308 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL, 



[October, 



9. 0/1 ihe cdiap.i and mean/! of prevention of the Oscillation of the 

 ll'/ieelx of jMcomotire Engines. By Mr. Hkaton. 



IMi. Heaton exhibited a machine representiiifj a hicomntive en- 

 gine, to jirrive the cause and prevention of their oscilhition on 

 railways. He first showed tlie machine simply with the piston, 

 rod, and connecting-rod attaclied to the wheel. ^Vllen the ma- 

 chine was set in motion slowly, it remained steady on the table; 

 but by increasing- the velocity of the wheels, it began to oscillate 

 and jump about, although each wheel had a balance-weight in it, 

 equal to the weight of tlie erank-])in and the connecting-rod. He 

 then showed tlie machine with weights jilaced in the wheels equal 

 to the weight of the pistons and gearing, or all that moves in a 

 horizontal line. When the wheels of the machine were set in 

 motion with great velocity, the machine did not oscillate, but it 

 jumped perpendicularly up and down. 



iMr. Heaton then attached to the machine his improvements, for 

 the ])urpose of showing the importance of ])lacing moving weights 

 in opposite directions to each other at high velocities. He ob- 

 served that when an engine of 20-inch stroke with 6-feet driving- 

 wheels goes 15 strokes per minute, or 3 miles per hour, it required 

 one-tenth of the weight moving horizontally (that is, the piston 

 and gearing) to stop it and turn it again; at 35 strokes per 

 minute, one-half its weight; at 74 strokes per minute, once-and- 

 a-half its weight; and at 100 strokes per minute, four times its 

 own weight. 



A 



Reference to jtarts preventing 



Oseillation. 

 Auriliarv Cnnilf fi led an crank pin B. 

 Criukliin to ditto. 



Weiitlit to balance crank-pin in Wheel. 

 Connecting \\i\f\. 



II -Uer or liala-ice- weight travelling iuan 

 opiiosile (liifftinn to piston E. 



li'ference to parts causing 

 Oscittation. 



A. Drivinij-wheel of a Locomotive Engine. 



B. Crunk |tin in ivlieel. 



C. C ilinectifig rod. 

 1). SliileGear. 



1*. Pis'on and Rod. 



F. Steam t;ylinder. G. Pail. 



If a weight (6), with connecting-rod (4), and an auxiliary crank 

 (1), be attached to the head of the crank-])in (1), equal to the 

 weight of the piston (F) and its gearing, so as to make the weight 

 run to the left hand at the same instant the piston goes to the 

 right, the blow to stop the piston and make it return will be 

 received in the auxiliary crank (1), instead of in the wheel, pro- 

 ducing thereliy a neutral point in the centre and steadiness of 

 motion; for when the blow is received in the vvlieels, the cranks 

 being at riglit angles, it is communicated through the axle, and 

 gives a twisting motion to the whole framing of the engine: this 

 oscilliition is found to be greatest when tlie engine is running most 

 regular for speed, and flie piston going the same way with tlie os- 

 cillation of the carriage. 



Mr. Heaton then set in motion the machine with his improve- 

 ments, as shown in the annexed engraving, when there was not the 

 slightest oscillation or jumping to be seen. 



10. On a machine for Ventilating Coal Mines. By Mr. AVilliam 

 Bhunton, of Newport, Monmouthshire. 



Mr. Brunton stated that he proposed to describe the ordinary 

 means used to etfect rarefaction of the air in coal mines, so as to 

 ventilate the works; to make some practical observations on the 

 amount of power generated by these means, and the effects of the 

 ordinary application of them; to point out what appears to be the 

 inherent defects of the principle of heat as a ventilator to a coal 

 mine; and, lastl)', to describe the apparatus invented and erected 

 for 'j'homas Powell, Esq., of the Gaer, near Newport, and which 

 lie would recommend as a mechanical substitute for tlie furnace, 

 possessing much greater power of rarefaction, and in many respects 

 better atlapted to the varj'ing circumstances of coal mines gene- 

 rally. 



Mr. Brunton stated that the ease and facility with which atmo- 

 spheric air moves upon its receiving an increase of temperature is 

 the principle upon which the ordinary method of ventilation is 

 conducted. In sinking * shaft, the heat communicated to the air 

 ill descending, and its contact with the bodies of the men, is 



usually sufficient to create an ascending and descending current 

 for the supply of fresh air; and this is greatly promoted by a par- 

 tition dividing the shaft into two compartments, the downcast on 

 one side, the upcast on the other. The same thing is accom|ilished 

 by sinking two contiguous shafts. But little progress can be made 

 in working a colliery till a more effectual means of ventilation is 

 applied. For this purpose, a furnace, or large open grate, is con- 

 structed near to the upcast-shaft, upon which a constant fire is 

 maintained, over which the air passes, and is rarefied in its pro- 

 gress from the workings of the colliery to the upcast-shaft, when 

 its buoyancy creates a draught through tlie ramifications of the 

 mine back to the downcast-shaft. 



In order tojudge of this mode of rarefaction, Mr. Brunton con- 

 structed a Table fNo. 1.) of easy application, showing the expan- 

 sion and weight of air at every 10° of heat from freezing to 252°; 

 also a plain way of ajiplying it to any particular case. 



It must be evident that the ascension of air in the upcast is 

 owing to its being volume for volume lighter than the air in the 

 downcast, and that lightness is obtained by heating, and that the 

 expansion consequent on heat is the true measure of its levity or 

 tendency to rise. 



Let the figures A, and B, represent two shafts of equal depth of 

 900 feet; A. the downcast, B, the upcast. Let us suppose the air 

 in A, 62°, and the average heat in B, 182°. It will be sufficient for 

 all practical jiiirposes to carry out the calculation in perpendicular 

 feet of 1 foot area, tlien we have (see Table I.) — 



grains. grains. 

 A 90(1 cuiiic feet. 62° at 518 = 466.200 

 B, UOO „ \sl'^ at J20 = 378,000 -t- 618 = 730 



88,200 grains. 



Showing that 900 feet at 182° is balanced by 730 feet at 62°, as 

 in the diagram, leaving 170 feet at 518 = 88,200 grains, or about 

 12"5 lb. on the stpiare foot, as a gravitating power to propel the air 

 upward in the shaft B. 



Mr. Brunton was aware of various rules that have been laid 

 down for calculating the velocity and force with which the air 

 ascends the upcast-shaft; but he has never found them to tally 

 with experience, but often imposing a notion of security where 

 danger ought rather to have been a|iprehended. This induced 

 him to investigate the subject, admitted to be on all hands an in- 

 tricate one, and to submit the following hypothesis, which, if cor- 

 rect, may prevent the furnace as a jiower of rarefaction being rated 

 beyond its capability, as it has been many times, to the fearful 

 destruction of human life. 



The principle ujion which Mr. Brunton thinks the velocity of 

 the air in two shafts A, and 15, acting alone and unconnected 

 with the working of the cidliery, should be calculated, is analogous 

 to two weights A, B, suspended by a line passing over a pulley 

 (su])posed without friction), and the length of the line may re- 

 present the depth of the shafts. ^V'hilst the weights A, and B, 

 are equal, there can be no motion, for they neutralise each other; 

 but if a weight (C) is added to one of the weights A, or B, then 

 motion will take place, but the added weight C, will not descend 

 as it would if it descended alone freely, for it cannot move without 



