# Acrow prop specs

#### Norcon

Why the kilo newton techno jargon?
Its 10 ton.
I'd put 12 props under that assuming they are not extended.

#### iandandav

Why is this question relevant to what I asked ie the load bearing capacity of a single acrow prop extended to 1.5m

It is the correct use of the support, which matters

Im not disputing this. Please read the posts.

#### iandandav

Are we going to be told what this mystery load is, and why spacing of props is irrelevant?

The spacing cannot be deduced until the number of props are established. This is simple common sense.
Read previous threads for job in question Im not repeating it here.

#### iandandav

Im trying to find specs for standard UK acrow props. Im needing to calc how many I need for the job. Will use a No1 or 2 prop extended to 2.5m
Can anyone help

For both number 1` and 2 acrows, we work to the following safe working loads.
10% open 35kN
50% open 30kN
Fully open 25kN
As we do not know whether you are needling or sole and plate shoring, can give you no further advice.
Regards oldun

Thanks oldun, most useful
Those values are much higher than the values in the australian table i my first post. Do you know if Acrows differ significantly around the world.

#### iandandav

Why the kilo newton techno jargon?
Its 10 ton.
I'd put 12 props under that assuming they are not extended.

The quoted load is in kN as its taken from my calculations to deduce UB size and they are worked out using kN.
Calculations are done in Newtons as this is a unit of force, and we are dealing with force. Tonne is mass which is constant. Force can change depending on a number of factors.
Take the Acrow, if it is dead vertical and is supporting mass of 1 tonne then this is a force of 10kN. But if the acrow is tilted the mass remains the same but the force splits into two components, a vertical and horizontal both less than the original but adding up to the original. The vertical now becomes less, this is why force is used in these calculations instead of mass

#### iandandav

It's HOW you prop that is important.

True, and the props must be able to take the load regardles of how vertical they are or how the pressure is distributed evenly

#### ^woody^

**** me, it's like some top secret MI6 job, or the OP is on an old modem and being charged per byte of information uploaded .... and is too tight to go near his allowance.

#### iandandav

Are we going to be told what this mystery load is,

As mentioned see previous thread of mine for job.
You were very useful then tony

and why spacing of props is irrelevant?

I didnt say this or even imply it, just ignored the statement as it wasnt answering my question?

#### iandandav

f***** me, it's like some top secret MI6 job, or the OP is on an old modem and being charged per byte of information uploaded .... and is too tight to go near his allowance.

#### tony1851

The quoted load is in kN as its taken from my calculations to deduce UB size [/quote]

Factored or unfactored? - it makes a difference.

#### Norcon

Why the kilo newton techno jargon?
Its 10 ton.
I'd put 12 props under that assuming they are not extended.

The quoted load is in kN as its taken from my calculations to deduce UB size and they are worked out using kN.
Calculations are done in Newtons as this is a unit of force, and we are dealing with force. Tonne is mass which is constant. Force can change depending on a number of factors.
Take the Acrow, if it is dead vertical and is supporting mass of 1 tonne then this is a force of 10kN. But if the acrow is tilted the mass remains the same but the force splits into two components, a vertical and horizontal both less than the original but adding up to the original. The vertical now becomes less, this is why force is used in these calculations instead of mass

Are you an engineer stuck in an office job?
You are wrong about the part highlighted in bold if the load is vertical down.

Oh and btw. You never ever tilt an acrow prop unless absolutely necessary. Back to the drawing board for you son. Or I'll take you out unto site some day propping a few hundred ton of wet concrete. You'll learn more at that then reading a few books.
Especially when it bursts and you're knee deep in the stuff.

#### RonnyRaygun

Iandandav, people here are trying to help you, but you are making it very difficult for them...

You said "The spacing can't be deduced until the number of props has been determined."
However, this doesn't take into account that, for example, you may only need one prop for the applied load. However, you know very well you would need more than one prop.
So you can determine a minimum number of props for the load, but it won't necessarily be enough. One prop on a five metre span will not hold up the back of your house, regardless of the load applied. You also aren't going to want to space them at more than about 900mm or so, otherwise the brickwork will not arch between them. This is why spacing is also important.

If you use Strongboys and prop from one side only the capacity is greatly reduced due to the cantilever effect of the load applying a moment to the prop.

Finally, you are almost correct when you talk about props at an angle. There will be a horizontal and vertical component, but they are not additive. Forces are vector quantities, so, you use trigonometry or pythagoras to calculate the resultant force.

For example hyp = sqrt (opp² + adj²).

As Norcon said, you shouldn't install acrows at an angle anyway, but there will be an allowance in capacity tables for applied moments from props being slightly off vertical.

Anyway, theoldun has given you the capacity for a single prop. If you don't believe him, call your local tool hire company and they will have the figures available.

#### ^woody^

What a bloody palaver.

Out of sheer curiosity, I've gone searching for the mystery structure, and the top secret job.

Contrary to it being an extension to the SIS Building, it seems to be a wall removal in a poxy 3 bed terrace, with a 2.5 m beam holding up a first floor

Four props then. Thread closed

#### freddiemercurystwin

Jeez, you bunch of miserable lazy gits, you just cannot be bothered to trawl through the OP's previous threads! Honestly!

#### iandandav

I used 6, 12 would have been over kill, 2 insufficient.
2.5m was the final span of the opening, the acrows needed to support the whole width of the lounge and hall until the pillars were built. Thanks for all the posts its been amusing.

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