CHAPTER XXVI. STEAM-HAMMERS.

The direct application of steam to forging-hammers is without doubt the greatest improvement that has ever been made in forging machinery¹; not only has it simplified operations that were carried on before this invention, but has added many branches, and extended the art of forging to purposes which could never have been attained² except for the steam-hammer.

The general principles of hammer-action, so far as already explained, apply as well to hammers operated by direct steam; and a learner, in forming a conception of steam-hammers, must not fall into the common error of regarding them as machines distinct from other hammers, or as operating upon new principles. A steam-hammer is nothing more than the common hammer driven by a new medium, a hammer receiving power through the agency of steam instead of belts, shafts³, and cranks. The steam-hammer in its most improved form is so perfectly⁴ adapted to fill the different conditions required in power-hammering, that there seems nothing left to be desired.

Keeping in view what has been said about an elastic⁵ connection for transmitting motion and power to hammers, and cushioning the vibratory or reciprocating⁶ parts, it will be seen that steam as a driving medium for hammers fills the following conditions:—

First.—The power is connected to the hammer by means of the least possible mechanism⁷, consisting only of a cylinder⁸, a piston⁹, and slide valve, induction¹⁰ pipe and throttle¹¹ valve; these few details taking the place of a steam-engine, shafts, belts, cranks, springs, pulleys, gearing, in short, all such details as are required between the hammer-head and the steam-boiler in the case of trip-hammers or crank-hammers.

Second.—The steam establishes the greatest possible elasticity¹² in the connection between a hammer and the driving power, and at the same time serves to cushion the blows at both the top and bottom of the stroke, or on the top only, as occasion may require.

Third.—Each blow given is an independent operation, and can be repeated at will, while in other hammers such changes [110] can only be made throughout a series of blows by gradually increasing or diminishing their force.

Fourth.—There is no direct connection between the moving parts of the hammer and the framing, except lateral¹³ guides for the hammer-head; the steam being interposed as a cushion in the line of motion, this reduces the required strength and weight of the framing to a minimum, and avoids positive strains and concussion¹⁴.

Fifth.—The range and power of the blows, as well as the time in which they are delivered, is controlled at will; this constitutes the greatest distinction between steam and other hammers, and the particular advantage which has led to their extended use.

Sixth.—Power can be transmitted to steam-hammers through a small pipe, which may be carried in any direction, and for almost any distance, at a moderate expense, so that hammers may be placed in such positions as will best accommodate the work, and without reference to shafts or other machinery.

Seventh.—There is no waste of power by slipping belts or other frictional contrivances to graduate motion; and finally, there is no machinery to be kept in motion when the hammer is not at work.

Keeping these various points in mind, an apprentice¹⁵ will derive¹⁶ both pleasure and advantage from tracing their application in steam-hammers, which may come under notice, and various modifications¹⁷ of the mechanism will only render investigation¹⁸ more interesting.

One thing more must be noticed, a matter of some intricacy, but without which, all that has been explained would fail to give a proper idea of steam-hammer-action. The valve motions are alluded¹⁹ to.

Steam-hammers are divided into two classes—one having the valves moved by hand, and the other class with automatic valve movement.

The action of steam-hammers may also be divided into what is termed elastic blows, and dead blows.

In operating by elastic blows, the steam piston is cushioned at both the up and down stroke, and the action of a steam-hammer corresponds to that of a helve trip-hammer, the steam filling the office of a vibrating spring; in this case a hammer gives a quick rebounding²⁰ blow, the momentum²¹ being only in part [111] spent upon the work, and partly arrested by cushioning on the steam in the bottom of the cylinder under the piston.

Aside from the greater rapidity with which a hammer may operate when working on this principle, there is nothing gained, and much lost; and as this kind of action is imperative²² in any hammer that has a 'maintained or positive connection' between its reciprocating parts and the valve, it is perhaps fair to infer that one reason why most automatic hammers act with elastic blows is either because of a want of knowledge as to a proper valve arrangement, or the mechanical difficulties in arranging valve gear to produce dead blows.

In working with dead blows, no steam is admitted under the piston until the hammer has finished its down stroke, and expended²³ its momentum upon the work. So different is the effect produced by these two plans of operating, that on most kinds of work a hammer of fifty pounds, working with dead blows, will perform the same duty that one of a hundred pounds will, when acting²⁴ by elastic or cushioned blows.

This difference between dead and elastic strokes is so important that it has served to keep hand-moved valves in use in many cases where much could be gained by employing automatic acting hammers.

Some makers²⁵ of steam-hammers have so perfected the automatic class, that they may be instantly changed so as to work with either dead blows or elastic blows at pleasure, thereby²⁶ combining all the advantages of both principles. This brings the steam-hammer where it is hard to imagine a want of farther improvement.

The valve gearing of automatic steam-hammers to fill the two conditions of allowing a dead or an elastic blow, furnishes one of the most interesting examples of mechanical combination.

It was stated that to give a dead or stamp stroke, the valve must move and admit steam beneath the piston after the hammer has made a blow and stopped on the work, and that such a movement of the valve could not be imparted by any maintained connection between the hammer-head and valve. This problem is met by connecting the drop or hammer-head with some mechanism which will, by reason of its momentum, continue to 'move after the hammer-head stops.' This mechanism may consist of various devices. Messrs Massey in England, and Messrs Ferris & Miles in America, employ a swinging wiper bar [112], which is by reason of its weight or inertia²⁷ retarded²⁸, and does not follow the hammer-head closely on the down stroke, but swings into contact and opens the valve after the hammer has come to a full stop.

By holding this wiper bar continuously in contact with the hammer-drop, elastic or rebounding blows are given, and by adding weight in certain positions to the wiper bar its motion is so retarded that a hammer will act as a stamp or drop. A German firm employs the concussion of the blow to disengage valve gear, so that it may fall and effect this after movement of the valves. Other engineers effect the same end by employing the momentum of the valve itself, having it connected to the drop by a slotted or yielding connection, which allows an independent movement of the valve after the hammer stops.

(1.) In comparing steam-hammers with trip or crank hammers what mechanism does steam supplant²⁹ or represent?—(2.) What can be called the chief distinction between steam and other hammers?—(3.) Under what circumstances is an automatic valve motion desirable?—(4.) Why is a dead or uncushioned blow most effective?—(5.) Will a hammer operate with air the same as with steam?

1 machinery   

n.(总称)机械，机器；机构

参考例句：

• Has the machinery been put up ready for the broadcast?广播器材安装完毕了吗？
• Machinery ought to be well maintained all the time.机器应该随时注意维护。

2 attained   

（通常经过努力）实现( attain的过去式和过去分词 )； 达到； 获得； 达到（某年龄、水平、状况）

参考例句：

• She has attained the degree of Master of Arts. 她已获得文学硕士学位。
• Lu Hsun attained a high position in the republic of letters. 鲁迅在文坛上获得崇高的地位。

3 shafts   

n.轴( shaft的名词复数 )；（箭、高尔夫球棒等的）杆；通风井；一阵（疼痛、害怕等）

参考例句：

• He deliberately jerked the shafts to rock him a bit. 他故意的上下颠动车把，摇这个老猴子几下。 来自汉英文学 - 骆驼祥子
• Shafts were sunk, with tunnels dug laterally. 竖井已经打下，并且挖有横向矿道。 来自辞典例句

4 perfectly   

adv.完美地，无可非议地，彻底地

参考例句：

• The witnesses were each perfectly certain of what they said.证人们个个对自己所说的话十分肯定。
• Everything that we're doing is all perfectly above board.我们做的每件事情都是光明正大的。

5 elastic   

n.橡皮圈，松紧带；adj.有弹性的；灵活的

参考例句：

• Rubber is an elastic material.橡胶是一种弹性材料。
• These regulations are elastic.这些规定是有弹性的。

6 reciprocating   

adj.往复的；来回的；交替的；摆动的v.报答，酬答( reciprocate的现在分词 )；（机器的部件）直线往复运动

参考例句：

• Dynamic loading is produced by seismic forces, non-steady wind, blast, reciprocating machinery. 动荷载是由于地震力、不稳定的风、冲击波，往复式机器所产生。 来自辞典例句
• The prime mover may be a gas reciprocating engine. 原动机可能是燃气往复式发动机。 来自辞典例句

7 mechanism   

n.机械装置；机构，结构

参考例句：

• The bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人体的组成部件。
• The mechanism of the machine is very complicated.这台机器的结构是非常复杂的。

8 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。

9 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。

10 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。

11 throttle   

n.节流阀，节气阀，喉咙；v.扼喉咙，使窒息，压

参考例句：

• These government restrictions are going to throttle our trade.这些政府的限制将要扼杀我们的贸易。
• High tariffs throttle trade between countries.高的关税抑制了国与国之间的贸易。

12 elasticity   

n.弹性，伸缩力

参考例句：

• The skin eventually loses its elasticity.皮肤最终会失去弹性。
• Every sort of spring has a definite elasticity.每一种弹簧都有一定的弹性。

13 lateral   

adj.侧面的，旁边的

参考例句：

• An airfoil that controls lateral motion.能够控制横向飞行的机翼。
• Mr.Dawson walked into the court from a lateral door.道森先生从一个侧面的门走进法庭。

14 concussion   

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。

15 apprentice   

n.学徒，徒弟

参考例句：

• My son is an apprentice in a furniture maker's workshop.我的儿子在一家家具厂做学徒。
• The apprentice is not yet out of his time.这徒工还没有出徒。

16 derive   

v.取得；导出；引申；来自；源自；出自

参考例句：

• We derive our sustenance from the land.我们从土地获取食物。
• We shall derive much benefit from reading good novels.我们将从优秀小说中获得很大好处。

17 modifications   

n.缓和( modification的名词复数 )；限制；更改；改变

参考例句：

• The engine was pulled apart for modifications and then reassembled. 发动机被拆开改型，然后再组装起来。 来自《简明英汉词典》
• The original plan had undergone fairly extensive modifications. 原计划已经作了相当大的修改。 来自《简明英汉词典》

18 investigation   

n.调查，调查研究

参考例句：

• In an investigation,a new fact became known, which told against him.在调查中新发现了一件对他不利的事实。
• He drew the conclusion by building on his own investigation.他根据自己的调查研究作出结论。

19 alluded   

提及，暗指( allude的过去式和过去分词 )

参考例句：

• In your remarks you alluded to a certain sinister design. 在你的谈话中，你提到了某个阴谋。
• She also alluded to her rival's past marital troubles. 她还影射了对手过去的婚姻问题。

20 rebounding   

蹦跳运动

参考例句：

• The strength of negative temperature concrete is tested with supersonic-rebounding method. 本文将超声回弹综合法用于负温混凝土强度检测。
• The fundamental of basketball includes shooting, passing and catching, rebounding, etc. 篮球运动中最基本的东西包括投篮，传接球，篮板球等。

21 momentum   

n.动力，冲力，势头；动量

参考例句：

• We exploit the energy and momentum conservation laws in this way.我们就是这样利用能量和动量守恒定律的。
• The law of momentum conservation could supplant Newton's third law.动量守恒定律可以取代牛顿第三定律。

22 imperative   

n.命令，需要；规则；祈使语气；adj.强制的；紧急的

参考例句：

• He always speaks in an imperative tone of voice.他老是用命令的口吻讲话。
• The events of the past few days make it imperative for her to act.过去这几天发生的事迫使她不得不立即行动。

23 expended   

v.花费( expend的过去式和过去分词 )；使用（钱等）做某事；用光；耗尽

参考例句：

• She expended all her efforts on the care of home and children. 她把所有精力都花在料理家务和照顾孩子上。
• The enemy had expended all their ammunition. 敌人已耗尽所有的弹药。 来自《简明英汉词典》

24 acting   

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。

25 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》

26 thereby   

adv.因此，从而

参考例句：

• I have never been to that city,,ereby I don't know much about it.我从未去过那座城市，因此对它不怎么熟悉。
• He became a British citizen,thereby gaining the right to vote.他成了英国公民，因而得到了投票权。

27 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。

28 retarded   

a.智力迟钝的，智力发育迟缓的

参考例句：

• The progression of the disease can be retarded by early surgery. 早期手术可以抑制病情的发展。
• He was so slow that many thought him mentally retarded. 他迟钝得很，许多人以为他智力低下。

29 supplant   

vt.排挤；取代

参考例句：

• Electric cars may one day supplant petrol-driven ones.也许有一天电动车会取代汽油驱动的车。
• The law of momentum conservation could supplant Newton's third law.动量守恒定律可以取代牛顿第三定律。