Pulleys

[IRW]

Hi All,

 

I'm currently looking at converting our static lighting bars into winchable lighting bars, and I was after a bit of advice regarding some pulley suitability.

 

To cut a long story short, before my time at this venue, these bars used to be flown from motorised winches that were 'condemned' for, from what I can gather, a variety of reasons to do with the actual winches. When this has happened, the cheap way out has been taken, and the bars transferred onto studding that is lindapter-ed to the I-beams.

 

Now, due to the frequency of turnarounds, therefore increase of WaH, coupled with the fact that I'm the sole technician here, I've advised that we look into reversing this exceedingly annoying decision (that was taken before even my boss took over the department), and I've been asked to look into pricing to make it happen.

 

The current situation is that all of the old pulleys are still in place above the bars, having never been taken out and these comprise of 1, 2, 3, 4 and 5-way blocks of what I *think* are the older Hall's blocks. My plan to help keep installation and future costs down is to put the bars onto manual 250Kg winches mounted in a suitable location at the side of stage. Note, we're not a flying house.

 

I've priced this up today, and based on list/catalogue prices, per bar I'm currenly look at ~£700 per bar without pulleys, and a whopping £1,600 including replacing all the pulleys, so what I'm after from anyone in the know is what you're opinion on re-using pulleys like this would be:

http://www.irwdesign.com/br/pulley.JPG

 

Bear in mind that these have been in for a good 20 years at least, and there's no obvious signs of damage or huge amounts of wear, and they all still run smoothly. The line that you can see along the centre of the sheave is just where the paint has worn off where the SWR has been running. I caught our inspection man when he was in last summer and asked his opinion, and he said he would be happy with them, given the frequency (we're probably talking once every few weeks, if that) that they would be used. What I'm a little bit afraid of however is doing the work without replacing the pulleys, then getting a different guy in the future who takes exception to them and then end up having to spend the same amount over again replacing them.

 

For reference, these are three IWB's that previously had 5 drops (SWR) to them, connected to a clew plate that had one line to the winch, and I'd be replacing all other parts of the lifting system (i.e. new SWR, manual winch, mountings etc), and once the work has been carried out, the bars would be load-tested.

 

I think I've covered everything. Please no lectures on being qualified to carry out the work, I've got a very good understanding of rigging and know when to 'get a man in', it's just I'm in a bit of a quandry about this!

 

Thanks,

 

Ian

 

Edited for SPAG- shouldn't have started writing the post 10 minutes before home time!

[paulears]

when we had work done, our budget needed to be zero, and anything over this would be a problem. Our friendly engineering firm cut the winch costs considerably by using clew plates to bring the number of lines down to one that could be on a single drum winch - which are a lot cheaper than multi-drum ones. The downside is simply cable travel - so we do have some winches in some odd places, to allow the one wire rope going onto the winch to have enough travel. All our re-SWR ropedcounterweight bars use pulleys very similar to yours - put in by Halls originally, and all were put back into service - no new ones needed at all.

[ImagineerTom]

I've seen Hall's stuff older than I am still working just fine, pullys are very low tech and I'd take the view that provided they passed a visual inspection I'd have no problem bringing them back in to use.

 

£700/bar for some steel wires and a manual winch sounds ridiculously expensive though - where's the venue?

[stillwave]

Only apparent issue I can see is that they appear to be for a larger diameter rope such as a hemp set. Ideally the pulley should support the swr around more of it's circumference, whether the loler chap would pull you on this I can't say.

 

Regards

 

Ben Wainwright

[IRW]

I've seen Hall's stuff older than I am still working just fine, pullys are very low tech and I'd take the view that provided they passed a visual inspection I'd have no problem bringing them back in to use.

 

£700/bar for some steel wires and a manual winch sounds ridiculously expensive though - where's the venue?

 

Given how prolific these blocks must have been I did wonder whether other places had them in use. Thanks for all input so far!

 

The venue is in the east midlands- it's a typical 80's school venue, and hasn't had a huge amount done to it since then. That figure is based on list prices in the Flint's catalogue that I threw together today to give an idea for budgetary purposes, and also includes the electrical bits that would that will be needed.

 

Thanks,

 

Ian

[Giles Favell]

You may well find that some inspectors will (rightly) look askance at you for using rope pulleys for steel wire rope. It is an important principle to use appropriate fittings and hardware throughout an installation, and for good reasons. Rope pulleys are of smaller (relative) diameters than those for steel wire rope, (these may well be too small for swr, depending on the diameters of both) and all pulleys should be closely profiled to support the rope or steel wire rope that passes through them.

A wire rope pulley MUST be a MINIMUM of 18 x the wire rope diameter, whereas as fibre rope pulley only has to be 8 x diameter. For wire rope, the groove should be 7.5% larger than the wire rope diameter.

 

To all intents and purposes this is a new installation of equipment, (pulleys, lines, winch) and perhaps should be treated as such.

[Chas at Halls]

Hi There,

Always good to see our kit in decent nick after a generation of hard labour....! First off, the pulley you have there was designed for use with a hemp line, but our predecessors were perfectly happy to use them on wire rope installations and they always seem to survive. The only note of caution I would add is about 'porosity' which affects cast items - many of the old sheaves were cast and we've seen some right old 'honeycomb' stuff exposed once the running surface has been worn away....and that can shred either hemp or wire rope pretty quickly.

 

Nowadays - in these health & safety enlightened days - we realise the need for a specific sheave profile for each different type of running line and would not sell or use 'rope' pulleys for use with SWR. Giles is - as always - spot on with the ratio required and 18:1 is the minimum D:D acceptable today. For most applications, we run up to 32:1 on powered lines, ie a 6mm SWR pulley is 200mm in diameter/192mm at the bottom of the groove.

If I were in your position, I would 100% replace the 'header' block above the winch with the modern unit - at about £200 list. If you needed to replace all of the blocks, you would indeed be looking at £700.00-ish and that's not bad value as they'd last for another 50 years....

 

If your inspector is happy with the drop pulleys you have, I would take his advice/guidance....and certificate(!)

 

My only other question would be about the winch itself. Does it meet requirements.....?

 

The "Support" section on our website has a pile of info and data on the subject; http://www.hallstage.com/theatre-flying-systems

 

Drop me an email if we can help with anything.....

 

Cheers,

 

Chas at Hall Stage.