1 Topics Introduction Drive Chain Types Sprockets Sprocket Types MECH1200IntroductionDrive Chain TypesSprocketsSprocket TypesChain Drive SafetyRoller Chain Installation and MaintenancePlease read Chapter 11 in the text.
2 Introduction Chains have been used for thousands of years. MECH1200Chains have been used for thousands of years.Chains were used on bicycles in the 1800’sAdvantages of chain drives:Resistant to shock loadsCan transmit high torqueseconomicalDrive Chain Function and OperationMain functions:Material handlingPower transmissionSource:
3 MECH1200Chain Drive3 Basic Parts:ChainDriver SprocketDriven SprocketThe Relative number of teeth between the driven sprocket and the driver sprocket determines the speed and torque of the driven shaftRatio of the teeth can be selected to increase or decrease speed or torque to the driven shaft
4 Sprocket Ratio Formula MECH1200Sprocket Ratio Formula𝑅= 𝑁 𝐷𝑟𝑖𝑣𝑒𝑛 𝑁 𝐷𝑟𝑖𝑣𝑒𝑟R= Sprocket Ratio𝑁 𝐷𝑟𝑖𝑣𝑒𝑛 = Number of teeth on driven sprocket𝑁 𝐷𝑟𝑖𝑣𝑒𝑟 = Number of teeth on the driver sprocket
5 MECH1200Sprocket ratio is needed to calculate the speed and torque of chain drives𝑅= 𝑁 𝐷𝑟𝑖𝑣𝑒𝑛 𝑁 𝐷𝑟𝑖𝑣𝑒𝑟R= Sprocket Ratio𝑁 𝐷𝑟𝑖𝑣𝑒𝑛 = Number of teeth on driven sprocket𝑁 𝐷𝑟𝑖𝑣𝑒𝑟 = Number of teeth on the driver sprocketExample:Determine the sprocket ratio where 𝑁 𝐷𝑟𝑖𝑣𝑒𝑛 = 33 teeth and 𝑁 𝐷𝑟𝑖𝑣𝑒𝑟 = 20 teeth
6 MECH1200Chordal ActionThe chain does not ride completely along the pitch line because each link is a rigid bar that cannot bend to follow the circular pathThe chain links remain straight lines as they move around the pitch circle in chordal actionChordal action is similar to the motion a train makes as its straight cars move through a turn in the tracks.
7 MECH1200The Chordal action of the chain links causes some frictional losses between sprocket and chain.Friction occurs as each link engages the sprocket.The roller helps reduce the frictional lossThe rising and falling of the links cause a slight speed variation in the chain drive causing the driven sprockets speed to oscillate.The amount of oscillations depends on the number of teeth.If #teeth > 25, oscillation is less than 1% and is disregarded.
8 MECH1200The speed of the driven sprocket is determined by the sprocket ration. This is because the rate at which the teeth of the driven sprocket engage the chain is the same as the rate at which the driver sprocket teeth disengage the chain.Different number of teeth constitutes different rotational speed as well as effecting the torque.More teeth, less speedMore teeth, more torque
10 MECH1200Power is transmitted through a single strand roller chain when the driver sprocket rotates and its teeth engage the roller links, pulling the chain around it. This causes the chain to pull on the teeth of the driven sprocket, causing it to rotate.The chain drive uses the engagement (or interlocking) of the sprocket teeth and chain to drive it.
11 Four common types of chains MECH1200Four common types of chains
21 MECH1200Components of a Roller ChainThe pin of the pin link passes through the bushing on the roller link to make an assemblyRoller chain is made up of pin links and roller linksThe links mesh with the sprockets so speed and torque can be transmittedRoller links are similar to pin links, but are made of two side plates that are separated by bushings. The bushings support the rollers that are mounted to themRoller links flex at the junction between links allowing rollers to freely roll reducing friction between the chain and sprocket
22 Roller Chain Components MECH1200PinsPin Link PlatesRollerPitchRoller Link Plates
23 Drive Chain TypesMECH1200Roller Chain: most common type. ANSI numbers them such that first number is the pitch in eighths of an inch.Example: ANSI 50 indicates a chain of a pitch of 5/8’’Types of roller chains:Multiple Strand Roller Chain: used to increase chain power capacity without increasing the pitch of the chain.Heavy Series Roller Chain: have thick side plates, to withstand high shock loads. Identified by the letter H in the ANSI code.Double Pitch Roller Chain: the pitch is two times longer than in standard roller chains.Self-Lubricating Roller ChainO-ring Chain: O-rings seal the lubricant in the joints.Engineering Chains:Offset Sidebar ChainsPintle, Mill, and Drag ChainsSilent Chain: teeth are in continuous contact with sprocket, thus noise is reducedLeaf ChainPolymeric ChainsTabletop Chain.
24 Sprockets Face Width Length Through Bore Bottom Diameter MECH1200Face WidthLength Through BoreBottom DiameterOutside DiameterBorePitch DiameterSource: Drawing is in the public domain and was taken fromWikimedia Commons, Wikimedia Foundation
26 Standard Types of Sprockets MECH1200A type: A plate sprocket with no hubsB type: One hub projection (most common)C type: The sprocket has hubs on both sidesD type: A sprocket with detachable bolts on the hubs
27 Sprocket Part NumbersMECH1200American National Standards Institute (ANSI) maintains a standard for sprocket and chain design. Example 1: A sprocket has the number 25A36-3/8’’ Then it is for a roller chain of a ANSI standard size of 25 and a A-style hub with 36 teeth and a bore diameter of 3/8’’. Exercise 1: A sprocket has the number 50B21-7/8’’ What is its bore diameter? What type is it, and how many teeth does it have?
28 Special Sprocket Types MECH1200Split Sprocket: to allow for installation of halves around the shaft.Sectional Rim Sprockets: the rim is sectioned into three parts to allow for replacement without uninstalling the sprocket.Double Pitch SprocketShear Pin Sprockets: the hub is keyed to the shaft, the sprocket is free to rotate on the shaft when the shear pin that couples it to the hub is broken.
29 Chain Drive Selection Drive Ratio: at most 7:1 MECH1200Drive Ratio: at most 7:1Sprocket Size: As number of teeth increases, variation of chain speed resulting from chordal action decreases.Center Distance: a good design practice is to use a center distance of about pitches. It should not be long to avoid vibrations and pulsation.Idler Sprockets: a chain tightening device. Should have at least three teeth in engagement.
30 Roller Chain SafetyMECH1200Roller chain drives should be inspected after the first 100 hours of operation.Regular inspections should be made once every three week intervals.Chain safety guidelines: please read the guidelines on page 289 of the text.
31 Roller Chain Installation and Maintenance MECH1200Chain installation and maintenanceStore in a dry location in lubricantDrive interference: clean debris and built up material in between the sprocket and chain.Chain Case: the case is needed to protect personnel, isolate chain from contaminant, and facilitate lubrication.Chain and Sprocket Inspection:Check for chain stretch (Chain elongation), Chain elongation should not exceed 3% (0.36’’ per foot).Check side plates for misalignment, cracks, or wear.Check for stiff and frozen chain jointsCheck for corrosion in the chain drive parts.Check for wobbly and loose sprockets.Check for wear and scratches and changes on the teeth.
32 10 Steps for Chain Installation, Alignment and Removal MECH120010 Steps for Chain Installation, Alignment and Removal1 – Mount and level the motor and driven component2 – Inspect the Sprockets3 – Mount the Sprockets on the shafts4 – Mount the Chain5 – Align the Sprockets6 – Apply Tension to the Chain7 – Apply lubrication to the Chain8 – Run the Motor briefly to test the drive9 – Recheck the chain sag10 – Chain removal
33 Exercises You will be handed a sprocket. Measure the following? MECH1200You will be handed a sprocket. Measure the following?The bore diameterThe pitchThe number of teethWhat type is the sprocket?Compare your measurements to the ANSI number shown on the sprocket.Find the above specifications for the sprocket whose number is 60C80-5/8’’What is the pitch of the chain with the specification 60?What is the pitch of the silent chain specified as SC-608?