Glossary of Power Take-Off Terms

distance is .006 to .012”. This is example, a gear of 45 teeth driven checked at pitch line by on containing 15 teeth would provide a ratio of 1:3. Hence, a Constant Mesh – Relation of two gear of 15 teeth driven by one or more gears which always rotate containing 45 teeth would have a in continual contact with each gear ratio of 3:1. other. Aperture – Standard SAE size opening on either side of the transmission which permits the Installation of a power take-off. May be either six or eight-bolt opening

Helical Gear – A gear whose teeth Counter Shaft - Secondary shaft in are cut on an angle diagonally the transmission on which the PTO across the gear, either with a right drive gear frequently rotates. or left hand slant. In order for helical gears to mate, one must Deep Mount - PTO whose design slant to the right . . . the other to permits its input gear to extend the left. Adapter Gear – A single gear further into the transmission case, assembly which transmits torque to permit direct contact with the Horsepower – A measure of the between the transmission output transmission output gear. capacity of doing work per unit of gear and the PTO input gear. Used time. One horsepower is the Engine Speed – Revolutions per when the distance between gears energy required to lift 550lbs., one minute of engine crankshaft which is too great to permit direct foot in one second. meshing or to reverse PTO determines the speed available to rotation. the transmission or PTO.

Assembly Arrangement – Refers to the location of the output shaft in relation to the gear. The preferred arrangement is with the output shaft to the rear. Idler Shaft – Normally the shaft Filler Block – fiber or metal plate that the input gear rotates on, of various thicknesses, assembled transmits power to the output between the transmission and the gear and shaft. PTO for the purpose of extending the distance between drive and input gears to permit proper Backlash – Clearance needed meshing. between the meshing of two gears Gear Ratio - The relationship of the to permit quiet, smooth number of teeth on the output to operation. Recommended those on the input gear. For Glossary of Power Take-Off Terms

Intermittent Operation – transmitting that power to Normally a stop-and-go operation, another mechanical or hydraulic such as 5 minutes on/15 minutes device according to the speed and off, 10 minutes on/30 minutes off. torque required to operate the If heat builds up through repeated device. activity (through repeated cycling operations or high loads), the Pitch Line – The point on the gear Spur Gear – A gear whose teeth activity ceases to become tooth midway between the base are cut straight across the face fo intermittent and would then be of the tooth and the tip of the the gear. tooth. classified as continuous operation. Standard Assembly Arrangement Input Speed –Revolutions per Pitch (Gear) – The measure of the – Output shaft towards the rear of minute which the transmission size of the gear teeth determined the vehicle and below the PTO’s output gear is capable of by the number of teeth in a given centerline. area measured at the pitch line. delivering to the PTO input gear. Torque – Effort required to PTO gear pitch is normally perform a twisting or turning classified as 5, 6 or 7-pitch. motion, often referred to as the Pitch Diameter – The distance force necessary to overcome across the center of the gear resistance. measured form the pitch line of Transmission – A gear box which one tooth to the pitch line of the receives its power from an engine tooth directly opposite that tooth Input Gear - The PTO gear first and which operates as a torque accepting the torque from the Pitch Line Velocity -The speed of multiplier for the purpose of transmission output gear. rotation in feet per minute of a regulating speed and applying torque as required. Main shaft – The output shaft of gear measured at the pitch line. the transmission that sends power Abbreviations to the driven unit, such as a rear axle. Ft. lbs. – Foot Pounds. Torque Output Shaft – The shaft force developed or required to transmitting the torque from the overcome resistance. PTO to the device or unit which it fpm – Feet per minute operates, i.e., hydraulic pump, Pressure Angle – The angle gpm - Gallon per minute winch, etc. formed, measure in degrees, by a hp – Horsepower line drawn perpendicular to the Output Gear – The driving gear I.D. – Inside Diameter pitch line, and a line drawn from which activates the output shaft. O.D. – Outside Diameter the same point on the pitch line Plv – Pitch Line Velocity tangent to the tooth profile. p.s.i. – pounds per square inch Power Take-Off – A gear box (pressure) attached to a transmission, rpm - Revolutions per minute receiving its power through that SAE – Society of Automotive transmission for the purpose of Engineers.