[SML] Unistrut safety factor specs?

[Brian Munroe]

Sort of. Safety factor, also known as design factor, is ultimate breaking strength divided by the working load limit. So if you need to lift a 500 pound load with a safety factor of 10 you need a piece of hardware with a ultimate breaking strength of 5,000#. 

The missing piece of information that you need to know is what the manufactures safety factor is. Say, for example, a shackle manufacturer uses a safety factor of 5. Since you want a factor of 10, you need to reduce by half their load rating. In that instance you would need a shackle with a load rating of 1,000# (500# x 10 = 5,000 and 1,000# x 5 = 5,000). Not a shackle with a load rating of 5,000#

Brian Munroe 

Sent from a rather small device with big fingers

> On Feb 26, 2015, at 1:46 PM, Phil Haney via Stagecraft <stagecraft at theatrical.net> wrote:
> 
> As presented in Jay Glerum's book and class (Stage Rigging Fundamentals), I thought safety factor was something you multiplied your load by to arrive at the minimum rating for your hardware. 
> 
> For example, if you have to lift a 500 lb load and you want a safety factor of 10, you would use hardware rated at a minimum of 5,000 lbs.
> 
> Is that it, or am I missing something?