Rigid and Flexible
Rigid Couplings:*Rigid couplings produce the greatest reactions
on equipment. Mechanical Element type such as gear, chain, and grid
couplings produce moderate to high moments and forces on equipment
that are a function of torque andmisalignment. Elastomeric element
couplings produce moderate to low moments and forces that are
slightly dependent on torque. Metallic Element couplings produce
relatively low moments and forces w hich are relativelyindependent
of torque.*One-piece rigid couplings wrap around the shaft
providing high torsional holding power without the shaft damage and
fretting inherent when set screw style couplings are used.
Two-piece styles have the additional benefits of allowing for
disassembly and maintenance without removal of other components.
Two-piece couplings also feature opposing hardware for dynamic
balancing.
The most commonly used flexible couplings today are those that
produce the greatest flexibility (misalignment and axialcapacity) w
hile producing the low est external loads on equipment.
b. Flexible Couplings:There are three basic types of flexible
couplings:1. Mechanical Element2. Elastomeric Element3. Metallic
ElementThe mechanical element type generally obtain their
flexibility from loose-fitting parts or rolling or sliding of
mating parts or from both.They require lubrication unless one
moving part is made of a material that supplies its own lubrication
need (e.g., a nylon gear coupling).The elastomeric element types
obtain their flexibility from stretching or compressing a resilient
material (rubber, plastic, etc.) . The metallic element types
obtain their flexibility from the flexing of thin metallic disc or
diaphragms.*Besides these basic function flexible couplings
"sometimes" are required to do thefollow ing: Dampen vibration and
reduce peak or shock loads. Protect equipment from overload Measure
output torque of driven equipment Electrically Insulate the driver
from the driven equipment Position a rotor of a motor or generator
Be used to tune a system out of a torsional
critical.Source(s):http://www.couplings.com/seminar/section...jdsheth2004
8 years ago2Thumbs up0Thumbs downComment
Effecive power output=8Hp(80% efficiency)Calculation of
frictional torque-N=300kg=2943newtons=0.45(between tire and
gravel)weight distribution=F:R=35:65Length=L=1.778mRadius of the
wheel=0.2794mPositon of center of gravity=b=1.1557m from
front(c=0.6223m from rear)h=0.508m form ground.When
stationary-Weight on rear=1912.95NWeight0n front=1030.05NFr=*weight
rear=860.82NFf=*weight front=463.52NT=R*(Fr+Ff)=370.02NmWhen
accelerating-Maximum acceleration(a)= Fr
/weight=860.82/300=2.869m/s2Weight on
rear=(b/L)*N+(h/L)*weight*a=(1.1557/1.778)*2943+(.508/1.778)*300*2.869=2158.86NWeight
on front =784.14N
Drag force-Max. Frontal
area=Af=56*57*2.542*10-4=2.05m2Cd=0.3=density of
air=1.29kg/mm2velocity=45kmph=9.722m/s2Fdrag=.5* Cd*
*Af*v2=.5*.3*2.05*1.29*9.7222=37.49N
Weight of vehicle including driver= (220+80)=300kgCoefficient of
friction==0.45Radius of the tire=11inches= (11*2.45*10^-2)mWeight
distribution- 65%rear, 35%front REAR- w
N fWeight on rear wheels-W=(.65*300)=195kgWeight on one rear
wheel-w=W/2=97.5kg=(97.5*9.8)=955.5N
w=Nf=N=(.45*955.5)=429.97NTorque required at one rear
wheel-T=fR=[429.97N*(11*2.45*10^-2)m]=119.85NmTorque required at
both rear wheelsTrear=2*T=239.71Nm
FRONT-Weight on front wheels- W=(.35*300)=105kgWeight on one
front
wheel-w=W/2=52.5kg=(52.5*9.8)=514.5Nw=Nf=N=(.45*514.5)=231.525NTorque
required at one front
wheel-T=fR=[231.525N*(11*2.45*10^-2)m]=64.68NmTorque required at
both front wheels-Tfront=2*T=129.37NmNet torque
required-Tnet=Trear+Tfront=369.08Nm
