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what are plain bearings	- a suitable solid material fitted between shaft and support to reduce friction and wear - bearing may be dry rubbing bearing or lubricated
what types of lubrication can be used for plain bearings	- hydrodynamic - hydrostatic - solid-film - boundary layer
what is hydrodynamic lubrication	the shaft rotating in oil creates the oil pressure to lubricate the shaft
what are ball and roller bearings	the rotating load is converted to rolling contact of the balls or rollers
what are the parts of a ball bearing	
what is the difference between a journal bearing and a thrust bearing	- a journal bearing supports the shaft radially - a thurst bearing supports the shaft axially
when would one use a plain rubbing bearing	low load, low speed applications
what is the pV factor and what is it the product of	a measure of the bearing's ability to cope with frictional heat generation  p- pressure V- speed at contact point
what is the projected area of a radial sliding bearing	the area of a journal when looking down from it:
what is the thrust area of an axial bearing	area of the bearing that isn't holey  [$]\frac\pi4 \left(D^2-d^2\right)[/$]
what is the wear volume of an axial sliding bearing	the non holey area multiplied by the distance the bearing can wear down without issue  [$]YA_\text{thrust} = Y\frac\pi4\left(D^2-d^2\right)[/$]
what are the main properties of plain rubbing bearings (4)	- usually made of polymers - moulded to final shape - dry lubricants added - reinforcements added
what dry lubricants and reinforcements are added to plain rubbing bearings	- PTFE lubricant added - glass fibre reinforement added
what limits the pressure and speed a plain bearing can be operated at	strength and temperature, respectively
what differentiates oil lubricated porous bearings	- manufactured from sintered metal powders - porous and impregnated
how often does lubricant need to be replenished in porous bearings	roughly 1000 hours
list some of the lowest coefficient of friction bearing materials and their coefficient range	- babbitt metal (0.005 to 0.1) - POM (0.05-0.15) - cast iron and lead bronze with grease (0.05 to 0.15)
list the highest pV bearing materials	- babbitt metal (2) - cast iron and lead bronze with grease (1) - porous bronze (1)
what is the equation for wear factor, [$]K[/$]	[$]K = \frac{W}{FVt}[/$]  where $W$ is wear volume, $F$ is bearing load, $V$ is sliding velocity, and $t$ is elapsed time
what is the main issue with hydrodynamic bearings	surfaces touch at low speeds
draw the curve of friction against speed	
describe the properties of boundary lubrication	continuoous and extensive contactlubricant is smeared across surfacecoefficient of friction 0.05 to 0.2wear take place & limits life
what are the properties of mixed lubrication	higher surface speedsintermittent contact between surfacepartial hydrodynamic supportcoefficient of friction of 0.004 to 0.10very high local pressures can create elastic deformation of surfaces
what is elastohydrodynamic lubrication	fluid film lubrication where high local pressure create elastic deformation of surfaces
what are the properties of hydrodynamic lubrication	high speedsno contact between surfaces---no wearminimum film thickness of 8 to 20 micronsvery good surface finish and tolerances requiredcoefficient of friction between 0.002 to 0.01
what is the Sommerfeld number	a dimensionless number describing the relationship between a bearings dimensions, speeds, and fluid properties  [$]S = \left( \frac R h\right)^2 \frac{\eta n}{P}[/$]  where R is radius, h is clearance, [$]\eta[/$] is viscosity, n is angular speed, and P is bearing pressure
what is the equation for clearance of a bearing	[$]h = R_\text{bearing} - R_{shaft}[/$]
what is petroff's equation and what is it used for	[$]\mu = 2\pi^2 \frac{\eta n}{P}\frac{R}{h}[/$]  used for lightly loaded bearings
equation for hydrodynamic journal bearing capacity	[$]F = S\eta V \left(\frac{R}{h}\right)^2[/$]
equation for thrust capacity for hydrodynamic thrust bearing	[$]F = 6\eta\left[ \frac{Ln(1+n)}{n^2} - \frac{2}{n(2+n)}\right]\frac{VL^2}{h_\text{min}^2}[/$]  where  [$]n = \frac{h_\text{max}}{h_\text{min}}-1[/$]
what causes friction between components in relative motion	real surfaces have asperities which stick out and make contact with the other facewhen sliding, asperities catch and must be deformed or brokenthe forces required to do so is friction
what are the different rolling element types	
what are the types of ball bearings and what are their primary features	
what is the equation for static load carrying capacty	[$]s_0 = \frac{C_0}{P_0}[/$]  where s is the static safety factor, P, is the equivalent static bearing load, and C is the basic static load rating
dynamic load carrying capacity	[$]L_{10} = \left(\frac CP \right)^q[/$]  where L10 is the basic life rating in millions of revolutions, C is the basic dynamic load rating, P is equivalent dynamic bearing load, q is exponent of life: 3 for balls10/3 for rollers
what are the equations for equivalent dynamic load (4)	constant magnitude and direction: P = F axial and radial load: [$]P = XF_r + YF_a[/$] (X and Y from manufacturers data)roller bearings: P = F_rfluctuating loads: [$]F_m = \sqrt[3]{\frac{F_1^3U_1 + \cdots}{U}}[/$]
when would you have adjust life rating (5)	low reliabilityhigh temperaturehigh vibrationrisk of water ingressrisk of corrosion
why should a locating bearing be used in conjunction with a floating bearing	ensures journal does not slide about axially (i think)
what combinations of bearings can be used to support a shaft (5)	2 angular contact bearings - free sliding housing for axial adjustmentone ball + one roller - roller supports radial, ball supports axial and radial2 taper rollers - both support radial and axial, one bearing adjusted against other to required preload2 balls - radial and axial loads, one clamped axially on both races while other left free2 roller - accepts heavy radial load, some axial, each roller locates axially one in direction
when should you slide fit the inner race with the shaft	when the load rotates with the shaft
what is the difference between bolts, screws, and studs	bolts have an unthreaded core, and a matching nutscrews are threaded all the way and screw directly into a materialstuds do not have heads
draw a lap joint and the forces they are designed to handle	
draw a butt joint and the forces they are designed to handle	
what is a rivet	a non threaded fastener that is deformed around the parts to be joined
what are the types of rivets (3)	solidtubular - have a hole down the axisblind (pop rivets)
what are the advantages of rivets (5)	low costrapid assemblypermanentcan join dissimilar materialswide range of shapes and materials
what are the disadvantages of rivits (3)	slower than welding and adhesivespoor under tensile loadsjoints leak unless sealed
draw a welded but joint and forces is designed to handle	
draw a welded lap joint and the forces it is designed to handle	
draw a double fillet t joint	
draw a fillet cornet joint	
why are bolts pre tensioned	stops faces from separatingreduces fluctuating stresses experienced by bolt -> increases fatigue life
what is the recommend preload for non permanent joints	[$]F_i = 0.75A_s\sigma_p[/$]
what is the rceommended preload for permanent joints	[$]F_i = 0.9A_s\sigma_p[/$]
what is the tensile area of a bolt	[$]A_s = \frac{\pi}{16}(d_p+d_r)^2[/$]
what is the pitch diameter of a bolt	[$]d_p = d-0.6495p[/$]
what is the minor diameter of a bolt	[$]d_r = d-1.0825p[/$]
what can proof strength be approximated to if unavailable	[$]\sigma_p = 0.85\sigma_y[/$]
"what does the marking ""MX.Y"" mean on a bolt"	X - has tensile strength of X*100 MPa Y - has yield strength of Y*X*10 Mpa
what is the bolt torque pre tension equation	[$]T= KF_id[/$]  where K is torque coefficient (around 0.2 for most cases), and d is nominal diameter
how can the stiffness of a bolt be reduced (2)	reduce cross sectional areaincrease length
what stress reserve factor would you want for reliable materials under controlled conditions and known stresses	1.25 to 1.5
what stress reserve factor would you want for average materials with known loads and stresses	2 to 2.5
what reserve factor would you want for untried materials in average conditions	3 to 3.5
what reserve factor would you want for well known materials in uncertain conditions	3 to 3.5
what are the steps to select a bolt (6)	consider permanent vs non permanent, define external load, number of bolts, and reserve factorestimate preload by assuming hard joint (K_c = 3K_b)choose suitable bolt size and determine preload by using table 5 of bs en iso 898-1:2009calculate stiffness of bolts and componentscalculate maximum allowable external loadcalculate reserve factor
why is a pre tensioned bolted joint beneficial for cyclic loading	pre tension raises mean stress which increases fatigue life
what must be considered when using helical gears	axial load generated
what are the properties of spur gears between parallel shafts (4)	cheap to manufacturenoisyfew number number of teeth in contact at any given timesensitive to alignment
what are the properties of helical gears	teeth cut at inclined angle to axis of rotationcontact between teeth more progressive and longercarries higher loadsquietercan be mounted at right anglesdouble helical gears (herringbone) can cancel out axial thrust for smoother power transmission at high speeds
what is the pitch circle	circle upon which all calculations are based
what is circular pitch	the distance between two identical points on adjacent teeth on a gear
what is the module of a gear, m	[$]m = \frac d N [/$]  where d is pitch diameter, N is number of teeth
what is tooth thickness and width of space	[$]t = w = 0.5p[/$]  where p is circular pitch
what is the addendum	radial distance between pitch circle and top land  a = m
what is the dedendum	radial distance between pitch circle and bottom land  b = 1.25 m
what is the clearance	c = 0.25m  radial distance between bottom land of gear 1 and top land of gear 2
what is the whole depth of a gear	ht = addendum + dedendum = 2.25m
what is the working depth of a gear	hk = addendum + dedendum - clearance = 2m
what are the conditions for proper meshing between gears	module is samepressure angle is same
what are the common pressure angles	20 degrees14.5 degrees
what is the equation for centre distance betwen two gears	[$]C = \frac m 2 (N_1 + N_2)[/$]
what is the minimum number of teeth for standard gears of pressure angle 20 degrees	18
what is a simple gear train	each shaft only carries one gear
what is a compound gear train	a gear train where at least one shaft carries two or more gears
what is a reverted train	a compond train in which the input and shaft are colinear
what is a planetary gear train	has a sun gear, planet carrier, and one or more planet gears
what differentiates planetary gear systems	it has two degrees of freedomhas very high gear ratios
what are the common forms of gear failure	bending fatiguepittingmicropittingscuffing
what is a lower pair joint	joint with surface contact (pin in a hole)
what is a higher pair joint	a joint with point or line contact, such as a pin in a slot
what is rectilinear translation	points in the body move in parallel straight lines
what is curvilinear motion	points in the body move along idential curves so the link does not rotate with respect to the ground
what is the equation for degrees of freedom of a mechanism (gruebler's)	M = 3L - 2J - 3G
what does it mean if a structure has negative degrees of freedom	it's preloaded or overconstrained
what is the grashof condition equation and what does it mean	S + L < P + Q: it is a grashof linkage and at least one link can make a full revolutionS + L > P + Q: non grashof and no link capable of making full revolutionS + L = P + Q: special grashof - either double-cranks or crank rockers
what is a limit/toggle test	checks if linkage can reach all positions without encountering a limit of toggle positiontoggle positons may be determined by collinearity of two links
what is transmission angle	angle between output link and coupler
what is the ideal transmission angle	90 degrees
what is the minimum transmission angle	40 degrees