THE FARMER'S MAGAZINE. 



471 



THE LEADING FEATURES OF THE IMPLEMENT DEPARTMENT 



OF THE CHESTER SHOW. 



We now proceed to glance at the important de- 

 partment of steam engines — the mode adopted to 

 test their working capabilities ; and the result of the 

 tests applied. The following we believe were the con- 

 ditions under which the engines were admitted to 

 compete for the honour of the prizes awarded- Portable 

 engines : The diameter of cylinder, for eight-horse 

 engines, not to exceed 93 inches ; above eight-horse, 

 and not exceeding twelve, two cylinders each, not ex- 

 ceeding 8 inches' diameter. The exhibitors were 

 bound to provide specifications, along with longitudinal 

 and sectional plans, to the Society, these latter showing 

 the action of the fire upon the flues, and the whole af- 

 fording the following particulars of information: (1) 

 The thickness and quality of the boiler plates ; (2) The 

 diameter of cylinder ; (3) The length of the stroke of 

 piston ; (4) The number of revolutions, and the 

 diameter of the crank and crank-shaft, both of which 

 must be made of wrought-iron ; (5) Diameter and 

 weight of fly-wheel ; (6) The diameter of driving 

 pulley, which must not be less than six inches wide, nor 

 move at a less velocity than 1,600 feet per minute ; (7) 

 The number of horses' power the engine is calculated to 

 work at. 



The tubes in the boiler were to be not less than 

 2^ inches inside measurement, nor less than No. 12 

 of the metal gauge in thickness. The distance 

 between the tubes not to be less than one inch. The 

 tube plates to be either of " Lowmoor," or " Bowling'* 

 iron ; with the trade marks of the company on each 

 plate. 



The engine to be provided with a good water-gauge, 

 and with a stout piece of pipe tapped to fit the junction 

 of a pressure-gauge. The force-pump not to have 

 more than two valves, and where a " heater" is used, it 

 must be so constructed that the engine will work inde- 

 pendently of it. 



In "fixed" steam-engines, the (nominal) power en- 

 tered was not to exceed 10 horses ; the diameter of 

 cylinder not to exceed 11^ inches. The exhibitor to 

 supply the Society with plans and exhibitions of the 

 boiler employed by him. Such boiler to possess a ca- 

 pacity of 25 superficial feet of heating surface, and i of 

 a foot of effective fire-grate for each nominal horse- 

 power of the; engine. No tubes of tubular boiler em- 

 ployed are to be less than 23 inches inside measurement, 

 nor less in thickness than No. 12 of the metal gauge. 



In carrying out the trials of the engines, they were 

 set to work for a short time with steam at a pressure of 

 45Ib8. to the square inch, and then stopped and suffered 

 to cool down. The exhibitor of each engine was at this 

 stage required to take the working parts of the steam- 

 engine to pieces — in the presence of the judges — to with- 

 draw the piston, valve slide, expansion valve, and pump 



valves, for examination. Two men only were allowed to 

 assist in tliis operation, the time of taking to pieces and re- 

 placing the parts being carefully noted. When the whole 

 were put together again, the engine was put to the trial in 

 the ordinary manner in connection with the " dynamo- 

 meter," of which the following description will convey 

 some idea as to its construction and mode of operation. 

 A framing supports two upright pedestals (« a), affording 

 bearings for a horizontal shaft (6) ; this carries a ver- 

 tical pulley (c), three feet six inches diameter; alongside 

 of this a large friction-wheel (d) is hung on the shaft 

 (b) ; the friction-wheel is embraced with an iron strap 

 (e) and friction-blocks (/"), these being tightened as 

 desired by pinching-screws ((/) ; from a point opposite 

 the centre of the friction- wheel {d) a pointer (/*) is 

 attached to the friction-strap (e), and from the same 

 point a rod is hung, which supports a dish (i), carrying 

 a certain number of weights {k). The driving-belt from 

 the driving pulley of the steam-engine under trial is 

 passed over the pulley (c) on the shaft {b) of the dy- 

 namometer, to which motion is thus communicated, "a 

 certain weight being placed in the dish (i), and the 

 friction-strap (e) tightened up by the pinching-screws 

 {g) till the pointer (7i) is exactly opposite the centre of 

 shaft. The whole power of the engine is absorbed in 

 turning the pulley (e) and friction-wheel {d), its motion 

 of revolution being retarded by the friction generated 

 between the strap (e) and friction-blocks (/), this fric- 

 tion being maintained by the weight (/<:) in the dish (i) . 

 These weights become therefore a measure of the 

 power of the engine. The number of revolutions 

 which the pulley (c) makes during the time in which 

 the engine is working is registered by a counter appa- 

 ratus attached to the dynamometer. 



In working the engine, for each horse-power at which 

 it is entered, fourteen pounds of coal are given to the 

 engine man, whose duty it is to get the greatest number 

 of revolutions out of it during the time of working, and 

 also to extend the time at which it can continue to work 

 with the supply of fuel allotted. 



According to a certain formula, the weights in pounds 

 are calculated which are to be placed in the dish of the 

 dynamometer for each horse-power of the engine to be 

 tried, from four to ten horse, for every ten revolutions, 

 from 110 to 150 revolutions per minute of the engine. 

 The" minutes of duty" which the engine under trial 

 has performed are ascertaiued thus : Multiply the dia- 

 meter of the driving-pulluy of tlie engine by the number 

 of revolutions which it is intended to make per minute, 

 and divide this by the diameter of the driving-pulley (c) 

 of the dynamometer. Take the sum thus obtained as a 

 divisor, and divide by it the number of revolutions which 

 the dynamometer makes during the time of trial. The 

 " minutes of duty" thus obtained are used to ascertain 



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