Top Newel Post

[MortarThePoint]

18 minutes ago, Adrian Walker said:

That looks a lot stronger than most of the balustrades I have seen. Most are cheap wooden posts held on with a couple of screws and maybe some glue.

 

This metal post will be down the middle of a timber post that will add the vast majority of the strength of a solid timber post too.

[joe90]

2 hours ago, MortarThePoint said:

This metal post will be down the middle of a timber post

How do you plan on doing that?

[MortarThePoint]

8 hours ago, joe90 said:

How do you plan on doing that?

 

The plan is to use two 90x25 and two 40x25 timbers glued to make a 90x90 hollow square section. It's going to be painted and the narrower width timbers will be inline with the handrail and spindles so somewhat hidden.

 

I'm thinking the 90x25 facing the landing will get screwed to the Unistrut at 200mm intervals to couple the timber to the metal. Alternatively, perhaps the 40x25 pieces as they don't stop at the top of the beam.

[Gus Potter]

On 27/01/2024 at 21:15, MortarThePoint said:

but it feels solid.

Well that's a good start!

 

To keep you on the right side of things below are the design loadings from BS 6180 for domestic internal stairs, landings etc.

 

 

Your on the top line. Often the governing load for the hand rail is the horizontally uniformly distributed load of 0.36 kN/m (~36 kg per metre run of hand rail) and this load usually get transferred to the top of the hand rail. An important point here is that these are unfactored loadings.. thus no factor of safety built in.

 

The other important bit is the deflection of the overall asssembly, from the same code

The 25mm deflection is a key requirement.

 

If you want have a test of what you have. Take your hand rail length just say 3.0m and calculate the horizontal force at the top from the hand rail 3.0m  x 0.36 kN/m / 2 = 0.54 kN (~54 kg) Get a spring scale ( for weighing fish or something) and apply that load to the top of the uni strut. See how much it deflects by < 25mm

 

Next test for strength using the Eurocode factors of safety. Take the 0.54 kN load and and multipy by load factor of 1.5 = 0.54 x 1.5 = 0.81 kN ~ 80kg

Also make an allowance for material defects that may manifest later. Apply a material factor of 1.3 thus 80kg x 1.3 = 104kg ~= 1.02 kN test load.

 

Two things to remember. You are testing the newal post in isolation here and I'm not taking into account the potential  bracing effect of the handrail running perpendicular to the newal post down the sloping part of the stair. Some may and rightly say.. it's always stiffer than that once you put things together. I say.. your often right but can you imagine how hard that is to prove? and also you can often shift the problem somewhere else if you shed load from the newal post.

 

On the other hand 104 kg is about 16 stones.. there are plenty folk that are heavier than that.. and if you have a Rugby team partying, a couple of big lads could push the thing close to its design limits.

 

Report back.. check the deflections first in case the strut fails early.

 

 

 

 

 

[MortarThePoint]

On 29/01/2024 at 20:47, Gus Potter said:

Report back.. check the deflections first in case the strut fails early.

 

Pretty sketchy test setup pushing the post out over the void but I got some numbers. Only for the 1x case though (is no safety factor). As I have two posts I can use the other to observe beam twist. Laser level and pen marks plus a crane scale and brute force.

 

It's 1.8m between posts, so 1.8m*0.36kN/m=0.65kN. Peaked at 67kg force with a total deflection of 27mm, 7mm of which is from the twist of the underlying beam. So the Unistrut setup is deflecting 20mm which is within the 25mm limit, but I should stop the beam from twisting.

 

To stop the beam from twisting I an thinking of adding a hidden piece of channel acting as a counter leaver.

 

Addition of timber will stiffen posts too.

Edited February 7 by MortarThePoint

[joe90]

18 minutes ago, MortarThePoint said:

To stop the beam from twisting I a thinking of adding a hidden piece of channel acting as a counter leaver.

Surely surrounding the uni strut in solid timber will massively reduce the twisting effect 🤷‍♂️

[MortarThePoint]

1 hour ago, joe90 said:

Surely surrounding the uni strut in solid timber will massively reduce the twisting effect 🤷‍♂️

It'll reduce the Unistrut bending massively, but won't reduce the beam twist

[MortarThePoint]

Here's the Unistrut under the HCF to counter the beam roll/twist. I wanted to anchor it close to the secured side of the HCF to avoid HCF deflection rolling the beam

 

As both bits of Unistrut are about the same length it should serve to halve the beam roll

 

Edited February 7 by MortarThePoint