540 
Trials of Traction- Engines at Wolverhampton, 
greatest case not only fire but steer, and in every way control the action of 
the engine. The notch-bar, in which the spring-catch lever of the link motion 
is retained, is made to slide through a mortice in a bracket ; and its position 
can be regulated by means of a hand-wheel, and a screw of sufficient range to 
move the notch-bar a distance a little more than the space between any two 
notches. Tims the desired point of expansion can be reached with the greatest 
nicety. It certainly did seem to us that the simplest way to have effected 
this would have been the direct application of a screw, as is now very fre- 
quently practised in locomotive engines, but Messrs. Aveling and Porter say 
that tliey find it is somewhat cheaper to provide the arrangement they have 
than the single screw and nut. The feed-pump is fastened on to the left-hand 
bracket, which carries the second-motion shaft, and is worked by a separate 
eccentric on the crank-shalt. The pump is always at work, and the amount 
of water is regulated by a cock in an overflow-pipe. When this cock is shut, 
the whole of the water goes into the boiler ; when it is open the whole of the 
water returns to the tank. When travelling along a road with the tank full 
of water, in which state it contains 200 gallons, the feed-water is not heated, 
because the back-pressure of the steam is not sufficient to overcome the head 
of water. But when the engine is being used as a motive-power in a farm- 
yard, then a branch-pipe, which is led back to the tank from the waste steam- 
pipe heats the feed-water. The engine is provided with a governor, to make 
it self-regulating when acting as the driver of machinery. 
The toothed gearing of this engine was, with the exception of the wheels in 
the jack-in-the-box, of malleable cast iron. Mr. Aveling explained that in 
engines supplied to a customer these wheels also would be of malleable cast 
iron, but that he had not had time to get a set annealed. 
The first trial to which engines in this class were subjected was an ordinary 
dynamometer trial, by which for years pjast engines exhibited at the Society's 
Shows have been tested. 
Aveling and Porter's 10-horse-power engine. No. 7001, which we have de- 
scribed, was, in accordance with the liberty granted, declared at 115 lbs. pressure 
of steam and at 30-horse-power, and was supplied with the usual 14 lbs. of 
coal for each horse-power ; and with this quantity she ran at the declared 
revolutions — viz., 120 a minute — for 3 hours 44 minutes and 35 seconds 
mechanical time, showing a consumption of 3'73 lbs. of coal per horse-power 
jier hour. This is not up to the very highest standard of economy that has 
been attained with Portable Engines at previous shows: but then those 
engines were working only at their nominal power; they were provided with 
double slides to their cylinders, and were in the charge of numerous attendants ; 
while with respect to the engines in Class XVII. this year the power at which 
they were worked in all cases exceeded their nominal — in this instance, three 
times — the only exjjansion was that obtained by the use of the link-motion 
upon a single .slide, and they were worked in each case by one attendant only. 
Looking at these facts, we consider the performance of this engine, in 
developing a horse-power for 3'73 lbs. of coal per hour, extremely satisfactorj'. 
The indicated horse-power, as ascertained from diagrams taken during the 
run (a copy of which is given in Fig. 6), amounted to 35 horse-power, giving 
a consumption of only 3'2 lbs. of coal per gross indicated horse-power per hour. 
The evaporation was 7"C)2 lbs. of water for 1 lb. of coal. The average tem- 
perature of the feed was 175°. The oil and tallow used were 1 lb. 12i ozs., 
being at the rate of 2^ ozs. per actual horse-power per day of 10 hours. 
It is very gratifying, indeed, to be able to record at last the indicated horse- 
power of engines while being tried on the brake, because it gives one the 
means of comparing their performance with that of engines employed for other 
purposes, such as for driving machinery or for propelling vessels. In these 
