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CHAIN & STANDARDS

24 Nov

CHAIN & STANDARDS

     A chain is a reliable machine component, which transmits power by means of tensile forces, and is used primarily for power transmission and conveyance systems. The function and uses of chain are similar to a belt. There are many kinds of chain. It is convenient to sort types of chain by either material of composition or method of construction.

We can sort chains into five types:

  1. Cast iron chain
  2. Cast steel chain
  3. Forged chain
  4. Steel chain
  5. Plastic chain

     Demand for the first three chain types is now decreasing; they are only used in some special situations. For example, cast iron chain is part of water-treatment equipment; forged chain is used in overhead conveyors for automobile factories.

     There is much confusion over exactly what size, type etc. chain has been used on the primary sprockets of older British and American motorcycles. There are several “standards” for roller chain, including ANSI, ISO, BS, etc. Don’t trust a quick visual inspection, or comparison of only a few points of reference when buying a chain or sprockets. Some types that appear very similar are not compatible, typically due to differences in the roller diameter. Others will work acceptably with only slight additional wear.
    Chain dimensions are usually given in the following order: 1st = pitch, 2nd = roller width, 3rd = roller diameter. This is not all the useful data, and cannot be used reliably to determine whether chain repair parts (master link, connecting link, offset link, roller, repair link, etc.) can be interchanged. For pitch, roller width and roller diameter dimensions are given in fractional inches, decimal inches, and millimeters where practical.
ANSI (U.S. and commercial)
    These give pitch in 1/8” increments as the 1st number.
    The 2nd number refers to the chain being a roller chain, 0 = roller chain, 5 = bushing. E.g., #50 is a 5/8” pitch roller chain; #35 is a 3/8” pitch bushing chain.
    The suffix is the number of strands: -2 = duplex. E.g., 35-2 is 3/8” pitch dual row bushing chain.
ISO (Metric, British)
    These give pitch in 1/16” increments as the 1st number. E.g., 3/8” pitch =#06.
    The letter “B” means “European Standard”.
    The suffix is the number of strands in the chain: -2 = duplex chain. E.g., 06B-3 is a triple row 3/8” pitch European Standard.

A typical configuration for RS60-type chain is shown in Figure Figure 1.1 The Basic Components of Transmission Chain
                                       Figure  The Basic Components of Transmission Chain

Connecting Link

     This is the ordinary type of connecting link. The pin and link plate are slip fit in the connecting link for ease of assembly. This type of connecting link is 20 percent lower in fatigue strength than the chain itself. There are also some special connecting links which have the same strength as the chain itself. (See Figure 2.)

Tap Fit Connecting Link

     In this link, the pin and the tap fit connecting link plate are press fit. It has fatigue strength almost equal to that of the chain itself. (See Figure 2.)

Offset Link

     An offset link is used when an odd number of chain links is required. It is 35 percent lower in fatigue strength than the chain itself. The pin and two plates are slip fit. There is also a two-pitch offset link available that has a fatigue strength as great as the chain itself. (See Figure 3.)

Figure 1.2 Standard Connecting Link (top) and Tap Fit Connecting Link (bottom)
                         Figure 2 Standard Connecting Link (top) and Tap Fit Connecting Link (bottom)

Figure 1.3 Offset Link
                                                        Figure 3 Offset Link

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Posted by on November 24, 2011 in Final Year Projects

 

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