|Mine Safety Appliance Co.
This is part of my interest in DC motors (and generators). Blasting machines (Wiki) were/are used to supply the electricity to fire blasting caps (Wiki).
In all cases the idea is to provide the energy necessary to fire an electrical blasting cap, like the Army M6. The first generation rack and pinion push down blasting machines depended on how hard they were pushed and if insufficient force was used not all the caps in a series wired string would fire. If the power gradually increases as the plunger is pushed down the most sensitive cap will fire thus breaking the circuit for the other caps. One possible solution was to add a switch at the bottom of the stroke so that only at maximum power the circuit is completed. Another approach is to use batteries, but in the field a dead battery is a problem and a very specialized battery is a much bigger problem since you and not get it at the local grocery store. The newest blasting machines make use of an energy storage capacitor. There are a number of approaches to doing this such as (1) an add-on capacitor for an existing generator type blasting machine, a high voltage battery + capacitor, a low voltage battery and step up power supply + capacitor, and a multiple cycle manual generator + capacitor where it takes a few cycles of the manual generator to fully charge the capacitor before firing.
It turns out that the system developed by Edgerton to use a strobe light in a W.W.II bomber for night photography was later used by the Manhattan Project to trigger the newly invented Exploding Bridge Wire that has much more precise timing than the conventional blasting cap. See: Kryton Tube & Edgerton.
The handle turns a little less than 90 degrees and is spring loaded so returns to the starting position when released. This allows a switch to be fitted that only completes the firing circuit near the end of the twist to prevent a sensitive cap from firing early and disconnecting the other caps in a series string.
The label (see Fig 2 below):
10 Cap Blasting Machine
Capacity10 Electric blasting cap with 30 feet copper leg wires in series
Connect external circuit to binding posts: Twist handle vigorously to the right
CautionThis machine may lose capacity temporarily.
To Restore: Twist the handle vigorously a few times
Serial No. 27159
Fidelity Electric Co. Inc.
As received then the handle was turned smartly, there was a loud noise consistent with a dry bearing. I'm guessing this has not been oiled since it left the factory. The method of testing a blasting machine in TM 9-1375-213-12 is to connect a 500 foot length of 18 AWG copper wire and the number of caps the machine is rated to fire and see if it does fire them. Not a very practical method.
An email to a friend:
The blasting machine is an Army 10 Cap. Meaning it will set off 10 series connected blasting caps. Could be for mining, or blowing up a bridge.
The old Push down type blasting machine had a problem in that as the speed started ramping up from zero at some point the most sensitive blasting cap would go off opening the series circuit, not a good thing. They then put a switch at the bottom of the box so when the plunger hit bottom the circuit was completed which more or less works, except if a wimpy push down happens to set off one cap in a string ruining the shot. The latest units use a capacitor that first gets fully charged (a light tells you that) then fires so the energy is well controlled.
Some possible tests that can be done without caps. I tried connecting a few LEDs in series and to the blasting machine (after marking the terminals polarity) and the first time I twisted the handle it was clear that a switch completed the circuit near the end of the twist. The next time the LEDs were dimmer and the third time they did not light up. The current was too great and burned out the LEDs.
1. Connect DMM in DC Volts mode, Press RANGE until no digits to the right of the decimal, press Min-Max. After a sharp twist press Min-Max to read Max voltage. About 60 Volts.
By connecting a 2200 uF - 50 Volt capacitor, observing the correct polarity and sharply working the handle it will charge to about 30 Volts.
By connecting a DMM in DC Amps mode (press Range until only one digit is to the right of the decimal and them press Min-Max. Give a sharp twist then press Min-Max to see the peak current into a short. just over 1 Amp.
The best way to test may be with a scope and a load resistor, or better a number of different resistors.
Connect an Ohmmeter to the terminals and slowly twist the handle and notice that the resistance changes from an open circuit to a low value near the end of movement. Should be about 5 Ohms, but sometimes it's more like 144 Ohms. Maybe the switch needs to be cleaned? Ans. The screws under the test terminals were loose. When tightened the resistance measures about 5 Ohms.
Tried a two foot length of fine wire that measures about 0.2" as a bridge wire, but it did not fuse. Maybe need about 1.6 Ohm finer wire?
The battery is a specialized Silver Chloride cell, NSN: 6135-00-128-1632, Open Circuit Voltage: 1.0261.
The top scale is resistance in Ohms. Zero Ohms at full scale and 112 Ohms at half scale. 112 Ohms is the nominal internal resistance of the meter.
If the battery leads are shorted the resistance between the test terminals is 117.5 Ohms. Minus the two resistors (112 Ohms) leaves 5.5 Ohms as the meter internal resistance.
1.0261 Volts / 117.5 = 8.73 mA full scale. This is a safe current for a No. 6 blasting cap, so a guess would be that it takes more than 90 mA (10 X safe current) to set it off.
The bottom scale goes from 0 at the left (zero current) to 25 at the right (8.73 mA). What is the purpose of this scale? Let me know.
Showed up on eBay from Poland for about $200. Then from a U.S. seller for a lot less as "CANNOT BE FIXED SOLD AS IS!!!!!!!!". I got one of these.
Will make some measurements to see if it's been demilled or ....
Also called Detonators (Wiki).
Is the standard Army blasting cap and was/is a very common commercial blasting cap.
Resistance < 1.6 Ohms
Firing: not more than 0.45 Amps with no more than 16.3 Milliwat seconds of energy applied for betwen 10 and 24 micro seconds.
Strings of M6 caps typically require about 1.5 Amps.
Testing: 200 to 210 mA current for 5 seconds will NOT fire.
From Federal Business Op
New style 50 Cap plunger type machine NSN: 1375-00-141-9495
M32 uses AC generator, rectifier and capacitor. 10 Caps.
M34 like the M32 except for 50 caps.
M51 Test Set NSN: 4925-00-999-3454
WB-411 type 1 Blasting Galvanometer NSN: 6625-00-539-8444
The Du Pont No. 0 Blasting is a spring wound generator with a release button (1909 catalog)
This hand held blasting machine is of the capacitor discharge type. It uses a common 9 Volt battery as a power source.
4089035 Hand-held detonator, Don H. Smith, Tyler Holding Company, May 9, 1978, 361/251, 102/218 - HB-10 - - step up power supply converts 9 Volts to 100 Volts which charges capacitor that has resistor in parallel, so "Charge" button needs to be held down while "Fire" button is pressed.
Electrical tests:1. With DMM in fixed DCV range & Min-Max mode when fired the voltage is 98 Volts.
2. With DMM in Ohms range, no buttons pressed, the resistance is 1.96 k Ohms.
3. With the DMM in Ohms range, and the Fire button pressed and held for a few seconds, 1.96 k Ohms.
4. With DMM in capacitance mode when Fire button pressed reads 289 uF.
5. The resistor that came with the HB-10 measures 689 Ohms.
The energy stored in a capacitor is 0.5 * C * V * V = 0.5 * 289E-6 F* 100 V * 100 V = 1.1445 Joules (Watt Seconds)
In patent 3537399 below they mention 210 WS for firing 150 blasting caps, so 210 WS / 150 = 1.4 WS for a single cap. This blasting machine is rated for 10 series EB caps.
Fig 1 Box
Fig 2 with instruction sheet & test resistor
Fig 3 Inside bottom 9V bat & charge storage capacitor.
This appears to be a very old design hand held blasting machine. The case is copper sheet metal. The twister fits into the side, not the top like on more modern blasters, so maybe it predates the other blasters on this page. No, the generator uses laminated electrical steel instead of solid iron like on the earlier blasters. The patents (see below) have dates in the 1920s. The Davis No. 00 has a cylindrical body and top twist (See Hals Lamp Post-Davis No. 00). The Davis Single shot, per patent 1680261, is shown on Hals Lamp Post web page Davis Single Shot.
This was made by Davis Instrument Manufacturing Company of Maryland which I associate with weather instruments, like the all mechanical anemometer they patented in 1930 (1905444). My guess is that the label shown on the front side (Fig 3) is the Davis label and has worn away. The label on the back side (Fig 2) for Mine Safety Appliance Co. was added later.Permissible
The Davis label might have said:
Single Shot Blasting Unit
Approval No. 1207 (Davis No. 000: issued 11/18/26) (30 CFR Ch 1, Part 24) Approval and Certification Center Part 24 Single-shot Blasting Units)
(Seal of Department of the Interior, Bureau of Mines)
Issued to the
Davis Instrument Mfg. Co. Inc.
Approved for Safety
Reliability and Durability
Not permissible unless used with rubber covered leading wires of length not exceeding 600 feet of
No. 14, 350 feet of No. 16, or ??? feet of No. 18 wire.
Fig 6 Label: Davis Instrument Mfg. Co. Inc.
1383605 Magneto, Davis Alfred U, Davis Instr Mfg Company, Jul 5, 1921, 310/75.00B, 310/69, 290/1.00E -
1680261 Blast magneto, Alfred U Davis, Davis Instr Mfg Company Inc, Aug 7, 1928, 310/75.00B -
Fig 4 My best guess at Lube Points
two more on other side.
Fig 5 view under cover showing switch
Note a spring released when cover was opened.
In order to reinstall it you need to wind the handle until the ratchet holds it it place, then while holding the handle in that position install the cover. Note the top gear has a lever on it's axle that presses the micro switch and that lever needs to be on the actuator not above it prior to installing the cover.
Note small metal pin in end of handle. Why is it there?
It's not on the other end, see Fig 1
Fig 7 with 1/8 brass chain added.
Fig 1 Notice snap on front of leather flap.
Fig 2 Snap on leather flap snaps into back to hold open.
Fig 3 This unit was put in long term storage with battery installed. It corroded.
Fig 7 Notice wires going from main cavity into battery cavity in this and Fig 8. The resistors are marked 56 Ohms and measure within an Ohm of that value.
Fig 8 Note how 4 wires gown down into body.
Both screws under terminals were loose leading to
erratic resistance readings.
These are on eBay from Poland, but with a note that they are not functional. They didn't say that the bernerator had been removed. I.e. they have either been de-milled or were a poor design where the generator burned out.
The handle moves slightly more than 90 degrees. Instead of a Microswitch they just use a plunger and "U" shaped sheet metal strap for the switch. Care was taken to have low resistance. The label reads:
??TYP 12S1 160V 2A 80 (Ohms)
(can not read Polish writing)
The output terminals are marked (+) and (-).
Fig 1 with cap installed
Fig 2 with handle installed
Fig Inside showing missing generator
TM 9-1375-213-12 Operator's and Organizational Maintenance Manual, (Including Repair Parts and Special Tools List), Demolition Materials, March 1973 (with Change 12: 6 Nov. 1987).
But it does NOT talk about lube instructions for the blasting machines or talk about batteries for Blasting Galvanometers.
The Blasting Galvanometer uses a Silver Chloride cell with an output of 1.0261 Volts. It has #4 screw terminals.
TM 9-1375-203-12 Handle Operated Blasting Machine (have not found it - let me know)
Subcourse MM2605, Edition 4, US Army Ammunition Specialist MOS 55B, Demolition Firing Systems
The old style Army 10-Cap blasting machine may be patent 1771870 and the new style may be patent 2458687.
The 1771870 patent applies to theColumbia Powder Co - No. 2 blasting machine. Maybe it was the precursor to the Army 10-cap machine?
1771870 Blasting machine,Banzhof Charles P,
Fidelity Electric Co, Jul 29, 1930, 310/69
Columbia Blasting Machine No. 2
Patent date Jul 29, 1930
2458687 Blasting machine, Davis Alfred U, Jan 11, 1949
Fig 5 handle in rest position
Fig 6 just before switch closed
Fig 7 Switch closed
79268 Electric Fuse, H. Julius Smith, Jun 23, 1868 102/202.8 -
921049 Squib-igniter, Joseph A Wranischar, May 11, 1909, 102/202.8 - no open fuse in coal mine, much safer
93563 Electric Battery, H. Julius Smith, Aug 10, 1869, 310/309 -
173680 Electric fuses, H. Julius Smith, Feb 15, 1876, 102/202.14 -
173681 Electric fuses, H. Julius Smith, Feb 15, 1876, 361/248; 102/202.1 -
173682 Magneto-electric apparatus, H. Julius Smith, Feb 15, 1876, 310/70R; 310/54-
201296 Magneto-electric machines, H. Julius Smith, Mar 12, 1878, 310/69; 290/1E; 361/252 -
2081633 Method of and apparatus for firing explosives, Mcfarland David M, Atlas Powder Co, May 25, 1937, 361/252, 361/250, 310/69 - Push Down two switches on sides of rack.
2025907 Instantaneous circuit-closing device for electric shot firing machines, Konrad Schaffler-Glossl, Dec 31, 1935, 200/434 - for hand held top twist type machines.
201296 Magneto-electric machines, H. Julius Smith, Mar 12, 1878, 310/69; 290/1E; 361/252 -
353827 Dynamo-electric igniting-machine, H. Julius Smith, Dec 7, 1886, 310/69 - Push down type
My reading of the above two patents is that there is a normally closed switch that's opened at the end of the stroke. So the coils act like ignition coils generating a high voltage when the switch is opened. In the 1878 patent the switch is located at the bottom of the box, but it's been moved to the top of the box in the 1886 patent and a lid has been added. This was done because of problems with the bottom mounted switch which Julius attributed to moisture, but more likely was caused by pitting of the contacts when they sparked as they opened. This is why automotive distributors have a condenser across the points. Also it must have been hard work to press the rack down when driving a generator into a short circuit. Also a guide rod was added in the newer patent in an attempt to reduce friction (which may have been the effect of turning a generator into a short circuit). Note the machine pictured (from an eBay ad) does not have a guide rod so is based on the older patent, but has top mounted terminals like the newer patent rather than the side mounted terminals of the old patent.2779276 Demolition firing device, Clary Jr Frank A, Jan 29, 1957, 102/392, 102/257, 102/419 - pressure actuated detonating device incorporating an electrolytic cell time delay means in which the cell locks the pressure actuated detonating device against 7 operation until the cell has been activated for a predetermined time.- Large diaphragm as pressure input
3370220 Hand operated blasting generator, Bleich Kenneth E, Douglass Byron J, Universal Match Corp, Feb 20, 1968, 322/40, 310/83, 310/50, 310/69 - pumping hinged lever drives AC generator, rectified voltage builds op on capacitors, when at set threshold it is switched to output.
436023 Electric detonator or primer, Henry Julius Smith, Sep 9, 1890, 102/202.14 -
4381711 Hand-held shot tube detonator, Howard Lawrence, E.I.T. Corporation, May 3, 1983, 102/275.11, 102/200 - sort of a pen gun
495138 Magneto Electric Machine, J.N. McLeod, The Mcleod Electric manufacturing, Apr 11, 1893, 310/69 - push down/pull up type
534289 Art of blasting, Henry Julius Smith, Feb 19, 1895, 299/13 -
564437 Electric blasting-machine, James Macbeth, Jul 21, 1896, 310/69 -
694914 Electric apparatus for exploding mines, Sydney Evershed, Evershed Vignoles Ltd, Mar 4, 1902, 307/39; 310/155; 310/68B; 310/69; 310/83; 322/94; 322/99; 361/252 - heart is crank type telephone magneto
848153 Electrical blasting-machine, Lucien W Bowman, John H Lewis, Mar 26, 1907, 102/206; 102/202.1; 429/111 - box containing 4 wet cell batteries
877284 Electric apparatus for the ignition of mines, Otto Robert Percival Berglund, Walter Axel Wilhelm Emanuel Hjorth, Carl Ernst Ljungman, Jan 21, 1908, 310/69; 361/252 - heart is crank type telephone magneto
921049 Squib-igniter, Joseph A Wranischar, May 11, 1909, 102/202.8 - diagram shows phone magneto as power source
1072511 Dynamo-electric apparatus for firing mines, Konrad Schaffler Rekte Gloessl, Schaffler & Co, Sep 9, 1913, 310/75.00R - winding a spring the releasing, has the look of a hand operated machine, but not the same as the Army unit. This may be the pocket blasting machine advertised as just released by Du Pont in their 1913 magazine?
Note "a sharp twist" is not the wording if it was spring wound.
From 1913Du Pont magazine
From 1913 magazine
The directions for the push down blasting machine says:
"Try to knock the bottom out of the machine." As the rack bar approaches the bottom, it becomes more difficult to operate, because of the "building up" of the current; but the speed of the thrust should not be diminished, because the finish of the operation is just as important as the start. Do not be afraid of pushing the rack bar down too hard. The machine is built to stand it, and thei is the only way to use it successfully.
Later machines will add a switch so there is no resistance buildup and switch in the circuit just prior to the end of the stroke.
From 1922 Du Pont Blaster's Handbook
From 1922 Du Pont Blaster's Handbook
1209267 Electric blasting-machine, Ernest W Davis, Aetna Powder Company, Dec 19, 1916, 322/4; 322/83 - wooden box, crank type
1363585 Blasting-machine, George Haddow, Atlas Powder Co, Dec 28, 1920, 310/69; 290/1E - wooden box plunger type
1367608 Explosive powder, Arthur Langmeier, Hercules Powder Co Ltd, Feb 8, 1921, 149/8, 149/76, 149/69 - ammonium perchlorate explosive blasting powder
1479152 Dynamo-electric machine, Romaine Myers, California Cap Company, Jan 1, 1924, 290/1E; 310/69 - spring driven generator
1670419 Blasting gun, Mayer Walter S, May 22, 1928, 310/75.00A, - a pistol shaped device containing a spring powered generator, the trigger releases a pawl
1771870 Blasting machine, Banzhof Charles P, Fidelity Electric Company, Jul 29, 1930, 310/69 - early hand held type, symmetrical pin drive handle
1890445 Electric blasting machine, Asire Horace W, Martin Edward J, Perkins Wallace W, Du Pont, Dec 13, 1932, 310/69, 102/322 - push down type - multiple contacts on switch to minimize arcing
GB404181 Momentary Contact Switches for Electric Mine Firing Devices, Konrad Schaffler, Schaffler & Co., April 13, 1933 - has the look and feel of the Army 10-cap machine. The patent is all about the short duration pulse of current (10 to 30 mS long.
1999820 Delay cap, Henry E Nash, Hercules Powder Co Ltd, Apr 30, 1935, 102/275.9, 149/34, 149/108.4, 149/16, 149/37, 149/108.6, 149/15, 149/43, 149/79, 149/80, 102/202.13 -
2103432 Electrical firing device, Nash Henry E, Hercules Powder Co Ltd, Dec 28, 1937,102/202.3 - electrical delay cap for use with 440 VAC lines
1- Rack Bar
4 & 5 Contact Spring
8 & 9 Field magnets
16 revolving armature
34 rack bar handle
2129835 Electric shot-firing machine, Konrad Schaffler-Glossl, Sep 13, 1938, 310/69, 361/252 - requires generator magnetic field above some level in order to complete firing circuit by tipping mercury switch.
2280243 Switch, Lang Harold M, Stanolind Oil & Gas Co, Apr 21, 1942, 200/219, 310/69 - switch activated when plunger pushed all the way down completes firing circuit.
2313101 Blasting machine, Joseph Stuart, Hercules Powder Co Ltd, Mar 9, 1943, 310/69, 315/326, 315/76, 361/251, 327/261, 315/266, 361/248 - rack and pinion Push down type improved to provide high current, light bulb in box
2326696 Blasting machine, Stoddard Ralph N, Westinghouse Electric & Mfg Co, Aug 10, 1943, 361/251, 361/252 - rack and pinion push down type with AC generator & charge storage capacitor
2315823 Shunt for electric blasting caps, Smith Roscoe B, Hercules Powder Co Ltd, Apr 6, 1943, 102/202.3, 439/387, 102/202.12 - ships with cap for safety
2458464 Switch, Busacker John W, Perry Thomas M, Navy, Jan 4, 1949, 200/61.8, 200/61.33, 102/262 - un-shorting switch used in artillery shell.
2458687 Blasting machine, Davis Alfred U, Jan 11, 1949, 310/69 - Looks like the Army Liberty 10-cap hand held blasting machine.
2524005 Spring powered electric generator, Gottfred Boe, Specialties Inc, Sep 26, 1950, 290/1.00E, 310/75.00R, 185/39, 185/10 - to fire squibs to allow escape from aircraft
2543754 Detonator testing device, Beach Ronald O, Mar 6, 1951, 324/502, 200/61.64 - for testing electric blasting caps
2617851 Electric impulse generator, Bisch James L, Bisch Ind Inc, Nov 11, 1952, 361/252, 307/108, 310/50, 310/154.2, 310/154.36, 310/36 - Explosion proof design for use in mines.
2623922 Electric pulse-forming shot-firing device, Gary Muffly, Gulf Research Development Co, Dec 30, 1952, 361/251, 102/202.5, 361/252, 102/207 - has trigger output to start seismometer recording
2644117 Blasting machine, Schmitt Robert A, Swed James P, Williams Charles P, Du Pont, Jun 30, 1953, 361/248, 102/202.5 - for special caps that require over 10 amps to get enough heat to detonate.
2763812 Blasting machine, Mckinney Jr Charles D, Reitenour Jr Milton G, Hercules Powder Co Ltd, Sep 18, 1956, 315/205, 315/241.00R, 315/219, 315/241.00P - Battery drives vibrator - step up resonant transformer, rectifier and storage capacitor. Charge button, and fire button.
2784328 Contacting device for a dynamo-electrical igniting machine driven by a mainspring, Hans Schaffler-Glossl, Mar 5, 1957, 310/69, 200/18, 361/252 - energy stored in wind up spring then released.
2844747 Dynamo-electrical igniting machine, Hans Schaffler-Glossl, Jul 22, 1958, 310/69, 310/112, 361/252 - dual magneto for use in damp mines
2892128 Blasting cap electric firing system, Wolf Alfred A, Fidelity Instr Corp, Jun 23, 1959, 361/251, 102/322, 102/202.1, 361/252 - an add on capacitor charged from any type of blasting machine then disconnected from machine and connected to firing circuit.
2908847 Blasting machine, Williams Charles P, Witt Bickel Ferdinand De, Du Pont, Oct 13, 1959, 361/251, 102/218 - 525 Volt battery charges 50 uF to 1,500 uF capacitor
2933653 Blasting machine, Carter Elbert P, Du Pont, Apr 19, 1960, 361/248, 102/202.5, 102/301, 102/218, 102/209 -a battery drives a saturable-core transformer which charges capacitor to meet mine safety rules
3056349 Method and apparatus for blasting, Mcfarland David M, Atlas Chem Ind, Oct 2, 1962, 102/206 - prevents cap damage from too much energy
3342998 Spring-driven electrical generator, Anderson Walter F, Fidelity Electric Company Inc, Sep 19, 1967, 290/1.00R, 185/37, 185/39, 102/207, 185/10 - for blasting
3343493 Arming and firing circuit, Aulds Darrell D, Scheibe Jr Harold R, Sep 26, 1967, 102/220, 327/473 - 28 VDC supply
3537399 Method and device for blasting, Miller Paul H, Atlas Chem Ind, Nov 3, 1970, 102/218 - 150 parallel caps, 210 to 400 Watt-Seconds
Calls:3538414 Capacitor-discharge device for blasting, Janoski Florian B, Atlas Chem Ind, Nov 3, 1970, 361/251 - AC mains powered for up to 150 parallel caps
2644117 Blasting machine, Schmitt Robert A, Swed James P, Williams Charles P, Du Pont, Jun 30, 1953, 361/248, 102/202.5 - for heat type caps, uses vibrator supply
2892128 Blasting cap electric firing system, (See above)
2908847 Blasting machine (see above)
2961583 Detonator circuit for permissive explosion shot firer, Sorensen Andrew J, Femco Inc, Nov 22, 1960, 361/251, 315/241.00R, 307/110 -
3011096 Electrical timing circuit, Perdreaux Jr Rene J, Stanley Wallack, Nov 28, 1961, 361/251, 310/301, 307/110, 327/261, 102/219 - just adds delay
3141114 Blasting machine, Jenkins Richard H, Wieber Elmer H, Vibration Measurement Engineers, Jul 14, 1964, 361/251, 200/50.37, 102/206 - battery - capacitor type
3167014 Bridge wire for producing high temperature explosion, Louis Kopito, Baird Atomic Inc, Jan 26, 1965, 102/220, 102/202.7, 102/206, 431/357 -
3288068 Triggered exploding wire device, Jefferson Donald E, Kettenbach Carl W, Sec of Navy, Filed: Apr 30, 1964, Pub: Nov 29, 1966, 102/218, 102/202.7, 60/39.821
3717794 Blasting device, Higgins R, Yates P, Explosives Corp America, Feb 20, 1973, 361/251, 361/248 - 2 series connected batteries (maybe 22-1/2V each) and firing capacitor, no active circuitry
4089035 Hand-held detonator, Don H. Smith, Tyler Holding Company, May 9, 1978, 361/251, 102/218 - HB-10 - step up power supply converts 9 Volts to 100 Volts which charges capacitor that has resistor in parallel, so "Charge" button needs to be held down while "Fire" button is pressed.
Atlas Electrical Blasters Handbook - mostly about Ohm's law (Wiki), but also some good information in a plot of current vs. time.
PRC68, Alphanumeric Index of Web pages, Contact, Products for Sale
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