The Single Cylinder Engine

1
The Single Cylinder Engine

• A presentation by
• Chris Kopchick
• Matt Roon
• John Gesek

11/21/2005
ME 358
2
ABSTRACT

• We are to design a slider crank mechanism
  consisting of a crankshaft, connecting rod, and
  piston. The requirements for piston travel must
  not exceed 0.06m due to strict cubic inch
  tolerances. Within the cylinder or ground the
  velocity of the piston must not exceed 2 m/s with
  a constant crankshaft angular velocity of 600 rpm
  during the velocity analysis due to a weakness in
  the casting of the engine block. This particular
  engine will be operating at a constant velocity,
  however if we were to apply an angular
  acceleration of 10 radians/second to the
  crankshaft, we must not exceed a piston
  acceleration of 20 m/s2. This requirement will
  satisfy the side load tolerances on the ring
  lands. Our two main points of interest will be at
  TDC (Top Dead Center) and BDC (Bottom Dead
  Center) for piston travel and 45 degrees for
  piston velocity and acceleration. This slider
  crank assembly will be a Grashof mechanism with a
  DOF1. With an operational constant idle of 600
  rpm we designed a short stroke, long rod
  combination resulting in less torque. This setup
  will also provide extended bearing life and
  promote exceptional ring seal.

3
INTRODUCTION

• In this application we are using a Grashof
  slider crank mechanism better known specifically
  as a single cylinder engine. This internal
  combustion engine will be used in a constant idle
  application such as a household generator. Simply
  put, a force is exerted on the piston during the
  combustion process (a combination of fuel, air,
  and spark). This forces the piston downward,
  which through rotation of the connecting rod,
  causes the crankshaft to rotate. This rotation is
  the output of the mechanism and is widely used to
  power lawnmowers, snow blowers, generators, etc.

4
3-D MODEL OF THE ENGINE
5
ENGINE ASSEMBLY
Connecting Rod
6
2-D DRAWING OF THE ENGINE
7
CRITICAL PARAMETERS

• Applying to TDC, BDC
• 1) Piston travel must not exceed 0.06m due to
  cubic inch requirements
• Applying to 45 degrees
• 2) Piston velocity must not exceed 2 m/s at a
  constant crankshaft angular velocity of 600 rpm
  due to a weakness in the casting of the engine
  block
• 3) Piston acceleration must not exceed 20 m/s2,
  with an initial angular crankshaft acceleration
  of 10 rad/sec, due to side load requirements on
  the piston ring lands.

8
Results If Critical Parameters Are Exceeded
9
DEGREES OF FREEDOM

• Grueblers Equation
• DOF 3L-2J1-J2-3G
• L 4
• J1 4
• J2 0
• G 1
• DOF (34)-(24)-0-(31) 1 DOF

10
POSITION ANALYSIS TDC and BDC

• TDC Initial Conditions
• T2 0
• A 0.029m
• B 0.19113m
• C 0m
• TDC Calculations
• T3 180
• D 0.22013m

BDC Initial Conditions T2 180 A 0.029m B
0.19113m C 0m BDC Calculations T3 180
D 0.16213m

11
POSITION ANALYSIS 45 degrees

• Initial Conditions
• T2 45
• A 0.029m
• B 0.19113m
• C 0m
• Calculations
• T3 173.84
• D 0.210553m

12
VELOCITY ANALYSIS TDC and BDC

• BDC Initial Conditions
• T2 180
• T3 180
• A 0.029m
• B 0.19113m
• C 0m
• D 0.16213m
• BDC Calculations
• ?3 9.53343 rad/sec
• d/dt 0 m/s

• TDC Initial Conditions
• T2 0
• T3 180
• A 0.029m
• B 0.19113m
• C 0m
• D 0.22013m
• TDC Calculations
• ?3 -9.53343 rad/sec
• d/dt 0 m/s

13
VELOCITY ANALYSIS 45 degrees

• Initial Conditions
• T2 45
• T3 173.84
• A 0.029m
• B 0.19113m
• C 0m
• D 0.210533m
• Calculations
• ?3 -6.7803 rad/sec
• d/dt -1.4275 m/s

14
ACCELERATION ANALYSIS TDC and BDC

• BDC Initial Conditions
• T2 180
• T3 180
• A 0.029m
• B 0.19113m
• C 0m
• D 0.16213m
• ?3 9.53343 rad/sec
• d/dt 0 m/s
• BDC Calculations
• a3 1.51729 rad/sec2
• d2/dt2 0 m/s2

• BDC Initial Conditions
• T2 0
• T3 180
• A 0.029m
• B 0.19113m
• C 0m
• D 0.22013m
• ?3 -9.53343 rad/sec
• d/dt 0 m/s
• BDC Calculations
• a3 -1.51729 rad/sec2
• d2/dt2 0 m/s2

15
ACCELERATION ANALYSIS 45 degrees

• Initial Conditions
• T2 45
• T3 173.84
• A 0.029m
• B 0.19113m
• C 0m
• D 0.210533m
• ?3 -6.7803 rad/sec
• d/dt -1.4275 m/s
• Calculations
• a3 -14.7957 rad/sec2
• d2/dt2 -11.295 m/s2

16
Working Model Animation

• Animation of Single Cylinder Engine

17
RESULTS

• When analyzing TDC and BDC, our design
  satisfies all critical parameters. Our piston
  travel was calculated out to be
  0.22013-0.162130.058m. This is within our 0.06m
  travel and displacement tolerances.
• When analyzing the initial 45 degree condition,
  we calculated our piston velocity to be 1.4275
  m/s downward and piston acceleration of 11.295
  m/s2 downward. With our present initial
  conditions, this minimizes the chance of engine
  block fracture due to a weakness in the casting,
  and satisfies our piston side load requirements
  on the ring lands.
• Analyzing the graphs in Working Model, Our
  position, velocity, and acceleration results
  coincide very nicely with our calculated results.
  

18
CONCLUSIONS

• We can see that one of the main problems with
  this type of mechanism is controlling velocity
  and acceleration of the piston. For a given
  displacement, the piston speed and acceleration
  can be lowered by increasing the bore and
  decreasing the stroke. This reduces stresses on
  the block, connecting rod, and crankshaft. Also,
  increasing the length of the connecting rod would
  yield a slightly different piston position curve
  with flatter plateaus. This would also reduce
  stresses on the crankshaft and block.
• An improvement to the techniques used in
  analyzing this mechanism might involve building a
  mock-up of the engine and measuring deformations
  and heat produced in the bearings. This would
  give much insight about the critical parameters
  of the engine.

19
Resources Used

• Working Model (Slider Crank)
• Solid Works 3D 2005
• Design of Machinery, Robert L. Norton