rigging (UK lantern clamps)

[LDash]

At the weekend i was doing a show were we had to hire in some generics. these didn't come with the hook clamps attached. so me and my other lighting guy were debating on how the bolts should be attached to the hook clamp and the yoke. whether the wing nut should be facing up or facing down and which order the washers should go?

any help would be much appreciated

[Footer]

What kind of clamp did you have?



Or...



You should never use a wingnut to secure a yoke to the clamp. The only wingnut, if one at all, should be on a cheesebourough style clamp pictured above. Also, you always want a washer separating any nut from the piece you are tightening to. Same thing goes for the bolt on the other side.

[gafftaper]

Are you in the UK or Oz?

I'm wondering if you use a different type of clamp than we do here in the states?

[LDash]

in fact it was neither of those it was one of these...

Hook clamps for TV, film & theatre stages | Doughty Engineering

thanks Footer, but I'm sure you can use a wing nut all the theaters i have worked in have used them.

[LDash]

Are you in the UK or Oz?

I'm wondering if you use a different type of clamp than we do here in the states?

ya i am in the UK. hm i didn't think of that when posting

there isn't any UK techie sites as good as this one though unfortunately

[Footer]

Still don't like the idea of a wingnut being use to hold a load. Its one thing for it to hold a clamp closed, but another to hold a load. If they are selling it with the nut, fine, but don't substitute.

With that type of clamp, you always want the bolt head to stay with the clamp and the nut to connect the yoke to the clamp. Otherwise, you won't be able to get the clamp onto some pipes.

[gafftaper]

I was suspicious you were using something like that. We don't use those types of clamps here in the U.S. the picture above of the cast iron Altman clamp is our standard here. Those UK clamps seem way to flimsy to me. They look like they would not hold the fixture firmly in place and would be easily bent or wiggle. Is that true?

[LDash]

I was suspicious you were using something like that. We don't use those types of clamps here in the U.S. the picture above of the cast iron Altman clamp is our standard here. Those UK clamps seem way to flimsy to me. They look like they would not hold the fixture firmly in place and would be easily bent or wiggle. Is that true?

no they are extremely durable . these are our standard clamps. they are used for generic lanterns(Fresnel's,profiles,etc.) for moving fixtures we use clamps more like your standard ones.

[Footer]

I was suspicious you were using something like that. We don't use those types of clamps here in the U.S. the picture above of the cast iron Altman clamp is our standard here. Those UK clamps seem way to flimsy to me. They look like they would not hold the fixture firmly in place and would be easily bent or wiggle. Is that true?

You occasionally see those type of clamps on cheap DJ stuff. I would not hang anything overhead with them. Doughty does make some great stuff, this clamp is by far my favorite clamp ever made...

[LDash]

i have to say, i have never ever seen those before. and i wouldn't say those looked to sturdy :S

[derekleffew]

LDash, the most common method, from what I've seen, is wing nut on the bottom, under the yoke. This makes it slightly easier to adjust the pan of the lantern.

GELS FRAMES BARN DOORS CLAMPS

If it's a short yoke, and the rear of the lantern could hit the wing nut, it's not unheard of to put it the other way 'round.


http://www.theprolightingshop.co.nz/...roducts_id=109

Americans are leery of the "G-Clamp" or Hook Clamp, usually more out of unfamiliarity than any other reason. I've hung heaps of Vari-lites and PARbars with similar hangers without incident, but they are problematic when the unit is not desired to hang straight down under the bar. I recently worked a tour where all the MLs had hook clamps attached to the Omega brackets--probably the fastest clamp in existence.

See also this post: http://www.controlbooth.com/forums/l...html#post77295.

[kiwitechgirl]

there isn't any UK techie sites as good as this one though unfortunately

Check out Blue Room technical forum (Powered by Invision Power Board) - I'm fairly sure I'm not the only person here who frequents that forum as well!

Back to the hookclamp (G-clamp) debate; they're standard in New Zealand as well as the UK, much more so than the Altman clamps. They usually come with a SWL stamp of 50kg - at least all ours do - and they don't bend at all easily and you can lock them off very securely. If you hire a Mac250 down this end of the world, it'll generally come with two hookclamps to suspend it by (although the bigger moving units will have cheeseboroughs or half-couplers usually) - and I've never seen one fail, nor even heard a story of one failing. The thing that I like about them is that once one is on the bar, it can't slide off like an Altman can - whenever I'm rigging something with an Altman, I'm always (probably through unfamiliarity!) worried that before I've tightened it up, it'll slip off the bar....not that it's ever happened to me! To answer the original poster's question, we tend to run bolthead, washer, yoke, washer, clamp, washer, spring washer, wingnut. Occasionally on the heavier generics (big profiles mostly) we'll use an M12 bolt with a regular nut, but all the rest are M10 bolts with wingnut. We do buy bolts of the right length to do this though, so that you can get the clamp over the bar - occasionally some of our units still have old bolts in them which are too long and so then we turn them up the other way - or just loosen the nut off a bit, get the clamp on the bar and then tighten it up again!

[Footer]

Do you torque the thumbscrew down with a wrench or just finger tight?

[kiwitechgirl]

Our clamps are slightly different - rather than a thumbscrew they have one of those three-cornered knobs that you can get your whole hand around - like this

You can get them done up pretty tight just by hand - occasionally we get one which some gorilla has done up which us normal humans can't undo; there are a couple in our rig at the moment, but periodically we get the angle grinder out and cut them off....I spent a couple of years working in Britain where the thumbscrew type is more common and we just used to do them up finger tight. Anything rigged on more than about a 30 degree angle and we'd switch out the clamp for a halfcoupler.

[Sean]

Americans are leery of the "G-Clamp" or Hook Clamp, usually more out of unfamiliarity than any other reason. I've hung heaps of Vari-lites and PARbars with similar hangers without incident, but they are problematic when the unit is not desired to hang straight down under the bar. I recently worked a tour where all the MLs had hook clamps attached to the Omega brackets--probably the fastest clamp in existence.

See also this post: http://www.controlbooth.com/forums/l...html#post77295.

To reiterate what Derek said above, _Americans_ are the odd ones. We're the ones that are stuck on using heavy cast clamps. The clamps we use are subject to stress fractures, and often without a rating. From an engineering perspective, they are certainly inferior.

I'll be the first to admit I'm not a fan of using/handling mega-clamps, but they are better than cast clamps.

Just sayin'....


--Sean

[church]

I remember the UK clamps they are made out of 5/16 inch thick approximately 1.5 inches wide rolled steel bar (originally invented by Strand I think) if I remember correctly which is more than capable of carrying the load of a stage fixture. The nice thing about the design is that the hook part is actually long enough that when you are hanging the fixture it won't slip of the pipe. The wing nut alows you to tighten these things about as tight as you need to go. I must admit I prefer the use of a European steel clamp to a cast clamp which may have been stressed and now has a fracture in it just waiting to break.

these clamps are very different to the DJ type clamps you see on this side of the Atlantic.

[ship]

Overall US verses Euro type clamps are mostly similar for the most part in if you over tighten them they will bend. Lots of clamps out there and one cannot say one is really less prone to gorilla factor problems than another. A few above examples are for square tubing clamping which is problematic in clamping to a round pipe.

After that, bend a bent steel clamp if 5/16" stock say 1.1/2" wide size verses bending a C-Clamp of normal Altmant not HD type..., think a wash in problems or those applying over the intended use of the clamp.

Lots of clamps out there, some good, a few bad, a few of all failed.

[derekleffew]

...A few above examples are for square tubing clamping which is problematic in clamping to a round pipe. ...

I see no clamps pictured which are "for square tubing clamping which is problematic in clamping to a round pipe." Some may work on either round or square tube, but all are stated by the manufacturer/vendor "FOR ATTACHING LIGHTING FIXTURES TO A TUBE/POLE UP TO 50mm."

[Raktor]

Our clamps are slightly different - rather than a thumbscrew they have one of those three-cornered knobs that you can get your whole hand around - like this

You can get them done up pretty tight just by hand - occasionally we get one which some gorilla has done up which us normal humans can't undo; there are a couple in our rig at the moment, but periodically we get the angle grinder out and cut them off....I spent a couple of years working in Britain where the thumbscrew type is more common and we just used to do them up finger tight. Anything rigged on more than about a 30 degree angle and we'd switch out the clamp for a halfcoupler.

I'll echo all of this for Australia too.

[gafftaper]

Wow I have a hard time believing those are as strong as my cast iron clamps. The cast iron clamp has teeth that grip the pipe. I don't see how a thumb screw can possibly compete in securing the fixture in place. I'm not trying to start a war here... but I look at them and my brain says, "flimsy, likely to wiggle around, and impossible to properly secure". Could someone who has a substantial amount of experience using both types of clamps compare and contrast. So far the key advantage mentioned is that they won't stress fracture and break. But, although I've heard rumors here on CB of them breaking, I've never seen or hear stories from any friends of a cast iron c-clamp breaking.

Can you safely hang those UK clamps on a vertical pipe?

[kiwitechgirl]

Can you safely hang those UK clamps on a vertical pipe?

Parcans of any size, flood/cyc units and 650w fresnels/PCs, yes. Anything heavier than that, I don't tend to - but I have seen it done. I've never found them to be flimsy and haven't had trouble securing them - as I said, there's also less chance (in my brain, anyway!) of them slipping off the bar if some idiot does fail to do the clamp up properly than there is with a C-clamp. Gafftaper, maybe I should send you one of our clamps so you can try it for yourself! I've not used the C-clamps enough to be able to do a proper comparison - they're so seldom used here, although I think there are a couple kicking round in our tech store for some unknown reason!

[TimMiller]

Based on what yall are saying, the clamps that we get like you have are much more flemsy. I have bent them with my hands, but thats some cheap chinese knockoff. Using a piece of bent steel like that can support a lot of weight. We bend metal all the time at the shop for projects and have never bent anything, except for a CD-80 frame..........

[derekleffew]

...But, although I've heard rumors here on CB of them breaking, I've never seen or hear stories from any friends of a cast iron c-clamp breaking. ...

I'd like to think you consider me a friend (), and I have personally witnessed a cast iron C-clamp break--the result of over-tightening an overhung PAR64 on 1.5" BIP, by an IA stagehand with an 8" adj. wrench.

[Sean]

Oh yeah...

I've not had a clamp fail at a critical moment...yet...but I'm convinced it's just a matter of time. I've seen maybe a dozen or so broken clamps in the past ten years.

Cast clamps are brittle. They're also really not the best kind of hardware to use on booms. Yes, we all do it...but that doesn't mean it's a great choice. Budget allowing, I've been trying to reduce my reliance on cast clamp sidearms. Tees aren't an issue as they see very little force (as compared to their size), but go take a look at your older clamps. I'll bet you see that they're stressed/twisted/stretched a bit.

As for the UK, I know one of the pieces of hardware use as a sidearm is a piece of flat bar with a 90 degree twist. It's clamped the the boom, and the twist allows the fixture to be through-bolted to a hole in the end of the arm.

--Sean

[gafftaper]

So in the end this thread ends up as an ad for those clever people at The Light Source. Heavy duty extruded aircraft grade aluminum. Not bendable like the UK clamps and teeth to grip. Not fragile like the US clamps and most don't have an "F-nut" to break off. I own several of their mega claws, mega drop downs, and mega baby side arms. I Don't own any of their c-clamps but I've seen them in person and they look like excellent products.

I also believe they are the only product that has a safe working load rating. I've seen some cast iron clamps that have 500lbs stamped on the side but I've always been suspicious of the that number.

I'd like to think you consider me a friend (), and I have personally witnessed a cast iron C-clamp break--the result of over-tightening an overhung PAR64 on 1.5" BIP, by an IA stagehand with an 8" adj. wrench.

Well some friend you are. You never told me about it. That's one more vote for my 6" wrench rule.

[kiwitechgirl]

I also believe they are the only product that has a safe working load rating. I've seen some cast iron clamps that have 500lbs stamped on the side but I've always been suspicious of the that number.

All our hook-clamps are stamped with an SWL of 50kg on them...you can probably buy cheap Chinese variants that don't, but get them from any reputable manufacturer and they're rated

[2manydjs]

I'm in belgium and I use this kind of clamp for automated lights



but for par/profile/pc/4-bars I use those ones.

[church]

when I started doing lighting in the U.K back in the seventies the only choices I ever saw for hanging a ficture (lantern) was to use the clamp shown in the pictures made from bent steel or to use a bolt through a hole in a pipe or steel bracket. we hung the Strand Patt 223s and patt 243s using these clamps. After all the clamp was made from thicker steel than the yoke hanging the fixture itself