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Advanced Mechanics

Advanced mechanics is the form of mechanics that goes deeper into causes that create the failures. It's not simply the failure that is the interest to repair but a more deeper understanding of why the mechanical part failed.

It takes a vast amount of experience in the trade of mechanics to understand what has failed from a specific noise or a failure to perform in a mechanical device. That skill becomes evident after thousands of hours working as a mechanic in various different types of repair shops.

 

To become advanced in the trade of mechanics it takes a very open mind, conclusions are based on facts that show problems by finding out what is not the problem first. Like a deduction of possibilities by finding items that are in fact "not the problem" which lead to the actual causes of the mechanical problems. It is very rare to come across an easy problem with a mechanical breakdown, most people are able to do the regular maintenance on their own equipment and only bring the equipment to the shop when it cannot be repaired easily by anyone with a set of tools and willing to work.

 

 

In this set of Advanced Mechanics pages the identification of skills needed for the general mechanic to advance into a valuable journeyman mechanic and further into engineering their own mechanical projects and producing those are the intended goal.

 

 

Identifying Noises

 

 

There are reciprocating noises, rotating noises, and inertia noises. When a shaft is rotating it produces a specific sound over the parts that are reciprocating. Reciprocating mechanical parts produce their own sounds that are completely different from the rotating parts sound. Those are the first we will identify when something mechanical is not operating properly.

Reciprocation in a common gas or diesel engine would be engine head valves, rocker arms, push rods, engine pistons, and crankshaft connecting rods. 

 

In application an actuator, and hydraulic cylinder have a reciprocating motion. These two mechanical devices deliver the power in an outward extension and an inward retraction, a push pull affect delivering horsepower.

 

In a human powered situation pushing the clutch pedal, the brake pedal, shifting the transmission into gear are all examples of reciprocating motion. A bicycle pedal and sprocket is a perfect example of reciprocating motion into a rotational motion, the legs extend downward and then upward to rotate a sprocket, the muscles are the power that makes that happen. Most all internal combustion engines (engines that use fire inside and enclosed) operate from reciprocation into rotation. 

 

Rotation in a common gas or diesel engine would be engine crankshaft, cam shaft, flywheel, crank shaft balancer, engine cooling fan, water pump shaft and impeller, alternator shaft and pulley,  power steering pump and pulley.

 

After reciprocating motion is translated into a rotation then inertia can be experienced from momentum. A rotating flywheel has momentum that takes inertia to stop it, each speed increase in a revolution per minute (RPM) takes that much more inertia to stop it's rotation and that is called horsepower in an engine. Increasing the flywheel speed increases the pressure required to stop the rotation of it and is said to increase in horsepower rating.

 

Momentum developed from a rotating flywheel will develop a vibration when parts that reciprocate and rotate together become unbalanced. This results in a vibration which in turn causes heat at the points of unbalance.

 

Identifying these three fundamental noises will allow a skilled mechanic to easily determine a failure without having to disassemble the work to determine a repair solution and estimate the cost of repair.

 

All reciprocating and rotating parts need oil lubrication to survive inside the engine and in other mechanical situations. A lack of lubrication is associated with the failures leading to damaged shafts or damaged reciprocating parts.

Horsepower and understanding the potential.

 

Horsepower = A numerical rating of potential work that can be produced from an engine or primary mover. The work added to the total heat developed by the operation requiring the horsepower from the primary mover is called total horsepower consumed.

 

In advanced mechanics the mechanic will understand that a load produces resistance to the rotation of the engine flywheel. That resistance or load can affect the engine RPM (revolutions per minute) and this includes shafts from electrically driven motors. A motor is driven from a flow element and not reciprocating motion (oscillation) and is fluidic in nature. In either case the load resistance determines the final RPM of the primary mover. A horsepower rating comes from an engines ability to maintain a specific RPM under a load condition.

 

When horsepower ratings are made in any application fluid flow dynamics are used for applying the load and base line for the rating.

 

A fluid pump is used to rate horsepower and makes volume flow (GPM) gallons per minute and termed hydraulics. This flow outward, the volume in GPM can be restricted from flowing out it's conduit end and develops a pressure inside the conduit that is measured in pressure (Psi.) per square inch.

 

One horsepower will rotate a shaft that is connected to a fluid pump producing one gallon per minute flow out at a back pressure rating of 1,500 Psi. Pressure does not become observable until a flow of fluid is restricted to flow outward the pump. So flow needs to exist before the pressure can be developed inside the conduit outward. The load pump is attached to the rotating flywheel of the engine or motor, in the case of an engine which has a maximum RPM potential, the engine is run at it's optimum RPM for longevity and a load is applied from a hydraulic pump system attached and a rating is developed from the gallons of flow at the specific back pressure in Psi.

 

The following links will detail better the flow and backpressure in the fluid flow systems called hydraulic, (flow of fluids). Links are to this site pages Hydraulic - Open Center System - Closed Center System .

 

Horsepower and the work ratings it can produce.

 

One horsepower will produce a fluid flow of 1 Gallon Per Minute (GPM) @ 1,500 Pounds Per Square Inch (PSI). back pressure.

 

An electrical conversion in an electric motor is said to be true horsepower and is base for calculations.

One horsepower will produce a current flow of 746 Watts and it takes 746 Watts in electrical current flow (Amperes or I in electrical formulation) to produce one horsepower of work.

 

One horsepower is equal to a person lifting 550 pounds for one second. An engine produces two things, work potential and heat. In example a person would have to hold over their heads a weight to determine their horsepower and it's a linear equation. Half of 550 is 275 so that would be 1/2 horsepower, half of the 275 psi would be 137.5 or 1/4 horsepower.

 

Work has two factors, pressure and time - psi per second (psi/sec). An engine needs to produce it's rated horsepower consistently and steadily so the production of work in time should be a constant.

 

One horsepower for one second would require approximately 179 calories for a person. Work completed from an engine then becomes a division of GPM - PSI - Time and subtracted is the heat developed and dissipated through conduction.

 

At mechanics basic and fundamental goal of taking a fuel or animal or human and translating it's motion into a useable force for others is to simply translate horsepower into motion. The more work load in pounds per square inch the more horsepower is needed and dependent on the time constraints applied to a process.

 

You can do a specific amount of work like move a bail of hay upward to a height of 50 feet in 50 seconds with less horsepower than lifting it 100 feet in 50 seconds. So three factors are there weight, distance, and time. The faster you want to do something the more horsepower will need to be translated from the primary mover (engine) to the output device (final drive).

 

 

When an internal combustion engine is rated at 100 horsepower at 1,000 RPM (revolutions per minute) the actual horsepower delivered through the final drive may actually be 60 horsepower. The internal combustion engine and it's optimum horsepower rating at any specific RPM is dependent on fuel and octane rating, air to fuel mixture ratio, temperature, lubrication, and any one or all of those contribute to the efficiency factor of the engine. A 100 horsepower engine may only produce 30 horsepower as temperature rises and fuel is low on octane rating.

 

 

An electric motor no matter what the horsepower is constant with 746 watts electrical energy volume so the electric motor is basis for all calculations when designing equipment needing torque and horsepower.

 

 

For instance in an actuating situation a one horsepower electric motor will lift 550 pounds straight up for a period of time the primary mover (motor) is consuming 746 watts. So the resistance is in weight and the more load the more heat as a by product. Heat can be used to calculate efficiency of an engine. The more heat or thermal energy dissipated the more in-efficient the engine is said to be. Most problems hard to identify usually can be found with an infrared temperature gun, the problem place will be hotter than the rest of any operating system on the device.

 

 

For example an internal combustion engine does not have the power or sound like it used to when it was performing well. With a temperature gun you can shoot the spot on each exhaust manifold and tell just what cylinder in the engine is not running as well as the others. The cylinder not running will be cooler than the others. Also in a hydraulic situation if there is a problem with internal leakage that spot will read hotter than the rest of the system. It is easy to find the source of the problem with a temperature gun.

 

 

All this knowledge reduced into advanced mechanics reality is this fact, a regular taillight bulb (1157 with both elements working) will draw about 3 amps and depending on the resistance. 3 amps times 12 volts is 36 watts per second. With additional lighting and power amplifiers running as well as auto electrical operating the alternator robs one horsepower for every 746 watts of electrical current consumption. 746 / 12 = 62 amps. which requires fuel to operate each second.

 

 

The engines of the past and across the American manufacturers board a 350 / 351 cubic inch carbureted engines rated at 250 horsepower in all applications would get around 10 to 12 miles per gallon turning around 1600 to 2200 RPM. So going 60 miles per hour for one minute would net one mile of travel so the carburetor was flowing at a rate of 5 gallons per hour divided by 60 would be .0833 gallons per minute. A 460 cubic inch engine would get approximately 8 to 10 miles per gallon of gasoline burned. A 1000 cc motorcycle engine or 61 cubic inches would get approximately 32 to 38 miles per gallon. When the V6's came out a 2.2Litre or 123 cubic inches would get around 18 to 24 miles per gallon.

 

 

The newer fuel systems are getting way more efficiency compared to the carbureted models prior 1979. Fuel injection and computer controllers have made it possible to get higher fuel mileage per gallon by newer metal running at higher temperatures as well precise amounts of fuel determined by load and speed.

 

 

 

 

 

 

Accurate Measurement is a must to advance your mechanical skills.

This is a dial indicator caliper and it is necessary for accurate measurement of parts. This one is from zero to 6 inches and is a good choice over the digital ones.

 

You can purchase these for under 20 dollars and they are needed.