734 
The Trials of Oil Engines at Cambridge. 
Class II. — Portable Engines. 
General Description of the Engines. 
Messrs. Hornsby’s engine (First Prize, 50/.) is illustrated in 
fig. 25. It is in all respects an admirable portable engine. The 
general arrangement of working parts is precisely the same as 
that of the fixed engine and will need no further description. 
It is mounted on a light and stable carriage running on four 
wheels. The oil- tank is beneath the framework and the box- 
platform contains about 20 gallons of water. A circulating 
pump passes the jacket water from this tank through the jackets 
and over vertical boards in a casing very closely resembling 
in appearance a small vertical boiler. The exhaust passes up 
through the centre of this cooler and draws a current of air 
between the boards in the contrary direction to the flow of 
water. This forms a simple and compact arrangement, and 
answered admirably on the trials. Over the three days’ run, 
only 80 gallons of cooling water were required, a very small 
quantity compared with that needed by a steam-engine of similar 
power. A very efficient steam-engine, using, say, 20 lb. of 
water per indicated horse-power per hour would in the same 
time have consumed upwards of 670 gallons. 
At one projecting end of the crank shaft is mounted a fly- 
wheel, at the other a 3 ft. 10^ in. belt pulley. Upon both of 
these brakes were run during the trial to prevent the excessive 
heating of the flywheel. 
The arrangements for driving are good, there being clear- 
ance both ahead and astern, though in the latter direction only 
when the lower side of the belt is led at a considerable angle 
above the horizontal. A horizontal belt would not clear the 
following axle. 
The weight of the engine, which is of 1 2^ brake horse-power, 
is 81 cwts. empty. The width over axles is 5 ft. 8 ins. and the 
length 13 ft. 6 ins. The starting and running of this engine 
were faultless, and the oil consumption was low, though neces- 
sarily greater, reckoned on the brake horse-power, than that of 
the fixed engine, on account of the pump duty. It was 1‘09 lb. 
per brake horse-power hour on the three days’ run and T08 lb. 
on the 2 hours’ full-power trial. Per indicated horse-power, 
however, it compares very favourably with the fixed engine, 
consuming only 0'75 lb. per indicated horse-power hour on the 
full-power run. The mechanical efficiency was lower from the 
same cause — namely, 69 per cent., as compared with 83 per cent, 
in the fixed engine. 
The main consideration about a portable engine is not neceS' 
