Section VI
No. 4
A time delay device for use with electrical firing circuits can be made by using a watch with a plastic crystal.
Material and Equipment Required
- Watch with plastic crystal.
- Small clean metal screw.
- Battery.
- Connecting wires.
- Drill or nail.
Procedure
1. If watch has a sweep or large second hand, remove it. If delay time of more than one hour is required, also remove the minute hand. If hands are painted, carefully scrape paint from contact edge with knife.
2.Drill a hole through the crystal of the watch or pierce the crystal with a heated nail. The hole must be small enough that the screw can be tightly threaded into it.
3. Place the screw in the hole and turn down as far as possible without making contact with the face of the watch. If screw has a pointed tip, it may be necessary to grind the tip flat.
If no screw is available, pass a bent stiff wire through the hole and tape to the crystal.
IMPORTANT: Check to make sure hand of watch cannot pass screw or wire without contacting it.
How to Use
1. Set the watch so that a hand will reach the screw or wire at the time you want the firing circuit completed.
2. Wind the watch.
3. Attach a wire from the case of the watch to one terminal of the battery.
4. Attach one wire from an electric initiator (blasting cap, squib, or alarm device) to the screw or wire on the face pf the watch.
5. After thorough inspection is made to assure that the screw or the wire connected to it is not touching the face or case of the watch, attach the other wire from the initiator to the second terminal of the battery.
CAUTION
Follow step 5 carefully to prevent premature initiation.
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