Small but strong wall brackets for lighting bars

[johnb]

I'm hoping the collective knowledge of the Blue Room might be able to help me where my searching the internet has failed....

I'm looking at the possibility of mounting some permanent lighting bars in our church to run along the back of the existing high level beams.  The beams are limited in height, from memory about 250mm high, so that limits the options of some of the conventional stand off mounts or many of the standard right angle brackets as they are taller than the beam height.

After lots of looking around, I think the best arrangement I can see is something like this:

This would be a pair of Doughty T34100 brackets supporting a 1.2m length of ali bar above for the lights to actually hang on.  By mounting in this way it means that the bar and majority of the lights would be mostly hidden behind the beam, and at the height we're talking about I think we'd then be fine for the visual impact of having more lights.

The challenge I'm seeing is that the working load of the T34100 brackets is only 15kg.   So allowing for the bar and using two brackets that the total load we'd be able to hang would be around 20kg only which feels quite low, particularly when I'd be looking to move the two existing LED fresnels (5kg each + cabling) onto the bar before thinking about adding more (possibly another fresnel plus some LED pars). 

Looking at the Doughty range the bigger version of the same bracket, the T34000, has a diagonal brace and a higher working load of 30kg.  Sadly the beam height wouldn't allow me to use these, so I was wondering if anyone was aware of a smaller bracket similar in size to the T34100 but with a higher working load?

Alternatively I suppose I could put 3 brackets on each bar, or possibly mount one end to the wall and then use two brackets to support the middle and end, both of which would help.  However I thought I'd see if anyone has come across another supplier of similar but stronger brackets before heading down those routes.

...and before anyone says it - yes I'm aware we need to run through the structural side of this as well as church faculties, however at this point I'm trying to work out if the bracketry exists to do what I want so that I can then present that for assessment!

Thanks

John

 

 

 

[sunray]

what is the beam? Not everything can tolerate that much twisting force or take that many fixings.

[Stuart91]

This would be a fairly straightforward job for a local metal fabricator. If you were in Glasgow we'd be able to build you something to suit the exact height that you've got available. 

Another option would be to use UniStrut, which is essentially Meccanno for big boys. You can cut it to length, but would need a diagonal brace for any serious weight capacity. 

34 minutes ago, sunray said:

what is the beam? Not everything can tolerate that much twisting force or take that many fixings.

Definitely worth making sure the beam can take it, but a ~20kg load mounted quite close in hopefully shouldn't be much of a challenge. (If it is, I wouldn't want to be stood under that roof when it snows!)

[sunray]

6 hours ago, Stuart91 said:

Definitely worth making sure the beam can take it, but a ~20kg load mounted quite close in hopefully shouldn't be much of a challenge. (If it is, I wouldn't want to be stood under that roof when it snows!)

In principle I agree, however seeing some of the construction techniques I wonder how they do stand up.

Pressed steel Zed bars for example have very little rotational stability as discovered by a fairly local church hall when they added a curtain track, luckily the problem it created was a leaking roof where the Stramit roof slabs bacame misaligned, splitting the bitumous coating.

I've witnessed various expansion fixings in holes drilled into steel reinforced concrete roof beams (and verticals for that matter) which are potentially not a good idea.

 

So getting back to my first post, without knowing what beam we are talking about I am not in a position to make any assessments, even for 40Kg.

 

To give this a little perspective this is my initial mock-up of the product suggested, on the left showing an aproximate height of 250+75mm in blue and on the right using the same products in a hanging mode will just get it into the 250mm with clearance for a hook clamp.

 

I must stress this IS NOT my suggestion for an installation.

Edited September 30 by sunray

[johnb]

Thank you very much for the comments.  I'm very aware I need to get the structural side of the beam signed off before going anywhere with this.  The beam in question is a wooden beam which is a good 10 inches by 6 inches in dimension (I need to measure next time the scaff tower is out to know precisely).

@Stuart91 I can see this would be an easy job for a metal fabricator - it's a couple of pieces of angle and a single piece to brace it, but before going down that path and then working out who can give me the SWL for it I would hoping there might have been something off the shelf that people were aware of.

@sunray I'd already considered the depth of a hook clamp and was planning that anything hung here would probably use a half coupler, and also why I liked the over hanging the bar on the brackets.  I know I'm not going to be able to hide the lights entirely, but I know aesthetics will be a question asked, so it's a case of every inch I can gain will be a benefit.

At the end of the day what I'm probably most worried about is that someone comes along in the future and wants to add more lights without thinking too hard.  So (beam side for a moment) while 20kg may be enough for us right now, thinking about a 4 foot bar all it takes is someone to increase it to 4 LED fresnels and that's the full load gone before adding clamps and cabling etc.  Hence trying to see if I stop the brackets being the weakest part of the setup.

Cheers

John

[Stuart91]

1 hour ago, johnb said:

what I'm probably most worried about is that someone comes along in the future and wants to add more lights without thinking too hard. 

My other concern is the sort of scenario where someone slips on a ladder and grabs the bar to steady themselves. That's going to put far more force on the fixings than a couple more fresnels. 

[johnb]

59 minutes ago, Stuart91 said:

My other concern is the sort of scenario where someone slips on a ladder and grabs the bar to steady themselves. That's going to put far more force on the fixings than a couple more fresnels. 

I get that, however we do get start getting into playing "What if?" scenarios, and how many other installations would fall foul of limited headroom on the SWL to cope with the unknown scenario of someone hanging from it.  Either way I'd like to increase the headroom on the setup - I'm always amazed how low the SWL is on these types of bracket and looking for solutions about how I can increase it.

[Andrew C]

If going down the fabricated route - can you wrap the bracket around the beam?  Might make fixing into the beam less of an issue, whilst being stronger.

[Stuart91]

3 hours ago, johnb said:

I'm always amazed how low the SWL is on these types of bracket and looking for solutions about how I can increase it.

The SWL is a safe "working" load, so there's significant headroom built into that for shock loading etc. 

I'd be more concerned about the fixings into the beam than the brackets themselves. 

[J Pearce]

If it’s an install and you want compact, how about unistrut rather an a bar? Powder coated if you fancy a smarter finish.

[Dave m]

Photos of the beams might help?

[sunray]

22 hours ago, Andrew C said:

If going down the fabricated route - can you wrap the bracket around the beam?  Might make fixing into the beam less of an issue, whilst being stronger.

19 hours ago, Stuart91 said:

The SWL is a safe "working" load, so there's significant headroom built into that for shock loading etc. 

I'd be more concerned about the fixings into the beam than the brackets themselves. 

I thougt I replied to these last night but...

 

It is always my preferred method with timber, particularly so with elderly beams. Jon has already made the comment about Unistrut in place of tube.

As this is a church I wonder if DAC has been contacted yet, they may have preferred solutions.

Edited October 2 by sunray

[Robin D]

Could I just throw in one word of caution. I was asked to fit some temporary lights onto beams in an 8th century part of a local church adjacent to the permanent halogen floods professionally installed a few years before. When I got up there the wooden beam was scorched by each of these units. I am aware the OP is talking LEDs, but it's not just the loadings that need consideration.