V THE HORIZONTALLY-OPPOSED ENGINE

Among the first internal combustion¹ engines to be taken into use with aircraft were those of the horizontally-opposed four-stroke cycle type, and, in every case in which these engines were used, their excellent balance and extremely even torque rendered them ideal—until the tremendous increase in power requirements rendered the type too long and bulky for placing in the fuselage of an aeroplane. As power increased, there came a tendency toward placing cylinders² radially round a central crankshaft, and, as in the case of the early Anzani, it may be said that the radial engine grew out of the horizontal opposed piston⁵ type. There were, in 1910—that is, in the early days of small power units, ten different sizes of the horizontally opposed engine listed for manufacture, but increase in power requirements practically ruled out the type for air work.

The Darracq firm were the leading makers⁶ of these engines in 1910; their smallest size was a 24 horse-power engine, with two cylinders each of 5·1 inches bore by 4·7 inches stroke. This engine developed its rated power at 1,500 revolutions per minute, and worked out at a weight of 5 lbs. per horse-power. With these engines the cranks are so placed that two regular impulses are given to the crankshaft for each cycle of working, an arrangement which permits of very even balancing of441 the inertia⁷ forces of the engine. The Darracq firm also made a four-cylindered horizontal opposed piston engine, in which two revolutions were given to the crankshaft per revolution, at equal angular intervals⁸.

The Dutheil-Chambers was another engine of this type, and had the distinction of being the second largest constructed. At 1,000 revolutions per minute it developed 97 horse-power; its four cylinders were each of 4·93 inches bore by 11·8 inches stroke—an abnormally long stroke in comparison with the bore. The weight—which owing to the build of the engine and its length of stroke was bound to be rather high, actually amounted to 8·2 lbs. per horse-power. Water cooling was adopted, and the engine was, like the Darracq four-cylinder³ type, so arranged as to give two impulses per revolution at equal angular intervals of crankshaft rotation¹⁰.

One of the first engines of this type to be constructed in England was the Alvaston, a water-cooled model which was made in 20, 30, and 50 brake horse-power sizes, the largest being a four-cylinder engine. All three sizes were constructed to run at 1,200 revolutions per minute. In this make the cylinders were secured to the crank case by means of four long tie bolts passing through bridge pieces arranged across the cylinder heads, thus relieving the cylinder walls of all longitudinal explosion stresses. These bridge pieces were formed from chrome vanadium steel and milled to an ‘H’ section, and the bearings for the valve-tappet were forged solid with them. Special attention was given to the machining of the interiors of the cylinders and the combustion heads, with the result that the exceptionally high compression of 95 lbs. per square inch442 was obtained, giving a very flexible engine. The cylinder heads were completely water-jacketed, and copper¹¹ water-jackets were also fitted round the cylinders. The mechanically operated valves were actuated by specially¹² shaped cams, and were so arranged that only two cams were required for the set of eight valves. The inlet valves at both ends of the engine were connected by a single feed-pipe to which the carburettor was attached, the induction¹³ piping being arranged above the engine in an easily accessible position. Auxiliary¹⁴ air ports were provided in the cylinder walls so that the pistons¹⁵ overran them at the end of their stroke. A single vertical¹⁶ shaft⁴ running in ball-bearings operated the valves and water circulating pump, being driven by spiral gearing from the crankshaft at half speed. In addition to the excellent balance obtained with this engine, the makers claimed with justice that the number of working parts was reduced to an absolute minimum.

In the two-cylinder Darracq, the steel cylinders were machined from solid, and auxiliary exhaust ports, overrun by the piston at the inner end of its stroke, were provided in the cylinder walls, consisting of a circular row of drilled holes—this arrangement was subsequently adopted on some of the Darracq racing¹⁷ car engines. The water jackets were of copper, soldered¹⁸ to the cylinder walls; both the inlet and exhaust valves were located in the cylinder heads, being operated by rockers and push-rods actuated by cams on the half-time shaft driven from one end of the crankshaft. Ignition was by means of a high-tension magneto, and long induction pipes connected the ends of the cylinders to the carburettor, the latter being placed underneath443 the engine. Lubrication was effected by spraying oil into the crank case by means of a pump, and a second pump circulated the cooling water.

Another good example of this type of engine was the Eole, which had eight opposed pistons, each pair of which was actuated by a common combustion chamber⁹ at the centre of the engine, two crankshafts being placed at the outer ends of the engine. This reversal of the ordinary arrangement had two advantages; it simplified induction, and further obviated¹⁹ the need for cylinder heads, since the explosion drove at two piston heads instead of at one piston head and the top of the cylinder; against this, however, the engine had to be constructed strongly enough to withstand the longitudinal stresses due to the explosions, as the cranks are placed on the outer ends and the cylinders and crank-cases take the full force of each explosion. Each crankshaft drove a separate air-screw.

This pattern of engine was taken up by the Dutheil-Chambers firm in the pioneer days of aircraft, when the firm in question produced seven different sizes of horizontal engines. The Demoiselle monoplane used by Santos-Dumont in 1909 was fitted with a two-cylinder, horizontally-opposed Dutheil-Chambers engine, which developed 25 brake horse-power at a speed of 1,100 revolutions per minute, the cylinders being of 5 inches bore by 5·1 inches stroke, and the total weight of the engine being some 120 lbs. The crankshafts of these engines were usually fitted with steel flywheels in order to give a very even torque, the wheels being specially constructed with wire spokes²⁰. In all the Dutheil-Chambers engines water cooling was adopted, and the cylinders were attached to the444 crank cases by means of long bolts passing through the combustion heads.

For their earliest machines, the Clement-Bayard firm constructed horizontal engines of the opposed piston type. The best known of these was the 30 horse-power size, which had cylinders of 4·7 inches diameter by 5·1 inches stroke, and gave its rated power at 1,200 revolutions per minute. In this engine the steel cylinders were secured to the crank case by flanges²¹, and radiating ribs²² were formed around the barrel to assist the air-cooling. Inlet and exhaust valves were actuated by push-rods and rockers actuated from the second motion shaft mounted above the crank case; this shaft also drove the high-tension magneto with which the engine was fitted. A ring of holes drilled round each cylinder constituted auxiliary ports which the piston uncovered at the inner end of its stroke, and these were of considerable assistance not only in expelling exhaust gases, but also in moderating the temperature of the cylinder and of the main exhaust valve fitted in the cylinder head. A water-cooled Clement-Bayard horizontal engine was also made, and in this the auxiliary exhaust ports were not embodied²³; except in this particular, the engine was very similar to the water-cooled Darracq.

The American Ashmusen horizontal engine, developing 100 horse-power, is probably the largest example of this type constructed. It was made with six cylinders arranged on each side of a common crank case, with long bolts passing through the cylinder heads to assist in holding them down. The induction piping and valve-operating gear were arranged below the engine, and the half-speed shaft carried the air-screw.

445 Messrs Palons and Beuse, Germans, constructed a light-weight, air-cooled, horizontally-opposed engine, two-cylindered. In this the cast-iron cylinders were made very thin, and were secured to the crank case by bolts passing through lugs²⁴ cast on the outer ends of the cylinders; the crankshaft was made hollow, and holes were drilled through the webs of the connecting-rods in order to reduce the weight. The valves were fitted to the cylinder heads, the inlet valves being of the automatic type, while the exhaust valves were mechanically operated from the cam-shaft by means of rockers and push-rods. Two carburettors were fitted, to reduce the induction piping to a minimum; one was attached to each combustion chamber, and ignition was by the normal high-tension magneto driven from the half-time shaft.

There was also a Nieuport two-cylinder air-cooled horizontal engine, developing 35 horse-power when running at 1,300 revolutions per minute, and being built at a weight of 5 lbs. per horse-power. The cylinders were of 5·3 inches diameter by 5·9 inches stroke; the engine followed the lines of the Darracq and Dutheil-Chambers pretty closely, and thus calls for no special description.

The French Kolb-Danvin engine of the horizontal type, first constructed in 1905, was probably the first two-stroke cycle engine designed to be applied²⁵ to the propulsion of aircraft; it never got beyond the experimental stage, although its trials gave very good results. Stepped pistons were adopted, and the charging pump at one end was used to scavenge the power cylinder at the other ends of the engine, the transfer ports being formed in the main casting. The openings of these446 ports were controlled at both ends by the pistons, and the location of the ports appears to have made it necessary to take the exhaust from the bottom of one cylinder and from the top of the other. The carburetted mixture was drawn²⁶ into the scavenging cylinders, and the usual deflectors were cast on the piston heads to assist in the scavenging and to prevent the fresh gas from passing out of the exhaust ports.

1 combustion   

n.燃烧；氧化；骚动

参考例句：

• We might be tempted to think of combustion.我们也许会联想到氧化。
• The smoke formed by their combustion is negligible.由它燃烧所生成的烟是可忽略的。

2 cylinders   

n.圆筒( cylinder的名词复数 )；圆柱；汽缸；（尤指用作容器的）圆筒状物

参考例句：

• They are working on all cylinders to get the job finished. 他们正在竭尽全力争取把这工作干完。 来自《简明英汉词典》
• That jeep has four cylinders. 那辆吉普车有4个汽缸。 来自《简明英汉词典》

3 cylinder   

n.圆筒，柱(面)，汽缸

参考例句：

• What's the volume of this cylinder?这个圆筒的体积有多少？
• The cylinder is getting too much gas and not enough air.汽缸里汽油太多而空气不足。

4 shaft   

n.(工具的)柄，杆状物

参考例句：

• He was wounded by a shaft.他被箭击中受伤。
• This is the shaft of a steam engine.这是一个蒸汽机主轴。

5 piston   

n.活塞

参考例句：

• They use a piston engine instead.他们改用活塞发动机。
• The piston moves by steam pressure.活塞在蒸汽压力下运动。

6 makers   

n.制造者，制造商（maker的复数形式）

参考例句：

• The makers of the product assured us that there had been no sacrifice of quality. 这一产品的制造商向我们保证说他们没有牺牲质量。
• The makers are about to launch out a new product. 制造商们马上要生产一种新产品。 来自《简明英汉词典》

7 inertia   

adj.惰性，惯性，懒惰，迟钝

参考例句：

• We had a feeling of inertia in the afternoon.下午我们感觉很懒。
• Inertia carried the plane onto the ground.飞机靠惯性着陆。

8 intervals   

n.[军事]间隔( interval的名词复数 )；间隔时间；[数学]区间；（戏剧、电影或音乐会的）幕间休息

参考例句：

• The forecast said there would be sunny intervals and showers. 预报间晴，有阵雨。
• Meetings take place at fortnightly intervals. 每两周开一次会。

9 chamber   

n.房间，寝室；会议厅；议院；会所

参考例句：

• For many,the dentist's surgery remains a torture chamber.对许多人来说，牙医的治疗室一直是间受刑室。
• The chamber was ablaze with light.会议厅里灯火辉煌。

10 rotation   

n.旋转；循环，轮流

参考例句：

• Crop rotation helps prevent soil erosion.农作物轮作有助于防止水土流失。
• The workers in this workshop do day and night shifts in weekly rotation.这个车间的工人上白班和上夜班每周轮换一次。

11 copper   

n.铜；铜币；铜器；adj.铜(制)的；(紫)铜色的

参考例句：

• The students are asked to prove the purity of copper.要求学生们检验铜的纯度。
• Copper is a good medium for the conduction of heat and electricity.铜是热和电的良导体。

12 specially   

adv.特定地；特殊地；明确地

参考例句：

• They are specially packaged so that they stack easily.它们经过特别包装以便于堆放。
• The machine was designed specially for demolishing old buildings.这种机器是专为拆毁旧楼房而设计的。

13 induction   

n.感应，感应现象

参考例句：

• His induction as a teacher was a turning point in his life.他就任教师工作是他一生的转折点。
• The magnetic signals are sensed by induction coils.磁信号由感应线圈所检测。

14 auxiliary   

adj.辅助的，备用的

参考例句：

• I work in an auxiliary unit.我在一家附属单位工作。
• The hospital has an auxiliary power system in case of blackout.这家医院装有备用发电系统以防灯火管制。

15 pistons   

活塞( piston的名词复数 )

参考例句：

• Some pistons have seating rings of metal or leather. 有些活塞上有金属或皮革的密封环。
• A pump uses valves and pistons. 泵使用阀和活塞。

16 vertical   

adj.垂直的，顶点的，纵向的；n.垂直物，垂直的位置

参考例句：

• The northern side of the mountain is almost vertical.这座山的北坡几乎是垂直的。
• Vertical air motions are not measured by this system.垂直气流的运动不用这种系统来测量。

17 racing   

n.竞赛，赛马；adj.竞赛用的，赛马用的

参考例句：

• I was watching the racing on television last night.昨晚我在电视上看赛马。
• The two racing drivers fenced for a chance to gain the lead.两个赛车手伺机竞相领先。

18 soldered   

v.（使）焊接，焊合( solder的过去式和过去分词 )

参考例句：

• Three lead wires are soldered to the anchor terminals. 在固定接线端子上焊有三根导线。 来自辞典例句
• He soldered the broken wires together. 他将断了的电线焊接起来。 来自辞典例句

19 obviated   

v.避免，消除（贫困、不方便等）( obviate的过去式和过去分词 )

参考例句：

20 spokes   

n.（车轮的）辐条( spoke的名词复数 )；轮辐；破坏某人的计划；阻挠某人的行动

参考例句：

• Her baby caught his fingers in the spokes of the pram wheel. 她宝宝的手指被婴儿车轮的辐条卡住了。 来自辞典例句
• The new edges are called the spokes of the wheel. 新的边称为轮的辐。 来自辞典例句

21 flanges   

n.（机械等的）凸缘，（火车的）轮缘( flange的名词复数 )

参考例句：

• The engine-feed system interface is at the turbopump inlet flanges. 发动机与供应系统的交界是在涡轮泵的进口法兰盘处。 来自辞典例句
• The web and flanges of the main girders were fabricated from ASTM A441 steel. 主梁的腹板和翼缘用ASTM A441钢制造。 来自辞典例句

22 ribs   

n.肋骨( rib的名词复数 )；（船或屋顶等的）肋拱；肋骨状的东西；（织物的）凸条花纹

参考例句：

• He suffered cracked ribs and bruising. 他断了肋骨还有挫伤。
• Make a small incision below the ribs. 在肋骨下方切开一个小口。

23 embodied   

v.表现( embody的过去式和过去分词 )；象征；包括；包含

参考例句：

• a politician who embodied the hopes of black youth 代表黑人青年希望的政治家
• The heroic deeds of him embodied the glorious tradition of the troops. 他的英雄事迹体现了军队的光荣传统。 来自《简明英汉词典》

24 lugs   

钎柄

参考例句：

• "They put on a lot of lugs here, don't they?" “这里的人的架子可不小，是不是？ 来自英汉文学 - 嘉莉妹妹
• In this department, hydro-set plates are assembled and joined together at the plate lugs. 在这个工段，组装脱水固化的极板并通过极板耳连在一起。 来自辞典例句

25 applied   

adj.应用的；v.应用，适用

参考例句：

• She plans to take a course in applied linguistics.她打算学习应用语言学课程。
• This cream is best applied to the face at night.这种乳霜最好晚上擦脸用。

26 drawn   

v.拖，拉，拔出；adj.憔悴的，紧张的

参考例句：

• All the characters in the story are drawn from life.故事中的所有人物都取材于生活。
• Her gaze was drawn irresistibly to the scene outside.她的目光禁不住被外面的风景所吸引。