Distinctive equipment and devices

1. Square-type high speed engines

The R engine that the Crown was equipped with was first fitted in the Model RH Toyopet Super passenger cars and Model RK Toyopet truck in September 1953. This engine is a square type high speed engine where the bore and stroke dimensions are almost the same at 77 millimeters x 78 millimeters. It had already been in use for over a year when the Crown came onto the market, and performance and quality were stable. Nothing was mentioned with regard to the engine itself in the defect report the Inspection and Improvement Department put together just after the Model RS and the Model RR were launched.

The passenger car engines that were on sale through technology partnerships with foreign manufacturers at the time the R engine entered the scene in 1953, are listed in Table 1-42. Looking at the relation between the bore and stroke in these engines, long-stroke engines, where the latter is longer than the former, form the majority, and this was the same for domestic manufacturers Prince Motor Co., Ltd. (75 millimeters x 84 millimeters) and Ohta Jidosha Kogyo Co., Ltd. (61.5 millimeters x 76 millimeters). When the Crown was launched in 1955, however, a new 76.2 millimeters x 76.2 millimeters square engine (overhead valves (OHV), 1,390 cc, 43 hp) for the Hillman Minx had already appeared. Subsequently the R engine was improved to the 2R engine (78 millimeters x 78 millimeters, 1,490 cc), and with the 3R engine (88 millimeters x 78 millimeters, 1,897 cc) evolved further into an oversquare engine where the bore is larger than the stroke.

Table 1-42. Engines Used on Passenger Cars Produced through Tie-Ups with Foreign Automakers (1953)

Austin A-40 engine
Overhead valves, 1,200 cc, 42 hp
65.4 mm x 88.9 mm
Hillman Minx Engine
Single valve, 1,265 cc, 37.5 hp
65 mm x 95 mm
Renault 4CV engine
Overhead valves, 748 cc, 21 hp
54.5 mm x 80 mm
Austin A40: 'First Motor Show', Motor Fan, June 1, 1954, Hillman Minx and Renault 4CV: Photo article on new cars, Motor Fan, June 1, 1953

A small diesel engine was furthermore developed making use of the R engine's cylinder block. A prototype 1,500 cc class small diesel engine for passenger cars (development number: 3E, Model: C) was completed at the end of 1955, and its winning of the Japan Society of Mechanical Engineers Award in 1958 was mentioned earlier.

Model 22R, which was to be the last Model R engine (92 millimeters x 89 millimeters, 2,366 cc, 115 hp / 5,100 rpm), was fitted in the micro bus Coaster. Although the external dimensions of the cylinder block hadn't changed much, compared to the early R engine the displacement and output had been increased by 1.6 times and 2.4 times respectively. Incidentally, the R engine with the highest output was the Model 10R (86 millimeters x 80 millimeters, 1,858 cc, 140 hp/6,400 rpm, DOHC, twin carburetor) which was fitted in the first-generation Corona Mark II GSS.

In this way the R engines was continuously improved and by adapting it well to higher output and speed, it was successful for 41 years all the way until 1994.

2. Constant-mesh transmission with synchromesh

Toyota Motor Co., Ltd.'s early transmission was for all models-including the Model G1 truck and the Model AA passenger cars-a manually operated sliding mesh gear. A sliding mesh gear requires skill to make the two rotating gears engage smoothly, and also, depending on the way gears were shifted, called for an irksome operation called double-clutching.

In contrast the transmission employed in the Crown had three forward gears. By using a constant-mesh helical gear with synchromesh in the first and second gear, this provided a smoother gear operation than the sliding mesh gear.1 Subsequently, to make gear operation even easier Toyota Motor Co., Ltd. undertook to improve performance by, for instance, developing a transmission called all-synchro, or full-synchro, which employed a synchromesh mechanism at all gears. The technology in this field moreover evolved towards an automatic clutch that did away with clutch operation when changing gears (Saxomat), and an automatic transmission without the need for gear changes or clutch (Toyoglide).

Because of this the synchromesh transmission that was fitted in the Model RS Crown is also seen as the starting point at Toyota Motor Co., Ltd. towards 'easy driving'.

3. Front-wheel independent suspension and rear-wheel three leaf spring suspension

The Crown front-wheel suspension was the first at Toyota to employ an independent suspension system. Matching the state of the roads in Japan, the design improved reliability and durability, while also improving the universal wishbone type to provide a comfortable ride.

The rear-wheel suspension used a three leaf spring researched and developed by Dr. Atsushi Watari of University of Tokyo. This new spring model used three leaf springs with leaves of a large total length and width and it was not only light and pliable, but as there was little friction between the leaves and little vibration, it provided, coupled with the front-wheel independent suspension, a comfortable ride.

4. Reduction gears using the innovative hypoid gear

The reduction gear in the differential was the first in a Japanese car to use a hypoid gear. Because in a hypoid gear the drive pinion meshes with the ring gear below the center of the ring gear, the position of the propeller shaft where the pinion connects is lower, which allows for the floor of the body to be lower. As the range where the ring gear and the drive pinion mesh is wider and can tolerate great force, smaller and lighter reduction gears are possible.

By adopting this hypoid gear the overall height (1,525 millimeters) and the standard floor height (320 millimeters) for the Crown could be lowered and on the other hand the minimum ground clearance (210 millimeters) could be increased. While ensuring a better running stability because of a lower center of gravity, this also provided more clearance when driving on unsurfaced bad roads by increasing the distance between body and ground level.

For hypoid gear finishing, the U.S. Gleason Corporation hypoid gear cutting machine was imported by May 1953. As the first vehicle of the primary prototype of the Model RS passenger car was completed in June of the same year, it is clear that vehicle planning and design, manufacturing equipment procurement, and prototype manufacturing proceeded in a coordinated manner. In a survey conducted immediately after the launch, no reduction gear defects were reported.

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