I'm trying to figure out a way to make sure that the amp always sees a load in case a bulb blows.
So the only way I could think of to keep a resistor in the circuit all the time is to put it in parallel with the bulb ...
red speaker wire > 20W (?) lightbulb in parallel with a 20-50W 8ohm resistor > speaker
black wire as normal.
But this doesn't work. The bulb's resistance goes up as the wattage increases, which means the load drops. That's the opposite of what I want.
Any ideas?
I'm specifically interested in building a lightbulb compressor, not any other type of attenuator.
Quote from: midwayfair on June 10, 2013, 11:32:23 AM
I'm specifically interested in building a lightbulb compressor, not any other type of attenuator.
Something like a Wien bridge (with other resistor values):
(http://diale.org/circuits/Dynamikkompressor.jpg)
I wonder how much compression you can get out of it.
Edit: Actually is more like an expander than a compressor, much like you describe, but it has the advantage that if any of the lamps fail, nothing "bad" will happen. To get a compressor you should put the lamp in series with the speaker.
http://sound.westhost.com/project45.htm (http://sound.westhost.com/project45.htm)
> a load in case a bulb blows
OR gets hot?
IIRC, a 120V 60W lamp is 16 ohms cold but over 50 ohms at a dull glow (and obviously 240 ohms at full 120V bright-white).
So the amp "loses its load" any time that the lamp is warm.
I think you want something like this:
(http://i.imgur.com/nDYbBGw.gif)
OR: drive the lamp and dummy-load with an LM386, then run that signal into a real amplifier. Because a lamp-limiter in the speaker side *must* absorb *most* of the power that you dragged to the gig. If you need 10dB of limiting (not a lot), then a 50 Watt amp puts 5 watts in the speaker.
Quote from: PRR on June 11, 2013, 01:30:01 AM
> a load in case a bulb blows
OR gets hot?
IIRC, a 120V 60W lamp is 16 ohms cold but over 50 ohms at a dull glow (and obviously 240 ohms at full 120V bright-white).
So the amp "loses its load" any time that the lamp is warm.
I think you want something like this:
(http://i.imgur.com/nDYbBGw.gif)
THIS looks more like what I'm after.
It occurs to me that I could borrow a friend's Night Light and see how it does the compression setting. I think that has a constant load regardless of the use of the bulb.
Edit: is that a 4-ohm speaker? Do I make any changes if it's an 8 ohm?
Hey folks.. ran across this old thread while searching for "light bulb compressor" schematics. Has anyone achieved good results from PRR's circuit, or similar 'light bulb' arrangements?
Thanks, -Corey
Hi
off the top of my head, I can't see a reason why this wouldn't work in a stompbox.
The 'driver amp' might be an LM386 and the bulb from a 6V flashlight. Replace the speaker with a 'sensing' load (a JFET source follower or BJT emitter follower). Or even another 386 for a compressed stompbox micro-amp.
Surely this has been done before?
cheers
hey jon,
if memory serves, you can wire 4 60 watt 120v lightbulbs in series/parallel and get a reactive load that will handle 200 watts or so. each lightbulb is a reactive load, and close enough to 8r for rocknroll.
i asked kevin o'connor (TUT) about doing this about 10 years ago, and he said it would be fine and not hurt my amp.
never actually tried it tho... just fwiw
Quote from: pinkjimiphoton on August 20, 2013, 12:39:07 AM
hey jon,
if memory serves, you can wire 4 60 watt 120v lightbulbs in series/parallel and get a reactive load that will handle 200 watts or so. each lightbulb is a reactive load, and close enough to 8r for rocknroll.
i asked kevin o'connor (TUT) about doing this about 10 years ago, and he said it would be fine and not hurt my amp.
never actually tried it tho... just fwiw
The issue was ensuring that there can never be no load if the bulb blows. Using four bulbs might make it less likely they'd all fail, but not necessarily fool-proof in the way that a resistor is. I'm still not sure if PRR's schem means that if the bulb blows there's still a load. I don't know how speakers work. I scrapped this idea because I'm too afraid of damaging my amp and just haven't had time to learn what I need to know to ensure it's not damaged. I'd RE my friend's Night Light to build myself, but it's not like Swart overcharges for the thing (it's cheaper than many other attenuators).
In PRR's scheme the bulb is in series with the speaker and they are both in parallel with the 8 Ohm resistor. If the bulb blows it breaks the connection to the speaker but the amp still has the 8 Ohm resistor as a load.
> if memory serves, you can wire 4 60 watt 120v lightbulbs in series/parallel and get a reactive load that will handle 200 watts or so.
Don't try that.
One 120V 60W lamp is 16 ohms cold. Great! I wired it to a 10 Watt tube amp, cranked, and got WAY too much voltage, and a dim glow. Turns out this much power drives the lamp to about 100 Ohms, the amp is nearly un-loaded.
Four series-parallel just gives you the same deal at 40 Watts. I wouldn't even expect that to be a "good load" at the 10W level.
BTW: the lamp is not significantly reactive, and we don't want reactive loads for basic amp *testing*. Yes, speakers have complex reactances; melding test-resistor results to loudspeaker results is yet another layer of fun.
The lamp *attenuator* plan I posted will not leave the amp un-loaded (I know better).
No, it is not generally useful except E-V used it as tweeter protection. The lamp heat/cool times do little for music. But Jon wanted to try it, was not interested in any other type compressor, so WTF.
well, as we both know, i'm far from an ee paul!!! lol
but... unloaded would be an open circuit i would think, not 100r! amps can usually handle much higher resistances better than too low...as i recall from my more adventurous days (read: willing to blow up high voltage tube stuff ;) ) an 8r speaker goes ALL OVER THE PLACE as a "resistance" (i don't fully understand the concept of impedance, other than it changes at different frequencies)... i mean, from 40-50r to zero ohms at some point... zero ohms, it's no longer a resistance, it's a conductor. while you (or me)'d think that would be an issue (and it would be if it stayed there) but apparently it's not cuz it's intermittent.
when i first got the idea of using light bulbs in place of speakers, i contacted kevin o'connor (author, The Ultimate Tone and London Sound amp guru) about it and asked him if indeed i could hurt anything trying it. he said it would be fine, the amp doesn't care if it's a speaker or a lightbulb, as long as it has a load on it. i asked him about the series/parallel thing, and he said that would be fine.... not to argue the point, cuz we both (all) know i don't know $#I7 about stuff, but if ya think about it, just reading the resistance of a light bulb isn't enough. like a speaker, to find the impedance you would need to input a 1k sine wave. at other frequencies, an 8r speaker could be anywhere from 4. some odd ohms to 12, and still be an 8r load.
speaker line level is up to 70v or so, so a 60-100 watt lightbulb that can handle 120 + volts shouldn't burn up.
the 60watt bulbs i'd measured were reading about 8r, but i'd imagine it could vary by brand and size etc.
again, not to argue, but just to learn more is why i'm bringing this up. i've seen tube amps that were designed just to drive relays, which are definitely not like speakers!! (i've taken them and hooked up speakers to the same output transformers that were for the relays and it worked fine, indeed it's currently one of them as the OT in my tweaked out princeton)
i find it interesting to see two completely different viewpoints from two such respected techs as you and kevin.
anyways. :icon_mrgreen:
Quote from: PRR on August 20, 2013, 07:56:32 PM
But Jon wanted to try it, was not interested in any other type compressor, so WTF.
Aw, I hardly think 'not interested in any other compressor' described me. There are very few compressors I'm not interested in. :) This was just a type I hadn't built yet, and you already co vinced me that it wasn't a great method. ;)
:icon_mrgreen:
> Aw, I hardly think 'not interested in any other compressor' described me.
I know you have wide-ranging interests.
However in *this* thread someone put these words in your post:
I'm specifically interested in building a lightbulb compressor, not any other type of attenuator.
If you let the thread expand to cover "all" compressors, I can point you to about 4 decades of bedtime reading.
Many grizzled designers think that Power Amps are the toughest job in audio design (mostly the blow-up proofing issues). I'm starting to think dynamic range processors are a strong #2. They don't blow up (usually), but they don't just "pass signal", they have to jack-around the signal yet slip under the listener's radar (sonar?), and never slip-up (burp, fade, swell noticably, dropout, garble, bobble, fuzz....).
So in that sense I have STRONG interest in SIMPLE compressors that are 90% good with <10% parts of a "proper compressor". Selected LDRs are a low-risk easy path.
You are right that 100 ohms is not the same as infinity.
Kevin may have blown-up more amps (or seen more blown-up amps) than I have. One blow-up mode is when there is not enough resistance to damp the kick-back of an OVER-driven tube amp's output transformer. It doesn't have to be Infinite ohms to puncture the winding insulation. It *may* have to be more than 10X the design load. And from 16 to 100 is less-than 10X. But all these safety margins are very approximate. And the OT is a major expense. I prefer not to get even close.
Lamp impedance versus frequency.... I have tried this, so have many others. Small lamps are used as test-loads for small radio transmitters, At 2MHz or 5MHz they become a little inductive. Over the audio band they are dead-flat. For another evidence: common 240V 3W lamps are used to stabilize audio oscillators over the 20Hz to 200KHz bands. If there were any deviation of impedance, the output level would change.... it doesn't.
Speaker impedance should NEVER be "zero". Speakers without crossovers will never dip below their DC resistance. See speaker impedance curves. Here is one, bottom of the page. (http://www.usspeaker.com/jensen%20p10Q-1.htm) DC resistance Re (incorrectly reported as impedance) is 6 ohms. Audio impedance is above 8 ohms at 45hz, peaks at 50 ohms at 88Hz, drops to 7 ohms 200-300Hz, rises to 8 ohms at 800Hz, and 20 ohms at 5KHz.
Tubes used to drive relays are not normally transformer-coupled, nor fed raw audio.
70V speaker lines are a somewhat different situation.
We are not so much worried about the lamp Burning-Up, as it not being the expected value. All physical resistances change with temperature-- that's the way atoms are. if you heat copper about 100 degrees its resistance doubles (and that matters in some high-power loudspeaker work). Resistor-metal is picked for a lower resistance/temperature change, but even so if a resistor heats 100 degrees we usually say "Wow! Hot!" and go no further. However a lamp filament normally, safely, heats a thousand degrees. 10X more than a hot resistor. And Tungsten has a pretty high resistance/temp rise (which is key to light-bulb stability). So even 100 degrees in a lamp, far-far below glow, is a Large change of resistance. And a poor test-load.
Use a fry-pan. You won't easily get it wow-hot, and you can feel the heat directly instead of through a vacuum.
thanks for not tearing me up on this brother. you make all valid points.
but one question.... when i was playing with stuff a long time ago, i had a fluke i used to read the resistance of the celestion in my princeton... and it was definitely hitting 0 ohms at times while i was playing... i just had it hooked up and was watching while i was playing (silly hippy is dangerous to be around i think). i watched it go up and down.... if it's hitting 0 ohms (or something so low as to be close enough for the meter to think it was zero) does that mean the OT is passing dc? if it is, i'd assume it's shot.... or was i having one of them big hallucinations again? ;)
Hi
there is enough DC resistance, inductance(s) and capacitance(s) in most '8 ohm' speakers to allow low AC resistance (a couple of ohms). (PJP: the OT is passing AC, not DC. Transformers cannot pass significant amounts of DC (and near-DC)).
I've not heard that going 'open' or a bulb going high resistance is much of a problem for an amp's output section.
Re: LDRs
If only LDRs were better behaved, they'd be great. But they have slow turn-on and slow turn-off (at different rates, so it doesn't help to just increase the compressor's sensitivity to the slew-rate).
I wonder what the rate of resistance change is like for the electricity to heat conversion in the lamp? Faster or slower than an LDR? More or less symmetric? More or less 'musical'?
cheers
Quote from: brett on August 21, 2013, 01:46:52 AM
Hi
there is enough DC resistance, inductance(s) and capacitance(s) in most '8 ohm' speakers to allow low AC resistance (a couple of ohms). (PJP: the OT is passing AC, not DC. Transformers cannot pass significant amounts of DC (and near-DC)).
I've not heard that going 'open' or a bulb going high resistance is much of a problem for an amp's output section.
Re: LDRs
If only LDRs were better behaved, they'd be great. But they have slow turn-on and slow turn-off (at different rates, so it doesn't help to just increase the compressor's sensitivity to the slew-rate).
I wonder what the rate of resistance change is like for the electricity to heat conversion in the lamp? Faster or slower than an LDR? More or less symmetric? More or less 'musical'?
cheers
From memory the rise time of a "typical" automotive indicator filament lamp is in the order of 100 - 200 milliseconds. No idea about decay times, but I assume it's all related to filament mass v. surface area, with skinny low current filaments quenching quicker. An internet search may yield manufacturer data for lamps used in applications where this may matter.
Regarding slow LDRs: Yeah, cadmium sulphide ORP12s and the like are pretty glacial, but vactrols designed for higher speed applications use different photosensitive compounds (cadmium selenide?) I use these:
www.silonex.com/datasheets/specs/images/pdf/104058.pdf (http://www.silonex.com/datasheets/specs/images/pdf/104058.pdf)
As with all vactrols the actual attack and recovery times depend on the amount of current you hit them with (and for how long), but attack times of a few ms in combination with a recovery time of a couple tens of ms are vaguely ballpark. More current = faster attack + slower decay and vice versa. As a bonus just 1mA liberates a resistance of about 300R. I like 'em!
If any newbies are reading this thread I'd like to point out that running a valve amp without a vaguely suitable load across the output transformer secondary is only marginally less silly than poking your genitals into a bee's nest. It's a bit like closing your eyes while driving at 70mph and counting to ten before opening them again. It may not end in tears, but no good will come of it. :icon_lol:
I don't know if there's such a thing as a "musical lamp". Perhaps the singing arc (http://en.wikipedia.org/wiki/Plasma_speaker) would be a better choice.
:icon_mrgreen:
that was sig-worthy.
i know the OT is ac on the secondary, but what i'm talking about is the speaker kinda going thru zero for lack of a better explanation.
i remember the meter being set on low scale r, and watching it go up, and down, and occaisionally hitting zero with a "-" sign displayed.
it is entirely possible i was misunderstanding it, but i took it as the speaker varying from an inductor (8r-ish) to a conductor (0r-ish).
was i misreading this? i mean, we're talking 14-15 years ago, and i knew even less than the picayune things i've learned now... ;)
if it's conducting, even for a few brief milliseconds...slow enough to be noticeable on a digital meter.... wouldn't that mean the speaker is putting out dc at that point? wondering if that's what makes some speakers blow, by pushing them past their point of induction and popping the voice coil.
i mean, guitar signals thru an o-scope, even if you don't know what you're doing like me is pretty cool to watch.... and way more complicated than a 1k sine wave.
oy... my head hurts at this point
anyways, generally the only time i've seen dc on an output transdormer other than that experiment was if the primary was shorted to it or arcing. usually that sounds like a blown speaker, right around F# above and below middle c. you hit those notes, or CLOSE to those notes, and suddenly the amp craps out. lay off the note, it comes back on. (i hate it when that happens. ;) )
> when i was playing with stuff a long time ago, i had a fluke i used to read the resistance of the celestion in my princeton... and it was definitely hitting 0 ohms at times while i was playing...
You had the ohm-meter across the speaker *and* OT, *WHILE* you were playing??
> silly hippy is dangerous to be around i think
Snort some orange-juice and put your brain in gear.
The ideal OT has zero resistance (for perfect efficiency). In a real world it has a part-ohm resistance, say 0.6 ohms. 0.6 in parallel with 8 ohms is 0.56 ohms. Many ohm-meters won't read right below 1 ohm; some Flukes do but good sub-Ohm readings need special technique. So it _should_ read way-low.
Now think about how the Ohm-Meter works. It has a power source, puts a *known* voltage/current out the probes, and reads the current/voltage developed in the circuit being tested.
If there is ANY other power source involved, the meter does not know that and gives bad readings.
My Fluke will not read ground-resistance around my house. Always shows 2.8 Megs from power-ground to dirt-conductor. After much head-scratch, I put it in Volts. Most of the paths I tested had copper at one end and iron at the other. This plus damp dirt makes a 0.6V battery! Already there is a power-source the meter doesn't know about. But on AC Volts I get 2.5V to 3V AC. This is voltage-drop in my very-long line from the street. While the ohm-meter "should ignore AC", it is trying to measure <0.28V of DC, and apparently 10X that much of AC over-whelms it (which is reasonable, since I should not be reading resistance in the presence of stray voltages). It turns out that 2.8Megs is just the max reading for this model of Fluke (yet not high enough for it to read OPEN).
You've got several volts of AC (audio) across the speaker. One time it is high and the meter shows a high reading. Another time it is low or negative and the meter may try to give a negative reading. Something in there knows that negative resistance is probably a screw-up and rounds-up to zero. But it is reading a meaningless combination of meter self-assumptions and unexpected audio voltages.
> seen dc on an output transdormer
If it is "DC", then it will be there ALL the time. Or at least more than an instant.
If you mix AC signals with a DC-reading meter, sure it will cross zero sometime.
If you want to know speaker impedance, set up a signal generator to a power amp and then put 8r resistor in series with the speaker. Put 1V AC across the combination. Measure voltage across speaker. If it is 0.5V, the speaker must be 8 ohms. If it is 0.9V the speaker is 72 ohms. If zero, the speaker is zero ohms. Try the entire audio range. Try small and large drive voltages.
For extra tediousness, use o'scope so you can watch the current/voltage over the whole wave.
If you drive the speaker to "slap" with special drive waveforms you *can* get a reading lower than the DC resistance. This is stored energy in the cone mass/stiffness "generating" counter-voltage. I don't think this has been confirmed in real-life audio signals.
> high resistance is much of a problem for an amp's output section
Generally only in tube/valve amplifiers. And mostly when playing HARD. Transistor amps mostly do not have output transformers. The few that do work at such low voltages that undamped transients are not likely to exceed the ~~500V insulation. But a 400V tube, played HARD, with no load, can kick 4,000V spikes across the insulation. This happens same-way that a car ignition system kicks-up a 12V supply to 400V spikes at the primary (then transforms them to 40,000V spikes). If there is current in the coil, and you break the circuit instantly, the voltage rises to infinity. With practical switches and with lossy iron-core coils, the kick-up may only be 10X. (>20X in an ignition coil because they _want_ large kick.)
> rate of resistance change is like for the electricity to heat conversion in the lamp?
Like what Jonathan says, couple tenths of a second.
But also symmetrical. Cools down about as fast as it heats up. Most LDRs have considerably more decay than rise, which is fairly useful in audio compression. In fact the "un-natural" timing of the lamp may have been useful in the tweeter-protector application: the "wrong" sound led the user to suspect hot tweeter instead of other problems in the signal path.
A long time ago.. Paul R forgot more than I'll ever know about electrical matters.
.. ...
I may tinker with the light bulb scheme that Paul posted.. if I do, I let you guys know what I think of it...
^^^
indeed.
paul... thanks for all the explanation. i am actually comprehending much of it, and it explains my previous delusion...perfectly!!
thanks bro!!
Quote from: chptunes on August 22, 2013, 10:28:22 AM
A long time ago.. Paul R forgot more than I'll ever know about electrical matters.
.. ...
I may tinker with the light bulb scheme that Paul posted.. if I do, I let you guys know what I think of it...
If you do get around to it then I'll be interested to hear how it goes. Paul's observation that the "cooling" time of the filament lamp is similar to it's "lighting up" time means that in conjunction with it's sloooow response it can act as an RMS (i.e. energy or perceived volume) detector (I'm simplifying things because I believe that ballpark comes first and details can often wait...). While it doesn't offer a "sustain 'til Christmas" compressor, a few dB of reduction on sustained notes after letting attacks through at full bore might e.g. lead to a musical "sag" which may bring a bit more life to those teeny power amp IC's that we often press into service as late night practice amps. In any case it's certainly worth messing with, because it might be one of those subtle things (albeit not so subtle as $1000 speaker cables / capacitors!)
*Stream of conciousness alert*
It's just dawned on me that a lot of folks out there might have a box full of old EL34 / other power valve pulls. The hot resistance of the filament is *about* 4 Ohms and the cold resistance rather less (to my eternal shame I don't have a tube power amp right now to nick a valve out of for measurement purposes and the hot:cold ratio may be a bit less than for lamps 'cus perhaps heater filaments aren't run quite so white hot...). The filament dissipates about 10W on full chat and is generally very robust. It may be a candidate for a power soak limiter, possibly? Perhaps the filaments might be a bit massive and slow, but if not then couple of EL34s that light up in time with your palm mutes would look great... :icon_smile:
hy, the wien bridge speaker compressor/expander looks very interesting, i do build amps and guitars,
but here i am left abit confused, how does this work the way the speaker is connected between the outputs of the the transformer,
any help very much appreciated,
??? :icon_eek:
Quote from: tca on June 10, 2013, 02:09:35 PM
Quote from: midwayfair on June 10, 2013, 11:32:23 AM
I'm specifically interested in building a lightbulb compressor, not any other type of attenuator.
Something like a Wien bridge (with other resistor values):
(http://diale.org/circuits/Dynamikkompressor.jpg)
I wonder how much compression you can get out of it.
Edit: Actually is more like an expander than a compressor, much like you describe, but it has the advantage that if any of the lamps fail, nothing "bad" will happen. To get a compressor you should put the lamp in series with the speaker.
Welcome.
> how does this work the way the speaker is connected between the outputs of the the transformer
Make all four resistors/lamps the same value, there is no voltage across the speaker, no output.
Make them different, there is output.
Specifically: make the lamps zero, you have full voltage to the speaker. Very-low, you have most of your speaker voltage.
When the lamps heat-up, their resistance rises from very low to around (if properly selected) 10 Ohms. So heat shifts the speaker voltage from nearly-all to nearly-none.
thanks for the endless info and clarifications, paul.
dude. i have learned so much from your posts its not funny,
and i'm forever in your debt.
that kinda sums up what i found years ago... 60 watt incandescent bulb is around 8 ohms when hot, so i had sent kevin from london power an email asking about replacing speakers with lightbulbs as a reactive load. he said it should be fine, tho i never did end up trying it... i had envisioned using 4 in a series parallel arrangement to replace an 8 ohm load to use as a "dummy load" but never ended up getting around to it.
sorry for the ot... back to the original topic. peace!
> 60 watt incandescent bulb is around 8 ohms when hot, ... replacing speakers with lightbulbs as a reactive load.
120 Volt 60W lamp when lit is obviously 0.5 Amps at 120V or 240 Ohms. (240V 60W lamp is 960r.)
Incandescent lamps have negligible reactance at audio frequency.
I had a 120V 60W which measured 15 Ohms *cold*.
I put it on the 16 Ohm tap of a 15 Watt tube amp. Above a dozen Volts out, I got impossible results. At 15V I could see the filament dim-red. Obviously not "cold". I later verified it was going over 50 Ohms above 12V.
The time-constant around dim-red is several seconds. In others tests I have dumped 120V through a lamp into a dirt-rod (don't try this at home! Get the other guy to try it.) It would take a few seconds for the lamp to reach part-glow and the current stabilize. I'm not sure what the musical use is, of an effect that don't happen until a bar or two *after* a loud peak.
Quote from: PRR on January 15, 2018, 07:36:41 PM
>
In others tests I have dumped 120V through a lamp into a dirt-rod (don't try this at home! Get the other guy to try it.) It would take a few seconds for the lamp to reach part-glow and the current stabilize. I'm not sure what the musical use is, of an effect that don't happen until a bar or two *after* a loud peak.
LMAO
reminds me of the time i mis-wired a sewing machine "speed" pedal trying to control the leslie out of an old organ.
i didn't quite understand at first why the walls were vibrating and the lights were going dim as i worked the pedal.
ooopsies. ;)
Quote from: pinkjimiphoton on January 15, 2018, 08:27:47 PM
reminds me of the time i mis-wired a sewing machine "speed" pedal trying to control the leslie out of an old organ.
i didn't quite understand at first why the walls were vibrating and the lights were going dim as i worked the pedal.
ooopsies. ;)
That reminds me of a story I read about a guy developing industrial motor controls:
Quote from: BarryThese aren't lab stories, but they're funny all the same. I used to work at a drive system engineering firm, where they designed and manufactured the parts for the industrial lines that do things like make giant rolls of steel or toilet paper. There was a guy there who had worked out on the shop floor who told me a few tales of disaster that he'd seen in his time there.
1. In the days when digital motor controls were new, there were still a few bugs to work out. One day, one of the engineers was testing his work by powering up a drive system with a motor attached (the motor was mounted to a metal skid not too different from a shipping pallet, and these aren't little dinky motors – these could be anywhere from a few horsepower to a few hundred). Anyway, the current limiting portion of the control software hadn't been set up properly, so when he set it to spin the motor up to normal speed, the drive attempted to reach that speed *now*. A large BOOM rebounded off the walls of the shop: the immense torque rotated the entire motor, causing it to tilt sideways on one edge of the skid, and then when the circuit breakers heated up enough to trip a second or so later and shut off the motor, the whole thing came slamming back down.
2. There was another incident involving a runaway motor in which the drive system spun up the motor, but didn't level off. A few seconds later, a chunk of the rotor finally broke off, punched through the motor housing, and lodged in the ceiling 30′ up.
3. Apparently, there was yet another incident in which someone powered up a motor, but it spun up too quickly or oversped and came loose from its mounting to the floor and began rolling across the shop floor. As the story goes, my friend looked up to see a guy running in panic across the shop, the runaway motor tumbling after him.
Found in the comments at this post about ruined lab equipment (http://blogs.sciencemag.org/pipeline/archives/2007/02/01/how_not_to_do_it_ruining_stuff). Yeah, I bookmarked it.
a party ain't a party til the poltergeists trip the breakers. lol...
please remember i am a ten toed freek of a monkey with semi-opposable thumbs and a breadboard, so DON'T TRY THIS AT HOME.....
for real.
thanks for the link, i find stuff like this amusing. one time in a machine shop i used to work at, a bud was working on some kind of ridiculously expensive part for the government on a vertical turret lather <bullard>... kinda like a super king kong sized record player/cutter machine.
he was behind schedule and cutting hard n fast. but forgot one of the mounts on it or something... next thing we know, there's this like, 200k silver ufo flying across the shop, to crash into a nearby wall.
i got to clean up the mess. whatever it was, it was harder than the concrete walls were ;)
good times.
anyways sorry for Yet Another Pointless Hijack