MECH1200
Topics
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Introduction
Drive Chain Types
Sprockets
Sprocket Types
Chain Drive Safety
Roller Chain Installation and Maintenance
• Please read Chapter 11 in the text.
Introduction
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 Chains have been used for thousands of years.
 Chains were used on bicycles in the 1800’s
 Advantages of chain drives:
Resistant to shock loads
Can transmit high torques
economical
 Drive Chain Function and Operation
 Main functions:
 Material handling
Source:
Power transmission
http://www.osha.gov
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Chain Drive
3 Basic Parts:
• Chain
• Driver Sprocket
• Driven
Sprocket
The Relative number of teeth between the
driven sprocket and the driver sprocket
determines the speed and torque of the driven
shaft
Ratio of the teeth can be selected to increase or
decrease speed or torque to the driven shaft
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Sprocket Ratio Formula
𝑅=
𝑁𝐷𝑟𝑖𝑣𝑒𝑛
𝑁𝐷𝑟𝑖𝑣𝑒𝑟
R= Sprocket Ratio
𝑁𝐷𝑟𝑖𝑣𝑒𝑛 = Number of teeth on driven sprocket
𝑁𝐷𝑟𝑖𝑣𝑒𝑟 = Number of teeth on the driver sprocket
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Sprocket ratio is needed to calculate the speed and torque of chain drives
𝑅=
𝑁𝐷𝑟𝑖𝑣𝑒𝑛
𝑁𝐷𝑟𝑖𝑣𝑒𝑟
R= Sprocket Ratio
𝑁𝐷𝑟𝑖𝑣𝑒𝑛 = Number of teeth on driven
sprocket
𝑁𝐷𝑟𝑖𝑣𝑒𝑟 = Number of teeth on the driver
sprocket
Example:
Determine the sprocket ratio where 𝑁𝐷𝑟𝑖𝑣𝑒𝑛 = 33 teeth and 𝑁𝐷𝑟𝑖𝑣𝑒𝑟 = 20 teeth
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Chordal Action
The chain does not ride
completely along the pitch
line because each link is a
rigid bar that cannot bend to
follow the circular path
The chain links remain straight lines as they move around the pitch circle in
chordal action
Chordal action is similar to the motion a train makes as its straight cars move
through a turn in the tracks.
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The 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 loss
The 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.
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The 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 speed
More teeth, more torque
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Chain Drive Speed Formula
𝑆𝐷𝑟𝑖𝑣𝑒𝑟 𝑁𝐷𝑟𝑖𝑣𝑒𝑛
=
𝑆𝐷𝑟𝑖𝑣𝑒𝑛 𝑁𝐷𝑟𝑖𝑣𝑒𝑟
𝑆𝐷𝑟𝑖𝑣𝑒𝑛 = 1280 RPM
𝑁𝐷𝑟𝑖𝑣𝑒𝑛 = 41 Teeth
𝑁𝐷𝑟𝑖𝑣𝑒𝑟 = 12 Teeth
Chain Drive Torque Formula
𝑇𝐷𝑟𝑖𝑣𝑒𝑛 𝑁𝐷𝑟𝑖𝑣𝑒𝑛
=
𝑇𝐷𝑟𝑖𝑣𝑒𝑟 𝑁𝐷𝑟𝑖𝑣𝑒𝑟
𝑇𝐷𝑟𝑖𝑣𝑒𝑛 = 300 in-lbs
𝑁𝐷𝑟𝑖𝑣𝑒𝑛 = 26 Teeth
𝑁𝐷𝑟𝑖𝑣𝑒𝑟 = 14 Teeth
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Power 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.
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Four common types of chains
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Roller Chain
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Rollerless Chain
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Silent Chain
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Leaf Chain
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The roller chain is the most common type of chain used in
industrial chain drive systems
There are four basic types of roller chains
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Single-Strand Chain
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Multiple-Strand Chain
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Double-pitch Chain
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Offset Chain
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Components of a Roller Chain
The pin of the pin link passes
through the bushing on the
roller link to make an
assembly
Roller chain is made up of pin links and roller links
The links mesh with the sprockets so speed and torque can be transmitted
Roller 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 them
Roller links flex at the junction between links allowing rollers to freely roll
reducing friction between the chain and sprocket
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Roller Chain Components
Pins
Pin Link Plates
Pitch
Roller
Roller Link Plates
Drive Chain Types
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Roller 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 Chain
 O-ring Chain: O-rings seal the lubricant in the joints.
Engineering Chains:
 Offset Sidebar Chains
 Pintle, Mill, and Drag Chains
 Silent Chain: teeth are in continuous contact with sprocket, thus noise is reduced
 Leaf Chain
 Polymeric Chains
 Tabletop Chain.
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Sprockets
Face Width
Length Through Bore
Bottom Diameter
Outside Diameter
Bore
Pitch Diameter
Source: Drawing is in the public domain and was taken fromWikimedia Commons, Wikimedia Foundation
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Sprocket Nomenclature
Body (plate)
Hub
Teeth (rim)
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Standard Types of Sprockets
A type: A plate sprocket with no hubs
B type: One hub projection (most common)
C type: The sprocket has hubs on both sides
D type: A sprocket with detachable bolts on the hubs
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Sprocket Part Numbers
American 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?
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Special Sprocket Types
Split 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 Sprocket
Shear 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.
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Chain Drive Selection
• Drive Ratio: at most 7:1
• Sprocket 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 50-80 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.
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Roller Chain Safety
1. Roller chain drives should be inspected after the
first 100 hours of operation.
2. Regular inspections should be made once every
three week intervals.
3. Chain safety guidelines: please read the guidelines
on page 289 of the text.
Roller Chain Installation and
Maintenance
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1. Chain installation and maintenance
- Store in a dry location in lubricant
- Drive 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:
1) Check for chain stretch (Chain elongation), Chain elongation should
not exceed 3% (0.36’’ per foot).
2) Check side plates for misalignment, cracks, or wear.
3) Check for stiff and frozen chain joints
4) Check for corrosion in the chain drive parts.
5) Check for wobbly and loose sprockets.
6) Check for wear and scratches and changes on the teeth.
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10 Steps for Chain Installation, Alignment and Removal
1 – Mount and level the motor and driven component
2 – Inspect the Sprockets
3 – Mount the Sprockets on the shafts
4 – Mount the Chain
5 – Align the Sprockets
6 – Apply Tension to the Chain
7 – Apply lubrication to the Chain
8 – Run the Motor briefly to test the drive
9 – Recheck the chain sag
10 – Chain removal
Exercises
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1. You will be handed a sprocket. Measure the following?
- The bore diameter
- The pitch
- The number of teeth
- What type is the sprocket?
- Compare your measurements to the ANSI number shown on
the sprocket.
2. Find the above specifications for the sprocket whose
number is 60C80-5/8’’
3. What is the pitch of the chain with the specification 60?
4. What is the pitch of the silent chain specified as SC-608?