We need to be able to tilt the playing field against the wall to store it from day to day. We also need to be able to carry the playing field down a single flight of stairs.
We plan on building a field platform in 2 sections. The plan is to weld an aluminum riser frame and put 3/4" OSB on top of it. We will bolt the playing field to the risers. We will have a custom middle side section for the field perimeter so we can split the field in half easily.
I need advice for the construction material, should I use 3"x2"x3/16" aluminum angle ($490)? or 3"x2"x1/8" aluminum rectangular tube ($645)? or 3"x1"x1/8" aluminum rectangular tube ($522)? see sketch below
I’m concerned about the rigidness of the platform while the field is being reset, especially this year with stacks of balls that could roll around. Does anyone have experience building aluminum risers? or good with deflection calculations on a weldment, and could give me some advice?
I don’t have a final plan for leg supports. I will probably have (8) adjustable supports around the perimeter and add additional support in the center if needed.
I’m not sure that you will be able to carry that down the stairs. The aluminum specified in the drawing alone weighs about 250 lbs. On top of that, a single layer (72 sq. ft) of 3/4" OSB is about 180 lbs and you still need to add in the tiles and field perimeter. That comes out to roughly 450 lbs, a 6’x12’x1’ akward “box.” And you would have two of those to carry! Have you checked to make sure that it would fit down the stairs/stairwell as well as clear any corners and doorways that you would need to navigate? I would consider that borderline dangerous to carry down stairs.
As is, the design should be a sufficient with respect to the live loads you would encounter during field reset. Thinner plywood is used as the flooring for scaffolding across wider spans in construction regularly where (if I recall correctly) a safety factor of 4+ is required. I will pull the OSHA reference when I get the book in front of me if you would like.
Is there a need that the finished surface (below tiles) rests at 3.75" above floor? If not, I think you could save some time, money, and weight by simply doubling up on the OBS with no framing. If you laminate two layers together and make sure that the joints do not overlap, you would be perfectly fine design-wise for carrying that down the stairs or leaning it against a wall. Keep in mind though that each section would still weigh around 375 lbs. But you would save a lot of time welding and quite a bit of money. Also, there would be no spans to worry about. You would probably be fine with laminating a layer of 3/4" OBS to something thinner. All the second layer is doing is joining the multiple sheets of OSB together (because they come in 4’x8’ sheets). THis way your finished surface is 1"-1.5" above floor.
If you are adamant in having it raised to some degree, I would suggest looking into framing it with 2x4 pine instead of aluminum. You may need to add some cross-bracing, but you will save weight and money this way without any structural sacrifice. Your finished surface would be 4.25" above floor, if that makes a difference.
My bad on the aluminum weight, I think I accidentally grabed a steel value. Would you mind showing a cross section of the angle you plan to use? I’m not sure if you are talking about a corner bar or some sort of channel.
For the OSHA bit, the requirement is that all plywoods must be manufactured (rated). This means they are general 9 ply instead of 5 or 7 or OSB. However they are general much thinner and have to span 4 to 6 feet. With your studs on rough 16 inch centers you will be fine with 3/4 inch OSB. I would say you could get away with half the studs and probably be fine. I will do some math.
You would definitely need to add some support and bracing if you were going to elevate the field, regardless of if it were pine or aluminum. The wood would likely need more bracing, but at that point you are creating a permanent/semipermanent setup regardless of material choice.
I think 2 layer of 3/8 OSB may be the way to go. If you find it unsatesfactory, a third layer of 3/8 will definitely stiffen it completely. Only downside is the weight of course.
Here are the shapes I’m considering. I’ll pick one of these three. (I’m leaning towards the 3" x 1" x 1/8" wall rectangular tube.) These will be in 6061-T6 aluminum.
I would definitely advise you not to use the first angle without some sort of floor protection.
I can see a herd of our favorite young field re-setters seeing a field that is raised and doing an awesome dare-defying stunt man jump onto it (because what kid doesn’t like jumping onto a 4 inch ledge and Mario ground-pounding the landing) followed by a nails on chalkboard screech as the angles cut into the floor like a scene from A Nightmare on Elm Street.
In a more structural frame of mind, the angle will not handle a shear load on the surface of the field cause by the live load of re-setters getting on and off as well as the square tubes would. In this case it wouldn’t be a problem because it would take a substantial load to fold out 60 linear feet of 3/16" 6061-T6. For 30$ more I would agree that the 3x1 tube is better.
Of course that is assuming that you may use the field without it being raised. Once raised, the angle has no affect on the floor
I found the manufacturer’s spec on the OSB here.
Long story short, with your joists at 16" O/C you could get away with 7/16" thick OSB and still have the capacity for a max live load of 100 PSF and dead load of 10 PSF (pounds per square foot). For reference, areas designated for classroom use are typicaly designed for a live load of 40 PSF and a dead load of 10 PSF. On average, the live load in a classroom setting is really around 13-15 PSF.
With 3/4" OSB you could widen your aluminum out to a spacing of 24" O/C and still retain those performance parameters stated above. If you plan on laminating two thinner sheets together you may want to step down on your spacing to 20" O/C. If properly laminated you shouldn’t lose any structural performance, but it’s better to be safe.
I would not recommend using joists any thinner than 1" thick.
Also, here is a span calculator provided by the American Wood Council. After some fiddling around, it looks like it would be totally possible to build two raised deck sections out of 2x4’s and a few 2x6’s.
I will look into what the weight and cost of something like this would compare to the aluminum.
I also need to look into the load capacity of the 3x1 aluminum joists, capacity of the butt welds, and how your two 12 ft edge beams would handle the loads transmitted by the joists.
All that plywood will be really heavy by itself. So going with the Aluminum posts may not save all that much weight. Steel is much cheaper and may not be that much more weight compared to the plywood.
I know these are wicked expensive, but the design ideas are what you are looking for.
The folding legs and cross bracing is something to look at if you are looking for compact storage. Otherwise you have 2’ of pokey legs and the field perimeter. You also should make sure the bolts you use can handle the load as well.
Over engineering for load will be better in the long run from a safety perspective. You may say you want to use them for robots but who knows if they will be used for something else like a play later in its life.
We’re building a modular field riser…nine 4’x4’ sections, made from 80/20 T-slot. Pretty pricey, but it will last forever and the kids can assemble it completely (no welding). Deck will be 1/2" OSB sheeting, four at 4’x8’ and one at 4’x4’.
In a couple weeks I’ll post a complete BOM and price list. (We’ll be having one of our students doing this in SolidWorks, so it will take a bit of time). Our 80/20 dealer gives robotics teams 40% discount on the parts.
Several of our mentors work at companies that use t-slot material all the time, and a good portion of what we needed was donated.
We have a booth each year at the Monroe County fair, so this field riser can be used in sections for exhibitions. At the fair, we’ll assemble a couple 4’x8’ fields for demonstration and public interaction. Also, were building a VEX IQ riser the same way, and it can be built as a 1/4, 1/2, or full field.
That’s pretty cool, nice work. I got a quote for 80/20, I priced out 1" x 3" 80/20 (#1030). Two 6’x12’ frames would have been $430, no cross-members included.
There is a plastic attic flooring product designed to replace OSB/plywood in an attic, Attic Dek. It’s just a little too expensive for my budget. I wouldn’t mind a lightweight frame with an Attic Dek surface, it looks like it would be a nice light weight platform.
I was looking at poultry flooring, but I don’t think it’s rigid enough.
We built it mostly from 1530-lite (1.5" x 3") with 1515 (1.5" x 1.5") legs, with some 4080 metric mixed in because that’s what we could get donated from some of our mentors’ company’s maintenance shops. Not including the value of donations, we have about $1000 into these two field risers (one for VEX, one for VEXIQ). Building from wood, like a deck, would have been a lot cheaper, but no where near as long lasting or cool-looking:D
That attic dek is rated at 250 pounds per panel (not per square foot) so it seems less load than 3/4" OSB. If you could guarantee that it’s just robots and game elements, it might work, but people tend to get on these things. If we could only get the robots to reset the field themselves…
Plastic deformation of the panel could also make for some wavy fields. But it looks like a very cool product I may well want to use in my own attic.
I’ve received the 1" x 3" x 1/8" wall aluminum tube I ordered. Alro Steel gave us a nice discount on the material. I’ve started to cut and process the tube.
The requirements for the project have changed since I started planning. I came up with a design for a fold-able field with caster base. I hope it will be a really nice field platform for us. It should be able to roll through a standard doorway. We should be able to deploy the field in only a couple of minutes.
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