Description
The Nose Time Fuze Mk 42 was developed to supersede the Mk 18 when used in major caliber HC projectiles, because of the erratic performance of the latter fuze when so employed. The fuze is generally similar to the Nose Time Fuze Mk 61, differing only in that the primary driving force of the Mk 42 is provided by a heavy mainspring instead of by centrifugal weights. The driving force for the clockwork mechanism thus becomes substantially independent of the rate of spin of the projectile, and is applied during the entire running time of the fuze.
In addition to the spring-driven feature, the Nose Time Fuze Mk 42 also differs from the Mk 61 in that a heavy additional hammer is located in the recess in the nose cap of the fuze. This hammer is attached to the nose cap by a spring. On set-back, this hammer stretches the spring and strikes the conventional hammer, giving it additional force in striking the setting lug. This feature was found necessary because the low setback of major caliber projectiles failed to provide sufficient force for the usual hammer arrangement to disengage the setting lug from the setting pin.
This fuze is now considered obsolete. It was found during functioning trials that the auxiliary hammer did not function properly on setback. The Nose Time Fuze Mk 62 is designed to supersede this fuze in major caliber HC projectiles.
Functioning
The method of operation of this fuze is generally similar to that of the Nose Time Fuze Mk 61, except, of course, that the driving force is supplied by a mainspring. The force of setback, when the gun is fired, causes the auxiliary hammer to descend against the main hammer, disengaging the setting lug from the setting pin.
Centrifugal force causes the center arbor detent to move outwards against its spring and out of engagement with the center arbor. The mainspring is then allowed to exert its force on the center arbor, actuating the escapement controlled clockwork mechanism. All other features of operation are identical to those of the Nose Time Fuze Mk 61.
Hazardous Components
No information about hazardous components.
See Also
Source(s)
MIL-HDBK-146, Fuze Catalog (1982)
OP 1664, Volume 1 - US Explosive Ordnance (1947)
