It is of the utmost importance that every revolving or reciprocating
part of any machine should be as nearly as possible balanced, to
obtain smooth running with the least amount of wear.
The following are types of the most important devices and their
applications:--
=369. Balanced lever,= having a sliding cheese or ball weight fixed with
a set screw.
=370. Balanced cage of hoist.= It is usual to _over-balance_ the cage to
divide the work between the up and down journeys in hand-power lifts to
assist the load; but in power and hydraulic lifts the cage is
_under_-balanced so as to descend when empty.
=371. Hydraulic balance lift,= in which the dead or constant load of
cage and ram are nearly balanced by a loaded piston in a supplementary
cylinder; to raise the loaded cage the pressure water is admitted to the
upper side of this piston. Many varieties of this type are in use; see
Ellington’s, Johnson’s, Stevens and Major’s, Waygood’s, and other patent
lifts.
=372. Variable volute compensating balance= for revolving shutters,
blinds, curtains, &c., to maintain an even balance in all positions, The
weight chain is as thick as the coiling shutter on blind, so that the
acting radii of the shutter and weight are always proportional.
=373. Variable compensating balance= for hydraulic lift rams, to
compensate for loss of immersion of the ram as it ascends (Berly’s
patent). See also Stevens & Major’s patent, where bell-crank levers and
weights are employed instead of loaded chains. See No. 383.
=374. Balanced fly-wheel.= For balanced cranks, see Nos. 172 & 173.
=375. Increasing balance by sections,= lifted at intervals as the chain
rises.
=376. Balanced riveting machine.= See Tweddell’s patents.
=377. Variable lever balance.= For balanced cranes, see Section 18.
=378. In deep lifts,= to balance the weight of chain or rope, it is made
endless.
=379. Another method.= The loose chain hung from cage is of the same
weight per foot as the lifting chain.
=380. Balance weight on a screw arm= for adjustment, employed on
weighing machines.
[Illustration: 366.-380.]
=381 & 382. Worthington’s compensating air cylinders,= employed on
direct-acting horizontal pumps, working expansively, in lieu of
fly-wheel. The oscillating or vertical cylinders are air or spring
pistons, absorbing power the first part of stroke and giving it out
during the latter part.
=383. Variable balance weight= by bent lever.
=384. Variable balance weight= by double links and sliding joints.
=385. Dawson’s compensating governor.= See _Mechanical World_, August
25th, 1888.
=386. Balanced doors, hinged vertically.=
=387. Balanced sashes,= or vertical sliding doors.
=388. Method of balancing a bloom= in charging or withdrawing from a
furnace, or any similar use.
=389. Balance= for link motion.
=390. Weight= to keep a cord or rope in tension.
=391. Mode of balancing two sliding doors= so that they rise and fall at
proportionate speeds.
Hoisting and winding engines (see Nos. 1222, 1223) are balanced by
having an ascending and descending cage, and two ropes, one winding on
as the other winds off the drums.
Double cage hoists similarly balance themselves. Heavy slide valves,
and other reciprocating parts of steam engines, are balanced by small
steam pistons. See Nos. 1651-1654.
Foot treadles, when required to always stop at a point off the dead
centre, have a balance weight fixed to fly-wheel, at right angles to
the dead centre.
A water tank is often used to serve as a counterpoise, or balance, and
may be made variable by varying the quantity of water by a siphon or
other device.
For Balanced Valves, see Section 89.