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Fuzes |
Quick fuze is a contact fuze -- the shell goes off when it
touches something hard, like the ground, a tank, or trees.
This is the simplest and most common type of fuze.
When a quick-fuze shell explodes, some shrapnel sprays from the nose and tail of the shell, but most in an expanding ring out the sides. If the shell hits at a low angle of impact, the shrapnel that sprays upward into the air and downward into the ground is mostly harmless -- only the side-spray is likely to cause casualties.
However, if it hits at a high angle of impact (such as mortar fire), the side
spray will spread out in a large ring around the point of impact. As we'll see
later, high-angle fire has some limitations.
The shell goes off some time after it is fired. Usually, this is intended to give an air burst, which is most effective at about 20 yards above the target. However, setting the fuze correctly was tricky business. The US mechanical fuze seemed very unreliable and was only used to give a high-altitude registration burst for spotting. Wesely [2] says German fuzes were much better, about as reliable as the US VT fuze.
The VT fuze emits a radio signal and goes off when it detects enough of this signal is being reflected back from a hard object. The height of burst will increase if over dense foliage, swamp, water, or wet terrain; and it will decrease with high-angle fire.
1940's era VT fuzes had a minimum arming time of five seconds, so
the VT fuze cannot be used for close-in defense.
With the VT fuze, The minimum ranges in yards for several guns is shown below:
| Weapon | Minimum Range (yards) |
|---|---|
| 75mm Howitzer | 2,200 |
| 105mm Howitzer | 2,700 |
| 155mm Howitzer | 4,000 |
| 8" Howitzer | 6,000 |
| 240mm Howitzer | 9,000 |
The 1950 US Manual concludes that:
Present powder train fuzes are most effective to about 15 seconds of burning. Beyond that point, the advantages of VT fuze increase while many of the disadvantages are reduced.
With the delay fuze, the shell goes off some time after hitting a hard target. This can be used either to penetrate a target before detonation (such as a bunker), sink into the ground a ways before detonation (to produce craters), or to purposefully richochet and produce airburst effects. Richochets occur more frequently with low-angle fire and hard ground. Richochet fire should only be attempted if the observer can verify that at least 50% of the shells are actually richocheting. If not, another type of fuze should be specified.
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 Dispersion |
 Ammunition Types |
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