Costa Rica, a Windy Country – Parapente Pura Vida
Defined forces in kN, daN, N, kgf, and load limits
The newton (symbol: N) is the unit of force in the International System of Units (SI). It is named after Isaac Newton in recognition of his work on classical mechanics, specifically Newton's second law of motion.
One newton (1 N) is the force required to accelerate a mass of one kilogram at a rate of one meter per second squared (one meter per second per second) in the direction of the applied force.
It is common to see forces expressed in dekanewtons (symbol: daN) or kilonewtons (symbol: kN).
1 decanewton (daN) = 10 newtons (N)
1 kilonewton (kN) = 100 dekanewtons (daN) = 1,000 newtons (N)
On the Earth's surface, a mass of 1 kg exerts a force of approximately 9.8 N (downward), or 1.0 kilogram-force, 1 kgf.
1 kilogram-force (kgf) = 9.80665 newtons (N)
The approximation that 1 kg is equal to 10 N is sometimes used as a rule of thumb in everyday life and in engineering.
Here's a fun rule of thumb to help you remember the newton (N): on Earth, 1 N is roughly equal to 100 grams (g). Coincidentally, that's the mass of an apple. So, you can think of 1 N as if someone were hitting you on the head with an apple.
Kilonewtons (kN) are often used to indicate the safety load ratings of fasteners, anchors, and other components in the construction industry. They are also frequently used in specifications for paragliding, paramotoring, hang gliding, and rock climbing equipment (e.g., carabiners and shackles). Safe working loads for tensile and shear forces can be expressed in kN.
1 kN is equivalent to 101.97162 kilograms of load, but multiplying the kN value by 100 (that is, using a slightly conservative value that is easier to calculate) is a good rule of thumb.
Examples…
“Force: 18 kN” = 1,800 daN = approx. 1,800 kg
“Breaking load 1800 daN” = 18 kN = approx. 1800 kg
“Breaking force 2000 daN” = 20 kN = approx. 2000 kg
“Breaking load 2500 kg” = approx. 25 kN = 2500 daN
“Breaking force > 2500 daN” = 25 kN = approx. 2500 kg
“Guaranteed load 26 kN” = 2,600 daN = approx. 2,600 kg
“Breaking load 32 kN” = 3200 daN = approx. 3200 kg
“Tensile strength 40 kN” = 4,000 daN = approx. 4,000 kg
For more information, see Newton (unit) – Wikipedia, the free encyclopedia
Working Load Limit (WLL) and Minimum Breaking Load (MBL)
The working load limit (WLL), also known as the safe working load (SWL) or normal working load (NWL), is the maximum working load specified by the manufacturer. It is the force that a piece of lifting equipment, lifting device, or attachment can safely apply to lift, suspend, or lower a mass without risk of failure.
The WLL represents a force that is much less than the force required to cause the lifting equipment to fail or give way, which is generally referred to as the Minimum Breaking Load (MBL) or Minimum Breaking Strength (MBS).
The WLL is usually marked on the equipment by the manufacturer and is calculated by dividing the MBL by a safety factor (SF); that is, WLL = MBL / SF.
The SF is usually 5 (5:1, 5 to 1, or 1/5), although other values such as 4, 6, and 10 can be used. Paragliding, hang gliding, and paramotor equipment typically use an SF of 5, for example
For example, a shackle with an MBL of 2,250 kg would have a WLL of 450 kg if a safety factor (SF) of 5 is used: 2,250 / 5 = 450.
In other words, a shackle with a WLL of 450 kg would have an MBL of 2,250 kg if a safety factor (SF) of 5 is used: 450 × 5 = 2,250.
