Mounting lasers on stage

[Adrian Cavaleru]

Hi Dan, the first of those two looks incredibly flimsy. You need something much more substantial.

I have two truss clamp positions on my RGB that I use where possible, but also use a tripod when it's the best option (bearing in mind what Steve said about vibration and movement; I would only use the tripod on a solid concrete stage).

I think Carl B uses the mounting method that you described but I have installed the top hat mount in to the chassis of the projector, and from memory your toblerone has an extremely solid frame so maybe that's an option?

both may be good.
I should think about a way to rig the projector on that stand.

[buffo]

This is one reason why it's a *very* good idea to introduce yourself on the forum and tell us a bit about yourself, your experience with lasers and the general area where you live. By doing that we can then pitch answers that are meaningful to your particular situation without being condescending.

Well put, Jeremy. Yet so many new users omit this crucial step. (And worse, they then get testy if we assume that they know less than they actually do!) Here's a tip to all new members: FILL OUT YOUR PROFILE INFORMATION! Most people will check that first before replying to a new member. If you don't give us anything to go by, we will assume the worst.

Incidentally, I saw Jean-Michel Jarre this year, who seemed quite happy to stand in a static scanned white fan for some period of time and I'm guessing his lasers were 3W or above so what gives there?

Did you miss the post by MixedGas where he explained that trained crew members can be exempted from the rules if proper safeguards are in place and they've signed a wavier?

Considering that Jean-Michael Jarre's entire act consists of him interacting with his laser harp, it's pretty clear that he qualifies as a "trained crew member".

I also want an answer to my question

Doc's solution sounds reasonable. I've used tripods with that sort of mount before with no problems. But if you're dead-set against tripods, then what about Mliptack's suggestion?

And worst case, if you absolutely need them on the floor, then why not build a wedge-shaped wooden box with an angled top that you can set the projector on/in?

Adam

[smokeAndMirrors]

Well put, Jeremy. Yet so many new users omit this crucial step. (And worse, they then get testy if we assume that they know less than they actually do!) Here's a tip to all new members: FILL OUT YOUR PROFILE INFORMATION! Most people will check that first before replying to a new member. If you don't give us anything to go by, we will assume the worst.

Fair enough.

Did you miss the post by MixedGas where he explained that trained crew members can be exempted from the rules if proper safeguards are in place and they've signed a wavier?

Yes, but a laser rated at more than 1W firing a relatively narrow beam is going to cause skin damage irrespective of whether anyone's signed a waiver or not (heck the HS(G)95 says .5W will cause problems).

Considering that Jean-Michael Jarre's entire act consists of him interacting with his laser harp, it's pretty clear that he qualifies as a "trained crew member".

He wears gloves for the laser harp. I'm referring to the show intro:


Doc's solution sounds reasonable. I've used tripods with that sort of mount before with no problems. But if you're dead-set against tripods, then what about Mliptack's suggestion?

And worst case, if you absolutely need them on the floor, then why not build a wedge-shaped wooden box with an angled top that you can set the projector on/in?

Adam[/QUOTE]

[Doc]

I believe by "relatively narrow beam" they are refering to pencil beams.

That is a pretty wide fan in that shot, the energy density in such a fan is unlikely to cause skin burns, even with 5W+ though I wouldn't recomend on axis viewing.

[buffo]

Yes, but a laser rated at more than 1W firing a relatively narrow beam is going to cause skin damage irrespective of whether anyone's signed a waiver or not (heck the HS(G)95 says .5W will cause problems).

The half-watt threshold for skin damage is for a static beam. The picture you posted of the show's intro is a wide fan. Scanned patterns are completely different. As Doc already mentioned, in that instance you wouldn't need to worry about skin damage even with 5 watts of power.

Adam

[Jem]

I was also at the JMJ gig, as were quite a few others on this forum. What I can tell you is that the show was done by Hugo Bunk, a very well established and well respected laserist. I can also tell you that the lasers used were multi-watt OPSL with remote fiber optic fed scan heads.

I can also tell you that the person responsible for laser safety on the entire UK JMJ tour was James Stewart of LaserVisuals, who incidentally is also a member of this forum (even though he doesn't post very often). I can also tell you that James is an incredibly well respected person with vast amounts of experience. He is absolutely, unquestionably, categorically as straight as a die and does everything exactly to the rules. For instance, if you went to the London JMJ gig you would have experienced audience scanning. However, if you were at Manchester you would have noticed the distinct lack of audience scanning. This is because it was deemed unsafe in that particular venue as the safety criteria could not be met.

I therefore have no doubt in my mind that the JMJ lasers were absolutely safe

Incidentally, LaserVisuals run safety courses from time to time... Well worth the money for the experience gained.

Jem

[smokeAndMirrors]

Jem, I wasn't implying that the show was unsafe. I was asking for an explanation of why it was safe. Please don't be so aggressive.

As for the Wembley Arena shows, there was no scanning that I was aware of, it was all 15ft above my head, but that could be just where our seats were... Jarre says this on his blog:

"Finally the concert in Oslo started sounding and looking close to my expectations. There is something special with this venue, the audience (who was really great that night, many thanks to them) is really close to the stage, and it gives a feeling of proximity quite unique. In addition you don't have these far too strict regulations like in Sweden for lasers, so the audience could be truly immersed in the waves of light."

so they were clearly scanning at some venues.

[mixedgas]

How is J.C.OH these days. I thought he just did theoretical and enjoyed shows. Didnt know he popped in doing inspections.......
Met him a ILDA and LFX a few times, great guy.
Steve

[Jem]

Jem, I wasn't implying that the show was unsafe. I was asking for an explanation of why it was safe. Please don't be so aggressive.

Aggressive

I've just re-read my post and I don't think it was aggressive. Succinct, informative and to the point perhaps, but aggressive?, nah.

As to why it was safe...

Well, every aspect of the show was carefully risk assessed, measured, MPE's measured, considered, and finally when all safety criteria had been met it was passed off as safe for public viewing... and as safe for the performers.

Jem

[smokeAndMirrors]

Aggressive
I've just re-read my post and I don't think it was aggressive. Succinct, informative and to the point perhaps, but aggressive?, nah.

There was - to me - clear implication that I was alleging unsafe procedure. "I can tell you..." repeated several times, and allusions to slights on the reputations of individuals involved. Or you were simply name-dropping to impress me And yes, I'm impressed!

As to why it was safe...

Well, every aspect of the show was carefully risk assessed, measured, MPE's measured, considered, and finally when all safety criteria had been met it was passed off as safe for public viewing... and as safe for the performers.

Jem

That's a legal answer, not a technical one. Specifically I wanted to know how it was safe to stand in a fan from a powerful laser. From LaserSafe, a fan has higher energy density than any other scan pattern (all other things being equal). If you'd said "the distance to the emitter and the scan angle sufficiently attenuate the radiation" you'd have answered my question. Your actual answer was pretty much "it just was, ok?".