Advise on different platform plans

heuler

Member
So my friend and I are in charge to build a platform for a show our sports group is going to do in November (we are part of a circus for children and teenagers) and until this point we have two different plans and I was hoping to get some critique and advise on them.
But first the specifications we have to follow:
- the complete structure should be as steady as possible (obviously)
- it should be strong enough to hold about 300kg (about 660 lbs) (which will be moving)
- It should be movable, on little dollies or at best light enough to carry
- I has to be demountable, so it can be stored pretty easily, and put together and taken apart quite fast and easy.
- The dimensions should be 1,2m * 1,5 m * 4m (47,2inch * 59 inches * 13 feet)

So for my plan (lets call it plan H), it already was improved some times with the help and advise by people from reddit and imgur. If you're interested here are some links on the 'history' of plan H:
http://imgur.com/a/g0GW8
http://imgur.com/gallery/yzdEzfU (the left one obviously)

So now for the actual plan, I made some screenshots of the SketchUp plans, I hope they are enough to explain the structure. All the beams are 6cm*8cm (2 1/3 inch * 3,15 inch)

I tried doing this with integrated pictures, but it didn't work the way I wanted so here's the Imgur link:
http://imgur.com/gallery/iVWEu

On both models the top 'board' would be several sheets of OSB held in place by dowels in the beam structure.

Both plans have their advantages and disadvantages but I wanted to hear your opinion and advise.

Thank you in advance
 
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So my friend and I are in charge to build a platform for a show our sports group is going to do in November (we are part of a circus for children and teenagers) and until this point we have two different plans and I was hoping to get some critique and advise on them.
But first the specifications we have to follow:
- the complete structure should be as steady as possible (obviously)
- it should be strong enough to hold about 300kg (about 660 lbs) (which will be moving)
- It should be movable, on little dollies or at best light enough to carry
- I has to be demountable, so it can be stored pretty easily, and put together and taken apart quite fast and easy.
- The dimensions should be 1,2m * 1,5 m * 4m (47,2inch * 59 inches * 13 feet)

This doesn't sound like a realistic spec to me.

If I understand correctly you're planning a 1.5m by 4m platform 1.2m high with a design load of 300kg. This works out to just over 10 pounds per square foot. This is a very light design load and I wouldn't feel safe advising using such a platform to support people. Most likely a platform designed to support such little weight would deflect enough that the people would be worried about their safety. Your design weight should be about 700kg.

If by movable you mean this is to be a wagon that rolls across a level stage, that can probably be accomplished with appropriate casters (be sure to have appropriate wagon brakes as well), a platform this size would be very difficult to cary (perhaps if you have six people in a coordinated effort?).
 
This doesn't sound like a realistic spec to me.

If I understand correctly you're planning a 1.5m by 4m platform 1.2m high with a design load of 300kg. This works out to just over 10 pounds per square foot. This is a very light design load and I wouldn't feel safe advising using such a platform to support people. Most likely a platform designed to support such little weight would deflect enough that the people would be worried about their safety. Your design weight should be about 700kg.

If by movable you mean this is to be a wagon that rolls across a level stage, that can probably be accomplished with appropriate casters (be sure to have appropriate wagon brakes as well), a platform this size would be very difficult to cary (perhaps if you have six people in a coordinated effort?).
By movable I only mean that there are basically some spots where you can put dollies under the structure, when it is lifted, to move it to the side of the stage.

So if I understand you right you are consearned that the structure itself is to light and would slip or even tip, when there is some kind of horizontal force applied?
 
I can't see imgur since I'm at work at the moment, but from what I'm thinking we might have built something in the neighborhood of what you're trying to pull off. It amounts to a movable 4'x16' platform that was 3' high and on casters for a recent production of Pirates of Penzance. It was the boat that had to support the weight of 7 or 8 pirates and be pushed back and forth across a stage by 5-6 stagehands. I castered a few stock platforms then built 2' stud walls around the perimeter and a few horizontal ones spaced about every 6'. I set two straight casters to allow it to steer as the hands pushed it on stage (mostly so it didn't just drift upstage) and it moved like a champ. The studwalls were topped with stock platforms made from 2x4 and 3/4" ply and 24" joists made for a very sturdy deck. I'll try and upload some pictures when I get home.

The studwalls come apart pretty easy and it all breaks down into platforms and studwalls at the end. It's easy to skin or decorate to suit your project and the load rating on the studwall is way over what you had in mind. From what I've been told, oriented strand board is usable as platform material, but you have to be careful with the thickness when calculating your load rating. That being said, I've only ever used 3/4" sheathing plywood for decking material so I can't say much about OSB et al.
 
Holy crap on a cracker! Is that book really worth $680.00 or $860.00?!

No way. I just bought myself a copy back in March for $18.95. There's no way it jumped 45 times its value in 3 months.
 
Really weird, I bought a copy in March from Amazon and it was $16.50!!!
Must be a glitch on Amazon.
 
There are any number of ways to build a platform and I recommend you check out the links others have posted, but before you delve into those I wanted to raise your awareness to certain factors you need to consider when building a platform based on the design you've proposed yourself.

Your design is not optimal for construction with lumber, and is not structurally sound in how it handles the forces acted upon it.

In regards to structural integrity, your design is deficient in that you should have:
+ A horizontal, rectangular frame with that supports your sheet good surface, that either
......a) Rides on top of your legs, and your legs located directly under the pieces for the frame, or
......b) Rides just outside of your legs, which are located internal of the frame, and **bolted** to the frame. (difference here is that you're applying a shear force to your legs rather than a direct downward force, and need to reinforce your leg connections adequately)
+ The frame is ideally not larger than the size your sheet goods are supplied in. If your sheet goods available are 4'x8' and you need a 4'x12' platform, it's easiest to build (2) 4'x6' platforms or a 4'x8' and 4'x4', and bolt the two together.

The way your design is drawn, the primary force of the load is supported only on the legs. The horizontal braces between the legs are not structural and not designed to support a load upon them from above. As someone steps onto the deck above those braces, rather that diverting the load directly onto the legs, the load is transferred through the brace and the the fasteners holding the brace into the legs as a shear force. Also -- forget the angle brackets. Those are not intended to support a load and if you load them like they're shown, they'll either shear through your fasteners affixing them to the frame or they'll give out under the load and bend out of an L-shape into a "We should be calling 911, and then our lawyers" shape.

In regards to lumber construction:
+ Unless you're well-versed in making keyed joints like a professional carpenter would, avoid joints on legs where you have, at the same height on the leg, braces attached on multiple sides of the leg. In your corners, for example, you horizontal braces shown at the same height going down one length of the deck and down the other length of the deck. You cannot these connections with bolts, screws, or nails. That many penetrations into the legs at one point, especially criss-crossing, will make the wood susceptible to splitting, especially when people get rocking back and forth on the platform.

As for the whole saw-horse zig-zag thing -- don't even bother. A simple, rectangular frame, surface on top, legs below, and some horizontal-bracing at the bottoms of the legs is sturdier and much easier to build.

Don't base whatever you build based on my off-the-cuff remarks here though. Look at design options offered in the threads that have been linked to or, my personal favorite, that Stock Scenery book, and building your platform using plans someone else has already worked the kinks out of. From the designs you've proposed, I can gather you don't have the carpentry experience nor a big enough insurance policy for liability to wing this.
 
I contacted Broadway Press and there is a new edition coming out soon.
"Thanks for your inquiry about STOCK SCENERY CONSTRUCTION HANDBOOK. We are currently out of copies of the 2nd edition and are hard at work on the new 3rd edition. It should be ready for sale in 6-8 weeks."
 
Don't theatres have, or don't people know how to build, a set of parallels any more??

I'm afraid I'm not familiar with that term. As it doesn't show up underlined, would you mind defining it for our wiki?
 
Don't theatres have, or don't people know how to build, a set of parallels any more??

I'm afraid I'm not familiar with that term. As it doesn't show up underlined, would you mind defining it for our wiki?
Wiki will only auto-link the singular case, not the plural: http://www.controlbooth.com/wiki/?title=Parallels-scenery .

But to answer @JonCarter's question: No, Mr. Carter. In thirty-nine years of my theatrical career, I've never seen either type of parallels, scenery in use. (Unless one counts that light-duty version suitable only for trade shows where the X-legs deploy like a pop-up camping tent:
proxy.php
.)
 
Wiki will only auto-link the singular case, not the plural: http://www.controlbooth.com/wiki/?title=Parallels-scenery .

But to answer @JonCarter's question: No, Mr. Carter. In thirty-nine years of my theatrical career, I've never seen either type of parallels, scenery in use. (Unless one counts that light-duty version suitable only for trade shows where the X-legs deploy like a pop-up camping tent:
)

Just to make Derek feel young, I have, in my 46 years of experience seen them used. Three times.

Once in graduate school where I learned to hate them. (42 years ago )
Once ( kind of ) at the Asolo theatre where all platforms were built in the style of parallels, ( but max size was 3'6"" x 7 ') and nailed together. Very light weight. Very sturdy. ( 41 years ago )
Once in a theatre festival where a touring group used them because they would fold up small for their truck. ( 8 years ago )

That said, properly made they can solve some very tricky problems. They are light weight, sturdy, and fold up to be small.

On the other hand they are tricky to build correctly, take more time to construct, and are not as flexible as other styles.
 
I've built parallels, both of the traditional variety and ones that were essentially a studwall legging system, with the studwalls hinged together ala parallels. In situations where ease of setup and size of storage are important (like touring) they can be very useful. I'd guess these days, most people would just go steel in those circumstances.
 
Oh so THATS what those are called. I think I've seen one or two examples of those hanging around dusty high school auditoriums, but I've never built or used one .
 

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