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IWM Duxford Centurion Mk III (that one off the telly)

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Okay, not too sure where to start with this restoration project as I've only been working on it since Christmas.

I guess a good place to start is where I came in:

I've been a member of the Duxford Aviation Society Military Vehicle Wing for nearly a year, and got involved with the cent just after Christmas. At that point the engine was being fitted back into the bay. I think that took about 2 weeks (bearing in mind it was only being worked on on Tuesday's).

Well, the engine was dropped in, plumbed in and fuel added and we tried to get her to run.......

 

 

..... Nothing. The question was asked "was the engine tested before it was put in?"

answer "She used to run".

 

Anyway, myself and a friend carried out a compression loss test and found leaks past pretty much all the valves and into the crankcase. We then looked at the ignition and found it was about 50 degrees advanced.

A bore scope in A6 cylinder showed what looked like rag protruding from the inlet valves.

At this point the decision was made to remove both banks and see exactly what was wrong.

At this point I want to stress that the museum want this to be a useable tank.

So far we have re-faced the valves and seats in A bank, honed the bores, and counted the amount of o rings and seals that will be needed to rebuild the engine.

I've got a few photos at home that I'll put on later with some specifics about the engine and how we approached it.

Edited by Caddy
getting rid of a random emoticon

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Finally got home and here's some photos of the engine being hoisted into the bay:

 

IMG_9577_zps92efc9f0.jpg

 

IMG_9578_zpse8bc94b7.jpg

 

IMG_9581_zps47ed6a34.jpg

 

A little bit of advice for anyone who's trying to get one of these in or out; take the oil filter and the dynamo off first......

 

The engine is a Rolls Royce Meteor Mk4B, last serviced in 1977. The banks are of 2 piece construction and the crankcase, cylinder skirts, and heads are all alloy.

 

Anyway, we had a meeting with the IWM where we put our findings of the compression loss test to them (at best we were losing 56% of the air we were putting in and at worst 86% - 14% is pretty dire), and showed the images of the foreign object in cylinder A6. The result of this was that the museum gave permission to take both banks off, assess the issues and then cost the repairs needed.

 

So we then started to remove both banks.

 

DSCF1713_zps123564c6.jpg

 

But for some reason we were not allowed to remove the engine from the bay, which was nice.

 

With the carb set removed we found out what was the cause of the foreign object - rags and paper towels. Unknown to us someone had had the carb set off to paint the engine and forgot to remove the rags. One issue dealt with.

 

B bank was the first off, the cam assembly were in really good condition with no wear on the lobes and no rust anywhere. Unfortunately the tacho drive gears had been damaged, but we had a set on a siezed engine that came out of a donor cent so they were used to replace the broken set.

 

When we took a closer look at the pistons (and removed the quarter inch of oily coke), we saw that B3 piston had had a small bolt bouncing around inside it as it was covered with impressions of the screw thread, luckily there was no damage to the liner.

 

Think I'll stop here for the moment and read through what I've written before I really bore you all

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Here's a couple of photos of the intake manifolds just after we took the carb set off

 

B%20bank%20inlet%20port_zps54495254.jpg

A%20bank%20inlet%20port_zps8753983a.jpg

On the second you can just see the paper towel that was sticking through A6's intake valves.

 

When we got both banks off we then looked at how much work the valves and their seats needed, and whether we could get away with just lapping them in.

Unfortunately there was a lot of burning so we would need to re-face both the valves and seats.

The valves weren't a problem; the IWM workshop has a valve re-facing tool. The issue was re-facing the seats; again the IWM workshop had a vibrastone, but there were 2 problems:

The first was that with the skirt still attached to the head the tool could not be kept vertical above the valve seat.

The other issue was that the selection of spindles that fit into the valve guide to hold the stone central were all too small.

 

2 problems then. We spent quite a lot of time looking for a tool or a way to extend the vibrastone so that we didn't have to split the head and skirt. Unfortunately we had no luck there so we took the decision to separate them. The was fun, but with the aid of 2 20t hydraulic bearing pullers, some aluminium shims, and plenty of swearing A bank finally parted.

MY GOD! At this point I was very glad the engine didn't run as it would have stopped very quickly; the whole of the water jacket was full of something that looked like sand mixed with semalina and grease. Plenty of steam cleaning later had a clean jacket. The head got the same treatment and more of this stuff fell out (maybe it had something to do with the Cent coming from Shoeburyness ranges).

So we could now get to the valve seats but still needed a way to hold the spindle. 2 bits of brass, a lathe, and 5 weeks later (4 weeks to find a b*$£^y lathe) we had 2 top hat shaped pieces of brass that we could insert into the valve guides to take the spindles.

 

Now I keep on saying we, but the chap I've been working with on this is a very accomplised engineer, so it's been brilliant to learn all this stuff as I go.

 

SO we now have the valves and seat re-faced and lapped in for A bank. We did deviate from the spec slightly with the exaust seats which should have been cut to 44.5 deg, but we kept at 45 as the tool we were using isn't precise enough.

 

I know it doesn't quite sould like much work for over half a year, but we have also made a test bed out of a set of engine rails from our donor Cent (which were designed to be able to tilt 30deg either way so that we can drop the banks on vertically), this gives us the coolant circuit that we need to run the engine.

We have also been picking the brains of some very helpful people at duxford such as The Flying Legends, Old Flying Machine Co, and others with very detailed knowledge of RR Merlins so that we could fill in the gaps.

I have also been trying to source the spares we need including all the o rings and gaskets needed for the rebuild.

Thankfully we turned a corner on Tuesday, but we did notice an issue that has set us back.

We've got to figure how we're going to get rid of a scratch that has just 'appeared'

676A2787-F4AC-49F2-AFC5-BC19454FDAED-3876-00000650E9A3AF69_zps73ef265d.jpg

Edited by Caddy
Got a name wrong

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Ello Stranger.... Nice to see another of the gang on here!

 

It looks so clean and roomy in there with just the engine!

 

Compare and contrast with this old photo of the rear end of the other Cent in an almost complete state. It's so crammed in you have to lay across the top to access all of the hoses and connections.

 

Cent Engine Bay.jpg

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Compare and contrast with this old photo of the rear end of the other Cent in an almost complete state. It's so crammed in....

 

[ATTACH=CONFIG]67912[/ATTACH]

 

Looking at the photo it's obvious why the access is poor - someone's left a mechanic in there...

 

But for some reason we were not allowed to remove the engine from the bay, which was nice.

 

This would really worry me. I can't understand why, with an engine that's evidently got a number of issues and in a vehicle you want to be reliable, they wouldn't want to inspect the bottom end; particularly as it sounds as though some of those issues might potentially have damaged the crank / ends / rods and it's probably easier to do the job on the bench anyway.

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Looking at the photo it's obvious why the access is poor - someone's left a mechanic in there...

 

 

 

This would really worry me. I can't understand why, with an engine that's evidently got a number of issues and in a vehicle you want to be reliable, they wouldn't want to inspect the bottom end; particularly as it sounds as though some of those issues might potentially have damaged the crank / ends / rods and it's probably easier to do the job on the bench anyway.

 

I don't really know why either, but such is life. The biggest worry was getting the banks off without damaging or dislodging the cylinder liners. After both banks were removed we inspected the con rods and big end and all was fine. I'm really glad we can leave the bottom end in place.

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I've talked a lot about what we have done with the engine, but there has been activity on the rest of the tank by others so please don't think that this is just being done by one or two people. A lot of the work has been done on the exterior and interior, but there is a long way to go. Apparently there is a lot of discussion over the position of the bins on the turret to make it a Korea War spec, I don't know much about that so I will leave it to those who do.

 

A quick list of things to do:

 

  • Get the Meteor rebuilt and running on the test bed
  • Give the Aux Gen a service, and then get it running including checking the dynastart is fully working
  • Check meteor dynamo
  • Check the main brakes are working
  • Check the wiring with a signal generator and oscilloscope
  • Fit Aux Gen and run power through the tank - check for smoke, fire, etc.
  • Fit Meteor, check it runs in the tank.
  • Fit clutch, and gearbox. Adjust linkages and fit shims etc.
  • Check drive chain works.
  • Fit fuel tanks, air filters, Aux Gen, etc.

 

 

I've probably missed some stuff out, shouldn't take too long :undecided:

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Looking at the photo it's obvious why the access is poor - someone's left a mechanic in there...

 

 

ah yes - that'll be it.

 

This would really worry me. I can't understand why,

 

I've come across my fair share of batty reasoning, but in this case it might be for a few reasons. It's a hell of a lump to move in and out and you run the risk of damaging things when you do so (after several years spent on the vehicle, that's a bit of a worry). Similarly, especially when there are 5 or 6 restorations going on at once with 20-30 part time volunteers at any one time, things can easily get mixed up and misplaced. The kit is generally safer when it stays in/on the vehicle. It takes a *lot* of sorting out if somebody picks something up and mistakes what vehicle it was from.

 

There's also a common sense element of don't play with something bleedin heavy unless you absolutely have to. Most of us spend a lot of time working on vehicles with tight access, and while it's not ideal it is often the best way of doing it safely for both the individual and the piece of kit.

 

If you'd absolutely had to take it out again, I'm sure they'd have let you.

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Good evening all, found 2 more photos that may or may not be of interest:

 

B25AE978-FB94-4861-8332-CF34EC7D5669-5208-0000087DC8003E1B_zps47aeab5a.jpg

We had a little issue with two exhaust studs that broke off; someone had fitted high tensile steel studs which went twang... Anyway, three solid cobal dorma stub bits later they were drilled out.

Problem was that in the process of drilling them out the threads were damaged, and we couldn't get hold of a thread repair kit. So my mate being of an ingenious persuasion and in posession of a length of ally rod though we should make our own threaded collars.

We turned down the alloy and put a 1/2" BFS thread on, drilled out the stud hole and tapped that for the same thread. We then inserted the plug , put the exhaust gasket on and marked where we needed to drill the stud hole. They were then drilled and tapped.

We were luck that we didn't have to go larger than 1/2" as this would probably gone through to the water jacket.

 

One of the skirt studs had to be given the same treatment.

 

The other photo is of our mascot:

E643698D-3EA1-462C-9310-461D8CA568A5-3876-00000650B57E34AE_zps9bad038e.jpg

 

We were lucky enough to be given a load of spares by a contact from nearby, it included this silencer for the aux gen. We only realised there was a stowaway when we unloaded it. Unfortunately the little fella looks like he got a bit stuck. We tried to pop him out using an airline, but he didn't move and the place just got quite smelly......

 

I'll be in Duxford on Sunday, I'll try to get some more photos of the rest of the engine and tank. I'm not too sure how much time I'll have as we may be moving a few items around, or I'll be in the Cent AVRE Mk5.2 helping a couple of friend trying to coax the aux gen into life. Anyone got a spare Meteor starter motor?

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Good evening.

 

So we managed to get a bit of work done on the Aux Gen; it's complete and did run about a year ago, but we thought we'd give it the once over.

47A89D2F-3EC7-426D-9C1C-A26810E341E9-1758-00000266985B7E22.jpg

 

On Sunday the Aux Gen control box was stripped and cleaned including all switches and connections.

EF746384-40E7-42CD-BAEB-5279F1776893-1758-00000266AE5C742E.jpg

I guess it goes without saying that we'll need this when we test run the Aux Gen. Can't wait to start on the charging unit.

 

Well the ignition system was checked from the feed to the filter through the coil, LT feed into the distributer and then the HT side.

The filter was in good condition, the coil is slightly confusing though. The Primary winding gave a reading of about 3.1 to 3.2 ohm when it should be between 2.6 and 3 ohm, the secondary winding had no information regarding testing values and seemed to be open circuit when we tested it. As apparently the engine ran (as we were told over and over), we have decided to leave the coil on and see what happens on the test.

The dizzy needed a clean and the LT path wasn't good, and the points needed cleaning up and the profiles re-flattened. The points were then set and left. We didn't test the condenser as it would have been a bugger to get off and we couldn't find anyone who wanted to hold it whilst we 'meggered' it....

The primary HT lead failed a megger test so was replaced, the spark plugs need to be cleaned up and gaps check (with brass or plastic feeler guages).

Next week hopefully we can get on to the fuelling side.

 

 

Oh, and here's a Valentine on the move (not under it's own power though)

F953ACA2-475D-4851-BDC2-AD7ED071AF4C-1758-00000266CA85B2F6.jpg

It's being swapped with a Grant (I think), from IWM London.

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Just a short update this morning as there wasn't much done, but i wanted to say thank you to Lauren Child and a new volunteer Terry for lending a hand and keeping the boredom away yesterday.

We spent the day going through the rest of the spare electrical control boxes checking them for any physical damage. I'm going to let my learned colleague to through them as he is amazing at that stuff.

I'm going to get some photos of the boxes and their serial no. as at least two of the boxes aren't for the cent so I hope someone on here might know what they are for, pretty sure they aren't Conqueror as the boxes are not particularly high amp units.

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Cracking thread - we like these - the inner guts of armour - you'll never know what you will find!

 

I wouldn't worry about the time it is taking.

 

Most of us on here who have tinkered with the MV stuff know only too well - a job done properly only needs to be done ONCE.

 

Keep it up.

 

Markheliops

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Cracking thread - we like these - the inner guts of armour - you'll never know what you will find!

 

I wouldn't worry about the time it is taking.

 

Most of us on here who have tinkered with the MV stuff know only too well - a job done properly only needs to be done ONCE.

 

Keep it up.

 

Markheliops

 

talking about the inner guts:

1C66DB5F-A1B0-4286-9F25-6C0AC30F2522-1265-0000024BC63A9ECA.jpg

 

As Spike Milligan once said: thank you for the support, I shall always wear it.

On a serious note it's good to hear that I'm not boring everyone.

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So while we wait for some O rings to turn up we needed to find a nice large flat surface to find out how much damage the scratch on the head has caused, and if the head has warped.

We found a lovely big laying out table (at least I think that's what the fella called it), so my mate can bring in his magnetic bases and dial guages and work on that next week.

We then turned our attention on to the electrical control boxes we've got. They have all had a clean and inspection for any loose wires etc, but they all need to be tested.

I've got a few pictures of the units we're working on:

 

Main Control Box:

2932982E-5872-4322-AB1C-13CD3A40F344-1876-000003698C12D43D.jpg

Sits in the drivers compartment and has the master switch, the ignition and starting switch for the meteor and bilge and light switches.

 

Aux Gen Control Panel:

EF746384-40E7-42CD-BAEB-5279F1776893-1758-00000266AE5C742E.jpg

Sits at the back of the fighting compartment on the bulkhead. Main function to control the Aux Gen, but also has the test switched for the magnetos on the Meteor.

 

Aux Gen Control Box:

6BB8A094-F700-49CD-915F-04EEBE5E510D-1876-0000036983A08D94.jpg

THE MOST IMPORTANT BIT OF THE WHOLE TANK! It's where the Boiling Vessel plugs into.

This box sits to the right of the control panel, and basically regulates how the batteries are charged. And it helps make the tea!

 

Main Engine Dynamo Control box:

C2F38EDF-5764-4570-8D3C-2FD849C879E5-1876-00000369951DC373.jpg

It does the same job as above, but with lower amperage and without the ability to make tea...

 

Control Battery Balancing:

874EDB9E-0E5C-4743-A4BD-966053FCEF53-1876-00000369DEBAB968.jpg

This provides 12v feed for anything 12v, as the rest of the tank is 24v and had 4 6v batteries it takes the charge from 2 batteries thus providing 12v. This creates an issue with the fact that two of the batteries with be discharging at a faster rate. To counter this issue this box allows charge to be drawn either from batteries 1 and 2 or 3 and 4 thus allowing the batteries to be balanced.

 

We've got 2 other boxes that we don't know what they are from so ideas on apostcard please!

39A5314E-3756-4D62-B351-667F49B5C3E0-1876-00000369E93A00DC.jpg

3FAC9C75-966A-46EB-95FE-F70E38CEBB19-1876-00000369F051BFFF.jpg

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The MG45CX box is a 12V regulator for Centaur, Cromwell or Comet.

 

 

Thanks for that Adrian, next time I'm in I'll mark it up and put it in for storage. Not too sure it'll ever get used though.

 

 

Okay, so we've had a bit of an issue with what to do next. There were 3 ways forward:

1. To check the damage to A bank head

2. To start splitting B bank so that we can re-face the valves and seats.

3. Get stuck in to the charging systems.

 

Issues with these 3:

1. We need to get permission to use the levelling table, but the chap we need is stuck in IWM London trying dealing with all the vehicle and exhibit moves. When he is back in Duxford he's trying to catch up on the rest of his work.

2. There are enough pieces of the engine laying around and being moved all over the place already, if we pull B bank apart then there'll be even more bits to go 'walkies'. There is also a 'political' issue at the moment which I'll go through later.

3. We got our hands slapped when we touched the Aux Gen by several people telling us that it works and should be left alone, also there is a lot of pressure on us to get the Meteor working.

 

SSSooooooo:

 

Last week was spent being told what we could do, and that we should 'bodge' more. Not too sure if I want to 'bodge' a 650bhp, 1500ft/lb engine. So this week we spent a lot of time thinking what to do. We were then ask if we really need to split A bank to re-face the valve, we said "Yes", they said "Are you sure?", so we tried to lap the valves in.

Luckily our chairman was about so after we lapped in B3 cylinder we asked his opinion, which was "Rough as a bears bum!", so we were told to do it properly.

 

We have now started to split B bank (against our better judgement), all the skirt nuts are off and the waterways are soaking in diesel to loosen the transfer ferrules.

 

We've got a bit of work to do to the B bank Head; things have been bouncing around in it:

7ED82476-EF67-492A-AA8A-C84E442DF660-1954-0000044BF878B9E6.jpg

 

Won't be going to Duxford for a few weeks, but I'll keep all up to date with what has been achieved by the rest of the motley crew....

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Thanks for that Adrian, next time I'm in I'll mark it up and put it in for storage. Not too sure it'll ever get used though.

 

 

As far as I know, the Comet that's in the Land Warfare Hall is (or was the last time it was driven) a runner. It may go with the Centaur command tank though - it's probably worth checking the parts for that.

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Good to see that politics and woolly thinking are still part of the Duxford scene:nut: Not much change in the 30 plus years since I was there. Keep up the good work and don't take the "bodge" route as I did. Regretted it ever since.

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Do you have any idea what's up with the ZSU-23-4 at duxford btw?

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Do you have any idea what's up with the ZSU-23-4 at duxford btw?

 

I think the plan is to get one running out of the two, with the second becoming a static display.

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Good to see that politics and woolly thinking are still part of the Duxford scene:nut: Not much change in the 30 plus years since I was there. Keep up the good work and don't take the "bodge" route as I did. Regretted it ever since.

 

Hi Colin, thanks for the support,

 

I've not been at Duxford a year yet, but I think the reputation for politics and wooly thinking needs addressing. Yes, we have had to go through a bit of this with the engine rebuild, but only from a few people who have been at Duxford for quite a few years and have probably been through the same thing as us too many times.

A lot has changed here, and I believe that the current committee are actually bringing about a real positive change in the MVW. I do feel that if an issue is approached the right way and if a solution is presented at the same time things can be achieved.

I guess the current financial climate, the huge re-jig of IWM London, and the complexities of working on what is effectively a Rolls Royce Merlin engine without the supercharger are going to make this a very difficult and time-consuming project.

It being a bleedin' Rolls Royce engine really doesn't help either.

 

We will get there though.

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I think the plan is to get one running out of the two, with the second becoming a static display.

 

Yep, that's what I heard as well.

 

One is off to a MOD base somewhere as a gate guardian, and the innards from that one will be used to get the other one working

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Got some really sad news today - our Vice Chairman died.

RIP Paul Lacey

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