Chains Flashcards
Power transmission chain
- used as a positive drive to transmit power between widely spaced shafts
- 98% efficient
Number one reason for chain wear?
-lubrication
Two types of Pre-lubricated chain
- sintered bushing
- o ring
Sintered bushing
- Bushings are charged with lubricant that is squeezed out when chain is under load
- has no roller
- lasts 5 times longer
- 10% less loading capacity than standard chain
O-ring
- intended to provide lifetime lubrication and to exclude contaminants. 10 times cleaner than without for food places
- stronger than standard chain but 5% less than sintered
Oilfield chain
- multiple strand chain that is made to ANSI dimensions and upgraded to API standards
- uses press fit instead of slip fit
Types of chain
- roller
- silent
Roller less chain
- designation #5
- run in sheaves instead of sprockets
- maintain tension where there is no or very little movement
Silent chain (timing chain)
- Consists of links made up of tooth side plates
- highest efficiency
- high speed
- widest range of speeds
- widest range of load
- compact
3 silent chain designs
- side guide
- centre guide
- duplex/serpentine drive
What tools do you need for sprocket alignment
-straight edge and feeler gauge
Chain wrap
-chain climbing up the back of the sprocket caused by too little tension
Appropriate chain tension
- slow to med 4-6% sag
- high speed or vertical drive 2-3% sag
Double Pitch
- same as standard chain but the pitch is double.
- used for long spans and low speed, low horsepower
Master Clip installation
- closed end in the direction of travel
- remember trailing edge (end with split) is the back edge
slip fit side plate
-reduces the working capacity of the chain by 30%
press fit side plates
-do not reduce working capacity
Too much chain tension
- will prevent lubrication from getting all around the shaft
- put undo pressure on the shafts, etc…
Chain lubrication
- apply to inside of slack span
- low speed drives (under 600 ft per min) use manual or drip feed
- chains at 1500 ft per min use bath lubrication
- forced (oil pump from above)
Elongation
-over 3% and the chain should be changed
Galled
-Metal has been torn away from the surface of the pin
Backstop
- restraining device that prevents the load from turning the drive when the drive is shut off.
- one way clutch is often used
Minimum chain wrap angle
-120 degrees
Double strand chain
- 1.7 times stronger than single strand
- side plates are press fit, but centre plates are slip fit
- higher load and speed capacity
Heavy Duty
- does NOT have a higher load capacity, but lets it last longer
- has thicker side plates
Single pitch offset link (half link)
- reduces the length of the chain by one pitch
- consists of two bent side bars that are riveted to a bush and roller at one end
Most common light duty chain
- # 41
- has 1/4 wide rollers
Hunting Link
- used when an odd number of pitches is required
- offset link
Joining pin or connecting link
- used to change the chain length by two pitches
- convenient for assembling the chain in the field
Chain Length
- 1/2 the total sprockets times the pitch which represents the length the chain will wrap around the sprockets
- then double the drive centre distance.
To order new sprockets
-you need to provide chain pitch, chain type, number of strands and hub style
Bushing Failure
- Caused by overload
- sprockets too small
- imperfect form on the sprocket teeth
- badly worn or oversized gullet on the sprocket teeth
Roller Failure
-Caused when the sprocket repeatedly engages the sprocket teeth under load
Stretch
- One way a chain can be elongated
- could jump off the sprocket
Pin Failure
- From constant flexing of the pin as each chain link moves over the sprocket.
- exposure to corrosives
Side Bar Failure
-Repeated stressing and unstressing of the chain as the links moved from the loaded and unloaded strands
Ways to improve service life on driver to driven
- increase centre distance
- change the speed in two steps using a jack shaft
Idler Sprockets
- used as chain tensioner
- to prevent chain whip
- improve chain wrap
- to provide reverse rotation of a sprocket outside the chain
Idler Sprockets mount?
-on the slack span to reduce wear on the chain and sprockets
Hub Style A
-flat sprocket that can mount on any hub
Hub Style B
-Hub on one side
Hub Style C
-hub on both sides
Hub Style D
-split in the middle so you can mount it between bearings without having to remove them.
Sheer Pin Hub
- Provides the sprocket drive with overload protection in case of a jam
- shears off with too much force
- Uses Type A sprocket
Sprocket
-toothed wheel designed to mesh with power transmission chains
Installing sprocket
-there should be .002-.005 clearance between the top of the key and the sprocket
-none on the sides (some applications allow .002
-
Sprocket runout
-.002
