Levers are of three orders (see Section 53). The fulcrum or rocking
centre may be at either end or at some intermediate point. In practice
the fulcra are usually shafts or pins (see Sections 76 and 77), and the
following are the typical forms in use.
=869, 870, 871, & 872. Elevation and plans of plain levers,= with end
bosses for rod attachments.
=873. Plan of plain lever,= with forked end.
=874 & 875. Bell crank levers,= with plain or forked ends.
=876. ~T~ or double cranked lever.=
=877. Forked end,= off-set.
=878. Fish bellied lever= of the 2nd order.
=879. Balance weight lever.=
[Illustration: 857.-879.]
=880. Hand lever,= with round handle.
=881. Hand lever,= with flat handle.
=882. Another form of round handle= sometimes used.
=883. Crank handle.=
=884. Starting lever,= with spring catch.
=885. Another pattern of ditto.=
=886. Similar lever,= with side or crank handles.
=887. Foot lever.=
=888. Foot treadle frame.=
=889. Wrist plate or ~T~ lever.=
=890. Hand lever,= adjustable as to length by means of a slot and
locking bolt. For this purpose a plain round rod passed through a
central socket and fixed at any radial length by a set screw, is often
used; or the hand rod may be cranked as No. 1784.
=891. Double hand lever.=
=892. Lever,= formed of two wrought iron or steel plates and distance
pieces.
=893 & 894. Rocking levers,= with sliding swivel joints.
=895. Forked lever,= to span a central bearing.
=896. Hand lever,= simple pattern; wrench or spanner.
=897. Headed lever,= for valve rod and other movements. See Nos. 149 to
152.
See also Section 97.