3.7 Inch Anti Aircraft Gun

[tiv]

I'm aware that the 3.7 Inch AA Gun was built in mobile and static form but there are a few photos showing what is clearly a mobile gun removed from it's carriage, fitted to a baseplate and mounted in an emplacement as a static. I've yet to find any reference to this and would appreciate any information you may have about it.

This is what I'm talking about:

 

[Gluteus Maximus]

It is certainly a Mk1 mobile mounting, the only one in which the layers faced forward. It has everything below the turntable base removed and replaced with a static holdfast, but still has the cranes used for raising the front axle. The photo was taken before the loading trays were removed in 1942.

Why? Not a scooby!

 

[tiv]

Not sure what you are asking for...

This is a 3.7 on a standard holdfast as used in most of the permanent AA locations. The upper carriage is basically the same on both mobile and fixes varients.

The two mountings are quite different. The mobile is rear trunnioned, uses equilibrators to balance the barrel and in the early models has davits fitted on the equilibrators to hoist the trailing axel of the carriage up on to the mounting.

Like this:

While the static has the trunnions in front of the breech, there are no equilibrators there being replaced by a counterweight on an arm behind the breech and the whole mounting is higher set like this:

The gun in the original photo is clearly a mobile but fitted to a baseplate on a holdfast in a gun pit. I was curious as to why?

 

[HE117]

The two mountings are quite different. The mobile is rear trunnioned, uses equilibrators to balance the barrel and in the early models has davits fitted on the equilibrators to hoist the trailing axel of the carriage up on to the mounting.

Like this:

View attachment 491479

While the static has the trunnions in front of the breech, there are no equilibrators there being replaced by a counterweight on an arm behind the breech and the whole mounting is higher set like this:

View attachment 491478

The gun in the original photo is clearly a mobile but fitted to a baseplate on a holdfast in a gun pit. I was curious as to why?

You are of course correct.. I was thinking of something else...!

 

[4(T)]

I'm aware that the 3.7 Inch AA Gun was built in mobile and static form but there are a few photos showing what is clearly a mobile gun removed from it's carriage, fitted to a baseplate and mounted in an emplacement as a static. I've yet to find any reference to this and would appreciate any information you may have about it.

This is what I'm talking about:

View attachment 491453

Possibly a trials gun at an experimental establishment?

If they were testing ammo or accessories for a mobile gun, it'd make sense to have most of that mounting present, but on a static base to help eliminate certain variables.

 

[Themanwho]

I'm aware that the 3.7 Inch AA Gun was built in mobile and static form but there are a few photos showing what is clearly a mobile gun removed from it's carriage, fitted to a baseplate and mounted in an emplacement as a static. I've yet to find any reference to this and would appreciate any information you may have about it.

This is what I'm talking about:

View attachment 491453

Two probable scenarios come to mind:

1. A training unit using refurbished kit not suitable for operational service (eg: life expired or battle damage and refurbed)

2. Exingencies of service (ie: "we need an AA gun at Borchester Docks, there's an emplacement for a static 3.7" but all we've got free is a mobile 3.7". Get the gun plumbers to do the necessary, there's a war on you know!")

Number 2 seems more likely to me, either is eminently possible.