Ideas on making a metal enclosure

I want to put a flat panel TV outside on our back porch, but since there is no overhang to keep it dry, I have an idea to make a metal
enclosure for it. By hitting a switch, the TV will rise out of the box using an electric actuator. I am thinking that the top of the box would be attached to the mounting bracket, so that when the tv goes back in, the top would seal against/around the edges of the box (to keep out rain and thieves). I am actually using a Keyed switch to raise and lower the tv, so it should be secure from thieves. The dimensions for this would be approximately 32" wide by 36" deep by 7" deep. I have a few questions on this project that I am hoping to get some info on.
1. What would be a better metal for this, steel or aluminum (protection from the elements)? I have never welded aluminum but do have the MIG conversion for my Weldpak 100HD and have always wanted to try and willing to learn. But I would want it painted and from experience , steel is much easier to paint for me.
2. I am thinking of using 12 or 11 gauge for this. Would that be adequate? There would be a thicker lip at the top of the box to seal against.
3. All the welding I have done so far has been with tube and angle iron. I have never really tried to weld any thin walled items into a three dimensional shape. What would be the best technique for welding something like this without too much distortion?
4. One idea for the process would be welding four side pieces together and then the bottom on. But it would seem that getting into the box for welding from the inside would seem difficult. Is that the normal way to weld an enclosure, or would it be possible to weld from the outside? A second option would be to use a brake to bend all the sides together, and have one seam to weld. Unfortunately I do not have a brake, although Harbor Freight has one for $200.
Any starting points would be very helpful.
Thanks, Tom Kuhn
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80g2000cwy.googlegroups.com:

ISTM that the #1 problem will be in providing a weather-seal. This can be simplified by having a "visor" across the top of the moving portion of the enclosure that, when down, will rest upon a rubberized gasket.
The "box" can be made of 1 piece of flat metal [Aluminum has its good points: easy to cut, doesn't rust, far cheaper than Stainless...] by laying out the back in the center and the top & sides connected along the edges of the back. (Don't forget to allow for re-inforcing "tabs" along the sides - this will both strengthen the "box" and offer an alternative means of construction.)
BTW, don't forget to pick up some rubber grommets to protect the wires from the edges of their access holes...
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RAM³ wrote:

make the box opening on the bottom. make the box go up, or the screen go down.

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The best metal in this case would be PLASTIC. Easy to work acrylic bonded with Weld-on brand cement will look great and last almost forever, well, longer than the TV. Or you might buy a Rubbermaid tup and just slot it out for the TV.
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From a security standpoint acrylic is probably worse than aluminum or steel.
daniel peterman wrote:

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Tom, whatever you do, be sure to provide vents. A "sealed" box outdoors WILL suck in damp air with temp changes and the moisture will condense and fill the box with water. I kid you not! Just a small screened hole or 2 on the bottom will do. RichD
Tom wrote:

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Hey Tom,
A brake would be nice, but I think I would just use aluminium angle for all the places, pop-riveted. Provides great rigidity. And why so "elaborate" as to having it a "Jack-in-the-Box"? Why not fasten it to whatever, in a box with a fold down face?
Put a small fan in the box that runs only when the "door" is closed to help keep it dry.
Personally???, even though I kid myself that I'm a metalworker, I'd make a wooden cabinet first, to try it for a year.
Brian Lawson, Bothwell, Ontario. XXXXXXXXXXXXXXXXXXXX

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Why not have the TV come down out of the box instead... Anything up in a box is going to have a hard time getting wet....
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Why not have the TV come down out of the box instead... Anything up in a box is going to have a hard time getting wet....
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Why not have the TV come down out of the box instead... Anything up in a box is going to have a hard time getting wet....
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<snip>
Put the TV in an upside-down fish tank.
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Don't be dismayed with yourself if you have considerable trouble MIG-welding 12 gage aluminum with a Weldpack 100HD. It'd work fine on 11-gage or 12-gage steel, though.
I doubt if you'll have much luck bending 12 gage on a $200 brake.
You don't need to make continuous welds on the inside. Just clamp the metal pieces to a square bar or piece of angle with a chamfer ground on the corner, so the inside corners of your sheetmetal just touch or don't quite touch and there's open space (the chamfer) underneath. Then fill up the open outside corner with weld. Coupla minutes with an angle grinder or disc sander and the corner will look like a bend with zero radius on the inside. You can stick a few gusset beads inside in places that are easy to reach. This isn't quite as strong as a bend but it's strong enough for most boxes, it's easy to do, it looks nice when it's done and painted and it's easy to have the dimensions come out pretty close to plan.
As others have said, vent the bottom of the enclosure so the water that can't possibly get in there can get out. Been there, done that! One trick is to use felt plugs in the holes. That excludes spray and wind-driven rain but allows condensation inside to wick out. This trick worked on elex control boxes for reefers mounted on the fronts of semitrailers that are routinely exposed to rain driven by 70+ mph wind while truckin' down the superslab, 10-4.
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[snip]
It's a very good point. Also to be considered is variation in atmospheric pressure as weather systems go by. The max pressure is about 31" Hg, and the min is about 29" Hg, so the total variation is almost 10%. This will pump moist air in, where it will condense on everything. When the pressure drops, the condensed water will not leave, and so will accumulate. There is no way to seal a sheetmetal box against this variation, so it must be provided for somehow.
One classic solution (<http://www.foundersofscience.net/interest1.htm , figure 4) is to connect a long piece of tubing to a fitting, where the total volume of the tubing is about 10% of the volume of the box. Then, the air inside the box is not exchanged with the atmosphere. But, ensure that anything condensing in the tube will drain to the outside, not to the box.
Joe Gwinn
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Key in on weatherproofing rather than box construction.
Think about all the times when it will be sitting there unused, in a very very very very ............. one more time for clarity ........... very humid situation.
A box is a box is a box. What's going to keep it dry when it's not being used?
That's what I'd concentrate on.
You could use Masonite and Liquid nails, and done right, get a better enclosure than someone who is using a $5000 TIG rig and aluminum.
You're building a box. Think outside it to get your answer, Grasshoppa.
Steve
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I'd also look into environmental limits... mainly how hot is the interior is going to get in peak summer heat; and cold during winter cold snaps. The TV's Storage and operating temp extremes will probably differ somewhat, and probably won't even come close to what something like a car stereo will tolerate. Condensation conditions, even minimal will probably be terminal to the set.
You will probably want to minimize rapid temperature changes to the set too, like for sure disallowing all direct sunlight to the enclosure.
Erik
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I forgot to mention yesterday that a 15 or 25 watt light-bulb placed inside the cabinet, along with a very small fan, will help with the moisture problem.
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Everybody has had great information for me so far, I want to thank everyone for that! I know some people are wondering about why such an exstravigant undertaking. The Box would sit at the outside edge of our patio, so it is basicly in the middle of the yard. I wanted it to sit low, right outside of the porch railing, so that when the tv is down, you can't really see it, but when the tv is raised, it will sit slightly above the railing. There are bushes on the other side of the box to protect it from some but not all sun. Good points have been brought up about the heat issue. Especially since I would like to paint it black to match the railings. Condensation should be suficiently conquered by the enclosure itself, as long as the TV is not left out overnight, and there are some vent holes on the bottom. I do like the wick idea using felt.
Brian Lawson wrote:

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So far:
I guess the brake is out and welding aluminum is out. I like the idea of using aluminum with rivets as it would be pretty simple to make. How would the bottom get riveted to the sides? or would thst be done first, with the sides after? I am guessing that the aluminum angle is for the corners and is riveted to the side and front pieces. The chamfered steel welding technique also seems simple to accomplish. To do that, you mention chamfering an edge. IS that just a portion of the whole edge of the piece, or is the entire edge chamfered? I think that plastic would be the best material for it, but it might be a bit cost prohibitive, as much of the funding for this project is going to the actuator.
Tom wrote:

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The chamfer is on one corner of the piece of square bar or angle that is used to jig the pieces of metal to be welded. It doesn't become part of the finished job. The chamfer is to create an airspace under/behind the welding zone so you can get full depth weld plus a bit without sticking it to the jig. You don't want the jig to suck heat away from the actual weld zone. With 12 gage, a 1/8" or 3/16" chamfer (on the jig) is ample.
If you use square tube as a jig, it's corners are already rounded so no further modification is necessary.
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Another quick thought... the TV is going to need to be able to cool itself during normal operation.
Erik
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