Flat engine vs Boxer: Here’s the Difference

Flat Engine vs Boxer

Flat engines are horizontally opposed piston engines. This concept was first introduced in 1897 by German engineer Karl Benz. The most common and popular type of the flat engines is known as the boxer engine.

Source: Auta 5p

There is a big misconception when talking about flat engines and saying it’s the same as boxer engines. All boxer engines are actually flat engines, but not all flat engines are boxer engines.

This misconception is deep to the point that in 1973 Ferrari produced the famous Ferrari Berlinetta Boxer. Reading the name, you would say that this is a boxer engine-powered car, but the truth is that it involves a flat 180° V12 engine that is again not a boxer engine.

Source: jalopnik

So what is the difference between a flat and a boxer engine?

A flat engine is actually a 180° V engine that works similarly to any other V engine. Each pair of pistons share the same crankpin, so one is in stroke 1, and the other is in stroke 2. While in boxer engines, each pair of pistons are connected to different crankpin, so they are mirroring each other.

The Flat  180° V engine

The flat engine is from its name is completely flat. It is the same as the V configuration engines but with a 180° angle between the cylinder banks.

The two opposing pistons will be moving in the same direction, but one is compressing, and the other is combusting. One piston will be at the top-dead-center, and the other will be at the bottom dead center.

Source: researchgate

Take a look at the following animation, so it makes more sense:

Source: By MichaelFrey / wiki commons

This motion is caused by having each pair of connecting rods to be mounted to the crankshaft with the same crankpin.

The Boxer engine

Coming to the boxer engine, it is again a flat engine but with a different configuration. It is the most common and most produced type of flat engines. It is still being produced and developed by Subaru and Porsche.

This type of engine has each pair of opposing piston connecting rods being mounted to the crankshaft using different crankpins. This simple modification will create a completely different type of motion compared to the non-boxer flat 180° V engine.

Source: Subaru

In the boxer engine, each opposing piston will be doing exactly the same stroke. They are actually mirroring each other. When the left piston is compressing, the right will also be compressing; when combusting, the second will also be combusting, and so on.

Take a look at the following animation to understand better:

Source: By MichaelFrey / wiki commons

This motion is caused by having each pair of connecting rods to be mounted to the crankshaft but through independent crankpins.

What are the advantages of flat engines?

Let’s focus again. When we say flat engines, we mean any engine that is flat, whether it was a boxer or non-boxer.

• Lower center of gravity: Having a more flatten than tall shape ensures a better placement of the engine and better handling of the car.

• Safer: Having the engine mounted down in the engine bay will reduce the risk during an accident, and the engine will drop down the passenger’s compartment rather than crushing into it.

Source: Subaru UAE

• Higher performance: Flat engines are known due to their configuration to have a better power transmission from the engine and having a better fuel economy.

Why the boxer?

Source: Subaru

Flat engines are not the perfect engines. They also have some disadvantages. They are complex to design, and maintaining them is harder compared to conventional V’s.

While choosing between a simple flat engine and the boxer engine, there are two main points to consider: cost and vibration/balance.

From a production perspective, the simple non-boxer engine would cost less to be produced since the pistons are connected to the same crankpin. So less crankpins produced, and simpler manufacturing process. Yes, this might not be a big issue, but it’s a fact that boxers cost more.

The second point is that the boxer engine’s motion has a great benefit to the engine’s overall performance. This boxer type of motion that resembles a real boxer punching with his gloves, dramatically lowers the vibration and cancels out forces.

Source: Nobert

Source: By Anynobody / wiki commons

This is why we are having more boxer engines being produced and developed in new car models.

Conclusion

To wrap it up, flat engines are not boxers, but boxer engines are flat!

The discovery of fusion energy gets scientists one step closer to unlimited clean energy

Source: Hiden Analytical

Now and again, a patch of Oxfordshire becomes the hottest point in the solar system. And it was disclosed yesterday that the exhaust gases from this location — Britain’s main nuclear fusion experiment — can be made cold enough not to kill anything they come into contact with.

Scientists think they have achieved a crucial step toward near-limitless clean power by demonstrating that they can release the heat of waste plasma, enabling the creation of smaller, cheaper, and more efficiently nuclear fusion machines.

“It is a success in one of fusion’s most difficult challenges,” said Professor Ian Chapman, CEO of the UK Atomic Energy Authority. Fusion is an appealing target not only because it is clean but also because it has a high yield.

Nuclear fusion is the method through which the sun is powered. In contrast to fission, the reaction utilized in today’s nuclear power plants involves connecting rather than dividing atoms, resulting in nearly little radioactive waste. To make it operate, however, temperatures over 100 million degrees must be maintained.

Source: BBC Science 

Some of the superheated plasma must eventually be permitted to escape. If it does not have time to release its heat, it will rapidly blow its way through components.

This is one reason why Iter, the world’s largest prototype fusion reactor, is located in southern France. Scientists are generally positive that by the end of the decade, Iter will create ten times the amount of electricity required to run it.

Britain’s nuclear experts are working in Culham on a Mast Upgrade project to overcome the next problem: making reactors economically feasible.

Make the reactor smaller, and it will be less expensive. Smaller reactors have the benefit of requiring smaller magnets to keep the plasma in place. The catch, however, has been the exhaust, which is stretched across a smaller area in a smaller device.

Source: Handelsblatt

This is the problem, according to Chapman, that has been fixed. The Super X diverter, as it is known, employs additional magnets to channel the exhaust around an ever-widening spiral, allowing it to lose heat for 20 yards. The power output of the reactor drops from that of a rocket thruster to that of a car engine.

Many more issues must be addressed before this can be turned into a functional reactor. A fusion power plant will be among the most sophisticated devices ever constructed. It must not only safely confine the plasma but also produce its fuel and be maintained by robots because people will be unable to enter the chamber once it is operational.

However, Chapman believes that humankind has no choice but to make it work. By 2050, much of the globe will have achieved the objective of zero carbon dioxide emissions. “We vastly underestimate the magnitude of that challenge,” he said. “It’s simply the most massive challenge.”

Timing Chain Vs. Timing Belt

 

Many individuals are not sure if there’s a distinction between timing chain versus timing belt, especially because they both have the same purpose in an engine system. They mistakenly believe they are the same.

Timing belts and chains are crucial elements of an engine that contribute to an engine’s smooth running, and every vehicle is equipped with either a timing belt or a timing chain. No vehicle has both.

Despite their comparable duty, there are significant distinctions between these two. That leaves you asking what may be the difference between a timing belt and a timing chain.

The Purpose of Timing

Simple explanation: timing belts and chains keep the fuel injection, air intake, and piston timing in harmony. Air and fuel should enter a piston as it goes downward.

An ignition spark plug then causes the gasoline to ignite, and the piston is pushed back down. As soon as it is done, the piston rises again to force the residual gas out of the engine and into the exhaust pipe.

In the blink of an eye, everything must come together in perfect harmony. Fuel injectors must be working while the crankshaft lowers the piston to ensure that the cylinder is filled with gas. Each of these parts is linked together by a timing belt or chain to control when the valves open to let air or fuel in relative to the pistons.

Engine damage might occur even if your timing is just a fraction off. Engine misfires can be caused by incorrect ignition timing, which results in unburned fuel. You’ll know something’s wrong when your car won’t start or idles strangely.

Watch this video to have a clear view of the engine timing and its importance:

Timing Chain

As a component of an internal combustion engine, the timing chain assists in keeping the camshaft and the crankshaft in sync, allowing the engine valves to open and close as needed during the exhaust and intake strokes.

In a cost comparison of timing chain vs. timing belt, chains come out on top (cost more), although they require less frequent maintenance. Aside from that, they aid in the operation of valves that deliver fuel to the combustion chamber.

In other words, the timing chain serves as a link between the top (valves and cylinder heads) and lower parts (crankcase and piston) of your vehicle’s engine.

The timing chain looks just like a bicycle chain and produces more noise than a timing belt. Proper valve timing and stroke timing in the cylinders of a car’s engine are critical to ensuring optimal engine performance, sufficient power delivery, and efficient fuel management.

Advantages of Timing Chain

Timing chains have a long lifespan:

The metal utilized to make it has a high level of durability.

Most manufacturers suggest that if you can maintain your engine properly, you may not need to replace your timing chain, which is true if you use the appropriate oil.

Doesn’t expand or elongate:

Timing chains are constructed of metal, so they don’t change in length or behave differently depending on temperature.

As a result, the chain tensioner is smaller, and the chain’s chances of breaking are minimal.

There is no slipping:

There’s no slipping involved with the timing chain, as there is with the belts.

Disadvantages of Timing Chain

Source: Nut Job / YouTube

Costly:

While a timing chain outlasts a timing belt, a chain is more costly than a belt.

Lubrication is required:

If you drive a car with low oil or a low-pressure oil pump, your engine may suffer. Your engine’s timing chain will last longer if you use high-quality engine oil.

Hydraulic pressure is necessary for chains to work:

Hydraulic pressure is required to operate the timing chains, which might sometimes be an issue.

Timing Belt

When compared with timing chains, timing belts produce less noise. With reduced friction, the piston and valves have less contact, preventing them from impacting one other.

The timing belt looks like a tooth or a circular belt with teeth on it.

Unlike the timing chain, a timing belt is constructed of rubber and fiberglass and performs the same duties as the chain. The camshaft is controlled by a belt attached to the ribbed gears at the ends of the cams and the crank.

Source: Brendma

The lifespan of a timing belt is less than that of a timing chain. They’re smaller, lighter, cheaper, and quieter.

The engine’s camshaft and crankshaft are linked by a timing belt, which allows the valves to open and close in time with the piston’s movement.

Advantages of Timing Belt:

• It does not create a lot of vibration
• High timing precision without sacrificing high-torque carrying capacity
• Minimal noise produced
• Rust-proof
• It’s lighter
• Much more affordable (No required lubrication, tensioning devices, and adjustments)

Disadvantages of Timing Belt:

• You should replace your belt on a regular basis
• For certain engines, it is dependent on the water pump
• It requires more attention and maintenance

Conclusion

A timing chain is preferable to a timing belt if you don’t pick an engine model with a history of timing chain failures. As much as it may cost to replace a timing chain, the chances are that you’ll never have to do it again.

On the other hand, the timing belt will probably need to be replaced two or three times during the course of the vehicle’s lifespan.

Changing the timing belt three times can cost you more than $2,000. As a result, there is virtually no reason to use a timing belt in a modern car, as timing chains are becoming just as quiet as timing belts.

The most important thing to remember is to stay up with all of your service intervals, no matter which option you choose.

What Happens If a Plane Gets Struck by Lightning?

An electrical discharge that happens within a cloud, between two or more clouds, or between a cloud and the Earth’s surface is known as a lightning strike. Nobody wants to fly in extreme storms. Even while it may seem unlikely, lightning strikes planes are far more often than you may expect.

Lightning strikes the Earth around 40 to 50 times every second around the world. It is also known that, on average, more than 100,000 commercial planes take off every day around the world. This means there is more than 1 plane taking off every second!

These numbers show that the probability of lightning striking an airplane is very high. Despite this, no planes have fallen from the sky due to a lack of electricity. Lightning may be dangerous, but how harmful is it to a plane and its passengers? What happens when lightning strikes an aircraft? And what measures do airplanes have to counter lightning strikes?

Accidents of Lightning Striking Planes

According to experts, lightning strikes airplanes on average once per 1,000 hours of flight time.

The last time a lightning strike caused a major disaster was in 1963. In Maryland, the United States, 81 people were killed when a Pan American Boeing 707 got struck by lightning.

It was found that the ignition part that is responsible for the ignition of the gasoline/air combination in the fuel tank was faulty. After the explosion, the outer left wing was lost, and the pilots lost control of the aircraft.

After take-off or landing, most aircraft is struck by lightning at an altitude of between 1,524 and 4,572 meters (5,000 to 15,000 feet). Another element that enhances the likelihood of lightning is the existence of rain in the area. Several systems cannot be rebooted in mid-air; therefore, if lightning strikes an airplane after take-off, it is normally returned to the airport from which it left.

Spring and summer are the most common seasons for lightning strikes. Lightning strikes are less likely to occur at heights greater than 20,000 feet (6,096 meters). Geographical conditions have a role as well, of course. For example, it is more prevalent in the equator than in the Nordics and Florida than on the West Coast of the United States.

Despite the fact that some passengers may find it an uncomfortable experience, modern airplanes are built to withstand lightning strikes. As part of their certification, they are subjected to a series of lightning tests.

How Dangerous is the Lightning Strike for the Airplane?

In most circumstances, lightning strikes on planes do not cause considerable physical damage or affect the plane’s safety. Lightning is more likely to strike the wingtips or the nose of an aircraft.

Source: lucaas / YouTube

Afterward, the charge goes through the plane’s metal and exits at a different location, like the tail. It will then go to the other side of the cloud structure. However, if it cannot locate an opposing polarity, it will instead strike a spot on the Earth.

Passengers and crew onboard the airplane may experience a flash and hear a loud blast if the plane is caught up in the cloud-to-ground lightning event. Damage to the plane is determined by various parameters, including the amount of energy discharged during the hit, the position of the hit, the exit points, and the duration of the strike. A single flash of light may deliver up to 30,000 amps or one million volts.

When lightning strikes, it can damage the avionics, including the radar, transmission, and antennas, but it can also penetrate the fuselage and leave a tiny hole in the tail. Additionally, lightning flashes can temporarily blind the flight crew, particularly at night.

In more extreme circumstances, engine shutdown can occur. Occasionally, following a lightning strike, one or more generators may fail, resulting in the loss of cabin lighting.

How Do Airlines Protect their Planes and Passengers?

When a lightning strike occurs, it has the potential to disrupt airline operations, resulting in unnecessary delays and cancellations, and of course, it might lead to the loss of the crew and passengers. In order to avoid such events, maintenance workers must be well-versed in lightning protection, inspection, and repair techniques.

Source: boeing

The typical approach for pilots is to stay at least 20 nautical miles away from cumulonimbus (dense cloud location) cloud formations. In addition, new airplanes are engineered to enable lightning to pass over the plane’s surface without causing any harm.

Source: Halldor Gudmundsson

Those are some of the safety guidelines that pilots and maintenance workers are trained to perform. But what about the plane itself? And how does the composition of the plane helps in reducing and maybe eliminating the damage caused by the strike?

Plane’s Composition

As we all know, aluminum conducts electricity, and lightning is more likely to strike a plane’s nose or the tip of its wing. For this reason, these parts are usually made from composite material, even though the plane’s fuselage works as a Faraday cage, shielding the cabin from the voltage as it travels along the container’s exterior.

Wing of the Airbus A220 made with carbon fibers
Source: Teijin

The use of composite and metal components is becoming increasingly common in modern airplanes. The fuselage of the Boeing 787 Dreamliner, for example, is 50 percent composite in weight. 53 percent of the A350 XWB’s airframe is constructed of composite materials.

In contrast to metal, composite materials like carbon fiber laminate do not transmit electricity. As a result, lightning-strike-prone composite parts must be equipped with supplementary lighting precautions. A layer of conductive fibers such as copper foil mesh is used to direct the flow of electricity.

Protect the Fuel from the Spark

It is critical to safeguard gasoline and other combustible compounds from sparks. Lightning bolts may cause serious damage to airplane fuel tanks if they get too close to them. Vents, access doors, and caps must be certified to meet lighting protection regulations.

Source: Sofema Aviation Services

A bolt of lightning may reach temperatures of up to 30,000 degrees Celsius. However, none of the surrounding metal, structural joints, access doors, vents, or fuel filler caps on an airplane are at risk of being damaged.

These concerns became the norm after the accident of the Pan Am 707 explosion in 1963 that we have already mentioned. An unprotected fuel tank caused the gasses to ignite due to the violent lightning strike. New fuels with fewer harmful fumes have also become commonplace in the airplane industry.

Flying an aircraft that has been struck by lightning requires the pilots to do a thorough check of all systems. Any problems should be resolved by making an emergency landing at the nearest airport.

However, even if the plane reaches its final destination unharmed, its maintenance staff will carefully inspect it upon arrival for any damage. The sites where the lightning entered and exited the fuselage may have developed little holes of less than a centimeter in diameter.

Conclusion

Yes, it is true that lightning strikes on planes are quite common, but nowadays, every modern airplane has been extensively examined and certified to withstand such accidents.

However, even with all these advanced technologies and protection for the plane, the likelihood of extreme turbulence makes it impossible to fly above, beneath, or through storm clouds.

So the next time you have a trip in a bad weather conditions, don’t get afraid of a lightning strike passing through the plane and causing it to explode. The aircraft industry has developed so much over the years, reaching a very high level of safety and protection.

This is What Happens if a Plane Window Breaks While Flying

Source: Shutterstock / The Telegraph

Even though it is considered a rare case, it has happened multiple times during commercial airline history. Breaking a window in an airplane is something that might seams not dangerous to many, but in reality, it is.

Windows breakage might happen due to multiple reasons. Whether it was due to an accident or some passenger trying to experience something new, it still has a devastating effect on the plane’s crew if not a smart action is taken immediately.

In the below sections, we will discuss multiple accidents that happened in history and find the reasons that caused them. We will also see scientifically what happens exactly on the plane when the window is broken. What dangers might arise to the passengers, crew and the plane itself? And how should you react if you happen to be there?

Real-Life Stories

Broken windows accidents actually happened multiple times and on different airways. This was not limited just to passenger windows. This indeed also happened with the pilot’s frontal windows!

British Airways Flight 5390

Source: Shutterstock / The Telegraph

On June 10, 1990, a trip took off from Birmingham Airport in the UK, heading towards Malaga’s Airport in Spain. The plane departed at 8:20 local time, taking on board 81 passengers along with the 4 crew members.

13 minutes later, the plane was over Didcot in the UK, and the pilot and the co-pilot were waiting for the meal. When the hostess was entering the cockpit, she heard a loud bang.

The left windscreen panel was open, and the captain was partially sucked out of the plane! His crew members reacted quickly and saved him. The co-pilot took the responsibility and landed the plane 15 minutes later at Southampton Airport.

The plane was not equipped with oxygen for everyone. So the co-pilot began an emergency descent immediately to reach an appropriate altitude. Even the communication with the airports was difficult due to wind noise.

The pilot was taken to the hospital suffering from fractures in his right arm, left thumb, and right wrist.

Sichuan Airlines Flight 3U8633

Source: CCTV / twitter

Another story that looks similar to the first happened on May 14, 2018, when a plane took off from Chongqing to Lhasa on a domestic trip inside China.

It was suddenly when the right windshield blew away at an altitude of 32,000 ft. The co-pilot was sucked halfway out of the window. The co-pilot was pulled back inside with the help of the crew members. He and another crew member were injured, but none of the 119 passengers.

The plane made an emergency landing in the southwest city of Chengdu.

Southwest Flight 1380

Source: FOX 5 DC / twitter

This time it is a story that happened with the passenger windows, not the pilot. This happened on April 17, 2018, on a trip from New York to Dallas when a rare engine explosion caused a passenger’s window to burst.

At an altitude of over 32,000 feet, the woman sitting next to the window was pulled out of it. Other passengers quickly reacted and pulled her back into her seat.

The plane was carrying 144 passengers and 5 crew members. The plane made an emergency landing in Philadelphia, but the passenger was dead.

Why does this happen?

If you are asking about the windows breaking, this is a rare accident that could be caused by multiple factors. A flying bird, a faulty window, or even an engine explosion as in the third story.

However, the interesting common thing in the 3 stories is the suction of the person sitting next to the window. Why does this happen?

When a window breaks at a high altitude in the plane, you’d hear a booming noise resulting from depressurization. Basically, the cabin air pressure is greater than the air pressure outside the plane in order to allow passengers to breathe comfortably.

The plane usually flies at altitudes between 30,000 to 40,000 feet. Air pressure outside the plane at these altitudes will be just 4 to 5 PSI. On the other hand, the pressure inside the plane will be between 11 – 12 PSI.

A broken window would cause the air inside to rush out rapidly, causing little objects like phones and magazines (and even larger ones, like people) to be carried away. This is all due to the high-pressure difference at high altitudes.

It’s also possible to experience lower temperatures and lower air pressure and mist or fog from condensation inside the plane.

Conclusion

Source: Marty Martinez, via Associated Press

The most essential thing to remember in this scenario, as in many others, is to remain calm. As a safety precaution, wear your seat belt at all times when seated. Make sure you put on your own oxygen mask before helping your child or other persons around you. Plane crew members will begin an emergency landing, and the plane will descend quickly to avoid passenger injury.

Traveling by air is one of the safest modes of transportation, and it’s only going to become better. On the other hand, depressurization emergencies are extremely unusual, and just 2.7% of all pressurization failure incidents are caused by a window.

Current (amp) drawn by an Electrical Equipment

let's just say I have a tank of 1000 ltr. and I put a hole in it at the bottom and fit a valve to control the flow of let's just say water.

Now let's say the level of water in the tank is voltage, the position of valve is resistance, the flow of water through valve is current, and last the size of valve is load.

Now if I open the valve completely, depending upon the level of water in the tank, the water will flow through valve. Higher the level of water in the tank the more water with high pressure is going to flow and vice versa I.e. Higher the level of water (voltage ) more the water (current) will flow ie. Current is directly proportional to the voltage.

Now let's talk about the resistance. The position of the valve is resistance right? if you completely open the valve water with high pressure will be flowing ( ie very low resistance) and as I keep on closing the valve the pressure will go on decreasing (more the resistance less is the flow of current). Ie. Current is inversely proportional to the resistance

Btw that is the ohms law: in a given close circuit current is directly proportional to voltage and inversely proportional to the resistance.

And the last thing is the size of the valve( ie size of the load) now if I remove the existing valve, drill the bigger hole and fit a bigger valve then existing one what is going to happen? Simple more water is going to flow. right? That means if we connect high rating equipments they are going to draw more current then the lower rated equipments.

So the current (amp) drawn by an electrical equipment will depend upon the given voltage, total resistance in the circuit, and the rating of an equipment.

Proof of 1 hp equal to 746 watts

They are both measurements of power, the rate at which work is done,

 i.e. work/time = force x distance/time

James Watt calculated the work output of a draught horse to be about 33,000 ft.lbf/min and called it one horsepower. However, one horsepower can mean different amounts of power depending on the applications used. Aaargh!

Hence we now use the metric system which is interchangeable between all the forms of power: mechanical, electrical, chemical etc., and the arithmetic is a lot easier too.

1 Watt = 1 Joule/second = 1 Newton.metre/second = 1 kg.m^2/s^3 = 1 volt.amp, etc.

There are two definitions for the horsepower.

According to the classical definition it is equal to 550 foot pounds per second.This works out to be 746 watts.

The metric horsepower is defined as 75 metre kilograms per second. This works out to be about 735 watts.

Proof of 1 hp equal to 746 watts

HP = Horsepower

HP and Watts are both units of power. Power can be electric or mechanical, and can be converted between the two. Any conversion will be less than 100 % efficient.

It is only for historic reasons that electrical power is measured in Watts not hp, like the way that tyre widths are in mm but rim diameter are in inches.

One pound is 4.44822 Newtons

so 550 foot pounds per seconds, converted to metric, is 550 x 0.3048 x 4.44822 Newton meters per second, which is 745.7 Newton meters per second, better known as Watts.

One foot is 0.3048 metres

1HP = 550 Foot Pound per second

1 Pound = 4.44822 Newtons

1 Foot is 0.3048 Meters.

1 HP = 550 * 4.44822 * 0.3048 meters

1Hp = 745.69 Newton meter per second.

Say 746 watts.

 James Watt invented a condensing steam engine which was very much more economical than the few Newcomen steam engines then in use for pumping water out of mines. He knew that mine-owners could easily compare pumping engines with the horse tread-mills then in use for pumping mines. He decided on a value of 550 ft.lb per minute for his horse-power which is a handy amount more than a horse can lift, day after day. (It has been tried, and the horse died after a 10 hour shift!) This meant that mine-owners could not argue the merits of his new device. 550 ft.lb/min is now given as 746 watts per HP using the power unit named for him. His steam engine was an unqualified success, with several hundred exported world-wide. Puimping engines put out 10 to 15 hp on average! This was the beginning of the First Industrial Revolution in 1770 in England.

The electrical energy consumption daily id measured in units. Hence, when we are talking of units, we are talking of energy. However, watt is a measure of power. Also, we know from the elementary formula,

Power=energy/ time

Hence, this gives us “watt-hour” as a measure of energy. Now we can effectively devise a relationship between watthour and unit.

1 unit= 1 KWh or 1000 Wh.

The following definitions have been or are widely used:^{[citation needed]}

Mechanical horsepower hp(I)	≡ 33,000 ft·lbf/min = 550 ft⋅lbf/s = 550 × 0.3048 × 9.80665 × 0.45359237 kg⋅m2/s3 ≈ 17,696 lbm⋅ft2/s3 ≈ 745.69987 W ≈ 76.04 kgf⋅m/s ≈ 76.04 kg × 9.80665 m/s2 × 1 m/s
Metric horsepower hp(M) – also PS, KM, cv, hk, pk, ks or ch	≡ 75 kgf⋅m/s ≡ 75 kg × 9.80665 m/s2 × 1 m/s ≡ 735.49875 W ≈ 542.476038840742 ft⋅lbf/s
Electrical horsepower hp(E)	≡ 746 W
Boiler horsepower hp(S)	≡ 33,475 BTU/h = 9,812.5 W
Hydraulic horsepower	= flow rate (US gal/min) × pressure (lbf/in2) × 7/12,000 or = flow rate (US gal/min) × pressure (lbf/in2) / 1714 = 550 ft⋅lbf/s = 745.69987 W
Air horsepower	=flow rate (cubic feet / minute) × pressure (inches water column) / 6,356 or = 550 ft⋅lbf/s = 745.69987 W

In certain situations it is necessary to distinguish between the various definitions of horsepower and thus a suffix is added: hp(I) for mechanical (or imperial) horsepower, hp(M) for metric horsepower, hp(S) for boiler (or steam) horsepower and hp(E) for electrical horsepower.

1 mechanical horsepower is equal to 745.7 watts.

1 metric horsepower is equal to 735.5 watts.

1 electrical horsepower is equal to 746 watts

1 boiler horsepower is equal to 9812.5 watts.

1 hydrololic horsepower is equal to 745.7 watts.

1 air horsepower is equal to 745.7 watts