How TorqueWorks

Torque is the force that tends to turn or rotate things. You generate a torque any time you apply a force using a wrench, such as tightening the lug nuts on your wheels. When you use a wrench, you apply a force to the handle. This force creates a torque on the lug nut, which turns the lug nut. English units of torque are pound-inches (lb-in.


Torque is the force that tends to turn or rotate things. You generate a torque any time you apply a force using a wrench, such as tightening the lug nuts on your wheels. When you use a wrench, you apply a force to the handle. This force creates a torque on the lug nut, which turns the lug nut.

English units of torque are pound-inches (lb-in.) or pound-feet (lb-ft); the SI unit is the Newton-meter (Nm). Torque units contain both distance and force. To calculate torque, multiply the force by the distance from the center. In the case of the lug nuts, if the wrench is a foot long, and you apply 200 lb of force, you generate 200 lb-ft of torque. If you use a 2-ft wrench, you only need to apply 100 lb of force to generate the same torque.

A car engine creates torque, and uses it to spin the crankshaft. The combustion of gas in the cylinder creates pressure against the piston, forcing it down. The force is transmitted from the piston to the connecting rod, and from the connecting rod into the crankshaft. The point where the connecting rod attaches to the crankshaft is some distance from the center of the shaft. The horizontal distance changes as the crankshaft spins; therefore, the torque also changes.

You might be wondering why only the horizontal distance is important in determining the torque in the engine. When the piston is at the top of its stroke, the connecting rod points straight down at the center of the crankshaft. No torque is generated in this position, because only the force that acts on the lever in a direction perpendicular to the lever generates a torque.

If you have ever tried to loosen really tight lug nuts, you know a good way to make a lot of torque is to position the wrench so that it is horizontal, then stand on the end of the wrench. You are applying all of your weight at a distance equal to the length of the wrench. If you position the wrench with the handle pointing straight up, and then stand on the top of the handle (assuming you could keep your balance), you would have no chance of loosening the lug nut. You might as well stand directly on the lug nut.

Torque comparison

To understand further how torque works, compare two different types of engines. One engine is a turbo-charged Caterpillar C-12 diesel truck engine. This engine weighs about 2000 lb, and has a displacement of 732 cu in. The other engine is a highly modified Ford Mustang Cobra engine, with a displacement of 280 cu in. It has a supercharger and weighs about 400 pounds. They both produce a maximum of about 430 hp, but only one of these engines is suitable for pulling a heavy truck.

The Caterpillar engine produces 1650 lb-ft of torque at 1200 rpm, which is 377 hp. At 5600 rpm, the Mustang engine also makes 377 hp, but it only makes 354 lb-ft of torque. If you put a gear reduction of 4.66:1 on the Mustang engine, the output speed would be 5600/4.66 rpm, or 1200 rpm, and the torque would be 4.66 x 354 lb-ft = 1650 lb-ft — exactly the same as the big Caterpillar engine.

You might wonder why big trucks don't use small gas engines instead of big diesel engines. In the scenario above, the big Caterpillar engine is loafing along at 1200 rpm, nice and slow, producing 377 hp. Meanwhile, the small gas engine is screaming along at 5600 rpm. The small gas engine will not last very long at that speed and power output. The big truck engine is designed to last years, and to drive hundreds of thousands of miles each year it lasts.

Common units of torque

SI: Newton-meter (Nm) 1 Nm = 0.737 ft lb

English: Pound-inches (lb-in.)1 lb-in. = 0.113 Nm

Pound-feet (lb-ft)1 lb-ft = 1.356 Nm

No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2015 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
Safety for 18 years, warehouse maintenance tips, Ethernet and the IIoT, GAMS 2016 recap
2016 Engineering Leaders Under 40; Future vision: Where is manufacturing headed?; Electrical distribution, redefined
Strategic outsourcing delivers efficiency; Sleeve bearing clearance; Causes of water hammer; Improve air quality; Maintenance safety; GAMS preview
SCADA at the junction, Managing risk through maintenance, Moving at the speed of data
Safety at every angle, Big Data's impact on operations, bridging the skills gap
The digital oilfield: Utilizing Big Data can yield big savings; Virtualization a real solution; Tracking SIS performance
Applying network redundancy; Overcoming loop tuning challenges; PID control and networks
Driving motor efficiency; Preventing arc flash in mission critical facilities; Integrating alternative power and existing electrical systems
Package boilers; Natural gas infrared heating; Thermal treasure; Standby generation; Natural gas supports green efforts

Annual Salary Survey

Before the calendar turned, 2016 already had the makings of a pivotal year for manufacturing, and for the world.

There were the big events for the year, including the United States as Partner Country at Hannover Messe in April and the 2016 International Manufacturing Technology Show in Chicago in September. There's also the matter of the U.S. presidential elections in November, which promise to shape policy in manufacturing for years to come.

But the year started with global economic turmoil, as a slowdown in Chinese manufacturing triggered a worldwide stock hiccup that sent values plummeting. The continued plunge in world oil prices has resulted in a slowdown in exploration and, by extension, the manufacture of exploration equipment.

Read more: 2015 Salary Survey

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
This article collection contains several articles on the vital role of plant safety and offers advice on best practices.
This article collection contains several articles on the Industrial Internet of Things (IIoT) and how it is transforming manufacturing.
This article collection contains several articles on strategic maintenance and understanding all the parts of your plant.
click me