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philm1

Scorpion/Scimitar Restoration in New Zealand

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Posted (edited)

To explain Andy's observation: a cannon typically uses the breech ring in various ways to connect the barrel to the recoil system.

Take away the breech ring and normally the barrel will just slide out of battery of its own accord if at all muzzle high. Beware as there is considerable momentum once it starts moving. Given that yours is obviously muzzle high, either it is rusted in place, the grease has gone solid or as Andy says, it may be welded.

What ever the explanation, it should not be sitting the way it currently is.

 

Were it a traditional French 75 (slay and recoil system) as used by almost all nations artillery and tanks up to WW2 the barrel would be connected to a slay, but would be free to slide without the breech ring.

 

Were we talking the special light design that came about for the Saladin, the recoil unit would be effectively a wet tube (inner and outer cylinders with piston rings and a spring) that would surround the barrel and be very compact with the barrel NOT retained by way of the breech ring.

But the Scorpion from what I can see in your photos uses a system half way between the 2 types mentioned above. It appears to have the barrel surrounded by a tubular mount but with separate return spring and piston tubes - most odd. There is no slay from what I can see. The barrel just slides in the housing - what is effectively the trunnion block/mantlet group. I would expect to find a large accurately machined bush in that housing and some means to lubricate it.

 

I cannot see that removal is a case of a twist and a pull, but who knows, as this is a rather curious system. The Centurion had a lovely quick change barrel using an interrupted thread. You undid a locking bolt on the breech ring, then turned the barrel something like 30° and slid it out from the front. This left behind the breech ring still attached to the recoil system. Your photos appear to show a flange forward of the breech thread that is hard against the mounting, so I would think the barrel could only

be removed rearwards.

 

Somebody in the Alvis AFV group must have a manual detailing the workings of the main gun?

 

Regards

Doug

Edited by dgrev

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Radiator Fan was seized which was expected so completely dismantled, sand blasted, powder coated, new bearings and reassembled. Now on the shelf patiently awaiting installation.

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Handbrake also recently completely stripped down, painted and rebuilt. Now re installed.

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Current emphasis is to get the Hull sitting back on tracks. All the tosion bars have been cleaned and are ready to go back in with new bearings in the wheel hubs. Pity we forgot some of the axle end brackets (for other side of Hull) which are sitting in another workshop now shut up for the Easter break. We did manage to get one set of torsion bars back in trying to get the measurements as close as possible for the torsion bar alignment.

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Whilst we were making good progress we also took advantage of the digger that is on site to move around some of the heavier items into the workshop - final drives and track. Hopefully we will get the final drives in place in the next day or 2. The tracks we have laid out to give a quick tidy up ready to go on.

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What effect will the hull being less than full weight have when setting the torsion bar angle / dimensions?

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What effect will the hull being less than full weight have when setting the torsion bar angle / dimensions?

 

We are setting them based on the manual 'Electrical and Mechanical Engineering Regulations - Chapter 6 - Suspension & Tracks'. When fitting them there is no downwards weight as obviously they are hanging freely. There is no mention of setting them at different angles depending on the full weight or otherwise of the vehicle. I can't imagine in the field you would want to be adjusting them depending on weights. All a learning curve for us but appreiciate any feedback before we refit the remaing ones.

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Phil

 

I would say Robin was curious due to his knowledge of older vehicles with torsion bars such as the Saracen and Saladin, IIRC

Stolly also.

On them, the height and weight distribution of the vehicle could be adjusted by way of the torsion bar settings.

 

I read up on the procedure a very long time ago, but if memory serves correct, on those vehicles it could be done

without having to remove anything such as suspension arms etc. Just how enjoyable a job it is I do not know.

 

The Ferret has a set of massive coils, which aren't any fun to install or remove either, even less so on the Aussie versions

due to the hull strengthening fillet.

 

Regards

Doug

 

 

We are setting them based on the manual 'Electrical and Mechanical Engineering Regulations - Chapter 6 - Suspension & Tracks'. When fitting them there is no downwards weight as obviously they are hanging freely. There is no mention of setting them at different angles depending on the full weight or otherwise of the vehicle. I can't imagine in the field you would want to be adjusting them depending on weights. All a learning curve for us but appreiciate any feedback before we refit the remaing ones.

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Phil

 

I would say Robin was curious due to his knowledge of older vehicles with torsion bars such as the Saracen and Saladin, IIRC

Stolly also.

On them, the height and weight distribution of the vehicle could be adjusted by way of the torsion bar settings.

 

I read up on the procedure a very long time ago, but if memory serves correct, on those vehicles it could be done

without having to remove anything such as suspension arms etc. Just how enjoyable a job it is I do not know.

 

The Ferret has a set of massive coils, which aren't any fun to install or remove either, even less so on the Aussie versions

due to the hull strengthening fillet.

 

Regards

Doug

 

Thanks Doug. Hopefully we get them all installed again okay. Learning all the time on this project and appreicate the feedback from others. Hopefully we don't do a coil on Brett's Ferret as that doesn't sound like too much fun.

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Posted (edited)
Thanks Doug. Hopefully we get them all installed again okay. Learning all the time on this project and appreicate the feedback from others. Hopefully we don't do a coil on Brett's Ferret as that doesn't sound like too much fun.

 

Phil.

 

Those coils are big heavy and powerful. I replaced the output seal in one bevel box and won't be doing that again for 2 reasons:

1) It made absolutely no difference to the leak rate. When I studied the design I realised there is a pumping action as the

challice moves in and out with suspension movement, however, the seal is cork

and just doesn't grip tight enough to seal effectively.

My experience is that if the vehicle is driven weekly, almost no leakage.

The seap happens sometime around day 10 onwards.

On my vehicle all 4 bevel boxes drain into the hubs, which then seap. People tell me that is not mechanically possible. If not, then how come I only ever let oil out of my hubs, I have never had to top them up.

2) A mate ended up at the hospital for stitches when a steel bar he was using slipped and he conked his head on the body

stiffening fillet. We were battling the coil tension at the time trying to reassemble. So no desire to risk life and limb again.

 

Ferrets are typical Pommie engineering. Having said that I still like my Ferret, lovely thing to drive.

 

When they designed the CVRT, they had 3 choices:

1) The older Yank philosophy (WW2 to 1970s), basic and reliable, but that would have meant bigger.

2) The German philosophy, way over designed, complicated and expensive, politically unacceptable.

3) The Pommie philosophy, way over designed, complicated, maintenance headache and thus less reliable.

 

But the main criteria was light weight and compactness and that came at the cost of size/strength/durability.

 

Lets take the final drives as an example - epicylic like the Ferret hubs. Both are very sensitive to lack of oil and quality.

Or the turret basket , why did they include those guide rollers on the hull floor? I don't recall

any other design that needed that? Baskets are supposed to hang from the turret ring and all the other designs seem to

do so very successfully.

 

As the Yanks never built a CVRT equivalent, you can't compare it. Perhaps with the German Hotchkiss and Wiesel 1 and 2. They are so few in private hands that they really don't count.

The CVRT design has the epicylic final drive, centrifugal clutch, crash change gearbox, hydraulic steering, non-replacable

track pads, road wheels that shed rubber if you so much as look at them: all are problematic. It just means that you must

stock up on parts and accept that as a cost of ownership.

There was a very good reason hydraulic steering was abandoned in the Universal Carrier (Bren Carrier) design, yet they

went back to it with CVRT.

 

I once costed getting a Scorpion. To be realistically secure for parts I factored in 5 sets of NOS tracks, 2 spare engines, 2 spare gearboxes, a couple of spare torsion bars, a spare set of dampers, lots of road wheels (hysteresis nightmares), 2 x final drives,

brake pads, a supply of the CVRT specific consumables such as the large toothed drive belt (for the fan?) and so on.

Back then, (about 10 to 15 years ago) it would have added 50% to 75% on top of the purchase price of the vehicle. The £ was

something like AU$2.35 to £1 and it was just too much money to get it all out here and any unexpected parts were a long

way away. Also back then, manuals weren't to be had.

 

I have driven one a couple of times and they certainly are cute. What really came across is that longevity of the vehicle is

very dependant on how they are driven and maintained. Dry storage being essential, perversely, for something designed

in the UK!

 

I do however realise, that they are the ideal "little tank" and are the tracked equivalent of a Ferret.

You can actually get them into a domestic garage! They are something that the average

person can aspire to own without having to be a millionaire in order to fund WW2 light armour, or post war medium or heavy armour.

There in lies the attraction.

 

Regards

Doug

Edited by dgrev

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Posted (edited)

Phil

 

Great news on how you are going about the refit. Yes manuals and good knowledge are key to doing the job right.

 

Grand work

Edited by robin craig

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I was given the EMER which gives the precise measurement of radial arm droop as measured from the bottom of the Sponson. Very useful if you have cause to believe that torsion bars have become weak (as some of ours have).

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Back from 10 days in sunny Australia on the Sunshine Coast north of Brisbane. Attended the Marrochydore Anzac Day parade which was hosting the 50th anniversay of Vietnam verterans of 86th Transport Platoon.

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A bit slow on it lately as winter approaches. Did finish giving the tracks a quick paint of chassis black so at least they will look good for the first photo before we go off into the mud. Amazingly easy to roll up but not so easy to move around when lying flat. These now back in the corner of the shed awaiting to be fitted.

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Starting to get cold here as winter sets in. Still aiming to paint lower hull so road wheels and tracks can go back on. This in mind we hired a LPG gas blower heater and set that going for a couple of hours to warm the shed up. Then managed to get a coat of undercoat on. My first time at spray painting but didn't do too bad. Brett, the more experienced painter was layed up on the couch with the flu.

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I have also put the commanders periscope back together following repairs and the replacement lens Nigel Moss kindly sent to us. Even managed to see through it and target the neighbours house. This unit will go aside pending fitting in the turret down the track.

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Thanks for the update Phil, I was getting withdrawal symptoms from not hearing. Once again doing an amazing job.

David

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Would be nice to see photo of Scorpion mentioned above. I wonder if the engine was any good when Spike removed it?

Nipper has bought tickets for Tankfest at Bovvy in a couple of weeks for Father's Day, like every year. He's not stupid, he gets his personal chauffeur and tour guide. All he has to do is buy tickets and burgers.

 

I'll have the big beast camera. See if I can get a half decent pic.

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Thanks for the update Phil, I was getting withdrawal symptoms from not hearing. Once again doing an amazing job.

David

 

Can't be having that. Perhaps a trip down under is on the cards??

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Another session cleaning up the road wheels ready for painting. Not being too precious but thought it best to clean any rust off the inner side steel bands then a coat of anti rust. Bit of fun for a Sunday morning and thanfully the stack got smaller.

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Posted (edited)
To explain Andy's observation: a cannon typically uses the breech ring in various ways to connect the barrel to the recoil system.

Take away the breech ring and normally the barrel will just slide out of battery of its own accord if at all muzzle high. Beware as there is considerable momentum once it starts moving. Given that yours is obviously muzzle high, either it is rusted in place, the grease has gone solid or as Andy says, it may be welded.

What ever the explanation, it should not be sitting the way it currently is.

 

Were it a traditional French 75 (slay and recoil system) as used by almost all nations artillery and tanks up to WW2 the barrel would be connected to a slay, but would be free to slide without the breech ring.

 

Were we talking the special light design that came about for the Saladin, the recoil unit would be effectively a wet tube (inner and outer cylinders with piston rings and a spring) that would surround the barrel and be very compact with the barrel NOT retained by way of the breech ring.

But the Scorpion from what I can see in your photos uses a system half way between the 2 types mentioned above. It appears to have the barrel surrounded by a tubular mount but with separate return spring and piston tubes - most odd. There is no slay from what I can see. The barrel just slides in the housing - what is effectively the trunnion block/mantlet group. I would expect to find a large accurately machined bush in that housing and some means to lubricate it.

 

I cannot see that removal is a case of a twist and a pull, but who knows, as this is a rather curious system. The Centurion had a lovely quick change barrel using an interrupted thread. You undid a locking bolt on the breech ring, then turned the barrel something like 30° and slid it out from the front. This left behind the breech ring still attached to the recoil system. Your photos appear to show a flange forward of the breech thread that is hard against the mounting, so I would think the barrel could only

be removed rearwards.

 

Somebody in the Alvis AFV group must have a manual detailing the workings of the main gun?

 

Regards

Doug

 

From enquiries my understanding is that unless our barrel is welded in some place then it should pull out.

 

The breech ring has interrupted screw threads which attach it to the barrel.

 

There is a metal oval shaped thing in front of the breach ring (technical term 'yoke') which then attaches to the recoil system. the yoke splits in 2 and fits over the bobbins at the end of the buffer cylinder and recuperator cylinder (our recuperator bobbin has been cut off) then the yoke halves reattached. this i understand holds the barrel in place.

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Edited by philm1

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first coat of green plus more road wheels prepared for painting.

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Some more painting completed. 2nd coat on underside of Hull plus road wheels, wheel stud bolts and some other bits and pieces. Slowly, slowly as winter has set in.

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Just be careful painting every surface.. locking rings, bolt heads, mating surfaces on the hubs etc. You might find the paint stops things fitting together properly. All the mating surfaces are usually left unpainted.

 

Chris

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I second Chris' comment. At the VW meet at Hessich (sp?) in Germany last week there was a VW Combie Ice Cream van that had been restored and the wheel fell off. The owner had painted the underside of the wheel bolts and the hole chamfer in the wheels where the bolts snug down. When the paint failed under dynamic load, the bolts came loose, the chamfer holes wallied out and the

wheel went its own way.

 

Embarrassing at best, dangerous at worst.

 

Regards

Doug

 

Just be careful painting every surface.. locking rings, bolt heads, mating surfaces on the hubs etc. You might find the paint stops things fitting together properly. All the mating surfaces are usually left unpainted.

 

Chris

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