184 ENGINEERING
indicator connections before they leave the shop,
which is eminently proper, as no engine builder, or
purchaser either, should be satisfied with the perform-
ance of a new engine until after it has been accurately
tested and adjusted with the indicator.
The main requirements in these connections are that
the holes shall not be drilled near the bottom of the
cylinder where water is likely to find its way into the
pipes, neither should they be in a location where
the inrush of steam from the ports will strike them
directly, nor where the edge of the piston is liable to
partly cover them when at its extreme travel, An
engineer before he undertakes to indicate an engine
should satisfy himself that all these requirements are
fulfilled. Otherwise he is not likely to obtain a true
diagram. The cock supplied with the indicator is
threaded for one-half inch pipe and unless the engine
has a very long stroke it is the practice to bring the
two end connections together at the side or top of the
cylinder and at or near the middle of its length, where
they can be connected to a three way cock. The pipe
connections should be as short and as free from elbows
as possible in order that the steam may strike the
indicator piston as nearly as possible at the same
moment that it acts upon the engine piston.
The work of taking diagrams is very much simplified
by having both ends of the cylinder connected to one
common tee or a three way cock as above described,
but for long stroke engines there should be two indi-
cators, one for each end and the diagrams should be
taken simultaneously if it is desired to adjust the
valves by the indicator. In this case an assistant
would be required to manipulate one of the instru-
ments.
