122:
256:, or under the heel of your boot. There is no need to crush the end of the tube completely flat. All that is required is to crush and dent the tube sufficiently to break the glass vial, thereby releasing the liquid contained within. Check the inspection hole next to the brass safety strip. If the inspection hole is unobstructed (i.e. it is possible to see right through to the other side) then the countdown has started and the brass safety strip (holding back the striker) should be removed and discarded. However, if the inspection hole is obstructed (before the safety strip is removed) the striker has been released so the pencil detonator should be discarded and another one selected. The final step is to insert the end of the pencil which has the actual
392:
383:
450:
368:. For example, a pencil detonator designed to fire 24 hours after being activated could in reality give a 30-hour delay - if the weather was very cold. Similarly, during hot weather pencil detonators designed to fire after a 12-hour delay could in reality trigger detonation within 10 hours. The main virtue of pencil detonators is their small size and light weight, plus the fact that they are very quick and easy to use. These are important points during covert operations.
187:
25:
286:. A piece of this lead was notched to a set diameter, the diameter setting the time delay. When the starting pin was removed, this wire was placed under tension by the spring-loaded striker, and began to gradually stretch. After a certain time, it would snap at the notch and allow the striker to hit the percussion cap.
226:
under tension and held in place by a thin metal wire. The timer was started by crushing the copper section of the tube to break the vial of cupric chloride, which then began to slowly erode the wire holding back the striker. When the wire eventually parted, the striker was propelled down the hollow
407:
For very high-value targets it is recommended that two pencil detonators from different batches be used together. That way if one detonator fails the other will almost surely blow the charge. Note that if both detonators were going to work, the explosion will occur at the earlier of the two times;
298:
Another type of time pencil had a percussion cap but no detonator attached. Instead there was a crimping attachment at one end to allow pyrotechnic fuse to be crimped on. When a time pencil of this type fired, it would light the fuse which would burn towards a detonator crimped onto the other end.
289:
The delay could be set from a matter of minutes to hours. Manufacture was entirely by MD1. Generally speaking L-delays were slightly less reliable and had shorter delays, but were more reliable underwater (if a No. 10 fuze developed a leak, water would dilute the corrosive liquid and increase the
238:
two or three minutes in an hour's delay, and plus or minus an hour in a 12-hour delay, though environmental conditions could affect this. The switches were typically issued in packs of five, all the switches in a pack having the same delay. In use, two switches with the same delay (from different
320:
time delay, which can range from 10 minutes through to 24 hours. No. 10 delays were normally issued in a tin of 5, all of the same delay, while L-delays were issued in a larger tin which included a mixture of different delays to suit a variety of operations. The time delay of a No. 10 varies
277:
known as the "Lead Delay switch" or officially "Switch, No. 9, L Delay". Instead of relying on the chemical action of a corrosive liquid on metal (which was subject to temperature variation), it used a piece of metal under stress – the metal in question being a
325:
of the corrosive liquid in the vial. It is widely reported that the wire thickness varied also, but in fact all used the same diameter of wire. The time delay of a No. 9 is determined solely by the thickness of the notch in the wire, the
345:(which did not require a booster) were particularly useful during the sabotage missions in which they were often employed. There were also a number of special charges issued with a time pencil already incorporated e.g. some types of
303:
burns at around half a metre per minute, it is not practicable to provide delays of more than a few minutes in this way. It was also possible to connect a pencil detonator to so-called "instantaneous fuse" (not to be confused with
445:
Approximately 12 million pencil detonators were produced in
Britain during the war. However, in recent years they have been superseded by electronic timers which are more accurate and provide much longer delay times.
364:
of plus or minus 15 minutes. Both No. 9 and No. 10 delays were also significantly affected by the ambient temperature, and were issued along with a chart of temperature corrections—but no
465:
used a captured
British pencil detonator inserted into a block of British plastic explosives weighing approximately two pounds. The bomb was set to 30 minutes and detonated as planned, but
473:
could not prepare the second block, though. He got rid of it while driving through the forest to the airfield. His driver, Leutnant Erich Kretz, reported seeing
121:
573:
89:
61:
352:
After being activated a pencil detonator is silent in operation. It does not fizz or make any other noise. However, unlike
198:
Number Ten Delay Switch (official name, "Switch, No. 10, Delay" and often referred to as a "timing pencil"), was made of a
356:
timers, pencil detonators only give approximate time delays. For example, a 2-hour pencil detonator might be accurate to
68:
470:
454:
617:
Arms Tech LS-1 Time Delay - a modern pencil detonator which uses same operating principle as "Switch, No. 9, L Delay"
108:
42:
75:
125:
An array of World War 2 pencil detonators displayed at the Museum of the
British Resistance Organisation at the
520:
186:
46:
57:
420:
487:
605:
234:
Number ten delay switches had delays ranging from 10 minutes to 24 hours and were accurate to within
599:
555:
35:
495:, finds that his stock has been rendered inoperative. Their use is also highlighted in the film
611:
391:
361:
126:
382:
82:
432:
300:
8:
631:
416:
330:
283:
215:
474:
239:
packs if possible) would be placed in the explosive charge in case one switch failed.
577:
525:
424:
342:
338:
150:
449:
439:
412:
616:
497:
327:
305:
270:
510:
228:
170:
625:
357:
322:
235:
219:
166:
515:
462:
346:
158:
594:
535:
492:
365:
337:. Pencil detonators could be used with any explosive provided a suitable
334:
162:
223:
530:
353:
308:) which had an unusually fast burn rate of over 7 metres per second.
257:
203:
146:
360:
5 minutes, whereas the version offering a 6-hour delay could have a
24:
612:
Electronic fuze detection method (cannot detect pencil detonators)
427:. A number of pencil detonators were used to detonate the massive
442:
of 1942. The ship exploded over an hour later than anticipated.
466:
453:
Pencil detonator used in the July 20 plot in 1944 exhibited in
428:
253:
249:
207:
154:
408:
thus this method will also slightly reduce the average delay.
199:
279:
264:
211:
142:
274:
195:
501:
during a part of the film detailing the July 20 plot.
218:(the liquid was widely and erroneously reported to be
491:when an undercover explosives expert, portrayed by
316:Pencil detonators are colour-coded to indicate the
49:. Unsourced material may be challenged and removed.
623:
282:alloy that was extremely affected by mechanical
477:throw something into the woods in his mirror.
260:fitted into the explosives and leave the area.
242:
222:), while beneath the vial was a spring-loaded
157:, hence the name. They were introduced during
153:. They are about the same size and shape as a
411:Pencil detonators saw heavy use during the
210:section at one end which contained a glass
485:Time pencils figure in the 1961 war movie
269:Another, subsequent type was developed by
181:
252:tube containing the cupric chloride with
109:Learn how and when to remove this message
448:
190:Cutaway diagram of a No. 10 delay switch
120:
16:Time fuze used by British Special forces
624:
606:Additional photographs of time pencils
554:
480:
290:delay or stop the fuze from working).
293:
227:centre of the detonator, hitting the
47:adding citations to reliable sources
18:
562:. Roundwood Press. SBN 900093-22-6.
231:at the other end of the detonator.
13:
455:Bundeswehr Military History Museum
311:
185:
14:
643:
588:
390:
381:
23:
461:The briefcase bomb used in the
34:needs additional citations for
576:. FilmReporter. Archived from
566:
548:
521:Exploding-bridgewire detonator
469:survived with minor injuries.
373:Boxes of No. 10 delay switches
265:L-Delay ("No. 9 delay switch")
145:designed to be connected to a
1:
541:
421:Special Operations Executive
7:
600:Photograph of a time pencil
560:Winston Churchill's Toyshop
504:
243:Using a No. 10 delay switch
10:
648:
595:Schematic of a time pencil
248:Crush the end of the thin
402:
176:
423:and groups such as the
341:was attached. However,
182:Number Ten delay switch
458:
262:
202:(or in later versions
191:
130:
127:Parham Airfield Museum
580:on 27 September 2007.
452:
431:charge hidden inside
246:
189:
124:
488:The Guns of Navarone
457:in Dresden (Germany)
43:improve this article
481:Cultural references
417:Special Air Service
149:or short length of
475:Werner von Haeften
459:
343:plastic explosives
294:Percussion igniter
192:
131:
58:"Pencil detonator"
526:Slapper detonator
425:French Resistance
321:according to the
299:Because standard
161:and developed at
119:
118:
111:
93:
639:
582:
581:
570:
564:
563:
552:
413:Second World War
394:
385:
135:pencil detonator
114:
107:
103:
100:
94:
92:
51:
27:
19:
647:
646:
642:
641:
640:
638:
637:
636:
622:
621:
591:
586:
585:
572:
571:
567:
553:
549:
544:
507:
483:
440:St Nazaire Raid
405:
400:
399:
398:
395:
386:
375:
374:
314:
312:Characteristics
306:detonating cord
296:
271:Millis Jefferis
267:
245:
216:cupric chloride
206:) tube, with a
184:
179:
115:
104:
98:
95:
52:
50:
40:
28:
17:
12:
11:
5:
645:
635:
634:
620:
619:
614:
609:
603:
602:(107 kB, JPEG)
597:
590:
589:External links
587:
584:
583:
574:"Stauffenberg"
565:
556:Macrae, Stuart
546:
545:
543:
540:
539:
538:
533:
528:
523:
518:
513:
511:Percussion cap
506:
503:
482:
479:
404:
401:
397:
396:
389:
387:
380:
377:
376:
372:
371:
370:
313:
310:
295:
292:
266:
263:
244:
241:
229:percussion cap
194:One type, the
183:
180:
178:
175:
117:
116:
31:
29:
22:
15:
9:
6:
4:
3:
2:
644:
633:
630:
629:
627:
618:
615:
613:
610:
608:(269 kB, GIF)
607:
604:
601:
598:
596:
593:
592:
579:
575:
569:
561:
557:
551:
547:
537:
534:
532:
529:
527:
524:
522:
519:
517:
514:
512:
509:
508:
502:
500:
499:
494:
490:
489:
478:
476:
472:
468:
464:
456:
451:
447:
443:
441:
437:
436:
430:
426:
422:
418:
414:
409:
393:
388:
384:
379:
378:
369:
367:
363:
359:
358:plus or minus
355:
350:
348:
344:
340:
336:
332:
329:
324:
323:concentration
319:
309:
307:
302:
291:
287:
285:
281:
276:
272:
261:
259:
255:
251:
240:
237:
236:plus or minus
232:
230:
225:
221:
220:sulfuric acid
217:
213:
209:
205:
201:
197:
188:
174:
172:
168:
167:Hertfordshire
164:
160:
156:
152:
148:
144:
140:
136:
128:
123:
113:
110:
102:
99:December 2007
91:
88:
84:
81:
77:
74:
70:
67:
63:
60: –
59:
55:
54:Find sources:
48:
44:
38:
37:
32:This article
30:
26:
21:
20:
578:the original
568:
559:
550:
516:Blasting cap
496:
486:
484:
471:Stauffenberg
463:July 20 plot
460:
444:
434:
410:
406:
351:
347:limpet mines
317:
315:
297:
288:
268:
247:
233:
193:
159:World War II
138:
134:
132:
105:
96:
86:
79:
72:
65:
53:
41:Please help
36:verification
33:
536:Pencil bomb
493:David Niven
438:during the
435:Campbeltown
366:thermometer
335:temperature
301:safety fuse
163:Aston House
151:safety fuse
139:time pencil
632:Detonators
542:References
333:, and the
141:is a time
69:newspapers
531:Primacord
362:precision
354:clockwork
258:detonator
204:aluminium
147:detonator
626:Category
558:(1971).
505:See also
498:Valkyrie
415:by the
339:booster
331:tension
318:nominal
224:striker
196:British
83:scholar
467:Hitler
429:amatol
328:spring
254:pliers
250:copper
208:copper
155:pencil
129:, 2007
85:
78:
71:
64:
56:
403:Usage
284:creep
200:brass
177:Types
90:JSTOR
76:books
433:HMS
280:lead
212:vial
143:fuze
62:news
275:MD1
273:of
214:of
137:or
45:by
628::
419:,
349:.
173:.
171:UK
169:,
165:,
133:A
112:)
106:(
101:)
97:(
87:·
80:·
73:·
66:·
39:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
