WWII U.S. Chemical Delay Firing Device, M1 (OSS Pencil Timer Detonator)

[rambob]

As many of you know I am very interested in Booby Trap and Firing Devices that are used to detonate explosives remotely on the battlefield. The URL link below points to an existing article on this forum, that I wrote concerning the subject of these devices and how they were used.

http://www.usmilitariaforum.com/forums/index.php?/topic/237922-wwii-us-booby-trap-and-firing-devices-my-updated-collection/

 

Today I added another interesting device to my collection that is used to detonate grenades, mines, Bangalore Torpedos and other explosives on a timed basis. The official designation for this timing device is Chemical Delay Firing Device, M1, but it’s nickname was the Pencil Timer due to it’s size and shape being close to that of a lead pencil. These devices were issued in quantity to the OSS and were very popular for sabotage missions behind enemy lines. They were designed to have a blasting cap attached to the end of the device before being screwed into whatever explosive device is desired, such as a hand grenade or mine. I am attaching an image from an ordinance manual that goes into all of the really gory details of the use of this device.

 

The device I am showing here is a yellow timer device that within normal temperature ranges of 30 to 90 degrees F, will give a detonating time of 16.5 to 4 hours after triggering the device. The small strip of metal located close to the screw adapter not only gives the color of the timer, but also acts as a safety mechanism. The strip must be removed after the device is triggered, by crimping the copper colored portion of the device at the end. This breaks a glass ampoule of a corrosive liquid inside the device which starts dissolving a wire that holds a spring loaded striker in the cocked position. Depending on the color of the device and the ambient temperature, the wire will break in a general time frame, the striker will hit the standard base igniter and the device will detonate the explosive attached to it.

 

This device is unissued and virtually mint, so it still has the little wooden dowel rod and the little rubber “condom” that protects the igniter from moisture. I did not want to bugger up the condom any more than it already was, so I did not screw the device into the grenade body I am showing. I hope you find this kind of thing as interesting as I do.

Bob

[rambob]

A grenade and the device.

[rambob]

Here is the ordinance manual pages for the device.

[Morlok]

Very nice! I have one of these in a display. I picked up the original box some time back. I still need to add it to the display!

 

 

 

[robinb]

Here's what a full box looks like.

 

[rambob]

Robin, Very Nice!! In looking at your examples they appear different slightly from mine at the threaded portion. Yours look like the manual diagram where the tips would have a blasting cap crimped over it. Mine has a sheet metal tube on the end like where a fuse or detonating cord could be inserted to be lit by the device. Not sure about the dowel rod, but it could have been used to keep the sheet metal tube from getting deformed. Any ideas?

 

Bob

[robinb]

Looking at others on Google; yours might be British.

[rambob]

Robin, the hollow tube on the end does seem to match British versions, but none of the images I found have the threaded part on them along with the tube. I will keep up the search though.

[Quartermaster]

I believe this is the Temperature Correction Table that accompanied boxes of "pencil timers".

 

 

[pzjgr]

I believe von Staufenberg used a Brit version of this in his suitcase bomb when he tried to kill Hitler....