PTOs: Selecting a power take-off unit

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

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

SPEED LIMITS • SIDE-LOAD LIMITS • CLUTCH TORQUE LIMITS.

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 of https://www.jbj.co.uk/e-publications/Mechanical-Power-Take-Off-selection-guide/5/index.html)

PTO Selection Procedure

1. 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 x F x 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 of the on-line PTO selection guide (https://www.jbj.co.uk/e-publications/Mechanical-Power-Take-Off-selection-guide/7/index.html) 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.

PTOs: Selecting a power take-off unit

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