Conversion of the MX991\U flashlight to 3-watt LED

This turned out to be quite easy. See http://users.goldengate.net/~dforeman/MX991_LED/
The MX991\U is a design that has been used by the military since 1940, is still in use AFAIK. It's light weight, rugged and waterproof. http://www.flashlightmuseum.com/flashlight_view.cfm?item_number=GT00005 They're cheap on EBay, often under $10. One recently went for $3.30.
I modified mine to accept the Maglight 3-watt LED "bulb" that sells at Wal-Mart for $18. The modification took less than 2 hours, not counting the trip to Wal-Mart.
It isn't as impressive with the LED as the 2D Maglight with the LED was, but it's far better than with the stock incandescant bulb and it's a lot lighter weight and easier to carry than a 2D Maglight. The Maglight does have a bigger and better reflector so it produces a better brighter beam with the same light source.
I figure battery life will be about 20 hours of full-brightness operation. Survivalists might like this because it's military-rugged, easy to carry, delivers constant full brightness for nearly the entire life of readily-available cheap batteries (D-cells), and at about $25 for both flashlight and LED module it's a hell of a lot cheaper than a lot of LED lights that aren't nearly as good.

On Sat, 23 Sep 2006 00:03:12 -0500, Don Foreman
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Does that mean you dont want me to send you some?
Gunner
"If I'm going to reach out to the the Democrats then I need a third hand.There's no way I'm letting go of my wallet or my gun while they're around."
"Democrat. In the dictionary it's right after demobilize and right before demode` (out of fashion). -Buddy Jordan 2001

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Geez, I'd forgotten about that, Gunner. I think one is enough for me at the moment, thanks. However, if you want to mod one of yours I'd be glad to make a bulb retainer for you. I know you could do it on one of your several lathes, but I probably have more time than you do. If you send me the positive contact I'll also stick a bump on it, and then nickelplate both parts. I turned the contact bump on my lathe. It's .090 dia with a .062 post that I stick in a hole and solder in place. I can't buy parts and build the LED and elex for what Wal-Mart now sells the Maglight 3Watt LED with pretty good elex. I'll say again that the 2D Maglight with LED is more impressive if ya don't mind the weight -- and put some Penetrox on the tailcap threads so it doesn't gall.
Another project in the wings: another correspondent has gotten into long-range shooting, wants to study the strain behavior at the muzzle of his rifle. There is some opinion that dispersion (group size) of a given rifle depends a lot on when the bullet leaves.
http://www.the-long-family.com/OBT_paper.htm
We don't entirely believe this simulation and would like to see actual data on a scope to directly observe OBT (optimum barrel time) on his particular rifle. The thesis is that each rifle will have a time window of OBT, time between pulses. Once that is known, one can then tune loads to be within that window. So he plans to stick some straingages on his rifle, my part is to cook a couple of postage-stamp-sized straingage preamps with risetime of under 2 microseconds. Don't want long leads on straingages if looking for 200 KHz bandwidth.

snipped-for-privacy@NOSPAMgoldengate.net says...
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Have you looked at piezo-sensors? They're often better suited to observing high speed transients than strain gages, and avoid the problems dealing with millivolt signals. The frequency response of strain gage based transducers (load cells, pressure transducers, etc) is quite low (10s of Hz?), primarily due to mechanical resonance - this may not be a problem if you're bonding the gages directly to the barrel.
Ned Simmons

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Piezo senses force. We want to measure strain or deformation. The straingages will be bonded directly to the barrel. I should check with Omega about intrinsic frequency response of foil straingages, but I see nothing that would prevent one from working up to frequencies where the straingage size would become a half-wavelength of sound in the material it's bonded to. They have very little mass and their resistance is low enough to make their capacitance and inductance negligable even at 1 MHz and above.
Also, straingages are only about 5 bux each.

snipped-for-privacy@goldengate.net says...
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I think I know where you're coming from, but both piezoelectric materials and foil strain gages respond to induced strain.
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Okay, that makes sense. The problems arise when, in order to get a reasonble output level from a transducer, the gage must be mounted to a relatively flexible member.
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Piezoelectric is probably cheaper than foil strain gages, or do you mean piezoresistive? Foil strain gages are certainly more accurate. If you want actual measurements rather than relative levels of tension and compression, piezoelectric may indeed not be practical.
How many points do you think you need to monitor? If I understand the goal, I expect you need to look at several points, and 2 or 3 axes per point, in order to get a clear picture.
Ned Simmons

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You're right.
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I think we're just interested in one point and one direction: diametral expansion of the barrel at the muzzle as fn of time. A second SG would be used near the breach just to trigger the scope or datalogger.

On Sun, 24 Sep 2006 20:37:04 -0500, Don Foreman
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You also need some way to tell which point of the compass the muzzle is pointing in as the bullet exits. No idea how to do that.
Gunner
"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences." - Proverbs 22:3

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The hole in the paper downrange gives a pretty good indication. Our interest is more in reducing dispersion from round to round to minimize group size. We can always re-zero the scope.

On Mon, 25 Sep 2006 11:13:17 -0500, Don Foreman
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True enough, but its a function of barrel harmonics and should be considered a testable variable.
Gunner
"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences." - Proverbs 22:3

snipped-for-privacy@goldengate.net says...
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I was imagining something more ambitious, along the lines of characterizing barrel deflection vs. time, as Gunner is suggesting.
Here's a link to the sort of inexpensive piezo film strain sensors I had in mind.
<http://www.meas - spec.com/myMeas/download/pdf/english/piezo/catalog_price_list.pdf>
Ned Simmons

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This sure looks a lot to me like PVDF2 , polyvinylidene fluoride piezo polymer film.
If you do something more ambitious, I'll certainly be interested in your findings -- and I'll be particularly interested in your methods for getting 200 KHz bandwidth with these piezo sensors.

snipped-for-privacy@goldengate.net says...
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Yes.
I'm afraid I've muddied the water here. When I said, "I was imagining something more ambitious," I meant ambitious on your part. My interest is purely academic.
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I'm not aware of any reason why their high frequency response wouldn't be at least as good as strain gages when mounted on the same chunk of steel. Am I missing something?
Ned Simmons

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I kinda wondered that might be the case.
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I'm not saying that piezo would be inferior to straingages in terms of high-frequency performance. However, the signal conditioning requirements are somewhat different. Piezo sensors present essentially a pure capacitance while straingages present a low resistance.

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I assumed piezo is what he was going to use..virtually everybody is using piezo these days for barrel work, PSI, etc etc
Id think that simple strain gages are way too slow.
Gunner
"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences." - Proverbs 22:3

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You might be right, but I think it bears checking. I don't see why a bit of foil on some Kapton film a few thou thick and weighing less than a gram wouldn't be able to track events in the steel to which it's affixed. We're talking motions of microinches in material (steel) with modulus of elasticity of 30 million PSI, so the force required to accelerate very small mass is certainly there. The RC and RL electrical time constants are well up into the MHz range.
I'll probably stick a SG on a steel bar, instrument it, see how it responds to hammer taps etc.

On Mon, 25 Sep 2006 11:54:53 -0500, Don Foreman
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Stick one on a rifle barrel and shoot it.
Gunner
"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences." - Proverbs 22:3

Strain gages are for mountains and bridges. Piezo is for high speed stuff and started in the late 60's into Navigation gear on airplanes.
I have some disks and rectangles from those days.
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member http://lufkinced.com /
Gunner wrote:
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On Mon, 25 Sep 2006 19:02:40 -0500, "Martin H. Eastburn"
So I hear. But see http://www.chuckhawks.com/pressure_measurement.htm and http://www.shootingsoftware.com/pressure.htm
In order to use a quartz piezo sensor, there must be a hole (pressure port) from chamber to transducer. A foil straingage is not as direct a measure of chamber pressure, but it is non-intrusive. We're more interested in muzzle behavior than chamber pressure, so the strain method is probably even more applicable. We'd use chamber pressure just as a trigger for the scope or datalogger.
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I do too. Those make great force, acceleration and vibration transducers, not so good for directly observing strain. Thing is, folks usually worry about strain in static or very low frequency dynamic sits -- as with mountains and bridges.
The PVDF2 thin-film polymer SG's might work nicely here -- but I didn't see much of a specsheet on them, nor a place to buy just a few for a few bux.
Foil SG's are very well-documented, and I happen to have a few on hand. I try to work with what I have unless someone else is paying for the research at market rate. I don't see any purchase orders sliding under the door!

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Can't do that in my shop/lab, Gunner. We'll get there. Stuff doesn't always work the first time in my lab, but things nearly always work eventually.