All-electric simulated machine gun?

[cluttonfred]

I have often daydreamed about my own replica WWI or WWII fighter, complete with faux machine guns, just like Eric Clutton's original FRED in its "FRED Baron" guise. It still wears the replica gun today, but in a yellow 1940s RAF trainer scheme.

I have seen some propane-powered gunfire simulators in use by the replica Nieuport Dawn Patrol and others, but that solution strikes me as complex, heavy and potentially dangerous. It strikes me that there has to be a better way.Has anyone tried, or does anyone have any bright ideas on, an all-electric machine-gun simulator?

The way I see it, there are three components to making it work: 1) the flash, which should be easy to do with bright modern LEDs; 2) the noise, which could be as simple as an MP3 recording of a real machine gun firing played through a hidden speaker; and 3) the smoke, which ought to be possible with light machine oil or glycerine squirting on an electric element as used in electric trains. Of the three, I'd say the smoke is optional (flash and noise would already be pretty cool, cleaner and require less maintenance) but it would be the icing on the cake.

I definitely see some challenges in terms of sychronizing the three effects and I wonder if the noise would be loud enough and the smoke visible enough. Maybe something other than a speaker would work better, some sort of snapping relay or spark effect? Maybe the glycol mixture used in smoke machines would be an alternative? It might be good to find a way to generate the smoke at a single point and pipe it to as many guns as are needed.

Just imagine a replica Hurricane or Mustang tearing down the runway with all guns blazing!

Suggestions welcome!

Cheers,

Matthew
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[rwanttaja]

I think you'll have a hard time getting a loud enough "bang". If you want the noise self-contained in the machine gun, that really limits the size of the speakers you can use.

Getting a decent flash might be a problem, too. Can't pack many LEDs in a barrel diameter. With something like a Vickers, you could cover the whole disk area of the end of the cooling shroud. That would look good at a distance, but would look funny close up, especially when the gun WASN'T firing...

Ron Wanttaja

[cluttonfred]

I was thinking that this would be a "stand off scale" effect only, so the speaker could well be elsewhere, perhaps a powerful car subwoofer with built-in amp in the rear fuselage pointing 45 degrees down and forward. I doubt anyone on the ground would be able to tell where the sound is coming from. On the LEDs, I don't agree, those new surface mount ones are pretty darn bright, blinding even.


I think you'll have a hard time getting a loud enough "bang". If you want the noise self-contained in the machine gun, that really limits the size of the speakers you can use.

Getting a decent flash might be a problem, too. Can't pack many LEDs in a barrel diameter. With something like a Vickers, you could cover the whole disk area of the end of the cooling shroud. That would look good at a distance, but would look funny close up, especially when the gun WASN'T firing...

Ron Wanttaja

[Jeremy Leasor]

About 35 years ago there was an article in The Vintage Airplane about a guy who built a full scale Fokker DVII with a 200HP Ranger turned upside down (i.e. cylinders on top, like the Mercedes). He made a "working" machine gun which I seem to remember used oxy-acetylene gas and an intermittent electric igniter for the muzzle flash and Ground Speak speakers mounted behind the dummy radiator grille, playing a loop tape for the sound. These apparently made for a highly authentic machine gun effect, both visually and aurally. He had enormous fun beating up airfields and bouncing other aircraft, until he picked on a Stearman, which, unknown by him, was flown by a WW2 fighter ace, who showed him how it was really done.

[rwanttaja]

I was thinking that this would be a "stand off scale" effect only, so the speaker could well be elsewhere, perhaps a powerful car subwoofer with built-in amp in the rear fuselage pointing 45 degrees down and forward. I doubt anyone on the ground would be able to tell where the sound is coming from. On the LEDs, I don't agree, those new surface mount ones are pretty darn bright, blinding even.

Don't have any experience with modern LEDs, but would love to experiment. I'd use a 555 timer, but would probably need a power transistor or relay, assuming those bright LEDs suck a bit of juice. Could probably power it with some C-cells (or even AAs). I'd love to play around a bit, could you pass some part numbers/references for those LEDs?

Noise-wise, I'm a bit skeptical about getting a speaker strong enough to be heard a couple hundred feet away over the sound of the engine. On the PLUS side, you don't need good sound quality, just a hugmungous spike every 20th of a second or so. Just discharging a capacitor into a speaker might be enough for that. You'd need a bank of capacitors to get a high enough rate, of course. A Gatling gun! :-)

Another way might be strictly mechanical. Imagine a speaker cone with a wire connected to the apex, anchored by a strong spring. If you could "pluck" the wire at the right rate, you'd get a series of pulses from the speaker. A motor with a cam might do it.

Remember, when guns on FREDs are outlawed, only outlaw FREDs will have guns....

Ron Wanttaja

[cluttonfred]

Don't have any experience with modern LEDs, but would love to experiment. I'd use a 555 timer, but would probably need a power transistor or relay, assuming those bright LEDs suck a bit of juice. Could probably power it with some C-cells (or even AAs). I'd love to play around a bit, could you pass some part numbers/references for those LEDs?

Here are some examples of what I had in mind as components: http://www.superbrightleds.com/cat/component-leds/filter/Millicandela,10001,28,25000:


Noise-wise, I'm a bit skeptical about getting a speaker strong enough to be heard a couple hundred feet away over the sound of the engine. On the PLUS side, you don't need good sound quality, just a hugmungous spike every 20th of a second or so. Just discharging a capacitor into a speaker might be enough for that. You'd need a bank of capacitors to get a high enough rate, of course. A Gatling gun! :-)

I was thinking of a powered subwoofers, something like this: http://www.crutchfield.com/p_108BASSLIN/Infinity-BassLink.html?tp=114


Another way might be strictly mechanical. Imagine a speaker cone with a wire connected to the apex, anchored by a strong spring. If you could "pluck" the wire at the right rate, you'd get a series of pulses from the speaker. A motor with a cam might do it.

Not sure about that but the mechanical solution would be a lot harder to adjust.


Remember, when guns on FREDs are outlawed, only outlaw FREDs will have guns....

;-)

[danielfindling]

Here is a link on a gas powered machine gun. (Oh, I am looking for Lewis Machine Gun parts - anyone?)

http://www.kcdawnpatrol.org/machine-gun.htm

[rwanttaja]

Here are some examples of what I had in mind as components: http://www.superbrightleds.com/cat/component-leds/filter/Millicandela,10001,28,25000:
Mentioned this project at EAA Chapter 26 last Thursday, and one of the members put me on to a local electronics store that carries a bunch of high-intensity LEDs. Bought a 5W unit that runs on 12V. They had a 10W unit, but it needed 30VDC and I figured you didn't want to pack 20 AA cells. :-)

Got some other goodies with which I hope to gimmick up a flasher. Perhaps by next weekend I'll be able to post a video showing the daylight visibility over a distance.

A local Boredom Fighter builder named Bill Sayre has been monitoring this conversation, and sent me some pictures of his dummy Vickers guns.

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One advantage of the Vickers is that the barrel is at the bottom of the cooling shroud, which gives you a big, flat surface at the business end for mounting your flashing light. Bill has flashlight reflectors mounted in his. He's also got small LEDs mounted on the sides of the shrouds as an indicator that the guns are firing (as if the sight of flaming Huns wasn't obvious enough.... :-).
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This is a neat way to get a broad light-emitting surface without wrecking the appearance of the gun. Obviously, you could make little covers for the reflectors on those times when the groundlings are going to be close to inspect the airplane. Just remember to whip them off if you're going to go fling some photons at the local Cessnas.

Bill also sent me the schematic he used for the flasher circuit. It appears to mess with the control input of a standard voltage regulator chip. This works on Bill's incandescent bulbs, but I don't know if it'll work on a high-intensity LED. In the immortal words of Commander Montgomery Scott, "I'll let ye know."
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Ron Wanttaja

[danielfindling]

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Ron Wanttaja
An Arduino micro controller would seem appropriate for the project as well. The flashing LED is simple code and a MIDI file for the sound. . .

[cluttonfred]

Great stuff, guys, glad to see that I have planted a seed!

Ideally, it would the great to this developed as an open-source solution for at least light and sound that could be easily adapted to suit different types and numbers of guns by changing firing rate and changing the MP3 file if recorded sound (or otherwise adjusting the sound if generated otherwise). I have some contacts in the gun collecting world that might be able to provide MP3 files of the sound of key historical guns: Lewis, Vickers, Spandau, Parabellum would cover most WWI types for a start. I'll pass the word and see what I can come up with.

[rwanttaja]

An Arduino micro controller would seem appropriate for the project as well. The flashing LED is simple code and a MIDI file for the sound. . .
Oh, you gol-darn kids...having to put a microprocessor in everything. I swear, it makes me want to disassemble a rotary switch to control the light, with up a key-wound clockwork mechanism to turn the switch and make the light flash.

And get off my lawn!

Actually, we *might* have to go with a microprocessor, for one key point: Synchronizing the flash with the bang. Everything we talked about so far treats the light show and the audio show separately. Sure, Einstein and Mach make sure the flash reaches the eye before the bang hits the ear....but if the visual is going FlashFlashFlashFlash and the audio is going bang....bang...bang...bang... well, heck, that's just gonna be weird. Could adjust the flash circuit to match the rate of the audio file, but there's a good reason to automatically synchronize them (I'll get to it in a bit).

However, there's another realism point to consider: What you hear from a gun three feet away is NOT what you'll hear from a gun a hundred feet away. A close-in recording is going to get the sound of the gun's action moving, the bolt slamming shut, the belt sliding, and the brass hitting the ground. Playing that recording with a big *** amplifier is going to amplify these ancillary noises, too, and again, that'll be unrealistic. So a recording of a Lewis, Vickers, or Spandau may not be the way to go.

The *right* sound would be a *single shot* from a bolt-action rifle, repeated electronically. Bolt-action, so there's no mechanism noise involved. You'd take that noise, and repeat it. For one thing, that'll let you fire a burst of unlimited length. Most of the recordings probably are of the approved short-burst variety. Just re-starting the short-burst MP3 will also be weird.

Repeating the sound would be easy, but properly synchronizing it with the flash might not be. A simple microprocessor may not be able to play an MP3 file simultaneously with toggling an output line.

All right: Here's why I want the noise and light to automatically sync up: I visited the Historic Aircraft Restoration Museum in Creve Coeur, Missouri last fall. They've got a replica Sopwith Pup, with not only an original LeRhone engine, but an operable Vickers machine gun with a working interrupter gear. Our guide had actually flown the Pup with live ammo. He pointed out that the rate of fire of the Vickers *depends on the speed of the engine*.... That at low RPMs, the gun could put out more bullets before the prop blade intervened. So if you dive the plane, the gun shoots slower...and starts shooting faster as you pitch up and start climbing.

And if you have the audio automatically syncing with the flash in our simulator, you could vary the firing rate by airspeed.....

Ron Wanttaja

[cluttonfred]

OK, in that case I vote that we get someone to record a 7.62x54R Mosin-Nagant, preferably one of the short carbine versions, as they make the most impressive boom and muzzle flash of any standard-caliber bolt-action I have seen.

Seriously, I do get your point and I agree that a recording right next to the gun might pick up wanted mechanical noise, but if the microphone is a few yards away I don't think it will matter. Regardless, sample recordings of the real guns would give confirmation of the rate of fire in actual use and a point of comparison for how realistic the simulation sounds. That said, you may well be right that recording just a single shot and looping it in synch with the light would be the easiest solution.

[danielfindling]

Here is a nice sound clip of a Vickers: http://m.youtube.com/watch?v=hPv_f_aSyP4

Lewis machine gun: http://m.youtube.com/watch?v=hPv_f_aSyP4

Spandau machine gun: http://m.youtube.com/watch?v=hPv_f_aSyP4

[rwanttaja]

Mentioned this project at EAA Chapter 26 last Thursday, and one of the members put me on to a local electronics store that carries a bunch of high-intensity LEDs. Bought a 5W unit that runs on 12V. They had a 10W unit, but it needed 30VDC and I figured you didn't want to pack 20 AA cells. :-)

Got some other goodies with which I hope to gimmick up a flasher. Perhaps by next weekend I'll be able to post a video showing the daylight visibility over a distance.

A local Boredom Fighter builder named Bill Sayre has been monitoring this conversation, and sent me some pictures of his dummy Vickers guns....Bill also sent me the schematic he used for the flasher circuit. It appears to mess with the control input of a standard voltage regulator chip. This works on Bill's incandescent bulbs, but I don't know if it'll work on a high-intensity LED. In the immortal words of Commander Montgomery Scott, "I'll let ye know."
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Ron Wanttaja
I built the circuit last night, didn't seem to work right with the high-intensity LED. I suspect that the timing is thrown off by using the LED vs. an incandescent bulb. The power draw is probably way less, and incandescent bulbs are somewhat self-regulating.

No matter. I'll rig up a 555 and use the LM317 as a switch for the LED (don't think the 555 can drive a 5W device directly).

Ron Wanttaja

[Frank Giger]

Here is a link on a gas powered machine gun. (Oh, I am looking for Lewis Machine Gun parts - anyone?)

http://www.kcdawnpatrol.org/machine-gun.htm

For a good, inexpensive "stand off" replica - http://www.foxflier.com/lewis/ - including some examples that were turned to gas powered. I'd show you pics of my 7/8th scale one, but it's not assembled yet.

I always thought that if I were to go the 'lectric route to make it fire, I'd put the speaker behind the seat and let the empty rear of the fabric covered aircraft act like a big sounding drum to amplify it.

[cluttonfred]

I did some digging and what might work here is a "color organ" or "light organ" circuit for synchronizing lights with music, though you want one specifically for LEDs and 12v not for incandescent lighting and the home stereo system. Most are multi-channel -- here's an example including a link to instructions and a circuit diagram (http://www.theledart.com/blog/archives/1543) -- but it sounds like Ron or others would have no trouble understanding the circuit diagrams and creating a simplified, single-channel version for the machine gun flash.

If someone is looking for a project, it might be worth making the multichannel example in the link and then testing it to decide which frequency response works best for this application. The input would come directly from the speaker feed, which would solve any synchronization issues.

The next step would be to rig up a cheap way to feed the speaker with a looped recording of a single rifle shot as has been discussed. A simple loop would work, but for best sound, I think it would be great if the shots could be overlayed like this, with the next shot firing over the continuing reverberation of the previous one, if you see what I mean:

BANG - r e v e r b e r a t i o n
__________BANG - r e v e r b e r a t i o n
____________________BANG - r e v e r b e r a t i o n

Cheers,

Matthew

[rwanttaja]

I did some digging and what might work here is a "color organ" or "light organ" circuit for synchronizing lights with music, though you want one specifically for LEDs and 12v not for incandescent lighting and the home stereo system. Most are multi-channel -- here's an example including a link to instructions and a circuit diagram (http://www.theledart.com/blog/archives/1543) -- but it sounds like Ron or others would have no trouble understanding the circuit diagrams and creating a simplified, single-channel version for the machine gun flash.

If someone is looking for a project, it might be worth making the multichannel example in the link and then testing it to decide which frequency response works best for this application. The input would come directly from the speaker feed, which would solve any synchronization issues.

I agree the flash should be triggered by the bang....and considering the size of the bang we hope to issue, triggering shouldn't be any problem. The main trouble is, the flash is basically binary...it's on or it's off. We're talking about wave-shaping the bang, but the flash is going to be pretty simple in comparison.

The organ circuit takes the music input, and runs it through low-pass, band-pass, and high-pass filters, with each filter turning on a bank of particularly-colored LEDs when a threshold is reached. The organ circuit has the right idea...but we'd end up needing multiple high-intensity LEDs to try to implement it. It's going to be tough enough to have one LED bank bright enough to be visible 500 feet away on a sunny day; packing in three or more is going to look really funny. Plus, the closer it gets, the more obvious the flashes are coming from slightly different positions.

What would be nice is if we could input a waveform to the LED and have it track it by *brightness*. An initial high-intensity, dropping off over the next quarter-second or so. Doable (especially if we end up with a microprocessor anyway), but it is getting a bit complex.

If brightness weren't an issue, I'd install a big LED at the muzzle and a trail of additional ones leading forward. Do the big flash, then sequentially zip through the others real fast.


The next step would be to rig up a cheap way to feed the speaker with a looped recording of a single rifle shot as has been discussed. A simple loop would work, but for best sound, I think it would be great if the shots could be overlayed like this, with the next shot firing over the continuing reverberation of the previous one, if you see what I mean:

BANG - r e v e r b e r a t i o n
__________BANG - r e v e r b e r a t i o n
____________________BANG - r e v e r b e r a t i o n

I'm not sure how much reverb would be present; again, not only are the listeners going to be hundreds of feet from the gun, but the gun itself is going to be well off the ground. I found the following spectrum of a gunshot online:
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I'm guessing the initial sound pulse is the shot itself, probably the "slap" of the air compressed by the passage of the bullet (and possibly a supersonic shock wave). Note the incredibly short time duration, and the high amplitude compared to the rest of the waveform. Following up 8 milliseconds later is a reflected shock wave (probably an environmental effect we can ignore).

About 15 ms after the first shock is the muzzle blast...probably the "reverb" effect we're looking for. Note, though, how much lower the amplitude is.

It's my contention that the muzzle-blast effect would be severely attenuated by the time it would reach an observer 500 feet away. Hence, we should be primarily interested in reproducing the initial "pop."

Remember that the pop is massive. Hearing protection would be a must if your sound system actually reproduces the sound of the gun, at least in close proximity.

This reproduction has its problems (like most, I guess :-). If you want to SOUND like a gun firing, you need to move the same amount of air at the same speed, within the same short span of time, with amplitudes so high that you need earplugs. If we say that spike is on the order of ~0.2 ms wide, that needs a speaker with decent a frequency response of 5000 hz. So we have two conflicting requirements... we need to move a LOT of air (we need a big woofer!) at a fairly high frequency (we need a tweeter, which generally don't push large masses of air).

Most of us have probably been present when a gun is fired. And we all realize that they don't SOUND like the guns we hear in movies and TV. Hollywood can't reproduce the pop, which is the major sound component. I live a quarter-mile from a police gun range, and when it's active, all I hear is a series of pops.

But...and this part makes me giggle, just a little bit... maybe we DON'T want to be real. Most people are accustomed to Hollywood gun sounds, and that's what they'll expect. Let's give them "Bang chugaluggalugga Bang chugaluggalugga" or whatever sounds like Sylvester Stallone.

Seems to me that microprocessor should be able mix two overlapping waves of the same sound so the reverb effect on the first shot can continue through the second. We'd probably want this anyway, for the folks who might install two guns.

Ron "This is a lot more fun than reading accident reports" Wanttaja

[rwanttaja]

Remember that the pop is massive. Hearing protection would be a must if your sound system actually reproduces the sound of the gun, at least in close proximity.
Which reminds me of the importance of another piece of safety equipment: A volume control.

The local gendarmerie will Not Be Pleased if they get a whole bunch of phone calls from folks claiming there's machine-gun firing coming from the house down the street ("You know, the quiet guy..."). If you're based at a controlled field with airline traffic, you might get an intimate visit from the TSA....

Ron Wanttaja

[rwanttaja]

Well, I do love an experiment.

I built a simple light-flashing circuit using a 555 timer chip. As it doesn't have enough capacity to directly drive my high-intensity LED (12 v, 5 watt), I added a solid-state NPN power transistor as a switch.

The problem is, there's an unavoidable voltage drop across the power transistor. I was using the an old Odyssey battery, which was down to 11.5 volts. With the ~1.5 v drop across the transistor, the high-intensity LED was only getting 10V. From ~150 feet away outside, it really wasn't that visible. The camera even had trouble picking it up, probably related to the flash rate

When I connected the LED directly to the battery, it was a LOT brighter, and very visible in daylight.

One way to get rid of that 1.5 v drop is to use a relay. I had picked up a 12V relay at the local parts store, and wired that in, instead. A quick test shows that it's nice and bright...in the video, a wide swath of the camera pixels are actually saturated.


http://www.bowersflybaby.com/test_vid.wmv

So.... a high-intensity LED would probably work. One problem, though, is that the relays are generally not that good for flashing at high speed (simulating a higher rate of fire). So either one has to find a lower-voltage high-intensity LED (so the Power Transistor loss doesn't affect it) or be satisfied with a lower rate of fire.

Ron Wanttaja

[Dana]

How 'bout a solid state relay? Much faster than a mechanical one.

[cluttonfred]

Perhaps an Arduino-based solution like this could be used to drive a solid state relay for the flash and also run the sound component? http://arduino-info.wikispaces.com/ArduinoPower

I can't offer much more than moral support, Ron, but I am cheering for you!

[rwanttaja]

Perhaps an Arduino-based solution like this could be used to drive a solid state relay for the flash and also run the sound component? http://arduino-info.wikispaces.com/ArduinoPower

I can't offer much more than moral support, Ron, but I am cheering for you!

Well, at least I'm having fun. It's been about twenty-five years since I last soldered parts onto printed circuit boards. Spent a bunch of time finding my old pencil soldering iron with the teeny-tiny tip. Obviously, way out of practice...the flasher circuit didn't work until I wiggled the power transistor. But I also got to let the magic smoke out, then made a Saturday-evening trip to the mall to go to Radio Shack for some replacement parts. Just like the good old days.

The Arduino system is interesting. It'd be fun to pick up one of the experimenter packages and fiddle with it. My last attempt at using a microprocessor to control external hardware was trying to build an adaptor board to work Christmas lights with my VIC-20. It Did Not End Well for the computer. The user community around the Arduino looks like they've got some great ideas.

However, I don't think it's the best solution for this problem. It's got a sound playback option, but I didn't see any waveform-combining or similar functions.

But...it did give me an idea. There are a lot of good sound editing packages on PCs. Seems like it'd be easy to build the right sound on a PC and duplicate it so you have 30 minutes or an hour of shooting.

Why so long? Simple: Because we're going to use a Smart Phone (or an IPod) as the playback device. Transfer the sound to the device, then, just before you take off, start it playing. Set the file to repeat, if you like. Have your trigger switch just connect the output of the smart phone to your amplifier system.

Note this lets you "change guns" whenever you like. Load any number of sound files, for any type of gun. Put "Hitler's buzzsaw" on your FRED.

OK, now what about the flash?

I used a common 555 timer chip in the "astable mulivibrator" mode to generate the series of pulses in my video. I was just the IC with two resistors and two capacitors. However, the 555 also has a monostable mode...if the voltage at one pin exceeds a given value, it causes the 555 to issue just one pulse.

So... in addition to the amplifier, we can feed the headphone output of the smart phone into a small half-wave rectifier, consisting of just a diode, a resistor, and a small capacitor. The rectifier converts the sound to quickly-varying DC...and when the DC gets high enough (like a big pulse when the gun fires) the 555 goes active for what ever time we wish...let's say 1/10th of a second.

The 555 could drive a solid state relay, but being a solid state device, it's going to have some resistance loss that'll reduce the voltage to the high-intensity LED. I'm also a bit cautious about SSRs just because I have no experience with them... they're used mostly to control high-voltage AC circuits from computers.

So we can just use that same old power transistor setup I had.

But what about the low voltage it was providing the LED? Silly rabbit... why are we fixated on using 12 volt power to start with? Why not use two six-packs of AA batteries and run the thing from 18 volts. That gives plenty of extra room to power the high-intensity LED decently. "Head Spacing" if you will.

Even if you do have a 12V battery onboard (you'll need it for the amplifier) you can add a two-pack of C cells and get the gun power up to 15 volts for the gun electronics... still enough head spacing.

So... I'm thinking my wife's Ipod is going to disappear in a day or so....

Ron "Five drops of sinister sauce" Wanttaja

[rwanttaja]

But...it did give me an idea. There are a lot of good sound editing packages on PCs. Seems like it'd be easy to build the right sound on a PC and duplicate it so you have 30 minutes or an hour of shooting.

Try it out? Of COURSE I had to try it out:

http://www.bowersflybaby.com/combined.mp3

I found a Mosin Nagant audio clip online, cropped it down to 0.5 seconds (it was pretty quiet by that point), duplicated it for 20 seconds, then duplicated the track twice with ~0.16s offsets each time. This gives us an effective rate of fire of about 360 rounds per minute.

Ron Wanttaja

[Frank Giger]

I'm very intrigued with the LED, particularly if it can be powered by six AA batteries!I'm afraid of the weight of a sound system, though. Might have to settle for yelling BANG BANG.

[rwanttaja]

I'm very intrigued with the LED, particularly if it can be powered by six AA batteries!I'm afraid of the weight of a sound system, though. Might have to settle for yelling BANG BANG.
The LED I've been fiddling with is a 12 volt unit, so we'd need at least eight cells. I'm thinking two six-cell holders to run the thing with 18 volts, and limiting the voltage that actually reaches the LED.

Don't know how long AA cells will last, but how often does one expect to be actually firing the thing? "Bricks" of AA batteries are cheap at places like Costco or Sam's Club. For those of a greener persuasion, 12 NiCads would still give 15 volts, plenty for the application.

Ron Wanttaja

[Frank Giger]

Pre-Foster mount on my Nieuport 11 - it only has to flash 47 times for my Lewis gun, as I'm not going to stand on the seat to reload. ;)

[rwanttaja]

Pre-Foster mount on my Nieuport 11 - it only has to flash 47 times for my Lewis gun, as I'm not going to stand on the seat to reload. ;)
So, AA batteries for you, then. Or should we call them, "Archie" batteries? :-)

Ron Wanttaja

[rwanttaja]

Pre-Foster mount on my Nieuport 11 - it only has to flash 47 times for my Lewis gun, as I'm not going to stand on the seat to reload. ;)
To go serious for a moment, I'm always amazed at how LITTLE ammunition fighters carry. That 47 rounds equates to about 12 seconds of firing. Yes, you carry extra drums, but there's no way you're going to change them in combat. And the P-51D had six .50 cal machine guns, each loaded with 400 rounds, and each gun shooting at 800 rounds per minute. How'd you like to fly to Berlin and back in 1944 with only 30 seconds of firing time?

Ron Wanttaja

[cluttonfred]

You think that's bad, how about the Hawker Hurricane IIC and other British planes that used the early Hispano 20mm cannon with 60 round drums? Some of the bigger aircraft like the Beaufighter had a second crewman who could load new drums, but not the single-seat fighters. At 600-850 rpm that meant that the Hurri only had 4-6 seconds of ammunition, 8-12 if only two cannon were used at a time. Later Spitfire, Tornado and Tempest fighters had belt-fed Hispanos with twice the ammunition capacity.

From my virtual experience in online flight simulators, however, I can say that it's not necessarily a problem. You learn to hold your fire until you get the shot, and when you do, it only takes a short burst of 4 x 20mm to finish the job.


To go serious for a moment, I'm always amazed at how LITTLE ammunition fighters carry. That 47 rounds equates to about 12 seconds of firing. Yes, you carry extra drums, but there's no way you're going to change them in combat. And the P-51D had six .50 cal machine guns, each loaded with 400 rounds, and each gun shooting at 800 rounds per minute. How'd you like to fly to Berlin and back in 1944 with only 30 seconds of firing time?

Ron Wanttaja

[Frank Giger]

The other side is Rene Fonck, who shot down three planes using only seven rounds.

Then again, he used to practice gunnery by shooting rabbits with a rifle while driving a motorcycle.

[rwanttaja]

I've worked on this, on and off, for the past couple of weeks. Basic flasher we've got; I've been working on the audio-triggered flash.

Built the color organ, couldn't get it to do what I wanted...think the impulse of the gun just confuses the simple filters.

However, I used the front amplifier from it into the comparator input of a 555-based monostable multivibrator, and got it to work tonight... LED flashes at the rate of the gunfire playing on the smart phone. The flash seemed to skip a bit, now and then, and I thought I had a problem. Until I listened carefully to the sound, and realized the skip was where the audio looped.

Biggest problem is that there seems to be a slight delay...the flash comes slightly after the bang. Gonna look into that a bit more.

Overall, I'm not too happy with the circuit...two transistors (three when I add the power transistor for running the big LED), a 555 timer, half-dozen resistors and a batch of capacitors. We'll see.

Ron Wanttaja
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[cluttonfred]

Ron, glad to see you are still slaving away to make this idea a reality. I wish I could be more help, but nonetheless BRAVO! I can't wait to dogfight your Fly Baby with a Yak-like Taylor Monoplane.

[Frank Giger]

I wouldn't sweat a milisecond here or there - or even longer - between flash and bang. Nobody outside of the pilot is going to notice.

[rwanttaja]

I wouldn't sweat a milisecond here or there - or even longer - between flash and bang. Nobody outside of the pilot is going to notice.
Yeah, but it's ****ing me off. :-)

I think it's due to capacitors charging. The audio input is a strong impulse, and most designs are slanted towards music. The big whomping voltage hits, and doesn't get passed until the capacitor's charged. No question it started working better when I reduced the RC time constant for the 555.

But I'm having a good time. Don't think I've built a transistor amplifier for nearly 30 years; worked some IC stuff slightly more recently. Been having some construction issues...worked fine in breadboard, but DIDN'T work when soldered onto a board (yes, I heat-sink the transistors). Gotta work that one out. I used to hand-solder ICs to circuit boards without sockets, and I'm hoping the hands have not lost what cunning they used to possess.

Ron Wanttaja

[rwanttaja]

I wouldn't sweat a milisecond here or there - or even longer - between flash and bang. Nobody outside of the pilot is going to notice.

Looks like it was just an audio power issue. I was testing the single-shot mode using an old cassette-type walkman, and the machine-gun mode from the audio of my smartphone. I have a speaker to monitor the gun sound, and it was obviously must quieter on the smart phone. So I made a tape of the machine-gun sound, and things seemed to work right. Here's a brief video showing the result:

http://www.bowersflybaby.com/gunvideo2.wmv

Note that the rhythm of the gun is a bit uneven (I just strung together duplicates of one Mosin-Nagant shot) but the high-powered LED is tracking it pretty well.

I want to fiddle with the circuit a bit, but otherwise, I'll be posting a schematic in a couple of days.

Ron Wanttaja

[cluttonfred]

Great stuff, Ron! Just counting by ear and watching the time on the video clip, it seems to me that you are getting a "rate of fire" of about 200 RPM. Any thoughts on how you might get that a little higher, and how to get the sound loud enough to be heard over an engine and prop?


Looks like it was just an audio power issue. I was testing the single-shot mode using an old cassette-type walkman, and the machine-gun mode from the audio of my smartphone. I have a speaker to monitor the gun sound, and it was obviously must quieter on the smart phone. So I made a tape of the machine-gun sound, and things seemed to work right. Here's a brief video showing the result:

http://www.bowersflybaby.com/gunvideo2.wmv

Note that the rhythm of the gun is a bit uneven (I just strung together duplicates of one Mosin-Nagant shot) but the high-powered LED is tracking it pretty well.

I want to fiddle with the circuit a bit, but otherwise, I'll be posting a schematic in a couple of days.

Ron Wanttaja

[rwanttaja]

Great stuff, Ron! Just counting by ear and watching the time on the video clip, it seems to me that you are getting a "rate of fire" of about 200 RPM. Any thoughts on how you might get that a little higher, and how to get the sound loud enough to be heard over an engine and prop?
Rate of fire isn't an issue. Rate is set by the audio file, and the one I'm using was built by stacking single shots atop each other. Just have to pack them tighter. I'll have to try a higher rate, though, to be sure the flashes just don't blend into a constant beam. Might need a slight change in resistors.

Making it loud enough? Don't have any idea, other than a big amp and a ruggedized speaker. That is going to be difficult, and is going to take some heavy-duty power.

Ron Wanttaja

[rwanttaja]

Rate of fire isn't an issue. Rate is set by the audio file, and the one I'm using was built by stacking single shots atop each other. Just have to pack them tighter. I'll have to try a higher rate, though, to be sure the flashes just don't blend into a constant beam. Might need a slight change in resistors.
OK, dropped a resistor a bit and eliminated some attenuation on the input, and it worked at about a ~400 RPM rate. One issue is that the flash becomes basically, the LED on constantly with a bit of a flicker. If you're going with that high a rate, I'd just use a simple flasher circuit and not bother to have the synchronization. I like the way it syncs to the slower fire rate in the video...if you watch "The Blue Max" again, you'll hear fairly low firing rates for the machine guns. The guns might be spec'ed at 500 RPM, but you put an interruptor gear in there.... Not applicable to Frank's Lewis, of course.

In any case, the schematic is attached. Everything but the high-power LED can be bought at Radio Shack. The resistor and capacitor on the input is what I used on my ~200 RPM audio file. Wire the audio input directly to the base of the first transistor if you use a high firing rate.

And I'm not done. I want to try some improvements to the "Flash only" circuit I put together a month or so back. It struck me that I might be able to gimmick the output to produce a series of pulses that might not sound too bad after being run through an amplifier. Less complex, easier to build...and the quality issues will be less important at 500 RPM. We'll see.....

Ron Wanttaja

[cluttonfred]

You are my hero, Ron. Red Baron, look out, here comes Snoopy!

[rwanttaja]

OK, the simple flasher-only circuit was...err, simple. One IC, one transistor, three resistors, two capacitors. With the addition of a third capacitor, it does provide an audio output that could be amplified.

http://www.bowersflybaby.com/gunvideo3.wmv

This example has a small speaker attached... does give a "Takatakataka" sound. Shove it through a mondo amplifier, out a rugged bullhorn-type speaker, and distorted by the slipstream, it'll probably sound close enough.

I'm going to solder up a PC-board version for Frank, I'll post a schematic and pictures when done.

Ron Wanttaja

[Frank Giger]

I got to thinking that a bullhorn itself might be the best solution. Self contained and built to make stuff loud, if not in high fidelity.

The only problem is that they tend to be unidirectional....but if placed behind the seat in a fabric covered aircraft facing aft, it might turn it into a drum-like amplifier (hmmm, maybe to dubious effect?).

Cutting the horn down might do the trick...

http://www.thunderpowermegaphones.com/Compare-ALL-Megaphones

[rwanttaja]

I got to thinking that a bullhorn itself might be the best solution. Self contained and built to make stuff loud, if not in high fidelity.

The only problem is that they tend to be unidirectional....but if placed behind the seat in a fabric covered aircraft facing aft, it might turn it into a drum-like amplifier (hmmm, maybe to dubious effect?).
They're cheap enough, on the link you posted...buy two, face one towards ~10 o'clock and the other towards 2 (then have 2/3rds of a Dr. Pepper, I guess). Guns are directional, too ('cept when I'm shooting) so if there's a bit of a null aft, that's not so bad.

The hard part, for any electronic solution, is going to be the tremendous drag on horns. Depending on the engine in the Nieuport, you could perhaps mount them on the firewall below the engine, "firing" through the lower open section of the horseshoe cowl.

Ron Wanttaja

[Frank Giger]

Yep, that's where it would go....on the firewall below the engine, pointed down about 30 degrees. That Nieuport is one big exercise in how to induce drag through design....no need to add to it.

Hmmm, and I am going light on the engine, so adding five to seven pounds would be okay.

[cluttonfred]

Perhaps behind the seat, angled down and forward about 45 degrees? For a WWII type, the megaphone could be disguised as a bomb on a centerline rack.

[Frank Giger]

I was actually thinking of taking the horn off of the main unit and running wire, putting the heavy bits (electronics and batteries) in the cockpit nearest the CG.

Being a skinny little guy sure does help in the W&B.

[rwanttaja]

Okay...time to put the lipstick on this pig and roll it out.

Attached is a PDF file that gives some information, and includes schematics for both circuits. Notice the previous schematic for the audio-synchronizing version had a wrong transistor call-out; this version corrects it.

Ron Wanttaja

[cluttonfred]

Bravo, Ron, thanks so much for all your work on this. Now I just need to decide whether or not I want to go with an RAF hawker Hurricane scheme for ther Taylor Mono, in which case I'll need eight, or the winter white Soviet Yak-1, in which case I'll only need two but will have to figure out how to put one in the spinner. ;-)

[danielfindling]

Okay...time to put the lipstick on this pig and roll it out.

Attached is a PDF file that gives some information, and includes schematics for both circuits. Notice the previous schematic for the audio-synchronizing version had a wrong transistor call-out; this version corrects it.

Ron Wanttaja

I think I might just have to try to build one. Thanks!

[Flyin'Bryan]

Ron and all, just when I thought I might be researching something that nobody else is really doing yet, I run into this group of like-minded individuals, and I am very happy that I did. I had to wait a day or two to get my forum account set up before I could reply. My LED adventure began with the flashing stop signs I started seeing at various intersections around town. Further research lead me to the understanding that these were most likely 3 watt high powered LEDs. Initially I was not really concerned about in-flight visibility as I was with close up on-the-ground visibility, but this thread has changed my "attitude" about that.

My next progression down this path occurred during a visit to a local Radio Shack, when I stumbled across a little Velleman minikit MK102 that has 2 flashing LEDs. It uses a pair of manually adjustable potentiometers to change the rate of either of the two LEDs, and after I soldered it all together it worked great. At that point I figured I would just need to upsize the components to handle higher powered LEDs and duplicate the same module as many times as necessary for my application. While it seem that most of you are working with the WW I gun applications, I am trying to come up with a WW II application with multiple guns firing at slightly different rates.

I then also became interested in adding some sound to the mix, and my current plan was to use a CB PA speaker (or 2) with a looped sound file on a USB stick, with the sound and light modules all wired into the trigger on the joystick. I had not even thought about the possibility of designing something that would actually synch the sound to the flash rate of the guns. Ron you have now opened my eyes to that solution so thank you for that. My current mounting plan was to attach one or two speakers to the bottom of my forward baggage compartment, with a mock grill on the outer skin that would emulate the same rectangular series of holes found on the sides of P-51 Mustang.

I currently have a test bed of a variety of different LEDs coming from Super Brite LEDs, as well as strobe controller unit that really captured my attention when I watched the video. The digital controller has 10 modes, and I am really only interested in one of them that gives a machine gun-like affect. It has a 2 amp max capacity and I was going to try to run it with 4 LEDs. Ron I really appreciate the test videos with the 5 watt light, and you now have me thinking more about in-flight visibility. I will now have to assess the ability to fit lights that are bright enough but may be a challenge to fit into an in-wing gun port installation for my application. All really great stuff on this thread. Looking forward to the sound tests!

[rwanttaja]

Ron and all, just when I thought I might be researching something that nobody else is really doing yet, I run into this group of like-minded individuals....

Good to hear from you, Bryan. Hate to start out with a spelling flame, but I have to point out that "Stupid half-mad b******s" is NOT spelled, "like-minded individuals." :-)

Thanks for your insights and the results of your own research/experiments. One of the things we also haven't considered much is the *directivity* of the light emission. Most of these systems concentrate light in one direction, which means that only the people within ~20-30 degrees of the boresight get the full-power flash. There are really few instances where we would be flying directly at the people on the ground who we want to see the flash.

Guys with the WWI replicas might consider putting their high-power LEDs on adjustable mounts. If you're going to be doing low passes with the crowd on the left, set the LED to point ~45 degrees in that direction. Looks bad close-up, but sure should be more visible to the general (Shakespearian term, doncha know).

Your point about the multiple guns in a WWII fighter not be synchronized is a good one. We're all, again, attuned to the Hollywood machine gun sound, where eight .30 calibers make a single rat-tat-tat sound.

The nice thing is, with those flashers using the 555 timer, the natural variation in the values of the resistors and capacitors will make the firing rates slightly different. If the capacitor value varies by just a 10% variation, that changes the firing rate by nearly 50 rounds per minute! So any two circuits side-by-side are NOT going to sync up, and will be discordant just like a real set of guns.

Along that note, they make a single IC (the 558) that includes *four* of the 555 timers. So a single chip could provide four slightly different gun flashes. You'd still need separate power transistors for each one, of course.

Ron Wanttaja

[Flyin'Bryan]

Hehe. "Roger that" Ron. We all have to be at least a little crazy, so right there with ya on that. Regarding directivity - really good point. Also gives rise to the fact that flying down a runway line will only allow one side of a wings lights to be potentially seen by "the crowd." To see both sides would require a bit of side slip with the leeward wing slightly high for a good effect. And of course the directionality also comes into play as you stated. For that I see a small servo connected to a bracket that connects all the light mounts that will allow you slant the lights as much as necessary to expose as much of the light as possible to the on-lookers. My brain is working overtime trying to come up with a good mounting solution for all that. I think it is totally do-able though.

Also thanks for the heads up on the IC 558. I knew about the 555 but have not had a chance to play with either of them yet. That said, I have tried out several of the lights I received from SuperbriteLEDs, as well as the strobe controller, and I have to say I really like the effect I get from one of them above all the others. It is their part number WLED-RLX, which is a 1 watt non-polarized wedge mount Red LED. I'll have to rig it up for some outside tests, but inside it just about blinds the heck out of ya-and that from using just a 9 volt battery. The strobe effect is also pretty cool, and would pass for machine flashes pretty nicely I think. I'll look into the 558 chip and use your schematic and see what happens. I'll grab some pics and video and post those as well.

[cluttonfred]

I have the two "filament" version of this single 3W LED bulb in the bullet-shaped tail lights on my truck. I am very impressed by the brightness and the dispersion of the beam from the integrated lens.

http://www.superbrightleds.com/moreinfo/tail-brake-turn/1156-led-bulb-single-intensity-1-x-3-watt-high-power-led-w-reflector-lens/921/

For a WWII set-up, I can easily envision eight 1156 (BA15S) sockets set in the wings below the surface of the leading edge under fake "doped red patch" covering the "muzzles" but with each hole actually covered by removable clear tape circles. For the big show, you remove the circles and plug in the eight bulbs with the sockets just deep enough to leave just the lens projecting beyond the leading edge. That ought to be visible from any angle when firing but otherwise not jarring from a distance. See this detail photo of an actual Hurricane I at the Imperial War Museum in Duxford.

2894

[Flyin'Bryan]

Eric, that is awesome. Yup, I can see those lights working well for an in wing WWII assembly. Looks like they are just over 2 inches long and 3/4 inches wide. Unfortunately I am chained to the task of emulating the flared gun ports of a P-51D Mustang, which basically consists of a stacked wedding cake-looking assembly of metal coming out of each gun port. I wish I could get away with the open port design of the Hurricane (thanks for that photo). That would make things so much easier. Then I was milling about in an RV trailer hitch store today and found some plastic plumbing parts that immediately grabbed my attention - not for using them on my trailer, but as an almost perfectly scaled gun port for my application. Here is a pic:

http://i47.tinypic.com/2ur5aqa.jpg

Not too bad for a gun port on an experimental plane I think! I plan on glassing the gun farings onto the wing for that true P-51 gun port look. Taking the SportAir Composite class in about a week so I am getting excited about that.

This site has some good close ups of the gun ports on the 51:
http://www.crazyhorseap.be/Mustangs/Mustangs/G-MSTGJanie/G-MSTG.htm

It all comes down to measurements now. If I can house all of the light assembly inside the gun port housing, then I only need to drill holes in the LE of the wing large enough for the wires to attach to the base. Otherwise the base will get mounted just inside the leading edge of the wing as you have stated, probably on a small aluminum bracket that I will attach to the nose of each rib in the bay where the guns will be located. Above all, I will need to ensure that the gun port assemblies are able to withstand the flight loads without coming apart, and I think flight testing will be the only real way to assure that.

I was also trying to figure out what to use for a weatherproof cover for the ports, and was encouraged by reading your post and seeing the specs from the 1156 light which includes a reflector lense. Then I was disappointed again when I read the fine print that states that they are non-weatherproof and for indoor use only, unless in a weatherproof housing. I have a local company where I live that handles all sorts of vehicle lighting that I plan to visit next week to see if they can offer up a small profile weather proof enclusure for a light light this. Or perhaps a simple O-ring will do the job. Either way - no question that I will have to do whatever is necessary to keep the moisture out.

Still having fun piecing all this together.

[Frank Giger]

On waterproofing - how hot do the LED assemblies get? If they don't get hot, one would think some shrink wrap might be a super low-tech solution. If they do get warm, perhaps a cardboard tube to insulate from the guts of it and then shrink wrap.

Or just don't fly in the rain! :)

I was going to experiment with a glass or plastic tube when I rig up the gun for dispersal of light - the barrel of my 7/8 scale Lewis gun is about a quarter inch around, and I wondered if I put a glass rod in it up to the flash supressor if the light would scatter back enough from the end to show from the sides through the slits.

Perhaps if it were frosted....

[cluttonfred]

On the waterproof installation question, I remember seeing some low-cost marine lights made by essentially screwing the bulb-holder through the inside of a baby food jar lid into the roof or bulkhead of the boat. The wires were fed through a rubber grommet-lined hole in the lid. You then screw on the jar itself for the "lens" and you are done.

With that principle in mind, depending on the bulb holder you use, you ought to be able to to find a small clear plastic pill jar that would fit over the end of the bulb and with liberal use of silicone sealant you could make it waterproof. I don't think heat would be an issue--the LEDs do not generate as much heat as traditional bulbs, and they will only be flashing intermittently in short bursts.

That said, these bulbs are probably a lot more water-resistant than you might think, they are just not intended to be installed completely exposed to the weather.

[Flyin'Bryan]

I have ordered the same 1156 LEDS and the bases that go with them - they might arrive tomorrow. In the mean time I am including two links, one of the raw mp4 video I shot of my light test with the strobe controller unit from SuperBriteLEDs. I will also post a link to my latest blog entry that also includes the same video, in case video only link does not work for some reason. I really liked the the effect. As my post states, I finally found a small round enclosed trailer LED light today that may just serve my purposes. Lots more testing to do yet, but man this is fun....

This small light seems to be weather proofed in front and in back, but still requires a good mounting base. Love the baby food jar idea, and so far my idea was somewhat similar by using a small round metal mounting plate that I will imbed in a glassed gun port faring as far in front of the leading edge of the wing as necessary for the gun port/light assembly to look good. I also still like the idea of making the lights removeable and putting some sort of cover plate over them. Also agree that they should not get that hot if they are being strobed in short bursts.


http://www.youtube.com/watch?v=Clll-5Sf5n0&feature=youtu.be

http://bryansrv8project.blogspot.com/2013/04/simulated-machine-gun-testing.html