This article was written according to aircraft standards but the principles of Chains remain the same but if applying the knowledge to low power chains on Bicycles, Then you can make your own risk economic based reduced standards. If working on aircraft, always refer to the Maintenance manual.
The purpose of chains is to transfer power from one sprocket to another transfer kinetic(motion) energy. To accomplish this task you need at least an assembly of chain(s)(manufactured to SBAC standards like BS228:1994 or ISO606-1982), sprockets(toothed wheels) and possibly other accessories like interplaner blocks for changing the direction of the chains.
We will start with the main unit called the chain. This is an assembly of:-
The pitch of the chain is taken from centre of one roller to the next one i.e. the distance between the bearing pins.
Maintenance
Chains riveted links are not allowed to be broken down and re-riveted and only accepted from an approved manufacturer, with the correct packaging and transportation precautions taken.
It is permitted that a bolted joint may be disassembled and re-assembled, but, it is worth while noting these next few points.
1) SBAC states that all nut and bolted chain assemblies must be peened with the exception of the 8mm variety which must be split pinned
2) All nuts used on the chains must be locknuts(this nut is normally part of the outer plate)
3) All attachments must be either riveted or bolted
4) SBAC have standardised four sizes of chains by pitch size
BUT
British Standards have laid down the proof load as one third of the minimum breaking load (mbl)
5) Continuous(endless) chains must consist of an even amount of gaps between rollers(pitches)
6) The following table is the four classifications of chains and their statistics.
PITCH — MBL(lbs) — PROOF LOAD(lbs) — BS
8mm ——— 800 ————- 267 ——————— 1
0.375″ ——- 1900 ———— 634 ——————— 2
0.5″ ———– 1800 ———— 600 ——————— 4
0.5″ ———– 3500 ———— 1166 ——————- 6
7) A non-reversible chain is a chain that may only fit a certain way round which can be achieved by correct unsymmetrical positioning by the outer plates fitted to the chain.
8) Irreversibility can be achieved by
9) When storing a chain it must be well soaked in the approved oil, laid flat on its side on top of greaseproof paper and coiled firmly (not tight but not too loose).
GENERAL INSPECTION
This unit is used as a high strength power transfer device. When inspecting the chain make sure to check the proceedure in the maintenance manual which should at minimum account for the Following
Percentage of Elongation (Method 1)
(Length Of Chain with Force applied x (No. Of Pitches x Pitch measurement)) / (No. Of Pitches x Pitch Measurement)
Note: All measurements are in inches and Tensile load required on Chain (Size is British Standard)
Size – Load (lbs)
1 —- 12
2 —- 16
4 —- 28
6 —- 28
Percentage of Elongation (Method 2)
(Measured Length / Original Length ) x 100