Polyclutch Slip Clutch Selection Guide

Polyclutch mechanical and pneumatic slip clutches have a long operating life of 20 to 30 million revolutions in slip condition and operate smoothly with reliable breakaway and continuous slip. In this overview, we will cover these topics:

  • How slip clutches operate
  • The design advantages and limitations of Polyclutch slip clutches
  • How to select the right slip clutch for your application
  • Product line overview
  • Calculating slip clutch capacity based on your application parameters

How Polyclutch Slip Clutches Work

All Polyclutch® slip clutches perform the basic function of controlling the torque between two elements. They can be supplied as a shaft-to-shaft coupling or a shaft to pulley, gear, or sprocket model. Polyclutch custom slip clutches can be provided with nonstandard bore sizes, keyways, low backlash or higher torque, minus housings and with pulley, gear or sprocket. Imagination and ingenuity have developed and created additional variations.

A Polyclutch consists of two parts: a cartridge and a housing (see diagram)

The cartridge is set screwed or keyed to the input shaft. The cartridge includes the clutch pack: outer plates, friction pads, inner plates

  • Plates are brass with a proprietary finish
  • Inner plates are keyed to the cartridge hub
  • Outer plates are keyed to the cartridge housing
  • Friction pads are a proprietary plastic-based composite (no asbestos)

The housing is either set screwed or keyed to the output shaft, or (as shown), attached to the output gear or pulley, with a bronze bearing to allow relative motion between the input shaft and the output gear/pulley.

Torque is controlled by changing the pressure applied to the clutch pack. In an adjustable style clutch, the torque level is controlled by compressing the springs with the adjusting nut. In a fixed style clutch, a collar is attached to the hub in a fixed position, and the torque level is set by pushing and locking the spring collar to a calibrated position.

All slip clutch torques are calibrated to +/- 20% but can be held to closer tolerances.

Backlash of 6° is standard for Slipper models and 2° for the Slip-Ease models. Slipper models can be held to 2° if required.

Our proprietary burn-in process insures that all clutches will perform consistently right out of the box, with no break-in period required.

Design Advantages & Limitations

Design Advantages

  • Smooth, reliable breakaway and continuous slip
  • Proprietary burn-in process = no-stiction: static friction lower than dynamic friction
  • No-break in period: Precise torque with consistent repeatability from day 1
  • No sudden shock on sensitive paper/film/wire/thread, etc.
  • Long life of 20 to 30 million revolutions in slip condition
  • Torque range from 0.5 lb-in to 750 lb-in
  • Fixed, adjustable and custom designs
  • Clutches are bi-directional
  • No lubrication needed
  • Lower cost alternative to servo motors
  • More compact/smaller and less expensive than magnetic clutches
  • No reset required, no clicker (compare to ball detent)
  • Offers mechanical safety in mechanically controlled systems
  • American engineered and made in the USA

Design Limitations

  • Max. 1.25″ shaft size on a through-shaft
  • Min. 1/8″ (3mm) bore size
  • Max. 750 lb-in torque limitation
  • Not to be used as a universal joint or a spring coupler
  • Does not de-couple at overload
  • Cannot be exposed to radiation
  • Contact a Polyclutch application specialist if slip clutch would be directly exposed to weather or wash down

How to Select the Right Slip Clutch for Your Application

Three key factors in determining the right clutch are the maximum shaft size, torque capacity of the clutch, and wattage capacity.  Please consider the limitations listed each Polyclutch product line.

  • For torque adjustment while clutch is in use (remote torque adjustment), see the Slip-Aire clutches.
  • For applications outside of these general limitations, please consult Dynatect

The clutch capacity is based on continuous operation at 50 RPM for over 25 million cycles. Torque, RPM, duty cycle and life are interdependent. A reduction of any of these will allow an increase in any other. (Running at 25 RPM will allow twice the torque, or running for only 10% of the cycle will allow higher RPM, etc.)

The limit is based on heat buildup measured in watts per:

Watts = Torque (inch pounds) x RPM x Duty Cycle* x 0.011.

*(% of the time the clutch is slipping, expressed as a decimal. For example, 0.5 = 50% of the time the clutch is slipping)

Please contact us to discuss high torque, high RPM, and rapid cycling applications.

Slip Clutch Line Overview

SERIES 16

  • Mechanical friction clutch
  • Our most affordable slip clutch
  • Can accommodate shaft sizes up to 0.375 inch
  • Torque capacities of up to 20 lb-in
  • Available in a fixed torque or adjustable torque configuration
  • Go to product specifications >

SLIPPER CLUTCH

  • Mechanical friction clutch
  • Our standard-duty slip clutch
  • Can accommodate shaft sizes up to 1 inch
  • Torque capacities of up to 500 lb-in
  • Available in a fixed torque or adjustable torque configuration
  • Go to product specifications >

V-SERIES SLIPPER

  • Mechanical friction clutch ideal for vertical mounting orientation
  • Torque control for driving, capping and other applications where thrust loads are applied
  • Can accommodate shaft sizes up to 1 inch
  • Horizontal and vertical installation without driveshaft modifications
  • Integrated ball bearing allows thrust loads of 150 to 650 pounds
  • Torque capacities of up to 150 lb-in
  • Go to product specifications >

 

SLIP-EASE

  • For applications where space is at a premium and low backlash is required
  • Can accommodate shaft sizes up to 1.25 inches
  • Torque capacities of up to 750 lb-in
  • Available in a fixed torque or adjustable torque configuration
  • Miniature size 12 version has extremely small footprint of only 3/4″ in diameter
  • Go to product specifications >

SLIP-AIRE

  • Pneumatic friction slip clutch
  • Can be adjusted remotely while the machine is in operation to accomplish quick, repeatable, accurate setup
  • Can accommodate shaft sizes up to 0.625”
  • Torque capacities of up to 300 lb-in
  • Go to product specifications > 

DOWNLOAD

 

Download PDF: Slip Clutch Overview

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