f the belt. The
endless belt does away with this trouble. Most dynamos are provided
with sliding bases, by which the machine can be moved one way or
another a few inches, to take up slack in the belt. To take advantage
of this, the belt must be run in a horizontal line, or nearly so.
Vertical belting is to be avoided.

The dynamo is mounted on a wooden base, in a dry location where it is
protected from the weather, or dampness from any source. It must be
mounted firmly, to prevent vibration when running up to speed; and the
switchboard should occupy a place within easy reach. Wires running
from the dynamo to the switchboard should be protected from injury,
and must be of ample size to carry the full current of the machine
without heating. A neat way is to carry them down through the flooring
through porcelain tubes, thence to a point where they can be brought
up at the back of the switchboard. If there is any danger of injury to
these mains they may be enclosed in iron pipe. Keep the wires out of
sight as much as possible, and make all connections on the back of the
switchboard.

_The Switchboard_

[Illustration: Connecting switchboard instruments]

The switchboard is constructed of some fireproof material, preferably
slate or marble. When the cost of this material is an item to
consider, build a substantial wooden frame for your switchboard. You
can then screw asbestos shingles to this to hold the various
instruments and with a little care such a switchboard can be made to
look business-like, and it is fully as serviceable as the more
expensive kind. The switchboard instruments have already been
described briefly. They consist of a voltmeter (to measure voltage);
an ammeter (to measure the strength of the current drawn, in amperes),
a rheostat (to regulate the voltage of the machine to suit the
individual requirements); and the usual switches and fuses. The main
switch should be so wired that when open it will throw all the current
off the line, but still leave the field coils, the voltmeter, and the
switchboard lamp in circuit. The main-switch fuses should have a
capacity about 50 per cent in excess of the full load of the dynamo.
If the machine is rated for 50 amperes, 75-ampere fuses should be
installed. This permits throwing on an overload in an emergency; and
at the same time guards against a short circuit. If the capacity of
the machine is under 30 amperes, plug fuses, costing 3 cents each, can
be used. I