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Car hacker secrets revealed: Clutching up a tank engine in a classic motor

A man. A V12 lump. A beaut of a project

+Diagrams Several people were kind enough to comment favourably on this article and asked for more information, pictures and video. We are delighted to oblige. Technically no one asked for poorly drawn diagrams, but I’ve included some of these as well.

First, the video.

Mark and chum turn over the Rolls Royce Meteor engine. The sound is spectacular

This shows the very first firing, with the rocker covers off, to check the oil flow. What really impressed us was that the engine fired on the very first crank of the starter motor. OK, it didn’t start until the second, but at least it showed willing after 20 years in a crate.

The second video, here, shows the firing with the rocker covers on. After this the videos get boring, the engine just runs.

Now, the clutch shaft assembly generated plenty of interest and requests for more details. Here goes, with diagrams.

In most car engines the crankshaft is longer than the engine and sticks out of the back.

Standard engine crankshaft

A standard engine crankshaft...

There is a flange on the end to which the flywheel bolts and the clutch then operates on the flywheel.

When you depress the clutch it presses on the flywheel which in turn imparts a longitudinal load along the length of the crankshaft. The crankshaft bearings are, therefore, designed to take this load. Clearly, for the clutch to work properly both it and the engine must remain fixed in relation to each other, so the gearbox is bolted to the engine and both have flexible mountings onto the chassis/monocoque.

Fitting a manual gearbox and clutch to the Meteor engine, that’s been more commonly found in Cromwell and Centurion tanks, raises three fundamental issues.

Standard flywheel

.... and standard engine flywheel

Firstly, the Meteor is derived from an aircraft engine, so the engine block is an aluminium alloy and not designed to have a gearbox bolted to it. That doesn’t mean that it wouldn’t take the strain, but there is no direct evidence that it would. So the problem is how do you ensure that the engine and gearbox remain in a fixed position relative to each other?

Next there is no evidence that the crankshaft was not designed to take the longitudinal load of a clutch working. Again, it might cope fine or it might not. So, we have to ensure that the clutch can be pressed but that the resultant load is not transferred to the crank.

Finally, the crankshaft in the Meteor finishes inside the crankcase. There is no waiting flange to which a flywheel can be bolted; rather there is a splined hole in the end of the recessed shaft.

Clearly the second and third problems are essentially self-inflicted wounds imposed by the desire to have a manual gearbox. However “we choose to build a Meteor-powered car in this decade, and do these other things, not because they are easy, but because they are hard.” The fun is in the process of solving the problems.

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