Bizarre request - how would you do it?

[Brooks Moses]

I presume he changes his tests. Even if it's only because each year he thinks of something new and interesting to try, or discovered last year that one of the tests didn't work out like he'd hoped.

Ah! I was right about questioning whether the real objective was to have the strongest box! (Well, sorta.) Sounds like to me that the _real_ objective of this experiment is to produce interesting results to describe, and for the students to get some experience in how different materials respond to various damaging things.

Just build something tough. Have fun. :)

And, for extra fun, I'd suggest giving the engineering student a list of the suggestions and possibilities, and have them make all the final decisions about how to build it.

- Brooks

[Dhakala]

Then each box will undergo only one test, right?

The variable to be measured is the material. All other factors should be held constant. Therefore, build four boxes of different materials but the same dimensions.

[TrailRat]

Many thanks got the picture now. Looks interesting to try any way.

TR

[Mike Berger]

[Morris Dovey]

| TrailRat (in [e-mail]) | said: | || 4: Intense heat with flame, (blow lamp) One face 5 Minute. Check || for damage/shape change

Hmm. I didn't handle this part very well. You might want to drill a tiny hole from each corner to the internal cavity and plug it with a small amount of wax to relieve pressure that builds up during this test...

Drilling from the corner should help prevent high temperature gasses from being blown directly into the cavity by the torch. The meltable wax seal /may/ help to prevent or retard flooding if there is a subsequent water test.

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA

[someone]

I would start with a 4x8 sheet of 3/8" plywood. I'd then cut it into 32 squares of equal size (slightly less than 1' squares). You won't use one of the squares.

I would take a router or scroll saw and cut 8" circles out of the center of

21 of the squares.

Using resorcinol glue, create a laminate of 5 full size squares and 21 hollow squares. Create a second laminate of 5 full size squares. You now have a box with an 8" diameter x 7 7/8" tall cylinder in it. Put the equipment in the cylinder and glue the lid on the box. You've now got a slightly less than 1' cube of laminated wood. To remove the equipment cut the top 5 layers off the box.

IMHO, that design should be waterproof, insulated, and able to support the weight of a car.

[W Canaday]

Nope. As a proto-type machinist / die-maker, I recognize the reflexive desire for symmetry .. but symmetry (that doesn't look like it's spelled right) is no advantage here and 'pretty' is not a design constraint / tested value.

Only drill from one corner. That will restrict the ability of liquid to flow into the cavity. Air is only about 1/16 as dense as water: make the hole tiny ... mebbe a #60 or so. Or. better yet, route / carve a WAAAAY shallow groove that curves 180 deg or more several times in a switchback pattern. The air under pressure will escape just fine (the test is for just a few minutes and all the designs so far provide for an insulating mass.) Incoming liquid will pressurize the compartment, slowing the flow of the liquid and allowing the fibers time to swell.

In fact, come to think of it, don't take the groove all the way to the cavity. Stop just a few thousandths short of it. The gasses will penetrate the cells but the liquid will not. If you overshoot the mark, glue a piece of craft paper over the oopsie. Same net result.

Paint the thing with fire-retardent paint such as used in restaurants. If the fire test comes first the swelling of the paint will give us bonus protection from the liquid. It might also shield the adhesives from heat failure.

We'll let the test, itself, provide the sealing, eh? ;-)

Bill

[Morris Dovey]

| We'll let the test, itself, provide the sealing, eh? ;-)

I like the way you think. :-)

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA

[Brooks Moses]

Huh? You handled it perfectly fine by ignoring it, I'd say.

Let's assume, for the sake of absurd argument, that this heats up the interior cavity to 300C. That's twice atmospheric temperature, so by the ideal gas law it's going to be at twice atmospheric pressure. A six inch square face is 36 inches square, times 15 psi, is about 500 pounds. Yeah, that's a fair bit, but the box should certainly handle. Besides which, if it does yield a little, it will thereby immediately develop a leak and relieve the pressure, preventing failure.

This is completely aside from the fact that heating the interior up to

300C means that the sensors inside are toast and the box has failed anyway regardless of whether it remains structurally sound.

And it's also completely aside from the fact that I would be very surprised if the back side of three inches of oak would even get _warm_ after only five minutes. There's a reason the Chinese use the stuff for heat shields on some of their space capsules....

- Brooks

[TrailRat]

All sounds like a great ideas.

Mr Doveys design in white oak. Errm what would you use to glue the the two halves together with?

Without ruining a good design I was also thinking of a peg system. Using 1x1 square pegs from corner to corner going through the crenallations on two sides to hold it together.

Nice idea about the fire retardent paint. Two things, No foreign materials and no fire, just intense heat.

TR