Meteor Engine magneto's

[Rob Dyba]

Anyone have any advice on fault finding a dead magneto on a Centurion Meteor engine, I have one dead Centurion & no workshop manuals, wiring diagrams etc..... neither left or right banks have spark, vehicle was running ok then just lost power & stopped. Any assistance or advice appreciated.

Rob

[tankbarrell]

Each magneto fires one plug in each cylinder, so if you have lost both sets of sparks, it may be the ground wires. If you are checking just the exhaust plugs, i.e the 'outer' ones, these all run on one mag. If she was running ok, then lost power and stopped, I would suspect the coils. They can break down when hot. If she stopped suddenly, as if the ignition was switched off, it could be the switch or the leads grounding somewhere. Try swapping the booster lead to the other mag and seeing if it fires, this may indicate a faulty mag.

If Adrian Tankbarrel's advice doesn't fix it Rob, I do have the Cent Mk.1/2/3 Handbook WO Code 1899.

It would be a mighty scan to cover all the magneto stuff, probably some 40 pages + diagrams; not impossible.

R.

[herr-pear]

I'm not familiar with these specific mags as my experence has been with aircraft. But for mags in general: first examine the points for burning/pitting. If there is light damage they can be filed smooth. Check also for continunity thru the points when closed and make sure the rubbing block (cam) really does open the points.

Check the condenser if one is present.

Some mags have a spring mechanism that 'snaps' the rotor thru the firing point at low speeds as a starting assist. If present, make sure it is not hanging up or frozen.

Carbon ring around the inside of the distributer cap?

Coil(s). Check continunity, short to ground and if you have continunity the resistance of both the primary and secondary.

And here is one that catches a lot of people. When you switch off the engine turning the mag switch GROUNDS the primary of the mag. Most people think of turning something 'off' opens a circuit. Mags are just the opposite; you close a circuit to ground. So, if the lead between the mag and the mag switch is grounded (shorted) anywhere, the mag is dead. On aircraft this lead is known as the 'P' lead.

Mechanical problem? Bearings out to lunch? Is the mag actually turning (drive coupler sheared)?

Really hope this helps. Please keep us posted.

Herr-Pear

[Paul Heise]

We had a problem with our Cent. at work, that just went dead...... ran out of gas. Quite the fuel pig.

Paul

[Neil Ashley]

I have read articles in the past suggesting that some Centurion owners have modified their engines by replacing the magneto's with conventional distributors.

I believe Nick Mead claimed to have done this on his Centurion.

Can anyone comment on the practicality of such a conversion as there would appear to be obvious advantages.

Originally posted by Neil Ashley
I have read articles in the past suggesting that some Centurion owners have modified their engines by replacing the magneto's with conventional distributors.

I believe Nick Mead claimed to have done this on his Centurion.

Can anyone comment on the practicality of such a conversion as there would appear to be obvious advantages.

That mod was done by a certain highly-strung bodger for a "Salvage Squad" TV programme Neil.

Because it wouldn't start a module from a V12 Jag was pressed into service in one mag. No one thought to question why the British Military would have unstartable tanks and some 14 countries would have bought the Cent which was the first and original mould-breaking MBT. Indeed the Cent engine was used in several late war tanks too and they all started on the button.

Correctly, it was identified that magnetos don't make sparks until their speed is sufficient to generate enough energy, even though the mags (but not rotor arms) do rotate at 1.5 x engine speed, and the Cent mags are not impulse types. The engine is of course ex-aircraft being a 27 litre RR Merlin but with no supercharger and softened cams and CR. This is of course the land based Meteor engine.

It has a boost coil and twin-finger rotor arms in the magnetos, in the aircraft application the boost coil is operated by a separate button thus allowing the engine to be turned and primed, owing to the very lengthy inlet manifold and huge blower casing volume, without any possibility of ignition and backfire.

In the tank version with simple updraught carbs in the V, the boost coil is activated with the single starter button and the system is now of an age when things fail. In essence the boost system is nothing more than a contact trembler activated by the core of the ignition boost coil making a continual shower of sparks, it should be audibly buzzing whan cranking a Centurion at some 500Hz on a 24V supply.

These sparks are fed to one mag only, the right hand, B bank - exhaust side, and then to the boost rotor arm finger that is 35º behind the the main rotor arm contact. The left hand magneto has this HT input blanked and in fact runs the opposite way round.

Thus the engine is started well retarded as each cylinder is fired when the sparks finally jump to each cap segment a little less than 35º ATDC, this means there can be no kick-backs on the direct starter drive and although the power realised when it fires is well below what should be the case, it is quite enough to accelerate the engine from a slow cranking speed, about 30 rpm, to the point where the mags start firing both sets of plugs on time and the start is secured with idle at 450 rpm. With a well primed and unmodified Spitfire you can see this happen as the exhaust stubs produce lazy flames of burning Ki-Gas prime fuel and the engine gathers pace against the prop load.

It is indeed the case that the engine stop is a ground connection to the magnetos that shorts the LT side of the magneto, but like an aircraft, the Cent also has two mag test buttons that can disable each mag in turn for the classic mag-drop test and in an emergency be used to stop the engine also.

Cents are so old now that all this wiring, point gaps and all HT cabling may well be faulty in some respect.

R.

[Rob Dyba]

Thank you all for the good advice, I will climb into the beast & see what I can come up with, I suspected a shorted out magneto coil earth wire, will keep you all posted with the result.

Rob

[Richard Farrant]

Rob,

I see you are in Brisbane. A friend of mine lives just north of Newcastle, NSW, and had two Cents at one time. I guess you could talk to him, if you are interested, I can PM his number.
He is in the Australian Armoured Vehicle Association and there are several members in NSW with Cents.

Richard

Originally posted by robobmc
Thank you all for the good advice, I will climb into the beast & see what I can come up with, I suspected a shorted out magneto coil earth wire, will keep you all posted with the result.

Rob

I wonder if this small schematic helps any.

R.

[herr-pear]

Upon further reflection realized the only thing both mags have in common is the ignition switch (well, and the accessory drive geartrain, but that's bulletproof). So if both mags are out give the switch a very carefull look-see.

Roger in Vegas.

[Hanno Spoelstra]

To download a Rolls Royce Meteor servicing manual, go here: http://www.aecmilitant.co.uk/downloads.html

[Alex Blair (RIP)]

Originally posted by robobmc
Anyone have any advice on fault finding a dead magneto on a Centurion Meteor engine, I have one dead Centurion & no workshop manuals, wiring diagrams etc..... neither left or right banks have spark, vehicle was running ok then just lost power & stopped. Any assistance or advice appreciated.

Rob

Rob..
Who makes the magnetos???
Scintilla-Bendix mags are timed to the engine in the full advance position...
Bosch mags are timed to the engine in the full retarded position...
I could give you the specs if I knew what type they were..

Originally posted by Alex Blair
Rob..
Who makes the magnetos???

Left hand mag (clockwise rotation) Simms FST 12 RG/3C
Right hand mag (anti-clock rotation) Simms FST 12 RG/3AC

LHS timed 5º BTDC Mk.4 engine or 0º-3º BTDC Mk.4A/B engine.
RHS timed 10ºBTDC Mk.4 engine or 5º-8º BTDC Mk.4A/B engine.

Timing mark "A1" is engraved on front mag case.

R.

[Alex Blair (RIP)]

Originally posted by Richard Notton
Left hand mag (clockwise rotation) Simms FST 12 RG/3C
Right hand mag (anti-clock rotation) Simms FST 12 RG/3AC

LHS timed 5º BTDC Mk.4 engine or 0º-3º BTDC Mk.4A/B engine.
RHS timed 10ºBTDC Mk.4 engine or 5º-8º BTDC Mk.4A/B engine.

Timing mark "A1" is engraved on front mag case.

R.

Thanks Richard..
I don't have any info on them fer-in RHD type mags...
LOL

[Rob Dyba]

Thanks guys, any info is good info. The current state of affairs is that the boost coil lead was shorting out, once this was replaced she started popping back through the manifold,the starter motor jammed on , and sparks started coming from the driver's control panel resulting in a plenum chamber fire the likes I have never seen before. After about 5 minutes of jumping up & down screaming "FIRE FIRE" mad hand turret traversing to gain acess to the batteries in wich the oil cooler sustained minor crushing 4 litres of water was poured down the inlets to extinguish the flames. The owner has been instructed to "recover" the vehicle from the gully where she currently resides & get it up to the shed where work can restart out of the elements. Will keep you all posted, unfortunately there are no photos of the thick black oily smoke pouring out of all the hatches. Magnificent!!!!!

Rob

[Richard Farrant]

Originally posted by robobmc
she started popping back through the manifold,the starter motor jammed on , and sparks started coming from the driver's control panel resulting in a plenum chamber fire the likes I have never seen before. After about 5 minutes of jumping up & down screaming "FIRE FIRE" mad hand turret traversing to gain acess to the batteries in wich the oil cooler sustained minor crushing 4 litres of water was poured down the inlets to extinguish the flames.

ha ha

Rob,

Reminds me of a few years ago, when I was asked by a museum to get their Cent running, it had stood outside for some time and the petrol was definitely off. No sign of life on turning it over. I took the top of an air cleaner and squirted some fresh petrol down the intake pipe. Got one of the museum staff with a fire extinguisher at the ready, while I got in the drivers compartment. After a few turns she fired up and carried on, along with a large cloud of smoke. I could not see anyone about, so stopped the engine and dismounted, when I eventually found the staff member, he said he thought that if there was a fire, it was not the place to be so he went off

Richard

[Col Tigwell]

If the Meteor engine was as sensitive to Mag drop, as the Merlin, you need some skilled help.

I presume you know about Doug.

If you do not know his site, go to the a google search.

Type in

Doug's Heavy Metal

That will take you to it.

Anyone by the way who has an interest in Armour should have a look.

However be warned you could spend a day just looking at this site.

Regards

Col Tigwell

[Douglas Greville]

[QUOTE]Originally posted by herkman
[B]If the Meteor engine was as sensitive to Mag drop, as the Merlin, you need some skilled help.

> I presume you know about Doug.

He sure does, he bought my last Bren Carrier (LP2), although the
last few emails I sent him have bounced. Changed your email
address and neglected to tell me Rob?

> If you do not know his site, go to the a google search.

> Type in

Here's the links:

http://www.users.zetnet.co.uk/lsm/dhmg/index.html (UK mirror site)

and

http://www.trackpads.net/sites/heavymetal/ (US mirror site)

That will take you to it.

> Anyone by the way who has an interest in Armour should
> have a look.

Oooo, shucks.

> However be warned you could spend a day just looking at this > site.

If you are paying attention whilst in there, you will see many
articles written by Richard. In context, is one about recovering
a Cent that had sat for many years near Richard's house.

Col

Where are you?

Were you on armour in Vietnam?

My email address:
dgrev@iinet.net.au

[Col Tigwell]

No the army would not have me (grin).

Was a C130 Loadmaster, so carried many APC's and of course Norm Rowe.

I think your site is the best, spend hours wandering around, nice to see such dedication.

Regards

Col

[Rob Dyba]

Gidday Doug, I'll bounce you my work adress as ze computer is in the same shape as the Centurion, inert after smoking.

Rob the destroyer of expensive things.

[Mike Cecil]

I know this is an old thread, but this page from Tim Vibert's 'handy hints' on Centurion might help.

Mike