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to some used in this country. Articulated rods are tin-bronze bushed at each end. These are very good quality castings. The material is uniform and unusually free from foreign inclusions. Hardness is Rockwell B 70. The knuckle-pin bushing is 1.03 in. in diameter by 1.57 in. long. Piston-pin bushings on both master and articulated rods are 1.24 in. in diameter and 1.81 in. long.

Knuckle pins (Fig. 14) are flanged at one end and locked in the master rod by lock plates screwed to the rod flange in the conventional manner. Pins are drilled from both ends leaving a web at the center. The end opposite the flange is plugged for bushing lubrication passage. As noted previously, the all-purpose steel is used. The specimen examined showed 0.040 in. case depth, Rockwell C 57 hardness on the case and 43 on the core.

Rod weights are etched on each

end of each rod approximately 0.93


and for

are the

knuckle-pin end and 1.72 lb for the piston-pin end of the master rod. Equivalent rotating master weight used is 37.6 lb. Apparently no correction is made for knuckle-pin displacement or for crankpin oil. Master rods are installed in 3F and


— Cylinder

construction is

of nitrided steel

3R cylinders.

barrel, aluminum-alloy head type, similar to American practice. See Fig. 15. Barrel cooling fins 0.45-in. deep are machined on the steel barrel. There are 21 fins covering a longitudinal length of 2.75 in., that is a spacing of 0.131 in. which is quite close. Attaching flanges are also turned onto the barrel and spotfaced for flat washers at the cylinder attaching nuts. A skirt length o f2.95 in. allows approximately a 2 in. projection into the crankcase interior.

Cylinder heads are characterized by quite closely spaced (5 per in.) fins which average 0.9 in. in depth. This design would appear to give relatively small cooling area for the output which could be expected from engine of this size. Relatively small angle between valves (56 deg. approximately) further hinders the application of fins at the top of the combustion-chamber dome.

Attachment of the head to the barrel (fig. 16) is by means of a

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  

screw joint using threads of 3-mm. pitch (8.5 threads per in.). The thread form is believed to be the International Screw Thread standard 60-deg. thread with radius tips and roots. A shrink-fit pilot is provided both above and below the threaded section of the joint. The joint is completed by screwing the tapered loser face of the head against the upper side of an angularly machined






machined with so that the tip

a differential angle of this angular fin

bears first during assembly. cylinder-barrel threads run out a relief. Head threads are milled

The into and




within the


of the


fin which is

no relief noted that

is provided. It will be there is a relatively ling














Excessive stress would be expected sections adjacent section.

concentrations at the thin wall to the heavy

The cylinder head is cast of the

aluminum previously

alloy described . It shows a Brinnel

hardness number of 60.

Two spark-plug inserts are screwed into the head. The left-hand threaded joint is tapered. No other locking means is provided. The inserts, of aluminum bronze, are located at the front and rear slightly off-center, and are approximately radial to the internal dome contour. Valve-seat inserts are shrunk into the bores in the cylinder head per conventional practice. The steel exhaust insert is alloyed with nickel,



quite high



a Rockwell

hardness of 87 B. Intake insert is aluminum bronze. See Fig. 17. Tin- bronze valve guides are used in both intake and exhaust. Valve rocker boxes are cast integral with the head and are very similar inform to those of one American manufacturer. The box is completely enclosed except for a small cover plate over the valve end for installation of the rocker and valve clearance adjustment. Evaluation of valve ports is impossible by inspection but they appear to be well worked out. Port diameters are as follows: intake at valve end 2.24 in., at connection end 2.16 in.; exhaust at valve end 2.18 in., at connection end 2.26 in. Connection with the intake pipe is


accomplished by means of a shrunk and pinned sleeve, the outer end of which is recessed inside and threaded outside to provide a packing gland type joint with the pipe. The exhaust connection int the head (see Fig. 18) is protected by a steel sleeve of the above ID approximately 0.07 in. thick by 0.94 long shrunk into the exhaust-port bore. Connection to the exhaust system is accomplished by means of a slip joint tube held in place by a lug and one stud. The exhaust connector used with the installation extends approximately 3 in. to a ball joint.

PISTONS — Pistons in this engine (Fig. 19) are aluminum-alloy forgings very similar to current American practice. A Brinell hardness of 100 is quite uniform. Pin bosses are drilled for splash lubrication. Heads are flat with no valve-clearance cut-outs. The underside of the head is ribbed at right angles to the piston-pin bore. The piston is fitted with six 0.09-in. wide piston rings in five grooves. The two upper rungs are flat-faced compression reins chromium plated on the outside diameter to a depth of 0.0007 in. (See Fig. 20) The third ring is a tapered-face compression ring installed with the scraping edge down. There are two scalloped oil- control rings in the fourth groove. These rings are conventional in that, in addition to the scallop0ed lower side face, the outer face is radiused at the upper side and stepped to form oil drainage spade below th scraping edge. The fifth ring, which is below the piston pin is a typical 45-deg. oil scraper. A relatively narrow land (0.23 in.) is provided above the upper compression ring. The next two lands are 0.17 and 0.14 in. respectively. Ring side clearance is approximately in accordance with American practice. Scraper rings are fitted closely (0.00 in. in fifth groove, and 0.003 in. in fourth groove) with progressively increasing clearances toward the piston head (0.006 in. in the third groove and 0.008 in. in grooves one and two). All rings have parallel side faces and approximately 0.2 in. radial depth. The piston pin (Fig. 21) is a low-alloy steel hardened throughout to Rockwell C 42. It is not case-hardened. The piston pin is retained by means of 17S aluminum-

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