Installs Suspending Line Arrays w/ Genie Super Towers

[MNicolai]

I got the numbers back from the rigging contractors on this project and it's really quite expensive to include the weight of line arrays on the lift lines for the truss. The use of line arrays may represent only one or two percent of the use of the venue in a given year. As such, I want to remove (2400) lbs of the safe working load (SWL) from the truss and knock it down to just the (1500) lbs for the lighting.

Doing that gives me a few different options. We can work out something with a structural engineer to make certain we can suspend line arrays from the roof structure that does not influence the SWL of the lighting truss, or we can suspend line arrays from a Super Tower (or equivalent). I'm about to contact a couple lift distributors to talk to them about the costs of renting or purchasing Super Towers. Really, it doesn't even make a lot of sense for us to own Super Towers if we'd only use them a few times a year. I worked a concert a couple weeks ago that even carried two Super Lifts in their truck for any venues they went to that didn't have locations to rig line arrays from.

So Super Towers? Are they any good? Are there any problems that we'd run into if we wanted to suspend line arrays from them? Are there reasons groups might not want us to suspend their arrays from these?

 

[Footer]

They have a rather large footprint from what I remember. Its a back pocket thing IMO. If you are going to be renting the array, adding the towers will be a drop in the bucket. I would have them point in a few points in your ceiling and walk away.

 

[MNicolai]

Ideally we could have get the points setup after we talk to the structural engineer, but the problem is that the location is directly above our orchestra pit covers. That means we can't drive a scissor lift over it because it weighs too much. Although, if we purchase a good one-man lift we can get high enough to hook the chains up each time.

I hadn't thought of that until now. I've done that a couple times on this project. I design around us not having a one-man lift, but it's gotten to the point I think it's just so much cheaper to buy the one man lift. We did truss because you could focus without needing a lift. I was thinking about not being able to have permanent points for chain hoists installed because we don't have a one-man lift to get to the points with. All in all, I'm just going to cut a lot of the crap out and include the cost of the lift in the project.

 

[mstaylor]

If you can make them hangable it is always better. A Supertower is a good lift but only rated for 600lbs so you have to think how big an array you want to hang. Also they do have a large footprint, as mentioned, and if you are putting them in the pit you have to make sure you have room to put them where they need to be but aren't hitting steps or pit walls.
I have used this method many times, you just have to make sure you have room.

 

[TimmyP1955]

This might be a good reason to review whether a line array is truly the right rig for the room. There may be a trap system that's as well or better suited that would cut the weight way down and allow you to stick with using the truss (Danley comes to mind).

 

[themuzicman]

A few outdoor gigs I worked used Super Tower's to raise our line arrays, from what I remember about using them was that the footprint was rather big, so 2 of our 4 arrays ended up being attached to the frame of the building and the other 2 were on super towers.

The super towers were great though, 1 operator, got the speakers off the truck, attached, and up in about 20 minutes! Load out was just as easy.

 

[MNicolai]

This might be a good reason to review whether a line array is truly the right rig for the room. There may be a trap system that's as well or better suited that would cut the weight way down and allow you to stick with using the truss (Danley comes to mind).

We already have a house system that's not a line array. As a roadhouse though, we want to make certain we have the ability to hang arrays when groups come in, either from the roof structure or from towers.

I'm trying to arrange getting rigging points setup that arrays can be flown from via hoists, but we'd need to use a lift to hook the chains to them. Our apron where these would be flown above is primarily a Wenger orchestra pit cover system, and even the part that's concrete is actually a concrete overhang that the orchestra pit is below. So the apron is basically a big shelf. If we can't use a lift because they're too heavy on those structures, we'd be screwed -- probably either way.

A one-man 40' lift would be required to rig the chains to the roof structure, or we would need to use Super Towers (or equvialents) to suspend arrays from, which would then also concentrate lots of weight onto our apron floor. So before we can proceed with anything, I need to get a structural engineer to tell us how much the concrete shelf can support, and Wenger to give us an idea how much their pit covers can support.

 

[Footer]

If you guys did not want to buy a lift, it might be cheaper to hang 4 motors "motor up". Not the best solution, but... there it is.

I would still move towards the installing the points and buying the lift... but its an option. You would have to take into account installing a controller in the building and all that fun stuff. It would cut down on labor later on if thats a concern. It might also give you some additional options in lighting world or something like that.

 

[BillESC]

I agree, if the points are available, motor up eliminates most if not all of your problems.

 

[fx120]

At my company we have a total of 8 super towers in our inventory that we have been using for about 15 years now and they're still going strong.
There are several problems with hanging arrays off of super towers, the main one being that the forks aren't long enough to support really wide arrays, so anything bigger than the "compact" arrays are out. Trim height and working load are also quite limiting, at only 24' and 600lbs respectively.

The large footprint isn't so much of an issue for us because we mainly use them outdoors or in exhibition halls where flat floorspace isn't hard to come by, but there are no available permanent points. But in a theater I could see it being much more of an issue.

I think in the long run you're going to miss having permanent points, even if they're not part of the lighting truss.

 

[mstaylor]

Since you don't have anything hung yet, it may not be that expensive to add the two points if there is something to hang from. How much difference in cost was there between the 1500lbs and the 2400lbs. Also did it change the truss length? Did both plans qoute 1 tons or were they going down to a 1/2 ton with the less weight? What was the length and size of the truss?

 

[MNicolai]

Since you don't have anything hung yet, it may not be that expensive to add the two points if there is something to hang from. How much difference in cost was there between the 1500lbs and the 2400lbs. Also did it change the truss length? Did both plans qoute 1 tons or were they going down to a 1/2 ton with the less weight? What was the length and size of the truss?

The original quote for $66k for a motorized line shaft winch suspending box truss, 40' long, with a black powder coat and connector strips, capable of supporting 1500lbs for lighting & 2400lbs for line arrays.

I've since reaffirmed with the contractors that we need the entire thing to be 60' long and will not need to have it support the additional 2400lbs for audio. We will talk to the structural engineer about finding a way to rig line arrays without using this lighting position.

Our problem remains that we are unable to confirm yet whether or not we can put even a one-man Genie lift on our pit covers and apron (which is a concrete overhanging shelf with a cavity below it for the pit area), which will determine whether or not we have to use truss. I'd prefer to use tri-battens, which I imagine is cheaper than truss to begin with, but we will have to use truss if we cannot use a lift on the apron because with truss we can put a person on top of it in a harness to focus the lighting, but with tri-battens we would need to have a lift.

The other complication is being able to access the rigging points for the line arrays -- if we cannot use a lift, we probably need to permanently install chain hoists up there such that we don't need to really have access to the rigging points once they're installed.

 

[mstaylor]

I don't want to get too far into rigging specs but 2400lbs for linearrays seems heavy unless you are using that as both arrays. Also, I would assume that the 60ft truss will have to be three points at least.

 

[MNicolai]

The rating on the truss would have to incorporate both arrays, whereas the individual rigging points would only have to support the individual loads. Based on similar sized roadhouses in the area that have had to suspend arrays, as well as from talking to a couple rental houses, we determined 1000lbs to be an adequate load capacity for each array in our venue. An additional 200lbs was added to each side for some additional headroom.

The 40' of truss that was quoted would've included a 5-lift line motorized line shaft winch. I suspect when the numbers are crunched for a 60' span, but with the lighter load capacity, it'll either be three chain hoists or a line shaft winch with seven lift lines. I'm guesstimating though, I leave the number crunching up to the rigging contractors.

 

[MNicolai]

I had a realization tonight! As many great ideas come to me, I was having a late night think tank session around 2am at a 24h coffee/breakfast place with a friend of mine. She's a student at the high school I've graduated from and I've taught her much of what she knows. So as I've often done, I was explaining my obstacle in this project: To have someone crawling around on a 20.5" box truss 40' in the air regularly to focus lights or to put a Genie one-man lift on pit fillers and hope they don't collapse.

As it turns out, our pit fillers are rated for 500lb point loads on 2" casters. The one-man AWP-40S lift weighs 1050lbs, plus for argument's sake, we'll say the operator is 150lbs plus another 50lbs for in the bucket for tieline, tools, gel frames, and maybe a light fixture in some circumstances. That puts 1250lbs in a relatively small footprint. So small, my email to Wenger Corp asking them if the pit fillers we bought from them was more hopeful than realistic.

So I'm sitting here at coffee with my friend describing my dilemma. She's smart enough to understand what I'm saying, but when I get into the more logistical parts of the rigging, I start to explain more in-depth what the different options are. When I decide it's too complicated to explain, I whip out a small memo book with grid paper in it and start making diagrams and drawings. It reached the point where the least painful (except for the cost) solution looked like purchasing a boom lift, which is outrageously expensive and otherwise overkill for focusing lights every few days and hanging speakers a couple times a year. About four or five concept drawings in of the different options and equipment involved, it dawned on me: I might be able to beat the system by tossing the lift on an Super-Straddle to give it a wider footprint.

I crunched the numbers on my napkin sketch of this idea and each point of the load would come in at 463.75lbs! I still need to verify with Wenger Corp that the footprint on the Super-Straddle would be wide enough to be safe, but I admittedly feel like I may have stumbled upon a solution that actually is quite crazy but might just work.

If this works, we won't have to train staff members to walk truss and will have a lighting position we can access easily for focus, and we'd also be able to easily access the rigging points for the line arrays.

The bonus is that I was already factoring in the cost of purchasing the Super-Straddle anyways (which right now we have to rent annually to replace our house lights), so I have my fingers crossed while I wait for Wenger Corp to call me back.

 

[mstaylor]

The Super Strandle looks it might be an advantage for you. The other thing to consider is, will the Stradle put you where you could have two legs on the floor outside the pit footprint? This would cut the weight on your covers in half.

 

[Footer]

What is the PSF that your cover can support? Has Wegner officially said that your covers can not support a lift, and if so, what lift?

If it can support a 500 PSF you should be fine. The footprint of a lift is at least 6sq ft. I don't think a straddle is the perfect option. I am always thinking of the guy who does not know the rules and pushes the lift out on the pit to run a focus. It could happen.

I would also think that overall, it might just be cheaper to re-enforce the pit covers themselves to increase the PSF rating. If you have the versa-light pit system they should be able to do that.

 

[MNicolai]

What is the PSF that your cover can support? Has Wegner officially said that your covers can not support a lift, and if so, what lift?

If it can support a 500 PSF you should be fine. The footprint of a lift is at least 6sq ft. I don't think a straddle is the perfect option. I am always thinking of the guy who does not know the rules and pushes the lift out on the pit to run a focus. It could happen.

I would also think that overall, it might just be cheaper to re-enforce the pit covers themselves to increase the PSF rating. If you have the versa-light pit system they should be able to do that.

Today was actually my lucky day. I showed up this morning and there was my lift. An AWP-40S in a Super-Straddle. Turns out today was the day they were renting it to replace all of the house lights. The electrician and I crunched numbers and looked for more info on the Wenger Strata pit fillers. I went back and reread the spec sheets on those. The details are worded a little funny. It doesn't actually say that it's got a load capacity, just that they can support loads of up to 500lbs on a 2" caster without leaving permanent marks.

Push came to shove and we had lights directly above the apron so we pushed it out over the pit fillers without the Straddle and the floor didn't collapse. I'm still going to track down more specific info on the platforms, but it doesn't sound like there should be any problems.

That said, a one-man lift and tri-battens it is. No need to screw around with fall arrest and truss walking.

 

[museav]

I would say that planning on only a 150lbs. person would be a bit wishful thinking for some of us. Since it would be within the ability of the lift, you might have to base the potential load to be supported on the rated capacity of the lift rather than on some assumed lesser load.

Maybe I'm envisioning this wrong but while distributing the load over a larger area may be beneficial, wouldn't using a Super Straddle still involve four points? The points may be in different locations but they would still seem to represent four point loads at the casters rather than a distributed load. In fact it seems like this might actually increase the point loads due to adding the Super Straddle's own weight. Thus I'm not clear how that would help. What might help would be to have the casters or entire lift sit on a very stiff and strong plate that did help distribute the load over a larger surface area.

Also, consider that the lift will be moving, thus introducing dynamic factors that increase the load actually applied to the supporting surface beyond just the static load.

 

[MNicolai]

I would say that planning on only a 150lbs. person would be a bit wishful thinking for some of us. Since it would be within the ability of the lift, you might have to base the potential load to be supported on the rated capacity of the lift rather than on some assumed lesser load.

Maybe I'm envisioning this wrong but while distributing the load over a larger area may be beneficial, wouldn't using a Super Straddle still involve four points? The points may be in different locations but they would still seem to represent four point loads at the casters rather than a distributed load. In fact it seems like this might actually increase the point loads due to adding the Super Straddle's own weight. Thus I'm not clear how that would help. What might help would be to have the casters or entire lift sit on a very stiff and strong plate that did help distribute the load over a larger surface area.

Also, consider that the lift will be moving, thus introducing dynamic factors that increase the load actually applied to the supporting surface beyond just the static load.

Though the weight of the Super Straddle frame would increase the total weight, the weight would be diffused across a larger area. The point loads on each caster would also increase, but again, the idea is that on the pit fillers, each rubber wheel would be on its own panel of the pit fillers, which would distribute the individual point loads across more of the truss work underneath the fillers.

The electrician and I talked ourselves in circles about this for awhile.

[potentially faulty logic]Because if the 500lbs is a point load rating based on casters, they must have assumed at least four casters. Also, the wording of their spec is ambiguous. It says the panels can sustain a point load of 500lbs on 2" casters without permanent marking. With that in mind, we looked at the stats on the Genie lift, which without the Straddle frame, had a sticker on it designating that each wheel was a point load of only 400lbs, and with rubber wheels, we weren't concerned about permanent marking or marring. [/potentially faulty logic]

Wenger Corp has been closed all week for the holidays, but next week they should get back to me with an official yea or nay on the lift. Meanwhile, our building and grounds supervisor was locked away in his office digging through catalogs, spec sheets, structural notes and interior detail plans for the building, and managed to find nothing beyond the generalized statement we were told at owner turnover, which was "Whatever you do, don't drive a scissor lift out on the apron." Scissor lifts weigh a lot more than this one-man.

As I recall from Wenger Corp though, those panels are supposed to at least be able to sustain the weight of a concert grand piano. I have not a doubt in my mind our concert grand weighs more than that AWP-40S.

The electrician got fed up with all of the uncertainty. He was already pretty peeved that they rented the one-man and the Straddle to change all of the house lights with. He said next time he's just going to rent an articulating boom lift himself and spare the entire day's labor for the half a dozen guys that had to push him around all day. That would also forgo having to even be on the apron at all with a lift. I imagine it's also a lot safer to work in because the odds of a one-man tipping over (even with the outriggers) are a lot more than of one of those articulating boom lifts.