How to select power take-offs

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Several factors must be considered in the selection process in addition to duty service, such as:


The selections are usual dry clutch disconnect type applications where engagements are infrequent and are at low (idle) input speed. Once engaged operation continues for one hour or more, engaging the clutch at higher input speed will reduce component life. Refer to the following duty classifications and examples

Application Data*:

SAE Housing Size.
SAE Flywheel Size.
Number of Engagements.
Pulley Pitch Diameter.
Pilot Bearing Diameter.
Input Power to Clutch.
Input Torque to Clutch.
Maximum Output Shaft RPM.
Load Centre-line "X" Dimension (side-load applications).

Determine duty classification (page 5)

PTO Selection Procedure
Calculate NET Input Power or Torque to PTO
2. Calculate imposed side-load using the following formula (side-load only):

(metric) L = 1945010 x kW x F x LF
                                     N x D

(imperial) L = 126,000 x HP xFx LF
                                      N x D

L = Actual Applied Load kg (lbs)
N = Shaft Speed (rpm)
D = Pulley Pitch Diameter mm (in)
F = Load Factor
1.0 for Chain / Gear Drive
1.5 for Timing Belts
2.5 for All V Belts
3.5 for Flat Belts

LF = 2.1 for reciprocating compressors and other ‘severe shock drives’ and 1.8 for ‘large inertia type drives’ (crushers, chippers, planers, etc.)

3. Use the PTO rating table on
page 6 and the side-load tables on pages 7 and 8 with the following information:

NET input power or torque to clutch.
SAE flywheel size.
SAE housing size.
maximum PTO output shaft speed.
calculated side-load (side-load applications).

Find proper duty class along top row and SAE housing & flywheel size along left-hand column of the rating table on page 6.

A PTO that has a power or torque rating greater than the calculated application power or torque rating is suitable for the application.

The PTO output shaft speed should be at or under the listed ratings for the drive rings.
Use PTO output shaft speed and calculated side-load and refer to tables on
pages 7 and 8 to verify that the side-load is at or under the load at the given speed.

Available now the new Mechanical Power Take-off selection guide from jbj Techniques Limited. The on-line guide to help select the most suitable PTO for a varied range of applications due to the wide range of product available. A guide through the selection process, duty classifications, allowable side loads, models, ordering codes, dynamically balanced drive rings, dimensions, spe...


Mechanical power conversion. Two new PTO selection guides to assist correct specification of power take-off units for a wide range of applications, hydraulically actuated power take-offs and mechanically actuated power take-offs from jbj Techniques Limited.

The on-line guides to help select the most suitable PTO for a varied range of applications due to the wide range of product available. A guide through the selection process, duty classifications, allowable side loads, models, ordering codes, dynamically balanced drive rings, dimensions, special units and more.

Power take-offs (PTOs) are used as a standard method for transmitting the power of engines in a great variety of industrial applications such as air compressors, agricultural machinery, crushers, road building machinery, cranes, shovels, pump drives and oil field service. A power take-off consists of a complete clutch assembly with shaft and bearings mounted in a cast-iron housing for easy engine installation.
Twin Disc offers power take-offs for all industrial engines. The IBF line is designed especially for today's high inertia applications and presently is offered in two- and three-clutch plate construction. This multiple-plate, ventilated design assures ample cooling area to withstand heat, and with solid friction plates, these PTOs can effectively handle the stress of higher engine speeds. The IBF units feature oil lubricated tapered roller bearings that extend lubrication intervals.


An extra margin of strength.

Actual design torque capacity of the clutches used in Twin Disc power take-offs is in excess of the horsepower rating listed. This permits Twin Disc power take-offs in proper adjustment to withstand temporary torque overloads. Rated torque can be transmitted while moderately slipping during short periods without permanent damage.



» Suitable for Duty Class II industrial applications with internal combustion engines up to 1243 kW (1667 hp) and with standard SAE flywheel housing dimensions from No. 6 through No. 00.

» Contain clutches ranging in size from one plate SAE 6.5 to one plate SAE 14; in two-plate size from SAE 11.5 to SAE 18; and three-plate size from SAE 11.5 to SAE 21.

» Standard sealed pilot ball or roller bearings eliminate the lubrication requirement and shaft rifle-drilling normally encountered with standard pilot bearings. Also available as options: ball bearing throw-out collars and finger springs.

» kW/horsepower and torque capacities listed can be increased by the use of sintered-iron clutch plates, which are available as optional equipment in the SAE 8 through SAE 21 sizes.

» All bearings, shafts and other parts are designed with liberal safety factors to maximize life under normal operating conditions.*

* To avoid overloading the shaft and bearings, use the allowable side-pull load data in this selection guide, and calculate the side load. The resultant value should be less than the corresponding maximum value listed for each power take-off.

The team of friendly, highly qualified and experienced engineers at jbj Techniques Limited are here to assist in the correct specification of mechanical power transmission and fluid power components. Telephone: +44 (0)1737 767493 or email