It is most likely that the connecting rod failed on the end of exhaust stroke, due to the
tensile force being
at the highest at TDC.
What causes connecting rods to fail?
Fatigue is the main cause of broken connecting rods–
especially
in older engines. The constant compression during the power stroke and stretching during the exhaust stroke, over thousands of times a minute, eventually wears the metal out and it becomes brittle and finally breaks.
What are the stresses on connecting rod?
The major stress induced in connecting rod during its operation is combination of
axial and bending stress
. The bending stresses are produced due to centrifugal effects, while the axial stresses are produced because of cylinder gas pressure and they are compressive in nature.
What would cause a connecting rod to bend?
The most common causes of a bent connecting rod are
detonation or over-revving
. If you know you have been driving in deep water it could have flooded your engine, leading to hydro-lock which will easily bend your connecting rods.
What are the forces stresses acting on the connecting rod of a single acting engine?
During each rotation of the crankshaft, a connecting rod is often subject to large and repetitive forces:
shear forces
due to the angle between the piston and the crankpin, compression forces as the piston moves downwards, and tensile forces as the piston moves upwards.
What causes a thrown rod?
A broken intake or exhaust valve may drop into the piston cylinder
. If the engine continues to run, the loose valve wreaks mechanical havoc in the cylinder, pulverizing the head of the piston and resulting in a thrown rod from breakage at the wrist pin.
What are the types of connecting rod?
- Plain type rod.
- Fork and blade rod.
- Master and slave rod.
- Billet conrods.
- Cast rods.
- Forged rods.
- Powered metal conrods.
What is the material of connecting rod?
A connecting rod with a tension load is made of forged steel, cast steel, or fabricated steel. Rods with a compression loading are cast
nodular
steel or aluminum alloy.
What is bending stress?
Bending stress is
the normal stress that an object encounters when it is subjected to a large load at a particular point that causes the object to bend and become fatigued
. Bending stress occurs when operating industrial equipment and in concrete and metallic structures when they are subjected to a tensile load.
What are the types of crankshaft?
The crankshaft
There are two types of crankshaft,
the monolithic type
(Fig. 8.1), used for multi-cylinder engines, and the assembled type (Fig. 8.2) fabricated from separate elements, which is mainly used for motorcycles.
How do you check a connecting rod bend?
One can check bend by
using two pins and v block
. In this method, two pins with exactly same diameter of pin bore and crank bore are used. Length of pins should be longer than the width of connecting rod and both the pins should be of same length. Connecting rod is rested on v block.
What is the difference between a bent connecting rod and twisted connecting rod?
Bend and Twist
A bend in the rod beam
results in the centerline of the big-end bore being out of alignment with the center of the wrist pin bore
. A twist in the beam throws the big-end bore out-of-plane with the small end.
What is a rod knock?
Rod knock is
the sound of one or more of your rods “knocking” against the crank as it changes direction through its rotation
. The connecting rod (we’ll just call it the rod from here out) is connected to the crank, and between the two there’s a bearing made from a softer material than either the rod or the crank.
Which force acts on the connecting rod?
The various forces acting on the connecting rod are as follows:
Forces on the piston due to gas pressure and inertia of the reciprocating parts
. 1. Forces on the piston due to gas pressure and inertia of the reciprocating parts. 2.
Which force is experienced by connecting rod?
Which force is experienced by connecting rod? Explanation: The connecting rod is subjected to the force of gas pressure and
the inertia force
of the reciprocating part. Hence, the Inertia force is the right answer.
Which force is not acting on connecting rod?
Explanation: Since there is no accelerated frame of reference having different velocities, therefore
coriolis force
does not act on the connecting rod.
What are the signs of a thrown rod?
- Knocking Noise From Engine. Listen for a knocking noise when the engine is running. …
- Low Oil Pressure. Check the oil pressure. …
- Excessive Oil Consumption. Determine if the engine is using excessive oil. …
- Visual Inspection.
Which stress is included in cylinder wall due to side thrust of the piston?
Thickness of the cylinder wall. The cylinder wall is subjected to gas pressure and the piston side thrust. The gas pressure produces the following two types of stresses :
(a) Longitudinal stress
, and (b) Circumferential stress.
What is a thrown rod in a car?
A thrown rod means
a portion of the rod is being thrown around inside the engine
. As you run the engine, it will continue to cause more destruction. In almost every case, if you’ve thrown a rod, complete engine replacement (at a minimum, most likely a shortblock) is needed to fix your issues.
What causes low oil pressure?
If the oil level on the dipstick is between “add” and “full,” a possible cause of low pressure would be
worn engine bearings
, especially if the engine has very high mileage. Excessive wear reduces the original flow restriction, which consequently drops the pressure.
What are the advantages of a connecting rod?
The advantages of the forged connecting rod:
A “new” metrology no deformation due to use
.
Connecting rods balanced to the nearest gram
.
A forged steel with much better mechanical characteristics
.
A shot peening treatment
.
Which of the following is suitable for connecting rod?
Explanation: Connecting rod is made of
forged steel
because the connecting rod should have light weight and high resistance. Connecting rod in the engine should be lightweight because it provides proper balance to the engine and it should have high strength because it goes through cyclic stress. 2.
Which of the steel is suitable for connecting rods *?
The connecting rods are usually made of steel alloys like
42CrMo4, 43CrMo4, 44csr4, C-70, EN-8D, SAE1141, etc
. Connecting rods are usually drop forged out of a steel alloy. Aluminum and titanium are both materials that are also used in the manufacturing of connecting rods for performance vehicles.
What are combined stresses?
Any state of stress that cannot be represented by a single component of stress
; i.e., one that is more complicated than simple tension, compression, or shear.
What is maximum bending stress?
The maximum bending stress is
proportional to the bending moment but inversely proportional to the square of the beam thickness
. Thus, the maximum stress is more sensitive to the thickness of the beam.
Which of the given types of stresses does bending produces in the parts?
Explanation: When a beam is in bending the layer in the direction of bending will be In compression and the other will be in
tension
. One side of the neutral axis will be shortened and the other will be elongated. Here stress is directly proportional to the distance of layer from the neutral layer.
How many types of pistons are there?
There are
three types
of pistons, each named for its shape: flat top, dome, and dish.
What happens during rod knock?
A rod knock is a deep rapping noise that comes from the engine. It is caused by wear or damage. When a vehicle’s connecting rods inside the bearings have excessive clearance, movement is affected.
When the piston changes direction, metal hits metal and produces a knocking noise
.
Does rod knock cause power loss?
loss of oil
when a Con-rod snaps and punches a hole in the engine-block. Unless the car dumped all the oil in the road, the lack of oil is probably the cause of the problem. In other words, you ran out of oil first, and that caused the knocking and power loss.
What are the three types of crankshaft?
- Cast Cranks. These types of cranks are around for a long time and are found in a lot of diesel and petrol engine. …
- Forged Cranks. These are a more robust crankshaft than a cast crank. …
- Billet Cranks.
What are rod journals?
A journal is the part of a shaft that rotates inside a bearing. … For extra confusion, the connecting rod journals are abbreviated to rod journals and also commonly called crank pins , or big-end journals . The rod journals are
connected to the main journals by webs
.
What happens if you have a rod knock?
Rod knock is a serious issue with your engine—it means the engine is not functioning properly. If you start to notice rod knock, this isn’t a problem that will just resolve itself—you
must take immediate action and replace the rod bearing while also fixing any other parts associated with the sound
.
How are connecting rods measured?
A Connecting Rod is measured
between the centers of the crankshaft journal bore and the piston pin bore
. It can be listed in inches or millimeters. The connecting rod’s length will impact Rod Ratio . Also, changing the rod length will require new pistons with the correct Compression Height .
Why is it important to measure connecting rod bores?
Regardless of the vehicle’s use, the
connecting rod must be free of defects, straight and on-size
. If the connecting rod is overlooked during an engine rebuild, the result is shortened engine life. The tunnel or housing bore of the rod plays a significant role in engine operation.
Can I replace just one connecting rod?
Occasionally, it may be necessary to replace one of these parts during the operational life of the engine. … Connecting rods with the same identifying letter are installed when the engine is new; if only one or two rods are to be replaced in the field, they must be those
marked
with the letter S.
Can a starter bend a connecting rod?
The starter does not have enough torque to bend a rod. Location: Uno, Pa.
Any liquid can bend a rod since it can’t be compressed
, but we’re talking about introducing that liquid into the cylinder at running speeds; a starter won’t do it.
Which force acts on crankshaft stress?
Shear stresses
are developed when the crankpin is in stress due to compressive forces developed by the combustion gases. And a moment is developed around the journal bearings, causing a shear force.
What is buckling of connecting rod?
Explanation: The buckling is
the Bending of the connecting rod
. The buckling of the connecting rod is in two different planes- the plane of motion and a plane perpendicular to the plane of motion. 5. The planes of the connecting rod are parallel to each other.
Which of the following expressions represent the angular acceleration of the connecting rod?
Explanation: Angular acceleration of the connecting rod is given by
(ω
2
. sinθ)/n
hence substituting the values will give the result as 379 rad/s
2
.
