CHAIN DRIVE: Introduction, Design, Advantages & Disadvantages.

INTRODUCTION

A chain drive is a power transmission element consisting of a series of pin connecting links.

This construction provides flexibility and allows the chain to transmit large tensile forces.

When power is transmitted between the rotating shafts, the chain is involved in the mating of gears called chain sprock.

Chain Drive

The most common type of chain is a roller chain.

The rollers on each pin provide very low friction between the chain and the sprocket.

Roller chains are categorized according to pitch, distance between corresponding parts of adjacent links.

Gradient is usually expressed as the distance between the centers of adjacent pins.

Standard US roller chains come in size specifications from 40 to 240.

The number (excluding the last zero) indicates the pitch of the chain in 1/8 inch.

For example, No. The pitch of a 100 chain is 10/8 or 11. Many rugged sizes (60H – 240H) with a H suffix on the 4-inch label have the same basic dimensions as a standard chain, except for the thick side plates.

Also available in smaller and lighter sizes: 25, 35, 41.

This data can be used for very slow drives, applications where the feature of the chain is to apply, or to support load.

For such applications, it is recommended to use only 10% of the average tensile strength.

For power transmission, the performance of a particular chain size should be determined as a function of speed, as described.

The commonly used ISO606 type has basically the same structural dimensions as many of the standard US- roller chains.

Next, the pitch and dimensions of the sprocket feature, as well as the bore size, are listed in meters of mm, making it more convenient to incorporate the known chain design into full meters.

ISO3512 contains chains of eight sizes used for high power transfer and lifting equipment.

Some of the pitches on these chains are also common US sizes.

Agricultural equipment such as tractor accessories, seed drills, harvesters and lawnmowers use many chain drives to operate the motion system.

ISO487 defines eight S designations covering a wide range of power transmission and traction applications.

Other types of chains include multi-strand structures, heavy chains, double pitch chains, and double pitch conveyor chains.

A variety of accessories are available to facilitate the use of the roller chain in conveyors or other material handling applications.

Attachments, typically in the form of elongated plates or brackets with holes, allow you to easily connect a rod, bucket, parts pusher, parts carrier, , or conveyor slats to a chain.

Figure shows the various chain types that are specifically used for conveyors and similar applications.

Such chains usually have a longer pitch (usually twice the pitch) than standard roller chains, and the link plate is heavier.

Larger sizes have cast link plates.

DESIGN OF CHAIN DRIVE

(1) fatigue of the link plates due to the repeated application of the tension in the tight side of the chain,

(2) impact of the rollers as they engage the sprocket teeth, and

(3) galling between
the pins of each link and the bushings on the pins.

The rating is based on empirical data using a smooth driver and smooth load (service factor = 1.0).

The nominal service life is approximately 15,000 hours.

Important variables are the pitch of the chain and the size and speed of the smaller sprocket.

lubrication is important for the chain drive to work well.

The manufacturer recommends type lubrication for certain combinations of chain size, sprocket size , and speed.

Power of 3 sizes of standard chain: No. 40 (1/2 inch), No. 60 (3/4 inch), and No. 80 (1.00 inch).

These are the typical types available in the manufacturer’s catalog for all chain sizes and can be used for any problem.

When the creates the final design and specifications, refer to the catalog data of the specific manufacturer of the you are using.

Note the following characteristics of the data:

Ratings are based on the smaller speed Expected useful life with sprockets and approximately 15000 hours.

At a given speed, the power capacity will increase accordingly the number of teeth on the sprocket.

Of course, the larger the number of teeth, the larger the diameter of the pinion.

Note that we use a small 3 chain.

For a particular sprocket size (specific number of teeth) , the power capacity increases as you speed up a certain point,then it diminishes.

Fatigue due to chain rule tension at low to medium speeds,the impact on the chain wheel reigns supremely at high speeds.

Each sprocket size has an absolute maximum speed of as seizure begins between the pin and the bushing on the chain.

This explains that the power capacity drops sharply to zero at the critical speed.

Ratings are for a single strand of chain.

Nevertheless multiple strands increase power capacity, but does not provide a direct multiple of the capacity of a single strand.

Multiply the table capacity by the following factor.

Two Strands: Factor = 1.7

Three Strands: Factor = 2.5

Four Strands: Factor = 3.3

Information provided by the chain manufacturer applies to Service Factor 1.0.

The power factor can be selected by combining the characteristics of the drive element and the driven machine.

Then compute the design power, Pdes, from,
Pdes = SF(P) where P is the power delivered to the chain drive.

ADVANTAGES

Can be used for both long and short distances.

It is driven by multiple shafts and a single chain.

They are compact and have small overall dimensions.

They do not present a fire hazard and temperature and ambient conditions do not affect their function.

DISADVANTAGES

Accurate alignment is required compared to belt drives.

They require frequent lubrication.

They have a lower load capacity compared to gear drives.

These operations are noisy and can cause vibration.

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