40 mm Bofors AA guns made in GB and US

[Bill Murray]

Anti Social.
Bill

[sapper740]

Originally posted by David_Hayward
.. or 'Anti-anything'?

It would still be known as A.A.......Anti Arsehole!

[nuyt]

found by Lorenzo Tonioli of Italy:
http://cgi.ebay.com/ws/eBayISAPI.dll...sPageName=WDVW
What type of 40mm Bofors?

[Godwin Hampton]

Lorenzo,

The gun seems to be an original Swedish 1936 Model. You may have noticed that there is no apparent sighting system, but this could mean that the Gun is controlled by a Predictor. This would work out where the Gun should be pointed to the 'future position' of the aircraft to hit it. This position would vary with Speed, Direction, Altitude, and Angle of Flight of the target.

The Predictor would move pointers on dials in front of the layers (not visible in the photo) and the layers would elevate and traverse the gun to match the pointers, without looking at the target. When the pointers were matched, the Gun would be fired.

[Mats]

Eric and Godwin

I agree that it's a gun of the original pattern, known in Sweden as the model 1936. A lot of small details gives it away.

[nuyt]

no text

[Stellan Bojerud (RIP)]

The Bofors guns sold from Sweden to the Netherlands i think were m/35.

NL had no predictors.

The gun has normal "Polish sights" but they are hidden behind the guncrew. The man to the right is looking into the sight. Left gun trainer is hidden behind the standing loader in his greatcoat.

[Godwin Hampton]

Stellan, you are absolutely right!

Now that you have pointed it out, I realised that there are 3 seats, and the one nearest the camera is the sight correction number, bent over the BOFORS COURSE AND SPEED SIGHT corrector ( in British Army terms). I suppose the man standing next to him is the Gun Commander,giving him the data about the target to feed into the corrector.
The loader is obscuring the sight, but the cable to the graticule illuminating bulb remains visible.

The apparent absence of the rather bulky sight cross tube mystifies me! Could it have been 'censored out' of the picture?

[Stellan Bojerud (RIP)]

The NL guns should have the m/35 FC (picture).

[Godwin Hampton]

Originally posted by Stellan Bojerud
The NL guns should have the m/35 FC (picture).

.......also known as the Course and Speed Sight.
This was/is a very ingenious piece of equipment. It is fairly complex, and must have been pretty expensive in those days.

It can be described as an on-board predictor, and from the data fed into it, it mechanically turned both sights left or right, as well as tilting the sight bar to incline the sights up or down. This so that the layers would keep the sights centered on the target while the barrel would be delivering the shells to the 'future position' of the aircraft.

Data would be inputted by turning the two handwheels, one to set the predictor to the range to the target, and the other to set to the aircraft speed. The pointer on the arc was for setting the angle of dive.

Maybe Rob Fast would be so kind as to post some pictures giving us more details of this intriguing piece of equipment......

[Rob Fast]

photo as requested

[Godwin Hampton]

Rob,

Those pictures are better than a year's supply of Playboy!

Now we can really start delving into this exotic piece of mind-blowing machinery! Do all the linkages on yours work? Did you study what happens when you muck around with those bits and bobs? Have you got any literature on how it ticks?

NOW the Forum is REALLY becoming interesting! ( Not that it wasn't, mind you, but this is something I always wanted to get to the bottom of, but never found the opportunity.)

[Rob Fast]

as you know I am lapping up all of the Bofors info being generated on this thread, but my replies are few and far between, I am getting real busy on my golf course. 2 to 4 inches of rain expected tonight, flash flood warnings, and I have a big creek running thru my track! Yes, it all seems to be operational, but I have not manuals on it. In the next week I will try and supply you with a little more detailed info, and pics, keep your expert info coming, this is great. A quick question. I have been testing my Bofors with blank/ black powder rounds, in antisipation of a salute to veterans at the Winnipeg Assiniboine Park , Friday July 1, CANADA DAY. What do I use to clean the pinned barrel? Soap and water? That powder turns everyting rusty, quickly. Suggestions? Cheers Rob

[sapper740]

What do I use to clean the pinned barrel? Soap and water? That powder turns everyting rusty, quickly. Suggestions? Cheers Rob [/B][/QUOTE]


Hey Rob, I've shot a lot of black powder in my day both in a model 1884 Trap Door Springfield and when using .44 S & W. Special ammo loaded with black powder in a Ruger Vaquero for authenticity at Cowboy Action shoots. The only thing that cleans BP residue is warm, soapy water and a lot of elbow grease! After cleaning I dry the barrell thoroughly before running a swab soaked in gun oil to protect the bore. Here's something you might want to try; mill a sub-calibre insert that holds a.50 BMG blank round for your gun. You'll get a loud report with no large, smelly cloud!

[Godwin Hampton]

Rob,

In the good old Black Powder days ( what's so good about dirty, smelly, foggy and corrosive Gunpowder? ) the Drill Book ordered copious amounts of Hot water to sponge out the barrel as soon as possible after firing. The 'sponge' was a short-bristled brush the size of the bore, attached to a long stave to reach all the way into the bore.

Sapper's suggestion is brilliant. I was thinking about something on those lines, using a piece of stainless steel tubing, plugged at one end,and loaded with six or eight charges of smokeless or black powder or a mixture of both.
The charges would be individually packed and bound with string, and connected together with a short fuse to set them off in quick succession ( half-second intervals ).

The first set off would obviously be the one nearest the muzzle, possibly using an electric igniter. I would someday like to try out a torch bulb, carefully broken to leave the filament intact, with wires soldered on and buried in the powder. Connecting the wires, via a switch, to a car or motorcycle ( or golf caddy??) battery should set the first charge off, starting the chain reaction.

This is up to now all theory, and I will seek the advice of a pyrotechnic expert, so DO NOT TRY THIS AT HOME!!!! ( He, He.)

[Tony Smith]

Originally posted by Godwin Hampton
Now we can really start delving into this exotic piece of mind-blowing machinery! Do all the linkages on yours work? Did you study what happens when you muck around with those bits and bobs? Have you got any literature on how it ticks?

The Australian version was strangely a mirror version of the one in Rob's picture (No Down Under jokes, please). I have the Handbook for this and it does go into some detail. The actual sights themselves are very unusual to find on an existing gun, most seeming to have the plain spiderweb or "Stiffkey" sights.

[Richard Suggitt]

Hello Tony,

I know its a long time since you posted the diagram of the sight corrector... bt can I ask where that diagram came from ?

Also, do you know of any disagrams that show the gearing in the axle assemblies that let the wheels 'kneel' and in the bar carrying the sights ?

Thanks
Richard

[Richard Suggitt]

I would like to take a moment to introduce myself and tell you why I'm here....
I am a volunteer with The Shuttleworth Collection (in effect, an aircraft museum, but I should not really call it a museum. Just about all the aircraft are regularly flown and the vehciles we have are regualrly driven and displayed).

The collection has a Bofors 40mm AA gun, which we display on flying days and invite the public to sit on and operate (which is a lot of fun if the aircraft are flying at the time).

We need to learn more about this gun, and do some maintenance on it during the winter.

This is the gun in it's weekday static display position in one of the hangars....

DSC00122.jpg

[Richard Suggitt]

There are a few things we are having trouble with. Firstly, this is the barrel elevation mechanism.

DSC00107.jpg

We have a slight oil leak from the bottom of the vertical column. We are not sure if this mecahism is supposed to run in an oil bath or actually be full of grease. It's possible that over time some of the grease has liquified, or that someone put oil in it and then topped off with grease. If anyone has some information about how this is supposed to be lubricated I'll be very happy to receive it.

[Richard Suggitt]

The next problem is the 'accumulator' springs. These are in the two horizontal tubes under the barrel and contain springs that compensate for the weight of the barrel. In our gun the springs seem to be very weak and let the barrel fall under its own weight. We assume that the springs need to be removes and re-tempered. Has anyone done that or know anything about it ?

DSC00109.JPG

[Godwin Hampton]

Tony,

Is the Handbook the 1941 version published by the War Office on 13/ 8/ 41? That handbook covers all versions in British Army service, whether bought from Sweden ( or Poland or Hungary ) or produced in Great Britain.

The Bofors Course and Speed Sight was only fitted to many, or possibly most, of the Guns ordered from Bofors.

The Guns produced in Great Britain, and later in the Commonwealth Countries,used Forward Area Sights when operating at direct laying, and the Kerrison Predictor when operating at indirect laying. The Predictor would lay the gun through a "remote control" system using electric motors/oil units to turn and elevate the Gun. Only the loader would remain on board, to feed and fire the Gun. Pretty impressive for 1941, eh?

Around 1944, the predictor gave way to the Correctional, or 'Stiffkey' sight on British, Commonwealth, and even American Guns. Towards the end of the War, RADAR replaced the Predictor on some of the Guns still fitted with the Oil Units, giving them the capability to engage aircraft invisible to the layers.

[Tony Smith]

Originally posted by Godwin Hampton
Tony,

Is the Handbook the 1941 version published by the War Office on 13/ 8/ 41? That handbook covers all versions in British Army service, whether bought from Sweden ( or Poland or Hungary ) or produced in Great Britain.

Yes, that's the manual I have, but it also has some loose leaf and pasted in Aust amendments.

The Bofors Course and Speed Sight was only fitted to the Guns ordered from Bofors.
The Guns produced in Great Britain, and later in the Commonwealth Countries, used Forward Area Sights when operating at direct laying, and the Kerrison Predictor when operating at indirect laying.

Ah! That would explain the lack of C+S sights on Aussie guns. I have seen many with Stiffkey sights and even a predictor unit.

[Stellan Bojerud (RIP)]

1. Am I right in thinking that the Bofors calculator could be turned 360 degrees around? That could be why Tony´s picture is a "mirror" version.

2. Tony´s picture is showing a Bofors FC m/35.

3. Rob´s is a Bofors FC m/38.

4. The first batches of Bofors guns delivered to UK from Belgium, Poland and Sweden had "Polish sights" = Bofors FC. The latter batches delivered from Poland to UK had no sights, since they should be used with the No 3 Kerrison Predictor and also be fitted by British crosswire-sights.

[Godwin Hampton]

Stellan,

Your identification of Tony's picture as an m/35 and Rob's photos as the m/38, in my opinion provides the solution!

Since the British ordered Guns fitted with this type of sight before 1938, they would be fitted with the m/35 sight. Those ordered last were fitted with oil units for the Kerrison Predictor (and forward area sights, but I agree with you that these may have been added by the British). Bofors continued development to the m/38, but these were sold to countries other than Great Britain.

The 1941 Handbook quoted by Tony has Plates showing three versions of Swedish/Polish Bofors Guns, thus;

Ordnance Mk.1 / Mounting Mk.1 / Platform Mk.1 (plates 11 to 13)
This version has bearing and elevation receiver dials, no sights, and 5 spoke/5 stud wheels

Ordnance Mk.1 / Mounting Mk.111 / Platform Mk.1 (plate 14 )
This version has Bearing and Elevation oil units, Forward Area Sights, and 8 spoke/ 6 stud wheels.

Ordnance Mk.1 / Mounting Mk. 1A / Platform Mk.1 fitted with the Bofors Course and Speed Sight, seen on its own (plates 45 & 46)

There is also a description and pictures of parts pertaining to the Mk.1B Mounting (a Mk.1 modified so that it could be fitted with the oil units if required.) and the Mounting Mk.11, similiar to the Mk.111 but with elevating and traversing handles that had to be removed for power operation, not like the Mk.111 handles which only required unclutching.

Unfortunately I do not yet have the expertise to post these pictures, but have not given up yet!

[Godwin Hampton]

Originally posted by David_Hayward
Has anyone got a photo of a CDSW Bofors tractor please?

David,

Have a look at www.canadianregister.co.uk Look through the MVT Kemble photos, particularly photo M010.

[nuyt]

In St Petersburg Artillery Museum

[Stellan Bojerud (RIP)]

The S:t Petersburg picture is of a 37 mm M 1939.

The Soviet Union bought at least one 25 mm m/32 Bofors gun and license rights.

The engineers L.A. Lokev and M.N. Loginov of No 8 Artillery Factory near Moscow made an upscaled version in 37 mm known as M 1939.

These were also produced in large quantities by factories 4 Krasnojarsk, 8 Moscow and 586 Kolumna.

After WW 2 this type of gun was also produced in China and Poland.

[nuyt]

That's funny, though my Russian is not perfect I understood from the small notice in front on the gun that this was a Bofors 40mm. There were other guns marked 37mm. They must have made a mistake?

[Stellan Bojerud (RIP)]

I think you are right.

Looking closer on the wheels and the outriggers I tend to think that it is a 40 mm US-made Bofors. Lend-lease I suppose. In such case made by Chrysler Coorporation. Chrysler made guns were the only type that had the welded version of the original riveted MK 1 type which if I remember right was US type M 2.

I was confused because the gun has russian sights. Could have been added later to facilitate training.

[Godwin Hampton]

Eric,

In my humble opinion it is a very American, very 40mm Bofors!