Aligning Centurion engine to gearbox

[Malcolm Towrie]

I think we have it figured out, Lauren. We're using the shaft from a old clutch installed between the engine and the gearbox. And using magnetic based dial indicators or maybe a laser alignment tool if I can borrow one to measure runouts at gearbox and engine ends.
The photo shows the shaft mounted to the gearbox. We don't have the engine in yet.

Malcolm

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[Lauren Child]

I asked the question today, and apparently we managed to borrow the special tool from a friend.

I guess that means we still have a 50/50 and ask the audience left for when the project restarts, but it looks like you’ve got it sorted anyway. I’d love to know how you get on

TTFN
Lauren

[Malcolm Towrie]

To close the loop here, I got the engine and gearbox aligned. Using the shaft from an old beaten-up clutch we had worked well. If you don't have an old shaft, seems to me you'd have to make something similar, which is quite a machining challenge.

I got really lucky. The runout readings taken with the dial indicator on the gearbox flange face and the crankcase face (see photos) indicated the engine was sitting about 1/4" low, relative to the gearbox. I made shims out of 3/16" plate and installed them under all four engine mounts. That brought the total indicated runout down from 0.060" to 0.020". Another 0.075" under each mount brought the TIR down to 0.008", which is within spec.

I was dreading this job, but it turned out to be simpler than I thought. I suspect that is due to the factory ensuring that the gearbox mounts and the engine mounts are parallel and that simply shimming up and down will correct misalignment.

I also suspect this spec is far too conservative for those of us running Centurions today. We're more likely to do 3 miles a year rather than 3000. So wearing out clutch, crankshaft, and gearbox components is pretty unlikely.

Malcolm

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[David Herbert]

Well done Malcolm !
That is not a job that I would have looked forward to. Now you get to install the world's heaviest clutch !

David

[Robin Craig]

Good old fashioned engineering not requiring a USB stick or an I phone. Great to see such work going on by such skilled dedicated people. Thank you for sharing your work Malcolm

[Malcolm Towrie]

Originally Posted by David Herbert

Well done Malcolm !
That is not a job that I would have looked forward to. Now you get to install the world's heaviest clutch !

David

Thanks, guys. Luck's been with me lately - I've also been finding parts that I thought I would have to fabricate, including one exhaust pipe from the manifold to the hull penetration.
The one part I can't find, despite seeing photos of it in this very tank, is the voltage regulator for the main engine-mounted generator. (I've no immediate plans to install the auxiliary Morris engine powered generator, although I think we'll have to if we get the turret traverse working.)
We have a few deuce-and-a-half's in the boneyard so I hope I can find a suitable regulator there. They're 28 volt, approximately 40 amp rated, so close enough.

David, the clutch in a T-55 is a beast too, but I think you're right, this one has it beat. In fact, that's my new worry, can I get it in without having to remove the engine or gearbox? The manual doesn't help - in the clutch removal section it says, remove the engine. In the replacement section, it says replace the gearbox. A bit confusing.

I can install and remove the bare clutch shaft I used for alignment easily by sliding the engine forward a few inches (I have the starter removed at the front and the fan drive pulleys and tensioners removed at the back) but the complete 450 lb. clutch might not be so cooperative.

By the way, that exhaust pipe I mentioned above - where it passes through the hull, it's a loose fit sealed by 2 piston rings! I thought that was a clever idea. It allows for thermal expansion and hull flex and still maintains a decent seal. And the old piston rings I removed from a Staghound engine recently were a good fit!

Malcolm

[MikeV]

Malcolm
And His guys are doing a great job I am Lucky to be a member of the same museum. Can't wait to see this tank roll out of the MVCC.

[45jim]

We found it easier to move the engine forward to replace the clutch. We marked the location of the engine on the mounts and cut some wood for positive reference between the engine and gearbox. It was a bear to lift out and replace the clutch but once installed it proved relatively easy to re-align the engine to transmission. The wood was used as a rough check as we were moving things into place and final alignment came from the reference marks we made during disassembly. We did have the element of experience as we had two old RCEME Cent guys assisting. I believe that while the suggested tolerances exist, the design is far more forgiving and while adhering to the suggested tolerances provides the maximum clutch and seal life a slight error will not affect its life as a parade vehicle.

As a side note, when a Centurion had sat for a period of time it is important to preserve the clutch during initial start up. Centurions stored outside often suffered from seized track pins, stuck brake shoes and there is always the possibility of a stuck clutch disc. We were told to warm the engine with the transmission in neutral clutch engaged. Once warm, a couple of light applications of steering tiller (while still in neutral) is applied to each side, not enough to effect a turn but to put some stress on the track and clutch. Once this was done and the brakes were known to be free only then was it moved forward or back to free everything up. Wonky track link got a smart smack with a sledge.

The Strathcona's stored their Centurions in Wainwright Alberta and they sat for up to 9 months a year (several months below -30C) with only a skeleton maintenance crew. All the training was done in a 3 month window from spring to early summer so every time the unit went up to train there was caution in how the tanks were brought out hibernation.