Aerial Rigging: kN? 

What the heck does “kN” mean and what does it mean to me as an aerialist?

kN confused me as I was beginning my aerial hardware/equipment research. I had to look it up and refresh my physics memory. *If I ever learned what kN meant when I took physics I definitely don’t remember it.

kN = kilonewton

Newton (N) is the international system of units (SI) for FORCE. Named after Sir Isaac Newton. One N is very small. A N is so small (at Earth’s gravity 1 N = a small apple) it is common to see forces expressed in kilonewtons (kN). When we see kN stamped on our hardware, it gives a measurement of what kind of forces it can withstand, or how strong it is.

This chart has helped me when looking up ratings and applying them to aerials:

kN (kilonewton) to lbf (pounds-force)

1kN = ~225 lbf
5kN = ~1124 lbf
10kN = ~2248 lbf
20kN = ~4496 lbf
30kN = ~6744 lbf
40kN = ~8992 lbf
50kN = ~11,240 lbf

Here is a simple calculator to convert kilonewtons to force pounds.

How do I calculate how much force I create as an aerialist?

This is a video of how much force an aerialist can create from just a simple drop.

This link shows how to calculate your weight and shock loads as an aerialist. It’s an eye opening read.

What does this mean to me?

  1. According to the link above there are a wide range of safety factors. You will need to decide which works best for you and your practice (*you may want a smaller SF if you are doing static motions with no drops, larger SF if you have multiple aerialists doing large drops, or different SF depending on if its for permanent equipment used daily vs temp. equipment used rarely):
    • 2,000-5,000 lbs (same as a car) = 9-22kN
    • Cirque du Soliel 10:1 SF (est. 900 lbs for in a drop) = 40kN
    • American National Standards Institute 7:1 SF (est. 900 lbs for in a drop) = 31kN
    • Professional artists standard 3:1 to 5:1 SF(est. 900 lbs for in a drop) = 12-20kN
  2. I can convert the ratings of my equipment into something more familiar to me. *Example: a carabiner with a 25kN label is rated to roughly 5500lbs.
    • My carabiners are 23-50kN (5,170-11,240lbf)
    • My swivel is 36kN (8,093lbf)
    • My aluminum rescue 8 is 45kN (10,116lbf)
    • My rigging plate is 30kN (6,744lbf)
    • My fabric is the weakest part of my rig at breaking strength around 2,000lbs. (With fabric it is more likely to tear before it completely breaks. Simply Circus Fabric testing)
  3. Knowing how my equipment is rated will also help me keep an eye on when it needs to be inspected and retired.
    *Sometimes I will practice a lot of static moves with slow fluid transitions. Other times I get in a “drops” mood and all I want to do is drop after drop. The drops are going to generate more force and more wear on the equipment.
    I should be inspecting my equipment more often when I’m creating more force on them. Consider how you are using your equipment and the forces you are putting on them.

Use the information above (kN/forces/ratings/calculations) to help make smart decisions about your aerial equipment. If you are unsure or confused, please ask for help and do more research.

NOTE: All carabiners (and other aerial hardware) have a kN amount etched into the spine. If they do not have an etching amount do not use them for aerial.

Other definitions:

  • Load definitions link
  • WLL = Working Load Limit
    The force that a object can safely lift without breaking.
    WWL = MBL (minimum breaking load)/SF (safety factor)
  • SF = safety factor also referred to as DF = design factor
  • Force = mass x acceleration

What are other things that you’ve found in your aerial or circus research/experience that has caused confusion or raised questions? There are other aerialist out there (like me) who have also been wondering the same things.

***I am NOT an aerial instructor or rigger. I am NOT a professional. My ideas for saftey may not be the same as yours or what a professional aerialist/rigger/instructor recommends. Please refer to professionals if you have questions. Facebook Saftey in Aerial Arts Group and Simply Circus site are a great resources.***