Hanging Movers

[paulears]

You need to put things in context. If you went to the local engineering company - even a small one, and asked them to make one for you - it would cost what? A couple of hours work - easily more than the real component. If your school cannot afford this, it's frankly an indication of how important they feel it is. It is, price wise, something that could be ordered from their low price consumables budget - and these are often within the control of the department. A few sheets of gel or a few lamps can easily cost this sort of money. If they're that skint - how do they pay for replacement of a broken window or smashed glassware in the science dept.

[greenalien]

I will probably get shot down for saying this, but provided they are properly engineered and tested, so that you can be confident that they can take the load, I don't see any problem in making your own, if you have suitable skill, facilities and materials available. Test load should be at least 10x working load. Mark them with SWL and you're sorted.

[Ashley R]

Trying to manufacture the actual bracket itself is nice and straight forward, but the actual omega part looks like a PITA to manufacture.

[timsabre]

Trying to manufacture the actual bracket itself is nice and straight forward, but the actual omega part looks like a PITA to manufacture.

 

All the ones I've seen have been a sawn off section of extrusion.

[greenalien]

All the ones I've seen have been a sawn off section of extrusion.

 

The OP says he has access to the school's engineering dept - perhaps they could do an aluminium alloy casting? It would have certainly been something that my school workshop would have loved to do - but that was a while ago!

[Tomo]

The OP says he has access to the school's engineering dept - perhaps they could do an aluminium alloy casting? It would have certainly been something that my school workshop would have loved to do - but that was a while ago!

Seriously, no.

Casting is something that is very easy to get wrong, and easy to get wrong in a way that gives you a part that looks right but has no strength.

 

There have been quite a few building and bridge collapses caused by dodgy metalwork. No school could ever countenance such a thing, and no sane person should either.

 

Either buy the right part or don't hang them. It's as simple as that.

 

Pretty much every lighting sales company will be able to supply these, so you can easily get several quotes.

[greenalien]

Casting is something that is very easy to get wrong, and easy to get wrong in a way that gives you a part that looks right but has no strength.

 

...which is why a proper engineering approach is needed, including adequate testing.

 

Just because stuff is supplied by a retailer, it doesn't mean it's perfect, just look at the dodgy stuff coming from some far-east sources these days. There's no need to be afraid of making stuff yourself.

[J Pearce]

The thing is, adequate testing for a casting means sonar or X-ray testing to check for cavities and fault lines.

It's not something you can really do in house.

[mac.calder]

At the end of the day, it comes down to what the prosecution would ask in court if the worst happened...

 

"So you MADE these brackets?"

"No... my school did"

"So instead of using pre-manufactured, properly tested brackets which are designed for the purpose of hanging the light, you got one manufactured by students?"

"Yes"

"I rest my case"

 

When rigging something like lights, where a (OEM) manufactured solution exists you should be using it - or at least an alternative created by an engineer - someone who understands the stresses involved and is willing to put their reputation, money and even personal freedom on the line with creating your bracket.

 

As an aside - in Australia under the new harmonised OH&S act, maximum penalties for rigging related injuries are "penalty level 3" which is 20 years in prison along with the potential for many thousands of dollars in fines + whatever the injured person gets out of you when they sue you - there are also real consequences for company directors/managers/owners - both monetary and prison based. There is a real push for personal responsibility and hitting every branch on the tree to try and keep people working safe.

[Nicktaylor]

Can I suggest both views have now been put. It is up to the op and more importantly his school what route should be taken. My additional view is less Mac hire this year and use the change to buy clamps for the school kit

[Pat]

If you want to safe money on safety equipment, you shouldn't go into the light and music business.

 

 

[paulears]

I'd rather look at things from the cost point of view for myself - but if the school has sufficient means in terms of skills and equipment, I really can't see what fabrication is such a problem. A teacher trusted and qualified to use what are in any workshop - dangerous machines should have the ability to make this kind of thing. In fact, whenever I see things home made - they're often over engineered, and testing isn't beyond them either. Aluminium casting that I did at school would often have voids or other strength reducing defects - but isn't this what we have safety bonds for? The bracket might break, a hidden flaw could reveal itself, and then your safety ratio in the bond would prove itself and all is well.

 

I needed to hang a pair of SX300 EV speakers and didn't have a flying frame, what I did have were some lengths of dexion, which took a saw and advice to produce a hanging frame in about half an hour. The bolt holes were even in the right place! I attached it with a hook clamp and 10mm bolt set. I used a proper HD safety onto the frame, and then just for security, put another through the side handle rigged taught around the scaff bar it was hanging from. My very unscientific test was simple to hang myself at 151/2 stone from the speaker, and it held for the time I could hold on. With two proper safeties - I cannot see any reason, practical or insurance based that prevents this from being safe. Not made from box section,like the real ones, but still perfectly usable.

[kerry davies]

Sorry Paul, can't agree. You yourself point out that compared to other expenditure the cost of the real McCoy is peanuts.

Mac has the reasoning down pat. What you don't want to see on the front page of the Daily Mail, don't write on the web, what you don't want to admit to doing in court, just don't do.

 

I believe in teaching good practice and adherence to MI's and even though some students in some schools are perfectly capable of building the kit I don't think they should. There is a right way, a wrong way and a home-made solution which could lead to bodgery. The latter should be frowned upon in educational settings, too many teachers are bodgers already.

 

Nothing personal, you and I and many other BR members are capable of creating safe kit but students cannot be made responsible and so should never be allowed the leeway to fail and hurt themselves or others. Fail, yes, hurt, never.

[Seano]

.. but isn't this what we have safety bonds for?

 

To enable the use of potentially unreliable hanging hardware? er.. no, imo, it isn't.

 

I've no problem with the principle of home-made hardware (subject to the usual caveats), but I don't think I'd want to buy even commercially produced hardware in cast aluminium (assuming there was anyone out there daft enough to make them that way) let alone something knocked up in a school workshop.

[timsabre]

I don't think I'd want to buy even commercially produced hardware in cast aluminium (assuming there was anyone out there daft enough to make them that way)

 

As far as I know all "C clamps" used for hanging standard lanterns in the US are made of cast aluminium. They have a lot more clamp failures due to fracture than we do with our steel clamps.