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首页 » 经典英文小说 » The Economy of Workshop Mainipulation » CHAPTER XXVII. COMPOUND HAMMERS.
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CHAPTER XXVII. COMPOUND HAMMERS.
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Another principle to be noticed in connection with hammers and forging processes is that of the inertia1 of the piece operated upon—a matter of no little importance in the heavier kinds of work.

When a piece is placed on an anvil2, and struck on the top side with a certain force, the bottom or anvil side of the piece does not receive an equal force. A share of the blow is absorbed by the inertia of the piece struck, and the effect on the bottom side is, theoretically, as the force of the blow, less the cushioning effect and the inertia of the pieces acted upon.

In practice this difference of effect on the top and bottom, or between the anvil and hammer sides of a piece, is much greater than would be supposed. The yielding of the soft metal on the top cushions the blow and protects the under side from the force. The effect produced by a blow struck upon hot iron cannot be estimated by the force of the blow; it requires, to use a technical term, a certain amount of force to "start" the iron, and anything less than this force has but little effect in moving the particles and changing the form of a piece.

From this it may be seen that there must occur a great loss of power in operating on large pieces, for whatever force is absorbed by inertia has no effect on the underside. By watching a smith using a hand hammer it will be seen that whenever a piece operated upon is heavier than the hammer employed, but little if any effect is produced on the anvil or bottom surface, nor is this loss of effect the only one. The expense of heating, which generally exceeds that of shaping forgings, is directly as the amount of shaping that may be done at each heat; and consequently, if the two sides of a piece, instead of one, can be equally acted upon, one-half the heating will be saved.

Another object gained by equal action on both sides of large pieces is the quality of the forgings produced, which is generally improved by the rapidity of the shaping processes, and injured by too frequent heating.

The loss of effect by the inertia of the pieces acted upon increases with the weight of the work; not only the loss of power, but also the expense of heating increases with the size of the pieces. There is, however, such a difference in the mechanical conditions between light and heavy forging that for any but a heavy class of work there would be more lost than gained in attempting to operate on both sides of pieces at the same time.

To attain3 a double effect, and avoid the loss pointed4 out, Mr Ramsbottom designed what may be called compound hammers, consisting of two independent heads or rams5 moving in opposite directions, and acting6 simultaneously7 upon pieces held between them.

It would be inferred that the arrangement of these double acting hammers must necessarily be complicated and expensive, but the contrary is the fact. The rams are simply two masses of iron mounted on wheels that run on ways, like a truck, and the impact of the hammers, so far as not absorbed in the work, is [114] neutralised by each other. No shock or jar is communicated to framing or foundations as in the case of single acting hammers that have fixed8 anvils9. The same rule applies in the back stroke of the hammers as the links which move them are connected together at the centre, where the power is applied10 at right angles to the line of the hammer movement. The links connecting the two hammers constitute, in effect, a toggle joint11, the steam piston12 being attached where they meet in the centre.

The steam cylinder13 which moves the hammers is set in the earth at some depth below the plane upon which they move, and even when the heaviest work is done there is no perceptible jar when one is standing14 near the hammers, as there always is with those which have a vertical15 movement and are single acting.

(1.) Why is the effect produced different on the top and bottom of a piece when struck by a hammer?—(2.) Why does not a compound hammer create jar and concussion16?—(3.) What would be a mechanical difficulty in presenting the material to such hammers?—(4.) Which is most important, speed or weight, in the effect produced on the under side of pieces, when struck by single acting hammers?

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1 inertia sbGzg     
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。
2 anvil HVxzH     
n.铁钻
参考例句:
  • The blacksmith shaped a horseshoe on his anvil.铁匠在他的铁砧上打出一个马蹄形。
  • The anvil onto which the staples are pressed was not assemble correctly.订书机上的铁砧安装错位。
3 attain HvYzX     
vt.达到,获得,完成
参考例句:
  • I used the scientific method to attain this end. 我用科学的方法来达到这一目的。
  • His painstaking to attain his goal in life is praiseworthy. 他为实现人生目标所下的苦功是值得称赞的。
4 pointed Il8zB4     
adj.尖的,直截了当的
参考例句:
  • He gave me a very sharp pointed pencil.他给我一支削得非常尖的铅笔。
  • She wished to show Mrs.John Dashwood by this pointed invitation to her brother.她想通过对达茨伍德夫人提出直截了当的邀请向她的哥哥表示出来。
5 rams 19ae31d4a3786435f6cd55e4afd928c8     
n.公羊( ram的名词复数 );(R-)白羊(星)座;夯;攻城槌v.夯实(土等)( ram的第三人称单数 );猛撞;猛压;反复灌输
参考例句:
  • A couple of rams are butting at each other. 两只羊正在用角互相抵触。 来自辞典例句
  • More than anything the rams helped to break what should have been on interminable marriage. 那些牡羊比任何东西都更严重地加速了他们那本该天长地久的婚姻的破裂。 来自辞典例句
6 acting czRzoc     
n.演戏,行为,假装;adj.代理的,临时的,演出用的
参考例句:
  • Ignore her,she's just acting.别理她,她只是假装的。
  • During the seventies,her acting career was in eclipse.在七十年代,她的表演生涯黯然失色。
7 simultaneously 4iBz1o     
adv.同时发生地,同时进行地
参考例句:
  • The radar beam can track a number of targets almost simultaneously.雷达波几乎可以同时追着多个目标。
  • The Windows allow a computer user to execute multiple programs simultaneously.Windows允许计算机用户同时运行多个程序。
8 fixed JsKzzj     
adj.固定的,不变的,准备好的;(计算机)固定的
参考例句:
  • Have you two fixed on a date for the wedding yet?你们俩选定婚期了吗?
  • Once the aim is fixed,we should not change it arbitrarily.目标一旦确定,我们就不应该随意改变。
9 anvils bd00446d0777d957f7cdfb2835dbf08a     
n.(铁)砧( anvil的名词复数 );砧骨
参考例句:
10 applied Tz2zXA     
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。
11 joint m3lx4     
adj.联合的,共同的;n.关节,接合处;v.连接,贴合
参考例句:
  • I had a bad fall,which put my shoulder out of joint.我重重地摔了一跤,肩膀脫臼了。
  • We wrote a letter in joint names.我们联名写了封信。
12 piston w2Rz7     
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。
13 cylinder rngza     
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。
14 standing 2hCzgo     
n.持续,地位;adj.永久的,不动的,直立的,不流动的
参考例句:
  • After the earthquake only a few houses were left standing.地震过后只有几幢房屋还立着。
  • They're standing out against any change in the law.他们坚决反对对法律做任何修改。
15 vertical ZiywU     
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。
16 concussion 5YDys     
n.脑震荡;震动
参考例句:
  • He was carried off the field with slight concussion.他因轻微脑震荡给抬离了现场。
  • She suffers from brain concussion.她得了脑震荡。


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