power transmission systems Flashcards
what are the purposes of a shaft
transmit power to a location outside the machine
used as an extension to other shafts
provide a means of operating the working components of the machine
examples of common shaft materials
cold rolled steel
hardened steel
chrome plated steel
stainless steel
what is included in shaft specifications
type of material
nominal diameter
diameter tolerance
straightness
length
function of a bearing
support and guide a moving machine member with a minimum amount of friction
what types of machines have an automatic lubrication system for the bearings?
machines with many bearing
radial bearing load
acts in a direction that is perpendicular to the axis of the shaft
use at least two bearings to secure the position of the shaft
thrust load
acts in a direction parallel to the shaft axis and opposite to the direction of force transmission
combination load
application with both a radial load and thrust load
only need one bearing, can be placed anywhere on the shaft in a way such that it can counteract the direction of the thrust load
two methods of bearing installation
arbor press
sleeve and hammer(only use if an arbor press is not available
two main categories of bearing used in industry
plain bearing- tyoe of bearing in which the surface of the moving machine component slides over the bearing surface, seperated only by a lubrication film
Anti-friction- rotate with the moving machine. this is accomplished by using rollers or balls that rotate within the bearing
two methods of shaft bearing mounts
pillow block- consists of a housing with two mounting feet oriented so that you can mount the shaft to a horizontal or angled surface.
flange bearing mount- consists of a housing with mounting feet that are oriented so that the shaft can be mounted to a surface that is perpendicular to the shaft
what are the two ways a pillow block can be designed
a single assembly or split assembly
zerk fitting
has a spring operated ball valve that allows grease to flow in, but not out
what are couplings used for
to connect one shaft to another
to connect two shafts to create one long shaft
four catagories of mechanical couples
rigid couplings- couple two shafts together rigidly so that they act as one continuous assemble
flexible couplings- connect two shafts together and allow for some misalignment. consists of two hubs and some type of flexible component that connects the two hubs
universal joint- allows two shafts that are not coaxially aligned to be connected
clutches- designed to allow two turning shafts to connect and disconnect from each other
shaft alignment
the process of the two shafts connected by a flexible coupling brought into line
five checks and corrections for shaft alignment
vertical angular- use shims to raise either the back or front of the motor
vertical parallel- raise or lower the entire motor
horizontal angular- loosen the motor foot mount and slightly turn it in the direction that corrects the misalignment
couple gap- set the gap to the manufacturers specifications
horizontal parallel- loosen the motor foot mounts and move all four feet an equal amount
four methods of measuring the amount of misalignment, in order from least to most accurate
straight edge and feeler gauge
face and rim method
reverse indicator method
laser alignment
mtbm
machine to be moved, usually the driver component
