Promoter to pull

Promoter to propeller thrust

a beam of light, as a searchlight projector.

Promoter. (Plast.) A chemical cata­lytic additive which increases the speed of gelation provided by a nonnal catalyst in a resin mix.

Prony brake. (Elec.) A mechanical device consiting of a special pul­ley, braking attachment, and a weighing scale, which is attached to a motor, to detennine the horse­power it will deliver under load.
Proof. (Print.) A printed impression made for inspection and correc­ tion.

Proof mark. (I) (print.) Mark or symbol used to designate correc­tion to be made in a proof. (2) In firearms, a mark or de~iced indi­cating that the weapon has been tested beyond the nonnal cham­ber load.

Proof planer (Print.) A block of hard­wood faced with felt. Used for taking stone proofs.

Proof press. (Print.) Any printing press upon which type fonns may be proofed without locking in a chase.

Proof-reader. (Print.) One who reads the proofs and checks the errors.

Propeller. TIle helical segment used for the propulsion of vessels. A propeller may be two-, three-, or four- .bladed.

Propeller-blade angle. (Aero.) The acute angle between the chord of a propeller section and a plane perpendicular to the axis of rota­tion of the propeller. Usually .called "blade angle".

Propeller-blade area. (Aero.) The area of the blade face, exclusive of the boss and the root, i.e., of a portion which is usually taken as extending 0.2 of the maximum radius from the axis of the. shaft.

Propeller-disk area. (Aero.) The to­tal area swept by a propeller, i.e., the area of a circle having a diameter equal to the propeller di­ameter.

Propeller efficiency. (Aero.) The ra­tio of thrust power to power input of a propeller.

Propeller hub. (Aero.) The central portion of a propeller, often con­taining a pitch changing mecha­nism from which the blades radi­ate and by means of which the propeller is mounted on its drive shaft.

Propeller rake. (Aero.) The mean angle which the line jointing the centroids, or center, of the sec­tions of a propeller blade makes with a plane perpendicular to the axis. Propeller root. (Aefo.) That part ,of the propeller blade near the boss. '

Propeller shafL (Auto.) Also called "drive shaft". It is the shaft wlii~h delivers the power from the trans­mission to the rear axle.
.Propeller thrust. (Aero.) The com­ponent parallel to the propeller Propeller tipping to pull a proof axis of the total air force on the propeller.

Propeller tipping. (Aero.) A protec­tive covering of the blade of a propeller near the tip.

Propeller turbine. (Aero.) Or pro­peller turbine engine; same as turbopropel1er engine.

Properties. (Plast.) In plastics, re­fer to physical strength, dimen­sional stability, electrical, light, and weather stability, color, heat and structural stability, machin­ability, and hardness. (See refer­ences given under individual plas­tic names.)

Proportional dividers. A divider or compass for drawing purposes, provided with two slotted and double-ended legs, united by a sliding pivot and screw, by the regulation of whose position it is possible to copy measurements at an increased or decreased pro­portional scale:

Proportional limit. (Metal.) That point at which elongation or de­formation ceases to be propor­tional to the load.

Proportionately. Having proper re­lation as to size, degree, 'quan­tity, value or importance; in pro­portion to.

Propulsive efficiency. (Aero.) The ratio of the product of effective thrust and flight speed to the ac­tual power input to the propeller as mounted on the airplane, con­sistent units being used through­out.

Proscenium. The front part of a theater stage including the arch over the stage, in front of the cur­tain.

Protein. ,(Chern.) A class of 'com­pounds containing carbon, oxy­gen, hydrogen and nitrogen, with sulphur usually present and some­times phosphorus, iron, etc. Ex­ample: egg albumen.

Proton. (Chern.) A particle in the nucleus of an atom having a posi­tive electrical charge.

Protractor. An instrument for mea­suring arid laying off angles on paper, used in drawing and plot­ting.

Prussian blue. (Chern.) Fe4 [Fe(CN)6]3' Made by action of po­tassium ferrocyanide on ferric salt. An intense blue precipitate used as a pigment. in dyes, colouring of paper, etc. Also, mixed in oil, it is used in the fitting of bearings to indicate high spots which must be removed by scraping.

Psychrometer. (I) Usually a ther­mometer having wet and dry bulbs for measuring atmospheric humid­ity. (2) In sling psychrometers there is only one bulb; readings are taken before and after moist­ening the bulb cover, to deter­mine the rate of evaporation.

Puddle. (Engin.) To settle loose dirt by application of water. (Metal.) The batch of molten iron in the puddling furnace.
Pugging. (Arch. and MasoTlJ.Y) A coarse mortar laid between floor joists to prevent passage of sound.

Pull a proof. (Print.) To take a stone