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268. The Nitty-Gritty

02/09/2016

The Shuttleworth Collection have peered inside the engine and made some preliminary findings which are a bit salutary.

First, there appears to have been some overheating of the cylinder heads. We’d kept a close eye on things during the test phase last summer, but there was no indication that anything was getting too warm; no discolouration at least. However, the exhaust valve springs are significantly weakened, and that’s a sure sign of things getting too warm.

It’s also possible there may be a problem with one or two of the valve stems, but we won’t know for sure until it’s had a full strip down.

Rotary Engine internals

Next, the whole of the inside is covered with black goo. This, they are reasonably confident, is as a result of using castor oil instead of Castrol R40. Apparently their own engine stays spotlessly clean. Also, there appears some evidence of grit in the goo, which certainly won’t help the state of the internals. The engine has no air filter, so it’s very prone to dirt ingestion.

It also seems likely that the piston rings haven’t bedded in very well. This is likely to be the primary cause of the loss of compression, and it will take more investigation to see why this has happened. It might be the gumming up caused by the castor oil. Or it could be distortion of the cylinders caused by uneven heating. Or they might not have been too well manufactured in the first place. American-made rotaries weren’t famous for the quality of their build.

So it needs a complete strip down and rebuild, and we’ll need to see what, if anything, needs replacing.

That’s going to take a month or six weeks, and it happens that Phil has a quiet spell before the winter rush, so Jean Munn was keen to get the engine out of the airframe so that the work could start immediately.

This left us with no choice but to abandon the Shuttleworth and Duxford air shows. It’s a bitter pill to swallow, but probably rather easier than the bill we can expect from Shuttleworth shortly!

That’s the bad news. Is there some good?

Well, yes.

First, of course, 1264 has kept going throughout an astonishing summer. The engine has 11 hours on it – more than most other rotaries do in a generation these days. We made it to Greece and to France, and we’ve completed the filming schedule. That’s certainly something to be very grateful for.

Second, thanks to one of Theo’s contacts, it seems we might be able to fit another (non-running) le Rhone engine for the remaining static displays until ours is sorted.

And Third? Well, thirdly, we’ve learned a huge amount about operating a rotary engine. Some of the issues – such as the overheating – we still have to find a solution for; it’s tempting to make changes to the cowling to improve throughflow, but we must never forget that first and foremost this is an exact reproduction, so whatever we do must be, as far as possible, historically accurate. But oil and air filtration are things we can probably fix. And it’s possible that once rebuilt, we’ll be able to get that extra 100rpm which will make all the difference to the performance.

In the meantime, we need to start some serious saving; 160 hours’ skilled labour doesn’t come cheap…

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From → Building, Technical

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