Manual Chain Hoists and Slack Chain

[TomHoward]

Afternoon all

 

In our venue we have a winch bar system for the majority of the bars, but due to structural restrictions (as in there's not enough room in the roofspace above the cyc bar to put a winch in) our cyc bar is fixed.

 

This is raising H&S issues, as whenever anybody wants to use a backdrop or we need the cyc removing etc, we have to do it manually from the top of ladders. This does involve some handling of weight at height and isn't ideal.

 

The cyc bar is a 10m ali scaff bar, fixed on steel ropes to the girders in the roofspace at four points spaced evenly along the bar. The drop to the floor is about 7m / 22 feet. The bar is marked as SWL of 250kg.

 

We ideally want to install some manual chain hoists to bring this to to ground. We're happy with manual, as it only gets lowered about six times a year, so we don't think it's worth investing in an electronic solution if a manual one can work.

 

The two options we see ourselves as having is either the possibility of two manual chain hoists, one at each end of the span, and replacing the bar with a ladder or piece of truss to avoid any flexing over the length (as it's pretty wide for two point on an ali bar) - or use four chain hoists, one replacing each original point along the bar.

 

One thing that's been raised, and I want to check if there's any problems with, is that if we had two chain hoists, with two people operating them, the chains would always both be taught / under tension. If we have four hoists with four people operating them, there is the possiblity that one of the chains could gain some slack in it while being winched up and down (if one person is more enthusiastic than the rest.)

 

It has been raised that this could cause the winches to foul - is this a likely occurance, and does this then throw the idea of four winches out the window, meaning we'll have to go with the truss, or would slack in the chain not really be that much of a problem?

 

A concurrent post has been automatically merged from this point on.

 

Just to add - about the heaviest thing we'll be loading the bar (excluding the weight of the bar itself) with is a pair of tabs, and a single tab is an easy one-man lift, so I'm guessing around 60kg each max, 120kg total. The hoists we are looking at are either 250 or 500kg each (depending on supplier) so we shouldn't be running into any problems of over-loading an individual pair of hoists if the remaining two go slack (worst case scenario).

[hadyn.williams]

If you want to stick with using 4 points but 2 chain hoists, could you use a bridle? So each chain hoist would then be taking the weight from two points.

[TomHoward]

Not really, as we haven't really got the points between the existing points to rig, so it would have to span into the centre from one of the ends. We've only really got a depth of about 60cm total from the ceiling to accomodate the winches, which I don't think would really be enough to span the widths as well.

 

I hadn't heard of chain hoists having problems with this before, and I'm not certain it will be a problem - but someone had raised it when I was discussing the problem with them and said we should go down the two hoists & ladder route, so I thought I'd better check if there was any weight to this.

[Simon Lewis]

Tom,

 

Two manual chain winches wth bridles on the truss would do the job but you still would need to get up a ladder to pull out and put back the chain in its bag. That might not be too onerous for the chain on a (say) 250kg winch, but it does still represent ladder work that you are trying to avoid and a slightly oily chain to handle.

 

Could you consider using small electric chain hoists? They're pretty compact and some can run off a 13A plugtop. You'd only need a 125kg or 250kg version, and it would allow you to drop the cyc truss whenever it's needed.

 

Simon

[paulears]

Is there no scope for fitting a simple, cheap wall mounted winch? We had some almost permanent heavy portals using up counterweight sets at our venue, and the company who look after them suggested that we could easily transfer them to hand winches, freeing up sets. What is installed is a single cable winch that splits into multi lines with a clew plate. Plenty of spare capacity, load wise, and would be much cheaper than any form of chain system - which always needs multiple people to raise or lower. All our suspended truss and single bars over the audience are on these winches now. They work really well, and only take one body to carry out lowering/raising.

[johnlinford]

If the bar is only really used for the cyc, you could always consider using a simple hemp set. Using manual chain hoists above a cyc in that fashion I'd be concerned about the chain rubbing on the fabric and leaving oily stains...

[TomHoward]

Tom,

 

Two manual chain winches wth bridles on the truss would do the job but you still would need to get up a ladder to pull out and put back the chain in its bag. That might not be too onerous for the chain on a (say) 250kg winch, but it does still represent ladder work that you are trying to avoid and a slightly oily chain to handle.

 

Could you consider using small electric chain hoists? They're pretty compact and some can run off a 13A plugtop. You'd only need a 125kg or 250kg version, and it would allow you to drop the cyc truss whenever it's needed.

 

Simon

We do have a tallescope to do the working at height - so although we would still be handling at height it wouldn't be anywhere near the weights we are currently handling on it.

 

Electric hoists aren't entirely out the question, although the problem is budget availability. The power isn't an issue, we could easily put dedicated 16As in for the hoists, as there's power available in spades in the roofspace. I would look into the cost of the hoists, but unless the whole job could be done for less than around £500/600 I can see it being a complete non-starter.

 

A concurrent post has been automatically merged from this point on.

 

Is there no scope for fitting a simple, cheap wall mounted winch? We had some almost permanent heavy portals using up counterweight sets at our venue, and the company who look after them suggested that we could easily transfer them to hand winches, freeing up sets. What is installed is a single cable winch that splits into multi lines with a clew plate. Plenty of spare capacity, load wise, and would be much cheaper than any form of chain system - which always needs multiple people to raise or lower. All our suspended truss and single bars over the audience are on these winches now. They work really well, and only take one body to carry out lowering/raising.

We did look into this as well, and the mounted winches I found were around £1500, plus specialist installation. There's also an issue with the space in the roofspace - the cyc is so far upstage in the room that there's almost no room at all above the original fixings in the corner. We've also had thoughts about the problems of a wall-mounted winch at ground level, as the hall is a mutli-purpose venue (read: exam hall) at other times.

 

A concurrent post has been automatically merged from this point on.

 

If the bar is only really used for the cyc, you could always consider using a simple hemp set. Using manual chain hoists above a cyc in that fashion I'd be concerned about the chain rubbing on the fabric and leaving oily stains...

This is a concern I've just had when Simon mentioned the oily chain - I wonder whether we could get away with chain bags on electic hoists instead.

[johnlinford]

Electric hoists aren't entirely out the question, although the problem is budget availability. The power isn't an issue, we could easily put dedicated 16As in for the hoists, as there's power available in spades in the roofspace. I would look into the cost of the hoists, but unless the whole job could be done for less than around £500/600 I can see it being a complete non-starter.

 

One of the issues that makes electric hoists expensive is the need for a double braked system when suspending loads above people (effectively a safety built in to the motor). If you could engineer your own secondary suspension (steel wire rope to two points running over some pulleys made off to a load rated point with suitably rated equipment for example), then you don't necessarily require the double braking motors. This should somewhat reduce the cost.

[TomHoward]

Once they were into position, we could put a secondary point on, by attaching and dropping them onto the original steels. We were thinking of doing that anyway to save the load on the hoists, as they would be up there for a couple of months at a time.

 

Does anyone have any comments on the application of the original manual hoists, and whether they would jam? I'll look into electric hoists but I don't expect we'll be able to get the budget to use them.

[Simon Lewis]

Once they were into position, we could put a secondary point on...

 

Or possibly fit a pair of load arrestors?

[TomHoward]

We could indeed. I'm still not sure however that an electric hoist is going to be a viable option, as much as I might like it to be.

[paulears]

Electric winches can actually be pretty cost effective now. Indeed, even second hand/recon ones are sometimes available. Out no 1 and 1a lx bars are on huge motorised over specified gear that was removed from another venue, had the number of pulley grooves reduced and sold on to us installed for less than replacing the old open gear worm drive winches.

 

I'd give these people a ring - pricing and quality of work I can recommend 100% - and they work with my penny pinching venue on an as-and when basis, fitting in work at a decent price in their quiet periods, if we don't mind longer work times.

TV & Theatre Services

Granary Buildings

Eastgate Street

North Elmham

Dereham

Norfolk NR20 5HF

 

Tel: 01362 667222

Joe or Les are the people.

[Seano]

One of the issues that makes electric hoists expensive is the need for a double braked system when suspending loads above people (effectively a safety built in to the motor).

 

A double brake is not 'effectively a safety built in to the motor'. This is a common misconception, and utter bilge I'm afraid. The brake is one component, and an added degree of redundancy there does nothing to increase the integrity of the rest of the motor.

There have been relatively very few examples of motors failing, usually it comes down to abuse of some kind, poor maintenance, or otherwise 'freak' circumstances - I've never heard of one where a second brake would've prevented it. If anyone knows of such an example I'd be interested to read about it.

 

The decision whether or not to apply secondary suspensions is more complicated than that (single brake - yes, double brake - no).

Essentially it comes down to risk assessment, now there's a surprise. It isn't uncommon to suspend loads over people using motors with a single brake (most often, naturally enough since they're so ubiquitous, the good old model L Lodestar). Of course that decision needs to be taken by someone competent to do so, things to be taken into account include whether or not there is a degree of redundancy in the system as a whole (such that the failure of one motor would not in itself cause the failure of the whole shebang), and whether the motors can be 'de-rated' to give an additional safety factor. (ie: using a motor to lift only a fraction of its rated load).

 

Something else to bear in mind is that applying secondary suspensions is also not without risk, and therefore when you look at the big 'safety' picture doesn't necessarily make everybody safer. Invariably there is work at height involved. Invariably the timing is not ideal - secondary suspensions frequently seem to get put on just before doors, or just before a sound-check - which can make working conditions less than ideal to say the least. There is also a risk with a more complex structure that a secondary may be missed when the time comes to take them off again - trusses have been broken (I mean, properly broken) this way on occasion.

 

'High Integrity' motors are available to several subtly different standards (BS7906: Part 1 Category A, BGV D8 Plus, BGV C1, blah blah), which the manufacturer will cheerfully tell you can be used to suspend loads above people. (Though those standards may encompass the lifting system as a whole - motor and controls.) These motors invariably do have a double brake (though there is one variant that has no brake at all) but there's much more to it than that. For example check out LTM's "Loadguard range.

 

 

Now - back on topic. The OP's original suggestion of 4 manual chain blocks (with or without secondary suspension) strikes me as a rubbish idea, soz. Not least of all because it doesn't make the WaH go away, introduces a load of unnecessary complication into the flying system, costs money and adds chainbags. You don't want chainbags if you don't have to have them.

 

Load arrestors? Get a grip, thats silly.

Secondary suspensions running over pulleys to a point elsewhere - ditto - if you can run ropes over pulleys to a suitable point make it the primary suspension and ditch the rest.

 

What you want is a primary suspension than requires little headroom, no secondary system and makes the work at height go away. And that strongly suggests a winch. Probably a wall-mounted manual winch. If you (the OP) think the room being multi-purpose rules that out, you're almost certainly wrong. There also may be the option of an electrically operated winch, and/or (since you mention there are winches in place for other bars) of diverting ropes to install the winch in a location that may not seem obvious.

 

This thread is a good example of where the Blue Room, and the internet in general, falls down. A degree of blind leading the blind, and if the OP lacks the ability to discriminate between good advice and poor its all a bit of a waste of time anyway. What you need, imo, is a proper conversation with a real person, in the real world. (Preferably in your venue, where that person can do a proper recce.)

 

If you do a quick search I think you'll find several threads where people recommend installers. I think its time to pick up the phone and talk to one or more of them.

 

Oh, and just to show I'm not above offering some half-baked advice, here's a daft suggestion of my own:

If your budget won't allow a 'proper' flown bar you could possibly replace the fixed bar with a fixed tab-track. You would still need to work 'at height' to replace the back cloth, but could do that in one location at the end of the track. This would give you the option to use a pulley and have the cloth roped up from the floor (gathered just so, and tied with a hitch a few feet below the top of the cloth) and supported while the person 'at height' is working - it takes away the need to support the weight of the cloth and tie it at the same time and also eliminates the temptation to roll an occupied 'scope.

 

A concurrent post has been automatically merged from this point on.

 

I'd give these people a ring - pricing and quality of work I can recommend 100%

 

Ha ha. There you go look, y'see? This was posted while I was editing my rant. -_-

Now thats what I'm talking about: time to pick up the phone.

[TomHoward]

Unfortunately replacing it with a tab track won't fly, as although it would work for upstage tabs it wouldn't help with the changing of cycs comprised of a single cloth.

 

While you say the four manual chain blocks costs money, it's far and away the cheapest option - a 250kg chain block will set us back about £80 a unit. Although the WaH still exists, we would not be handling loads at height, and it's much safer than the methods currently employed.

 

I'm afraid that a wall-mounted winch has already been explorered and ruled out, as we can't place the winch in the room. Two of the four mounting points are also virtually inaccessible from above (they are behind plasterboard, given the slope of the ceiling at the edges of the room), thus effectively out the possibility of pulleys above the ceiling (as are installed on our other bars).

 

However, we looked at opening them up and adding and eleventh winch to the existing system, with the ropes diverted forward, and the quotes were far too high for me to be able to get budget for them. Really we can't get this idea off the ground unless the whole thing can be done for less than around £600.

 

So that's where four manual chain hoists came in - it's crude, it still involves working at height, and it's labour intensive - but this bar only drops around once every two months, it's much, much safer than the methods that are being used currently, and we can afford it. My question is - is there anything intrinsically dangerous about using four hoists on a fixed straight bar, where the possibility exists for one or more of them to go slack?

 

If this is dangerous, the alternative appears to me to be to have two hoists at the outside edges, with a length of truss between them to spread the weight better. However, this would most likely work out more expensive.

 

I've also spotted these things, which would avoid the needs for chain bags and working at height. I could see these being a possibility - does anyone know of a reputable UK supplier of a similar item? I couldn't see my suggestion of ordering from the far east being an especially popular one.

[Seano]

Unfortunately replacing it with a tab track won't fly, as although it would work for upstage tabs it wouldn't help with the changing of cycs comprised of a single cloth.

Yes, it would. I explained why - it would enable you to hang the whole cloth while working in one place (one end of the track), and to have most of the weight of the cloth supported by an assistant from the floor while you do so. After hanging the cloth, you then slide it into position, and probably pay a brief visit to the other end to affix and/or apply a stretcher.

If you don't like the idea that's fine, it was just a thought, but you could at least take the time to understand it first.

 

While you say the four manual chain blocks costs money, it's far and away the cheapest option - a 250kg chain block will set us back about £80 a unit. Although the WaH still exists, we would not be handling loads at height, and it's much safer than the methods currently employed.

Pretty poor quality units then, prolly. You'll still be handling loads at height - you're either going to have to buy decent quality chain bags (which aren't particularly cheap) and bag the chains, or you're going to have to swap out the hoists when you dead-hang the bar.

Are you going to have to buy chainbags to go with the hoists?

Are your current flying points suitable for use with them (and are you qualified to answer that)?

What other rigging will you need to buy to make off the bar, suspend the hoists and bypass the hoists to dead-hang the bar when you're done?

What provision will you need to make for annual inspection of your hoists (and 6-monthly inspection of your lifting accessories) in accordance with LOLER.

Yes, its costs money - more than the cost of the hoists. I'm not suggesting its prohibitively expensive, just that it may not be good value for money. Even, possibly, a false economy - especially as its a far from perfect solution to your elf'n'safety concerns in any case.

 

I'm afraid that a wall-mounted winch has already been explorered and ruled out, as we can't place the winch in the room. Two of the four mounting points are also virtually inaccessible from above (they are behind plasterboard, given the slope of the ceiling at the edges of the room), thus effectively out the possibility of pulleys above the ceiling (as are installed on our other bars).

Explorered and ruled out by whom? By someone well acquainted with what's available on the market, and experienced in a variety of installations? Without seeing the room obviously I know nothing about your particular problems. Why would pulleys necessarily have to be 'above the ceiling'?

 

I've also spotted these things, which would avoid the needs for chain bags and working at height. I could see these being a possibility - does anyone know of a reputable UK supplier of a similar item? I couldn't see my suggestion of ordering from the far east being an especially popular one.

Haha - someone other than the reputable firm more or less on your doorstep who were glowingly recommended two posts back you mean?

 

It doesn't really matter where you get them, they're still going to be pretty crappy. If you have the headroom to sacrifice (60cm may not be enough), they may be acceptable - if you're going to use them merely to lift the bar into position and then immediately transfer it onto a dead hang. Bear in mind also that any 'lifting machine' you employ will need a thorough examination in accordance with LOLER every 12 months (at a minimum) - for relatively cheap crappy hoists it may be cheaper to replace them with new ones annually. (For really cheap crappy hoists you may find it impossible to find anyone willing to certify them anyway.)