Kilo newtons and kilograms

[timtheenchanteruk]

Hi, Im currently getting confused about Kn & Kg,

 

Basically we want to hang a static load of approx 25Kgs from a point, the confusion is coming as we have a mixture of Carabiners and strops some with Kg ratings and some with Kn ratings,

 

at the bottom end we want to use as small fixings as possible, the ones we have are rated at 6Kn, but for the life of us we cannot remember the equivilent Kg rating.

 

We want to sort this before we go home, so a swift response would be grateful, if not I will look it up at home.

Many Thanks

[Congo]

this is a good link

 

http://www.calculatoredge.com/enggcalc/wei...0conversion.htm

[Sirch Sound]

Remeber that the carabinners are for climbing use, hence rated in newtons instead of grams, I would stick with shackles even for such a small load.

 

Rich

[phawthorne]

The kilogram is a unit of mass. The newton is a unit of force.

 

From Newton's 2nd law, force is produced by the acceleration of a mass; the acceleration in the case of the newton is the acceleration due to gravity. If we assume that we're only talking about forces and masses here on earth then we can ignore gravity - for example we talk of someone's weight being 70 kg though 'weight' is strictly a force.

 

The relationship between the kilogram and the newton is that 1 newton is the force produced by the acceleration due gravity on a mass of 1 kg. So 1 kilonewton is the force produced by 1000 kg

 

Hope this helps... (though I suspect you've looked it up already)

[mumbles]

No... F=ma as you said, so for m = 1000kg, as a = 9.81m/s, F = 9.81 kN, taken as 10kN, not 1kN as you've said.

 

M

[Seano]

Newton's second law: Force equals mass times acceleration. So weight in Newtons = Mass in kg x g where g is about 9.8 ms^-2

 

Remeber that the carabinners are for climbing use, hence rated in newtons instead of grams

 

Also the rating given in kN on a karabiner (or climbing sling) is minimum breaking strength not safe working load. To derive a SWL you need to divide the ultimate strength by a suitable safety factor. SWL (or WLL) marked on bits of lifting kit is always given in units of mass; kg or tonnes in the great majority of cases, possibly lbs or tons in the US.

 

At the risk of sounding sanctimonious, even something relatively small and light should be rigged only by someone competent to do so.

[AndrewR]

Anything marked with KN is showing a breaking strain!

 

This is a very important thing to remember. (6KN is also the force required to deploy a standard fall arrest system BTW)

 

as mentioned before, the figure mentioned that you need to know is 9.81m/s². The force applied by gravity (per Kilo).

 

So a 6 KN karibiner could be used to with a WLL of slightly more than 100Kg (117.72 Kg I think... I've had a cocktail so don't take it as law! )

Thats working to industry CoP (5:1 safety factor) You can still meet CE regs and go for 4:1 (147.15 Kg)

 

All thats assuming I know what I'm talking about, and my calculations are correct, with the 'biner having a breaking strain of 588.6 Kg.

Personally I'd use half ton shackles, they're smaller than most karibiners I've seen. Although theres no reason not to use them, provided you are competent to determine a WLL etc...

I am now scratching my head... most of my kit is marked 25KN.. how small are your 'biners?

 

All the usual provisos apply!

[Glyn Edwards]

Anything marked with KN is showing a breaking strain!

 

I am now scratching my head... most of my kit is marked 25KN.. how small are your 'biners?

 

6kN would be about right for loading on the small axis though. If you can't tell the difference then you really shouldn't be doing this, as it could go horribly wrong. I'd throw my vote in with the others who have recommended 0.5T Shackles

 

 

Glyn

[adamharman]

I am now scratching my head... most of my kit is marked 25KN.. how small are your 'biners?

 

I was thinking that. I weigh 115kg, which wouldn't leave much to spare!

 

Just dug out the smallest karabiner I can find, which is a DMM screwgate and is rated 25kN.

 

It's also marked 7kN cross loaded and 8kN open. Are you sure you're looking at the right number?

 

 

 

Edit: Beaten to it by 1 minute!!!

[phawthorne]

No... F=ma as you said, so for m = 1000kg, as a = 9.81m/s, F = 9.81 kN, taken as 10kN, not 1kN as you've said.

 

M

 

Indeed so, mea culpa. Shows how careful you have to be with safety calculations and powers of ten!!!!

[timtheenchanteruk]

the small ones are about 1.5 inch long, and are have no screw gate,

 

The reason we need karabs at the bottom, is the hall has no flaying space, so the lines will be swung out sideways with no load, when they are dropped in, the load needs to be quick to attach.

 

just to add, this will be checked later in the week by a rigger, its just they are not available until tech night, so we wanted it rigged (with their agreement) for it just to be given the one over

[gnomatron]

25Kg will still kill you if it falls on your head... shackles are cheaply and easily available, just buy a 1t or 1/2t shackle for all they cost. You don't gain much time by using a karabiner and it's not really the right tool for the job.

[Seano]

so the lines will be swung out sideways with no load, when they are dropped in

 

Er.. If I understand what you mean correctly, sandbags might be neater.

 

You don't gain much time by using a karabiner and it's not really the right tool for the job.

 

Yes you do and, yes it is.*

 

Sean

x

 

* - not just any old karabiner though, obviously.

[GRisdale]

(6KN is also the force required to deploy a standard fall arrest system BTW)

Completely off topic, but it seems to have pretty much finished anyway - I thought that fall arrest systems limit the force excerted on the body to below 6KN, rather than that being the ammount of force needed to deploy them...? - Based on the original ejector seat trials in which it was found that body parts start to fly off at 12KN(?).

 

Back on topic - the short, equation free, answer to the original question is that 1 Newton expressed as "weight" on Earth= 108g (about the weight of an apple...), so 1KN = 108kg.

 

Gareth.

[stillgoingstrong]

If you must use a carabiner, how about a Petzl William or similar. It provides a twist lock, allowing it to be opened with a simple twist of thumb and finger yet locks shut once the load is in place. Again, it's rated at 25kN

 

Just my 2p