chain drives Flashcards
power transmission chains are used as a positive drive to transmit power between widely spaced ?
shafts the chain engages with toothed wheels called sprockets
name some power transmission limitations
do not slip on overload
adequate lubrication is hard to maintain
- service life is less than that of gears
what are power transmission chain characteristics ?
provide positive drive
- highly efficient 98% or better
- can be used with any distance between shaft centres
- number of shaft can be driven by a single shaft
-
two main designs of power transmission chains used they are?
roller chain and silent chain
chains are made of ?
hardened carbon steel
-stainless steel for corrosion
-synthtics such as nylon and various plastics
-
two basic types of links?
pin links and roller links
cotter pins are usually used on what numbers of chain?
80 chains and larger
spring clip retainers are used on#25 to #60
what is a connecting link?
unriveted link in a chain
-consists of a pin link with pins that are drilled for cotter pins or grooved at outer ends for spring clip
the connecting link changes the chains length by?
two pitches
another name for single pitch offset link?
half link- changes the length of the chain by one pitch
where is light duty chain used?
used on drives where space is restricted ,they have lower power ratings
what number is the most common light duty chain its used on garage doors?
41
true or false double strand chain is 1.7 times stronger than single strand ?
true
what is oil field chain intended for ?
severe service ond rilling rigs , uses press fit centre plates
name two types of pre lubricated chain?
sintered bushing chain -uses a powdered metal bushing lubricant is squeezed out under load
-0-ring chain -provide life time lubrication and exclude contaminates - can operate at high temps with special o-rings
where are pre lubricated chains used ?
designed for applications that do not permit regular lubrication.
the load capacity of a sintered chain is how much less
10% less than a standard chain
What corrosion resistant material is corrosion resistant chain produced with
stainless steel or by plating standard chain with a corrosion resistant coating such as nickel or a zinc compound
true or false -
Stainless steel does not have the tensile strength of carbon steel, and therefore load capacity is sacrifice for corrosion resistance
true
Plated chain has the same load capacity of standard chain, but it protects the integrity of the chain in a corrosive environment. However, the corrosion protective is lost when.
the platting wears off
Synthetic chains are designed for very light service. Such as instrument drives in office machines.true or false
true
Where woud synthetic Chain applications be
food handling and process equipment
-computer equipment
-instrument drives
-
what are synthetic chain advantages
light weight 15%-20% the weight of steel
- no lube required
-all links are master links
interchangeable with steel chain
-corrosion resistance is good
-
why is double pitch chain lighter ?
has half the number of pins and bushing and rollers, used for long spans and slow to moderate speeds with low HP.
instead of rollers what does roller less chain use?
bushings on pins at each joint -less expensive Tham standard roller chain
designated by the number 5 in the right hand part of the chain number
double pitch chains fits ?
standard sprockets since rollers and width are the same as standard pitch chain
where is silent chain used?
transmitting high horse power in a small space such as in chain driven speed changers
-high speed drives
-precision timing
silent chain is also called?
timing chain-contains tooth plates instead of rollers
where is a joining pin or connecting link used?
used on toothed links to change the length by two pitches, convenience way for assembling the chain in the field
where is a hunting link used ?
used on a tooth link when an odd number of pitches is required - an even pitch number is recommended
what are the 3 silent chain designs ?
side guides
centre guides
for serpentine drives
why do you do a chain inspection on a broken chain?
to try to discover the root cause of chain drive failure
silent chain advantages ?
high efficiency and HP in a narrow width
-lighter bearing load
-positive drive and durability
-smooth performance
-load shared by a number of teeth
how to measure the chain length?
measure old chain and divide by the pitch
-lay new chain beside the old chain
-
the master link must be installed with the closed end of the spring clip in what direction ?
the direction of travel
how do you remove old chain?
chain breaker
-torch -grinder
what kind of fit does a master link us?
slip fit
slip fitted plate reduces the working capacity by ?
30%
true or false? press fit side plates significantly reduce the capacity of the chain?
false .
multiple strand chains with press fit centres plates are used in ?
severe service applications such as drilling rigs
chains can be adjusted by ?
adjustable centres
using lighting idlers
What is the single most important factor in controlling the chains wear?
lubrication
What oil should you use when lubricating chains?
highest viscosity and still flows into the joint
manual drip feel lubrication is intended for ?
low speed drives under 600 feet per minute
name 3 methods of chain lubrication?
manual or drip feed
bath
forced
forced lubrication is intended for ?
heavily loaded drives operating above the speed limits of bath lubricaiton
bath lubrication is intended for chains at approx ?
1500 feet per minute
a warn sprocket destroys a new chain never install a new chain on a worn out sprocket
what is a sprocket ?
toothed wheels designed to mesh with power transmission chains
sprockets can be made of ?
allow cast iron -very large sprockets
medium carbon steel- small, medium and large sprockets
plastic-light duty sprockets
where are sprockets used ?
-on the drive unit
as idlers to tension chains
-on drives that provide accurate timing
-in roll cases
what’s the problem with small wrap angle ?
the chain may jump the teeth when operated at its designed maximum load
the wrap angle is always 120 deg when the ratio is?
3:1 or less regardless of the centre distance
a sprocket with fewer teeth results in ?
increases wear and vibration on the sprocket and chain
if a chain drive does not provide satisfactory service life because a smaller sprocket is to small what would you do ?
increase the centre distance
- change the speed using a jack shaft
vertical and angle drives are often used were?
industrial drives
sprockets with an odd number of teeth are called ?
hunting tooth sprockets
what is the advantage of a double pitch chain sprocket ?
wear is distributed over twice as many teeth
when ever possible use a sprocket with an odd number of teeth why?
different tooth engages with the chain on each revolution
where are idler sprockets used?
used as chain tensioners on fixed centre drives ,they mount on slack span reduce wear on the chain and sprocket
idlers can be used to ?
prevent chain whip
improve chain wrap
guide the chain around obstacles
provide reverse rotation of a sprocket outside the chain
hardened tooth sprockets are common and intended for greater wear resistance , they are beneficial when ?
the number of teeth is 20 or less
on drives that are heavily loaded
in abrasive conditions
on high speed drives
on drives that require extremely long life
hub style sprockets type
a
b
c
d
a= flat plate style sprocket can be welded or bolted
B= type b have a hub on one side can be mounted in smaller places
C= hubs on both sides
D=split design sprocket
keyless adapters are common on machines that require what?
accurate timing
tapered bore hub allows you to ?
use a tapered adapter bushing
what causes side wear on a sprocket ?
misalignment of the sprocket
what causes hooked teeth on a sprocket?
causes by wear caused by over tension inadequate lubrication abrasives or overload
after you have tightened the pull up bolts there should be how big of a gap between the sprocket and flange ?
1/4-1/8 gap
should you use more or less tension on a vertical or angle drive that on a horizontal drive?
more tension
should the slack be span on the top or bottom of a drive?
bottom
which sprockets would you use in an abrasive environment
harden tooth sprokets
when you see a chain not meeting properly with a sprocket and is pilling up on the sprocket what’s wrong
the chain or sprocket is worn
what is the advantage of a b type sprocket?
can bemoaned closer to the support bearing
