order.
AMES, IA.—The Engineering Division of Iowa State College, here will hold a three day conference on aeronautics May 27-29. There will be a program of papers and discussions on aeronautical subjects of interest to engineers, pilots, to those connected with air transportation, and to the public in general.
WASHINGTON, D. C.—Four bills affecting aviation became law during the closing sessions of the last Congress. They were: Senate Bill 5350, introduced by Senator Bingham, to amend the Air Commerce Act of 1926 with reference to the examination and rating of schools giving instruction in flying; Senate Bill 5544, introduced by Senator Bingham, to increase the membership of the National Advisory Committee for Aeronautics; House Bill 16131 (same as Senate Bill 5443), introduced by Representative Kelly, to enable the Postmaster General to make contracts for the transportation of mail by air from island possessions or territories of the United States to foreign countries and to the United States and between such island possessions or territories, and to authorize him to make contracts with private individuals and corporations for the conveyance of mail by air in foreign countries; House Bill 16839, introduced by Representative Britten, to provide for investigation of sites suitable for establishment of a naval airship base.
NEW YORK, N. Y.—In a recent meeting of Aeronautical Chamber of Commerce members, the following section was added to the by-laws. “Section 4. Council. To secure the advantages of continuity of service, all ex-presidents past and future shall be members of an advisory group styled 'The Council.'
CINCINNATI, O.—The LeBlond Aircraft Engine Corp. of this city has begun delivery on a power plant contract placed by the Joseph Kreutzer Co., Los Angeles. The LeBlond firm, furthermore, announces receipt of an order from the Arrow Aircraft & Motor Corp. of Havelock, Neb., for 100 of the “60” type engines to be delivered during March, April and May.
PITTSBURGH, PA.—The manufacture of airplanes will start in Pittsburgh in a few weeks, it was announced here by the Pittsburgh Aviation Industries Corp., a $6,000,000 holding company, with five subsidiary companies engaged in aviation activities.
MILWAUKEE, WIS.—A contract for 28 planes has been awarded to the Hamilton Metalplane Co. by the Seaboard Aircraft Co., according to a recent announcement. The planes will carry seven passengers and a pilot and will be equipped with lavatory, baggage room and other facilities.
TAMPA, FLA.—At a recent meeting of the aviation bureau of the chamber of commerce announcement was made that student aviators from Central American countries will arrive in Tampa early next summer to begin training here for commercial licenses.
FORT WORTH, TEX.—Three new Stearman mail planes were delivered here to Texas Air Transport, Inc., during the past week. The planes were flown from the factory at Wichita, Kan., by Texas company pilots. They will be used on the South Texas air mail routes operated by the firm.
HASBROUCK HEIGHTS, N. J.— Delivery of the seventh tri-engined Fokker for Pan American Airways, Inc., is announced at the Fokker plant here. Edward Musick, veteran P. A. A. pilot, came to Hasbrouck Heights to accept the craft.
NEW YORK, N. Y.—Thirteen long-established fire and marine insurance companies, and three casualty companies, with combined assets for the 16 corporations of more than a third of a billion dollars, have joined their interests to write aviation insurance, according to an announcement made today.
LOS ANGELES, CALIF.—An anouncement by officials of the Moreland Aircraft Co. states that construction will begin at once on a $500,000 airplane factory to be erected on a site adjoining Mines Field. The first building will measure 80 by 180 ft. in size, will be of hangar type construction and is scheduled to be ready for production before the first of July.
<p>BALTIMORE, MD.—The BerlinerJoyce Aircraft Co. has awarded to the M. A. Long Construction Co. of Baltimore, Md., the contract for the erection of the first unit of the aircraft manufacturing plant at Dundalk Junction, adjacent to the proposed municipal airport.</p>
GEORGE C. WESTERVELT, retired Navy captain associated with aviation for 14 yr., has been appointed manager of CurtissCaproni, Inc. During the war, Mr. Westervelt was in charge of the construction and inspection of naval aircraft in this country.
AVIATION SECURITIES CORPORATION of New England has been chartered under the laws of Delaware for aeronautical financing work.. The company will begin business with $3,000,000 in cash. It is understood that Hayden, Stone & Co., as well as other banking houses, will participate in financing the corporation.
Purchase of Curtiss Field, L. I., by the Seth Low interests which recently acquired Roosevelt Field, L. L, has been reported here. Plans to join the two contiguous fields and development of the tract into one large airport were included in the report.
It Has Been Reported That— —The S. A. F. E. firm, of which Erle P. Halliburton, Duncan, Okla., is president, will establish terminal buildings and hangars at Tulsa, Oklahoma City, Ft. Worth, and Dallas. —W. J. Patterson, secretary of the board of public works, Superior, Wis., is taking bids on construction of machine shops, offices, and a $25,000 hangar to be 80 by 100 ft.
Leading Aeronautical and Financial Concerns Buy Big Tract
NEW YORK, N. Y.—Ambitious plans, which if realized would give this city a huge airport on the New Jersey marshes, have been announced here by a group which includes representatives of leading organizations in aviation and strong financial interests.
NEWARK, N. J.—A conference between Government, city and N. A. T. officials was to have been held here Tuesday, March 12, to air the differences between the city and the transport company over use of the new municipal airport as the eastern terminal of the air mail system. N. A. T. representatives claim the field is not adequate for safe operation.
SAN DIEGO, CALIF.—About 35 acres of Lindbergh Field, the new municipal airport here, have been completed and the tract is being used by the San Diego Air Service Corp. The outline of the airport has been filled in and, at the present rate of dredging and filling operations, it is expected the first complete unit of 142 acres will be ready for use a year from now.
PITTSBURGH, PA.—An air service from this city to Columbus, St. Louis and intermediate points, was to have been inaugurated March 15 by the Mayer Aircraft Corp., one of the oldest air companies of this city, it was stated by President C. P. Mayer.
SAN FRANCISCO, CALIF.—Decisions of the War Department looking to abandonment of Crissey Field, which has been the Army aviation base in this region since the war, for a new air base and to establish somewhere within the San Francisco Bay area a large quartermaster depot for aviation supplies, have led many communities to offer sites for the two projects.
WASHINGTON, D. C.—Operation of the Cristobal-Mollendo, Peru, leg of the new air mail route linking the Canal Zone with Chile will be started April 1, it has been announced by the Pan American Airways. The entire route will be operated on and after May 1, it is said, when final arrangements have been concluded with the governments involved.
NEW ORLEANS, LA.—A new rotating airport beacon just installed on the hangar at the New Orleans Municipal Airport is to be supplemented by additional equipment at an early date, according to officials in charge of the field. Ceiling lights already have been placed and the installation of other illuminating equipment, including flood and boundary lights is being speeded.
SAN JOSE, CALIF.—Vernon Westbrook local air enthusiast, averted what might have been a serious air accident February 26. A northbound Maddux plane, bucking the winds from Los Angeles, was overtaken by darkness short of its northern destination at Alameda Airport.
WASHINGTON, D. C—Considerable progress in airways and air transportation development is revealed in recent figures released by the Aeronautics Branch. In 1928 the Government paid $7,430,225 for carrying the air mail more than 8,270,000 mi.
WASHINGTON, D. C—Bulletin No. 16, “Airport Rating Regulations;” a revised edition of Bulletin No. 5, “Airports and Landing Fieldsand “Airway Marking,” the report of the committee on standard marking, are available at the Aeronautics Branch.
Committee Representing Air Lines Makes Report at Capital
WASHINGTON, D. C.—The air transport companies propose to establish the aviation radio stations throughout the country, according to the recommendations made to the Federal Radio Commission at the conference here March 11 by the subcommittee representing the operators.
LOS ANGELES, CALIF.—Extensive aviation sign posting of southern California cities is being undertaken by the Southern Counties Gas Co. All sign painting is being done according to specifications of the Aeronautics Branch. About a dozen signs are to be painted on roofs of buildings owned by the Southern Counties Gás Co. in Santa Barbara, Ventura, Santa Monica, Monrovia, Pomona, Ontario, Santa Ana, Orange, Anaheim, and Newport Beach. The entire project is to be finished within 30 days.
PITTSBURGH, PA.—Clifford Ball, operator of the Pittsburgh-Cleveland air mail, will open a mail line from here to Washington, he has announced, as soon as the existing line has been lighted for night flying. The lighting is expected to be completed by the middle of April.
ALAMEDA, CALIF.—Marking another step in the progress of San Francisco bay district aviation, two-day dedication ceremonies were held here recently at Alameda Airport, newest flying field to be officially recognized in this section.
WASHINGTON, D. C—The Representatives and Senators who are to serve on the joint congressional commission to study the local airport situation include Representative Zihlman, Maryland; Underhill, Massachusetts; Nelson, Maine; Wright, Georgia; Oliver, New York, and Senators Bingham, Connecticut; Vandenberg, Michigan; Jones, Washington; Black, Alabama; Tydings, Maryland.
MINERAL WELLS, TEX.—The new 100 acre municipal airport here will be opened formally April 6 and 7. with an air meet which is expected to attract about 40 pilots. Amon Arnold has been appointed manager of the field. OTIS, COLO.—This town was scheduled to dedicate its new civic airport of 80 acres today, March 16.
KANSAS CITY, MO.—Announcement has been made here by officials of the Fairfax Airport Co., operators of Fairfax Field, that the Curtiss Flying Service has selected that field as the base of operations for a unit of its organization. Ray G. Sparks of this city has been appointed manager and will head all the Curtiss operations, including a flying school, aerial taxi service, aerial photography and mapping service, sales service of airplanes and parts and a department for the overhauling of planes and engines.
WASHINGTON, D. C—The following 32 communities have announced plans to establish airports : Huntsville, Ala. ; Azusa, Cal. ; Point Washington, Fla.; Atlanta, Ga.; Jacksonville and Chicago, 111.; Culver, Ind.; Hiawatha, Kan.; Wiscasset, Me.; Cambridge, Md.; Berkeley, Birmingham, Clawson and Royal Oak, Mich.; Natchez, Miss. ; Brooklyn, Chatham, Hicksville and Liberty, N. Y.; Rich Square, N. C.; Sterling, O.; Louisiana, Mo. ; Harrisburg, Lancaster and Philadelphia, Pa; Eagle Pass and Edinburgh, Tex.; Grottoes and Wing, Va.; Cleelum and Kennewick, Wash., and Milwaukee, Wis.
FORT WORTH, TEX.—Two more air passenger routes will be inaugurated within a month by Texas Air Transport, Inc., according to an announcement by A. P. Barrett, president. The lines will operate between Fort Worth, Dallas and Houston and between Fort Worth, Dallas and El Paso.
NEW ORLEANS, LA.—Immediate adtising for bids for the construction of an A-l-A airport on the shores of Lake Pontchartrain, on the outskirts of the city, were authorized at a special meeting of the Orleans Parish Levee Board recently held in the civil courts building.
WASHINGTON, D. C.—A suggestion for placing landing fields all over the country at intervals of 10 mi. in the form of a gigantic checkerboard has been made here by the Guggenheim Fund. The scheme is advanced as a remedy for the lack of sufficient landing area, which is called one of the two main problems of aviation, the other being airplane engineering perfection which is regarded as practically achieved.
OAKLAND, CALIF.—Construction of a miniature railroad for passenger and express transportation has been proposed for the local airport, and the purchase of a miniature railway used to carry passengers at the Panama-Pacific International Exposition in San Francisco in 1915 has been suggested to airport officials.
PARIS, FRANCE—French civil aeronautics have been reorganized into three systems or departments—continental Europe, the Orient and the Occident. Existing companies will cooperate in the operation of the department to which they are assigned. The International Air Navigation Co., and the Farman lines will combine for the operation of the continental Europe department.
The Canadian Department of National Defense has agreed to supply and maintain airway beacons between the principal Canadian aerodromes to aid night flying in the Dominion. Assistance will be given in the equipment of the aerodromes for night flying, also.
LONDON, ENGLAND —According to “Jane’s” 1928 edition of All The World’s Aircraft, the number of types in leading producing countries are as follows : Great Britain, 96; Czechoslovakia, 12; France, 109; Germany, 54; Holland, 11; Italy, 44; United States, 148. The number of engine types given are: Great Britain, 25; France, 40; Germany, 12; United States, 28. The division between military and civil types is as follows : Great Britain, 60 and 36; France, 74 and 35 ; Italy, 31 and 13; Lhiited States, 54 and 96; and Germany, 54, all of civilian type only.
MELBOURNE, AUSTRALIA — All children three years of age and under now may travel free of charge on planes of the Australian Aerial Service, if accompanied by an adult. Children up to seven years of age may travel alone on the planes but must pay the regular fare.
OTTAWA, CANADA — Insurance companies in the Dominion have received recommendations covering the problem of insurance to those engaged in aviation. The recommendations are the result of considerable study of the situation by an Aviation Rating Commission of the Actuaries Club.
YEOVIL, ENGLAND—Pilots of Westland Aircraft works, makers of military types and the Widgeon light plane, recently flight tested the concern’s latest product, a tri-engine commercial cabin monoplane accommodating four passengers, and designed as the Westland Limousine.
OTTAWA, CANADA—Airplanes imported into this country from the United States during the first nine months of 1928 totaled 89 as compared with 25 in 1927. Imports from England totaled 90 for the same period as compared with 6 in 1927. The aircraft imports represented an increase of 390 per cent, over 1927.
ELECTRIC FURNACES of the 60 K. W. circular pit type for heat treating airplane engine crank cases, cylinder heads, pistons, and other parts, are now being manufactured by The Electric Furnace Co. of Salem, O. These furnaces accommodate circular steel baskets 55 in. in diameter and 60 in. deep and have electrical capacity for heating to a temperature of 1,000 deg. F., 300 lb. of steel and 650 lb. of aluminum in l¼ hr.
PROBABLY THE hardest work in airport operation is the handling of planes between hangar and field, and usually several attendants are required for this purpose. To reduce this operation to a one-man task, the American Eagle Aircraft Distributors, Inc., 83 Huguenot St., New Rochelle, N. Y., has developed a power “dolly.”
Mr. L. C. M., of Highlandtown, Baltimore, Md., sends in a note—“Enclosed please find an extract from the Baltimore Sun of January 24 describing a rather unusual method of landing: THE LEAP From the top of the summit—fly: Look not down; look on high:
CONTENTS Fundamentals of Airplane Fitting Design By Richard C. Gazley Aeronautical Engineer, Department of Commerce Welding Aluminum and Its Alloys By W. M. Dunlap Metallurgist, Aluminum Company of America Patents Issued Technical Reviews
FITTINGS form a much more important part of airplane design than a casual consideration would tend to reveal and deserve more attention than is usually accorded them. They are nearly always in such positions that failure of one would wreck the airplane.
N.A.C.A. Technical Report No. 293. Two Practical Methods for the calculation of the Horizontal Tail Area Necessary for a Staatically Stable Airplane, by Walter S. Diehl. This report is concerned with the problem of calculation of the horizontal tail area necessary to give a statically stable airplane.
THE purpose of this paper is to supply information on the welding of aluminum and its alloys. A weld as defined by the American Welding Society is “The localized intimate union of metal parts in the plastic or plastic and molten states with the application of mechanical pressure or blows, and in the molten or molten and vapor states without the application of mechanical pressure or blows.”
Patent No. 1,700,948—Internal-Combustion Engine, John Scott Oliver, London, England. One Claim, An internal combustion engine having a piston and a cylinder, a rotary sleeve valve, two sets of inlet and exhaust ports in the cylinder ports in said sleeve valve for registering alternately with the inlet and exhaust ports of each set, the first set of ports extending from a point at or near the head of the cylinder to a point intermediate in the stroke of the piston and being arranged to be opened and closed at the correct times by the movement of the sleeve alone while the second set of ports subtend the a wider angle than said first set of ports and extend from a point intermediate in the stroke of the piston to a point at or near the bottom of the stroke of the piston and are arranged to be opened and closed at the correct times by the movement of the piston in conjunction with the movement of the sleeve.