The reciprocating motion of the pistons is essential to an automobile engine’s effective operation. Connecting rods link the pistons to the crankshaft and engine. Connecting rods are essential to the entire process, from maintaining engine power to transmitting combustion pressure.
Well, in this reading, we’ll explore what a connecting rod is, its functions, diagrams and parts, and types. We’ll also explore causes, and how to fix them.
Let’s begin!
What is Connecting Rod?
A connecting rod is an engine part that serves as a lever arm and transmits motion from the piston to the crankshaft. Cast aluminium alloy is often used to make connecting rods, which are intended to withstand dynamic loads from piston movement and combustion.
By use of a piston pin, the connecting rod’s tiny end is attached to the piston. The wrist pin, also known as the piston pin, serves as a pivot point between the connecting rod and the piston. Piston pin locks, also known as spring clips, are used to secure the piston pin.
A pivot point on the crankshaft is created by the connecting rod’s large end attaching to the crankpin journal. Connecting rods are made in single or two-piece parts. A rod cap is the detachable portion of a two-piece connecting rod that gives the crankpin journal a bearing surface.
Two cap screws are used to secure the rod cap on the connecting rod so that it may be installed and removed from the crankshaft.
Functions
The function of a connecting rod include:
- Its joins crankshaft and piston in a piston engine.
- It transforms piston’s reciprocating motion into crank’s rotation.
- It transmits piston’s compressive and tensile forces.
- In most common form allows spinning on shaft end and pivoting on piston end in internal combustion engines.
- It forerunner of mechanic linkage in water mills.
- Its mostly used in steam engines and internal combustion engines.
Diagram & Part
Parts Of Connecting Rod
The components of the connecting rod are as follows:
Small End: The small end of the connecting rod is the end that is fastened to the piston pin’s face.
Big End: The big end of the connecting rod is the one that is fastened to the crank pin’s side.
Bush Bearing: A bush bearing secures the connecting rod’s two ends. The solid eye is inserted into a phosphor bronze bush and fastened to the connecting rod’s tiny end. The crankpin is connected to the big end. The end is supported above the crank bearing shell and is separated into two halves.
Bearing Insert: Known as a bearing insert, it is located at the large end of the connecting rod and is attached to the bearing cap. These are constructed from two pieces that attach to the crankshaft. At this point, the connecting rod moves in the opposite direction.
Bolt and Nut: A few bolts and nuts are used to secure the huge ends on both sides of the connecting rod once it has been mated with the crank at the bottom. Thus, the connecting rod is prepared for use by assembling all of these parts.
Shank: In addition, every bolt and nut is used to join the bearing cover and connecting rod. Additionally, a section beam—known as a shank—is used. The rod might have a round, tubular, or rectangular form.
Wrist Pin: A hollow, hardened steel tube known as a wrist pin is used to join the engine piston to the connecting rod. Another name for it is gudgeon pin. The wrist pin pivots on the engaged piston after passing through the connecting rod’s short end.
Piston: A connecting rod, commonly abbreviated as the rod or Conrod, holds the piston and crankshaft together. The piston’s function is to function as a moveable plug in the cylinder, which makes up the combustion chamber’s bottom.
Bearing Cap: Shell bearings have a wear adjustment, but it also regulates running and permits proper tightening of the bearing cap due to side clearance.
Types of Connecting Rod
The following are the types of connecting rods used engines:
Master and Slave Rod:
Master and slave connecting rods are commonly used in radial engines. The single piston in this design is made up of a master rod that is directly attached to the crankshaft. The rings encircling the master rod’s edge are where other pistons attach their connecting rods.
Master-slave rods have the drawback of making the V-type engine vibrate more since the slave piston’s stroke is somewhat bigger than the master piston’s.
Fork and Blade Rod:
These connecting rods are utilised in V12 aviation engines and V-twin motorcycle engines. To fill this gap in the fork, a “blade” rod is tapered from the opposing cylinder, and a “fork” rod is split into two pieces at the large end of each engine cylinder pair.
This technique removes the rocking couple that happens when the crankshaft and cylinder pairs are balanced. A single wide-bearing sleeve that spans the whole width of the rod, including the middle gap, is present on the fork rod in the big-end bearing pattern.
Then, rather than on the crankpin, the blade rod passes straight outside this sleeve. As a result, the two rods oscillate, which lowers the surface speed and the force acting on the bearing. An important issue for lubrication is that the bearing speed also reciprocates rather than rotating continuously.
Powered Metal Conrods:
Power metal is also used in the construction of connecting rods since it is a good option for manufacturers. It is made by heating a combination of metal powder to a high temperature and pressing it into a mould. This blend is formed into a solid state.
Although it could need some minor machining, the result essentially originates from a finished product mould. Conrods made of powdered metal are stronger than cast rods and less expensive than steel.
Forged Rods:
Forging is used to make some of the connecting rods. A grain of material is forced into the form of the end to create these kinds of connecting rods. The material may be aluminium or steel alloy, depending on the necessary qualities.
Nickel and chrome alloys are frequently used steel alloys. Brittleness is not intended for the final result. As a result, alloys made of nickel or chrome make the connecting rod stronger.
Plain Type Rod:
Both inline and opposing engines employ the simple kind of connecting rod. The connecting rod’s large end is equipped with a bearing cap and fastened to the crankpin.
The connecting rod’s end has a bolt or stud that mounts the bearing cap. To ensure correct fit and balance, the connecting rod must be swapped out in the same cylinder and at the same relative location.
Cast Rods:
Cast rods are inexpensive to make and aren’t suitable for high horsepower applications. The cast rods are distinguished from the forged version by a prominent seam in the centre. Manufacturers like and develop these connecting rod designs because they can support the weight of a standard engine.
Billet Conrods:
Steel or aluminium are used in the design of billet connecting rods. They are stronger, lighter, and have a longer lifespan than other kinds of connecting rods. It is frequently found in fast-moving automobiles. It is occasionally made to ease into the billet material’s inherent grain and lessen stress risers.
Common Causes of Connecting Rod Failure
Flooded Engine:
A hydrolocked engine is one that is flooded with fluid rather than only air. When this happens, connecting rods may break or bend when your car is started. You must drain a hydrolocked engine before you may drive again.
Over-Revving the Engine:
The connecting rods experience greater force the more you rev the engine. Rods will eventually break if you have a tendency of overrevving them. Although over-revving is fortunately avoided by modern engine technology, it can still happen if you drive an older car.
Engine Modification:
Take caution if you decide to increase your car’s speed by upgrading its engine! Since the majority of standard connecting rods aren’t made to withstand significant changes, they may break if the improved pistons put too much strain on them.
How to Fix A Bad Connecting Rod
There is no simple way to break the bad news. A damaged connecting rod indicates significant engine damage. Your automobile will require some significant engine rebuilding even if you catch it before your engine throws a rod. The following might be on the list of damaged items:
- The actual connecting rods
- The bearings on the connecting rods
- The crankshaft
- The pistons
- The wrist pins of the piston The walls of the cylinder
- The valves
Additional relevant components to check out for:
In order to determine the degree of the damage, your mechanic must first disassemble your engine. Making a list of everything that needs to be fixed or replaced is the next stage, and it will require a lot of work. The cost of this will be high.
Depending on what your technician tells you, you could have to make a tough choice if this occurs to your vehicle. Your technician could present you with one or more of the following options, depending on the degree of the damage and the condition of the remainder of your car:
- Fix your broken engine and swap out any parts that are beyond repair.
- Switch out your complete engine for a remanufactured one that is covered by a warranty.
- Purchase a used engine from a car recycling facility; it won’t be covered by a warranty.
- Since the expense of repairs is far higher than the value of your car, sell your damaged vehicle to a scrap yard right away.
An engine with little damage is the first choice. If your automobile is relatively new and still has a lot of life remaining in it, the second alternative is worth performing.
In addition to being a cost-effective method of extending the life of an older vehicle, the third alternative will enable you to sell your vehicle in operational condition, which will increase its value.
If your automobile is old and worn out and won’t be usually dependable just because you changed the engine, the last alternative makes sense. It could be time to say goodbye if the final one sounds like your vehicle.
FAQs
What is a connecting rod used for?
A connecting rod is an engine component that transfers motion from the piston to the crankshaft and functions as a lever arm. Connecting rods are commonly made from cast aluminum alloy and are designed to withstand dynamic stresses from combustion and piston movement.
What happens when a connecting rod goes bad?
When a connecting rod fails the piston or connecting rod could smash right through the engine block at very high speed, damaging anything in its path. Symptoms of Bad Bearings: Rod Knock: A major symptom of a bad engine bearing is the rod knock symptom, which is a loud hammering sound in the engine.
What is the function of the connecting rod bearing?
A connecting rod bearing is a special type of plain bearing mainly mounted between the connecting rod and the crankshaft of an internal combustion engine. Its basic function is to support the connecting rod, allowing it to rotate smoothly on the crankpin while reducing direct friction between the metals.
What are the four types of connecting rods?
There are essentially four types of connecting rods that most engine builders use – cast, forged, billet and powdered metal – in two basic styles: I-Beam and H-Beam. Each type of rod has a purpose and limitations as well.