Tuesday, May 11, 2010

"the best is the enemy of the good" - Voltaire

The results of a four day long experiment - to see whether I could remove any of the warp from my 1" thick slab of phenolic-linen laminate - were inconclusive at best, because I failed to measure and write down the amount of warp when I started.  I think I removed some of the warp, but I don't think it was very much.

So this morning, using the big surface plate at work, I measured (and wrote down) the amount of warp which is in the piece now .  I'm going to take one more stab at bending the stuff over the coming week, and see whether a week long attempt has enough effect on it to be worth continuing.

If not, I'll machine it flat.

It occurred to me to ask, "what if I were to simply mill it flat, what would the consequences be?"

The first consequence is: I'd be removing around 0.1" of material (total) from the material thickness, or about .05" from each side.

That begs the question, how much strength do I lose by going from 1.0" material to 0.9"?

The answer to that turns out to be, "surprisingly little", because of how closely spaced the clamping bolts are.  Or rather, one loses exactly as much strength from the material as one would expect, but the "beam" length between any two supported points (pairs of bolts) is so short, it just doesn't matter.  I have tried to calculate all of the magnetic reaction forces in the launcher (with the calcs on the rest of the bus-work to follow soon) and it looks to me like the worst case is at the breach connections (which is what I expected).

When I apply the calculated force to the bream (and assuming preloaded Gr.5 bolts), the resulting deflection is so vanishingly small I had to do it three times and re-read the calculator instructions (yeah, there's a calculator for just about everything online, who needs to know any math?) before I believed the number.

My railgun containment structure is gonna be stiffer than John Holmes.


I haven't worked on the Mad Scientists Light Switch lately because the best fix I can think of to get that project out of the jam it's in requires four to six contiguous hours of focused work - contiguous hours I haven't had.

Actually, I did have the time available last weekend, but I used that time to work on improving the security of my workshop instead - yet another ongoing project with no end in sight.

I'll probably revisit The Light Switch this coming weekend.

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