1819.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL, 



165 



IMPROVED PUMPING ENGINE. 



The great economy of fuel that was first attained by the Cornish 

 engineers in their single-acting engines for pumping water from 

 mines,, some years ago attracted mucli attention among engineers 

 generally. The fact of the alleged economy having been really 

 attained, was first denied or doubted; then tlie subject was inves- 

 tigated, and the fact found not only to be true but easily accounted 

 for. It was nothing more than might have been expected from 

 the great degree of expansion effected in the steam-cylinder, effi- 

 cient coveriiig of all radiating surfaces, and generally great care 

 on the part of the engine workers. These were admitted by all to 

 be the great sources of economy; but many supposed that they 

 were in some way necessarily connected with single-acting engines 

 working on the Cornish plan. This led to the erection of several 

 Cornish engines for waterworks' purposes in various parts of the 

 country, and the saving of fuel has in all cases been found to be 

 very great, when compared with the former Boulton and Watt 

 engines. 



So slow, however, is frequently the progress of con-ect ideas on 

 mechanical subjects, that it is only now that those interested in 

 such works are becoming gradually convinced tliat the desired 

 economy of fuel may be attained without the cumbrous and ex- 

 pensive machinery of a Cornish engine. 



The peculiarities essential to the (Cornish engine are, that it is 

 single acting, and that it should not directly lift the water it is 

 intended to raise by its means, but that it sho\ild lift a ponderous 

 weight, which is then let fall, and in falling raises tlie water. The 

 faults connected with such engines are, that they are double the 

 necessary size, and do their work in an indirect manner; and the 

 only reason given for adopting this description of engine is, that 

 no other engine could work with the same amount of expansion. 

 But in the calculations of saving, all consideration of the loss of 

 interest arising from the greater first cost of the Cornish engines 

 has been omitted. This greater first cost arises not only from the 

 much larger size of engine required to do the same work on the 

 Cornish system, but also from the necessary concomitants— huge 

 balance-weights on the pump-rods, engine-houses and foundations 

 double the necessary size, and stand-pipes that have not unfre- 

 quently cost nearly as much as the engines themselves. The 

 interest on this large expenditure has frequently gone far to swal- 

 low up the saving on the fuel. 



We have been led to make these preliminary remarks in conse- 

 quence of inspecting a small engine, of 20-horse power, made for 

 the Richmond Waterworks Company by Messrs. Simpson, of Pira- 

 lico, which is a double-acting engine, and cuts off the steam at 

 one-fourth of the length of tlie stroke, so as to expand the steam 

 into four times its original bulk; and all the radiating surfaces are 

 neatly and efficiently clothed with non-conducting substances. 

 From several trials, it has been ascertained that the consumption 

 of fuel is only 2| lb. per horse-power per hour, and that even this 

 economy, it is expected, will be considerably exceeded when the 

 company have fixed a second boiler, the present one being only 

 one-half the size that the makers intended the engine to work 

 with. This result, we think, clearly proves the practicability of 

 emulating the Cornish economy of fuel with double-acting engines 

 judiciously constructed. 



This engine has another advantage not very common with 

 pumping engines, in being capable of working at the same speed 

 as an ordinary mill-engine. This is accomplished, partly by the 

 construction of the pump-valves and partly by the use of a new 

 kind of pump lately registered by Mr. Thomson, Messrs. Simp- 

 son's manager. 



The annexed engravings, figs. 1 and 2, show a section and ex- 

 ternal view of this pump, from which its action will be very easily 

 understood. It is, as will be seen, in many respects the same as 

 the old bucket-pump; but there is added to it the plunger pp, the 

 sectional area of which is half that of the pump-barrel b b. This 

 simple addition makes the pump double-acting, and suitable for 

 being wrought by a double-acting engine; for, when the bucket is 

 ascending, one-half of the water that it raises, instead of going 

 out at the delivery-pipe d, occupies the place previously occupied 

 by the plunger, and when the bucket descends, this part of the 

 water is then expelled by the phinger. Equal quantities of water 

 are thus delivered at each stroke, and the pump is double-acting, 

 while at the same time it has only two valves, and is nearly as 

 simple in its construction, and occupies as little space, as a single- 

 acting pump. In all pumps it is of the first importance that easy 

 access should be afforded to all the valves, and when this condition 

 is adhered to, and the valves made large and of the best modern 

 construction, those who have made double-acting pumps on the 



present system with four valves, know that they are both expen- 

 sive in their construction and unwieldy in their dimensions. 1 hese 



Fig. 2.— Internal View. 



Fig. 1.— Extetiial View 



View of Top. View of Valve. 



objections are very much obviated by the plan we have now de- 

 scribed, and much advantage is also derived from the water having 



