1844.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



91 



TliP materials of which such boilers should be constructed, are as 

 follows 



Furnaces, of best Low Moor iron sin. thick ; the grate and uptake 

 should be of the same kind and substance. The tube plates are some- 

 times made of mixed metal ; but we prefer Low Moor iron of a inch 

 gauge. The tubes (if of brass) should they be those made by Alston, 

 which are bare J in. thick, or 12 wire gauge. If made of iron, they 

 should be those of Russell & Co. 



A difference of opinion exists as to the advantages arising from the 

 use of brass or iron tubes, although practice has hitherto been almost 

 confined to the former ; but it appears likely that a great change will 

 shortly take place in this ])articular, arising from the injurious effects 

 produced by galvanic action on the iron shell of the boiler, which in 

 many boilers has occurred to an alarming extent. Of course this 

 would be actively obviated by the use of iron tubes, and the advan- 

 tage of the one over the other, is solely a commercial question, deter- 

 minable by practice only. We think the iron tubes will be found the 

 best in all respects, especially if means are taken (and they are sim- 

 ple) to prevent the accumulation of salt and calcareous deposits. 



The shell and chimney uptake may be of best Staffordshire iron, 

 i in. thick, and i in. below, say for 2 ft. up from the bottom, where the 

 decay is generally very rapid. Care should be taken in properly 

 staying every part. 



PARKYN'S DIRECT ACTION ENGINE. 



( fVith an Engraving, Plate 3.J 



Sir — I herewith send you a drawing of a Double Cylinder Engine, 

 which I patented in England last year. I have erected an engine, 

 similar to that shown on board, the Iron Boat, Prince Albert, built for 

 the Montreal and Laprairie Ferry. 



The engraving is a longitudinal section through the engine, showing 

 the method of connecting the cylinders with the air-pump, and trans- 

 mitting the power to the main shaft. The novelty of the plan is the 

 way in which the air-pump is worked, securing greater economy of 

 space and fewer moving parts, and consequently less friction — these 

 being the primary objects to be attained by all plans of direct acting 

 engines. The cylinders are 42 inches in diameter, and 5 feet stroke. 

 The air-pump is 28 inches, and the same stroke. The plunger of the 

 air-pump is worked down to within 3 in. of the flooring of the vessel, 

 thus securing the longest possible stroke for a given height, with an 

 adequate length of connecting rod, which in the engine shown is ten 

 feet. F, F, are the two foot valves — the discharge is at the side. 

 The two valves G, G, in the air-pump plunger are to allow for the 

 exit of any air that may collect in the pump. 



The valves of the engine are four in number, two for the steam on 

 the left, and two for the exhaust on the right they are of the kind 

 generally denominated the Equilibrium Valve, and worked by two 

 eccentrics, one for each pair ; this is adopted to secure the means of 

 cutting off the steam valve at any part of the stroke. The engine can 

 be started, stopped and handled by a force not exceeding 401b. ap- 

 plied to a lever 3 feet long. The condenser is immediately below the 

 nozzles, thus securing instant condensation. 



The engine at ordinary working makes 21 revolutions with a pres- 

 sure of steam of 181b. per square inch in the boiler, and cutting off at 

 half stroke, driving a wheel 20 ft. in, diameter, 7 feet wide with 20 

 inches of dip. The vacuum in condenser averages 28i inches as 

 indicated by the barometer. 



The boat is 178 feet long between the perpendiculars, 175 feet on 

 keel, 25 feet beam, depth of hold 8 feet, and 2 ft. 9 in. draught of water 

 when light. The boilers are upon the tubular principle, and con- 

 structed to burn wood fuel. The boat before the navigation closed 

 was 23 days upon her station, and seemed to answer all the purposes 

 for which she was built. 



I thus submit to the criticism of English engineers the first Double 

 Cylinder Engine that has been manufactured in Canada, and erected 

 on board the first iron boat built in the colony. 



I am, Sir, your obedient servant, 



William Parkyn. 

 fit. Mary's Foundry, 

 Montreal, Dec. 12, 1843. 



P.S. In such class of vessel as the Helen Macgvegor, described in 

 the Journal for November, an engine on the plan here submitted could 

 be got in the same space, having a feet stroke and 12 feet connectipg 

 rod. 



[It is very evident that Mr. Parkyn's engine is a copy of the 

 double cylinder engines of Messrs. Maudslay & Co. ; this engine 

 being in every respect, but one, exactly similar to that patented by 

 Joseph Maudslay and Joshua Field on the 7th of May, 1839, and de- 

 scribed in the Journal, p. 73, Vol. Ill, 1840. The only novelty, is in 

 placing the air-pump between the cylinders, and making it the guide 

 for the bottom end of the connecting rod; the air-pump is therefore 

 necessarily open topped, and working under the pressure of the at- 

 mosphere. This arrangement most undoubtedly reduces this kind of 

 engini> to a minimum of space per horse power, and admits of a 

 longer connecting rod than Messrs. Maudslay and Field's engine, for 

 the reasons given by Mr. Parkyn — his working the air-pump piston to 

 within an inch or two of the vessel's bottom. There is considerable 

 ingenuity in the scheme, although, if our memory serves us rightly, 

 we have seen it before printed and described in some work, but which 

 we cannot refer to just now. It possesses all the faults of Maudslay's 

 engines, and which we think have been urged against them with much 

 reason — namely, greatly unbalanced weight, and consequent irregu- 

 larity of motion, and perhaps of more consequence still — the surety 

 of a difference in the friction of the two pistons, throwing a heavy 

 strain, and wear and tear on'the piston rods and working parts con- 

 nected therewith. 



Mr. Parkyn's engine possesses all these disadvantages, to which 

 must be added his open topped air-pump, which adds to, instead of 

 reducing the unbalanced weight— for he has to bring up the bucket 

 or plunger against the atmosphere, which in a pump of 28 in. diame- 

 ter, is equal to four tons or close upon half the power of one cylinder 

 (vacuum pressure.) 



As the condensation water is, under ordinary working, about equal 

 to one fourth of the air-pump's content per stroke, it follows that the 

 power requisite for its expulsion into the hot well is exerted only 

 during the last quarter of its descent, and until it reaches that point 

 it is totally inefficient as a balance to the working parts, and then it 

 has become useless from their accelerated motion. Messrs. Maudslay 

 avoid this, although they increase their weight and space, by placing 

 the air-pump as shown in the drawing before referred to (Vol. III., 

 1840.) 



There is still another objection to Mr. Parkyn's plan. The velocity 

 of the air-pump plunger is double that generally given, it is necessa- 

 rily the same as the piston, instead of a moiety, and this would be a 

 serious objection in the minds of many English engineers. In the 

 case of a bucket with valves, we should agree as to its impracticability, 

 but we do not think the objection applies with so much force when a 

 solid plunger is used, (as by Mr. Parkyn,) and the delivery valves are 

 made of sufficient capacity. We know of several good engines, that 

 have the strokes of their cylinders and air-pumps equal, the Prince 

 Albert, of London, for instance, just occurs to us. The friction is, of 

 course, greater, in the ratio of 2 to 3, and probably the wear of the 

 air-pump would be considerable, from the oblique action of the con- 

 necting rod : but these are matters for practice to determine, and we 

 shall be glad to hear again from Mr. Parkyn, after his engines have 

 been at work for some time, and perhaps he can then favour us with 

 some indicator diagrams taken from the cylinder and from the under 

 side of the air-pump plunger— these would assist our judgment mate- 

 rially, and be very interesting. 



The steam and eduction valves, used by Mr. Parkyn, are those of 

 the Cornish engines— generally known by the name of double beat 

 valves; two sets of eccentrics are applied, and the expansion of the 

 steam is effected by a slot in the eccentric notch, which can be al- 

 tered at pleasure, and is both novel, simple and effective : but it is not 

 applicable to slide valves. 



On the whole it is a creditable production, although, as we have 

 said before, it is a decided infringement of Maudslay's patent, in so far 

 as the employment of two cylinders, piston-rods, T piece, &c., is con- 

 cerned. However, we cannot help again expressing our pleasure at 

 these liberal exchanges of practical knowledge, between the new and 

 old world, and feel gratified at our Journal being the means of com- 

 municating them to the public.]— Editor C. E. & A. Journal. 



Railways.— First Report fiam the Select Committee.— The Select Committee 

 appointed to consider whetlier any what new provisions ought to be introduced into sucli 

 railway biUs as may come before this House during the present or future sessions, for tlie 

 advantage of tile public and the improvement of the railway system, aud likewise to con- 

 sider whether any and what changes ought to be made in the standing orders relating to 

 railways, and who were empowered to report their opinion thereupon from time to time 

 to the House, have considered the toiatter referred to them, aud have agreed to the fol- 

 lowing clause be inserted in all the. railway bills now coming before or passing through 

 Parliament, viz., " And be it further enacted, that nothing herein contained shall be 

 deemed or construed to exempt the railway by this or the said recited acts authorized to 

 be made from the provisions of any general act relating to such bills which may pass 

 during the present session of Parliament, or of any general act relatiug to railways which 

 may pass during the present or any future sessioa of Parlisment," 



