Bofors help - Calling the Brains trust

[Tony Smith]

The Mk2 Bofors gun platform has two outrigger beams that are stowed in transit and fitted when deployed. These beams are approx 5in pipe that fit into a socket in the main chassis and are then secured with a 1in tapered pin that slides in by hand. The pin has a handle that then rotates and secures into a lug.

HELP! A mate and I have recently acquired a Bofors, which has spent some time outdoors, and these two pins are stuck fast and refuse to budge, meaning the outriggers are "permanently" in place making transport difficult. What suggestions do people have for encouraging these pins out? So far, the pins have had about a week with daily applications of WD40, Diesel, and light oil. There is not much space underneath to strike the pins upwards with a hammer. The handle has been persuaded to rotate with gentle taps from a 16lb sledge hammer, to no avail. Each side of the gun has been lifted on a hydraulic jack sitting on the exposed lower part of the pin, and a large person jumping on the platform, to no avail. Heat has been applied to the head of the pin, but the amount of metal in contact acts like a heatsink with little effect. Sure to get a result, we have tried heating the pin, lifting it on the pin on a jack and rotating the handle with the sledge hammer ALL AT THE SAME TIME, to no avail. And yes, before you ask, I have checked and the pin is not welded in.

I have to resort to the Brains Trust for a solution. Any suggestions?

Possibilities considered but not yet attempted include:
1. A large bearing puller clamped around the box girder and pressing on the bottom of the pin, and
2. Dismantle and re-assemble a 60 ton hydraulic brake press around the outrigger with the ram on the top of the box girder and the base of the press lifting the bottom of the pin (yes, I am that desperate!).

[cletrac (RIP)]

Try an air chisel with a blunt tool in it. If it rattles on the pin for a while it might loosen it up.

[Gunner]

Hi Tony:

Been there, shared the frustration!

Ours was in the same state when I acquired it and I eventually got the pins out but had to do some damage in the process.

The pins are machined as a straight piece of bar stock with a taper only on the last two inches. You are fighting several inches of rust and swelling. At the top the pins are stepped down to about one inch leaving a 1/2 inch high 'stud' at the top. The handle is drilled and then welded onto this stud.

If you have managed to move the handles but the pin stayed still then you are where I was. I ended up snapping off the handles and driving the pins from above where I could get a drift and a sledge hammer at the buggers! I then welded the handles back on as part of the rebuild.

If you got the handles to turn and the pins rotated with them then keep soaking and jacking... they should come loose. Be careful about using a torch as the outrigger leg has a large bronze bushing there and you don't want to slag it!

Welcome to the wonderful world of Bofors!

Ubique! Mike

[Phil Waterman]

Originally Posted by cletrac

Try an air chisel with a blunt tool in it. If it rattles on the pin for a while it might loosen it up.

I agree Tony an air chisel with a flat punch will get loose stuff that 20 ton press will not touch. I've gotten stuff apart this way by blocking the chisel body in place with just enough space to let the thing tap away, generally let it tap full preasure first to see if you get lucky. If not then I turn the air preassure down and just let it sit there and vibrate away. Reason for turning the air preasure down if you are just going to let it hammer is to keep the punch from heating up or spreading the body of pin out.

Obviously if you get any movement try switching directions of your attack.

With that much iron attached to the pins should make a nice noise.

Cheers Phil

[rob love]

Dig a hole and use a 5 lb short handled sledge. Unless you are parked over concrete that is.

For anything seized i always swear by heat. Heat followed by oil will suck the oil in to where it's needed. Mike's point about the bronze bearing is valid, so you don't want the pin glowing red in this case.

I got lucky with my Bofors....Brad did all the bullwork.

[Bob Moseley (RIP)]

Hi Tony - seriously though what heating method have you used. You need a large heating device like the flame torch I recently bought, that way a large area can be heated without the heat rapidly dissipating. Regarding the bronze bush, the melting point of bronze is 950c so you had better have your little glass thermometer with you.

Bob

[Alex Blair (RIP)]

Originally Posted by cletrac

Try an air chisel with a blunt tool in it. If it rattles on the pin for a while it might loosen it up.

I agree with the air impact chisel method..
I had an electric one that I used to remove fan shafts in roof top air conditioners for bearing replacements..
The tool impact end was flat mushroomed shaped and the last shaft I used it on was 2 3/16ths by 6' long..
It had 3 pillow block bearings on it and two squirrel cage fans of 20,000CFM each...
After I loosened the bearing locks and the fan housing set screws locks from the shaft I didn't even oil,clean or heat it..and it was on a roof top unit ..twenty years old..
I just started pushing on the end of the shaft with the electric impact and it started to move after 5 seconds and I pushed it right out of the machine in about 5 minutes..
slick as snot..that little pin should be no problem..Get an impact hammer...vibration is the answer..ask you girl friend..

[Godwin Hampton]

Should all else fail........

Cut the outrigger tube, 3 or 4 inches from the bronze bush! This will allow transportation immidiately, and also give access to the centre part of the pin to enable you to attack the rust. A good method is to heat the pin to red heat and immideately cool it with a hose pipe. This will make the rust flake and fall off. The outrigger bits can be tack-welded back on in situ after levelling everything, with the final welding and grinding being done in the workshop.

[colin jones]

Hi Tony, this might sound a bit difficult. You could try chaining a minimum 12tonne hyd jack to the underside of the pin. Wrap the chain around numerous times for safety. Once you put pressure on the jack you are then using the chassis for back pressure rather than having the jack on the ground and only using the weight of the gun for pressure. Once you have got a substantial amount of pressure on the jack, just leave it and let the pressure do the work. It would act like a hyd bearing puller. If you have got a 32 tonne jack an a big chain, all the better.
Good luck
Colin.

[notenoughtoys]

Tony - Maybe I'm "out in left field without a glove" on this - but maybe you'd be better off trying to chill the pins down if possible.

Heat sounds like it would be great at fracturing any type of rust bridge between the pin / bushing interface - but it will only be working in your favor if you are heating the outside bushing itself (expanding it in effect) - not the pin.

I'd try chilling down the pin itself locally with dry ice or perhaps an aerosol product (Loctite makes one I believe). It looks like you may be able to get access directly to the pin head and the tapered tip enough to make a difference (provided of course the bushing does not extend the full length of the internal cavity)........ If you were to chill down the pins you would in effect be shrinking the pin diameter thus increasing the clearance between the pin / bushing. Combine this with one of the above pneumatic methods of agitating the connection and you should be getting some movement.

I'd hate to see you have to hacksaw / reweld the stabilizers !!

Reid in Uxbridge Ontario

[Tony Smith]

Thanks for all the replies, but I ought to say that this one has been put to bed. Encouraged by Gunner's reply that there is nothing special retaining the pin, my thinking led to the same idea that Colin Jones also came up with.

I wrapped two lengths of chain around the outrigger box and hung a 3/4" steel plate on them. I then sat a 30 hydraulic Porta-Power on the plate and pressed againgst the bottom of the pin. A bit of a hooray, and up she rises! Pardon the quality of the photo, it was taken on a Mobile Phone.