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287. Engine Innards

03/04/2017

I managed to get to the Shuttleworth Collection today, and found substantial progress on the engine. The cylinders are back from relining, and Phil is delighted with the standard of work. the cylinders and liners are so thin that you can squeeze the sides together with your hands by 0.004in (4 thou, in engineer’s speak). This might not sound masses, but the bottoms need to be larger than the tops by exactly that amount.

That’s the reason the cylinder have to be fixed in a special jig to hold them rigid, otherwise the pressure of the honing tool would distort the cylinder wall and wreck the whole operation.

Because of that taper (or choke), the bores have to be honed by hand, and apparently they are accurate to two tenths of a thou. All nine cylinders, all round, and all the way up the bore – an even taper. It’s an astonishing achievement. we await the bill…

The holes in the pistons for the gudgeon pins (wrist pins, if you’re American) are slightly undersize and have gone away to be honed, but should be back in a day or so.

So here are some pictures of those gorgeous cylinders, and the state of reassembly of the rest of the engine.

The crankcase assembled, waiting for the pistons, rings and cylinders.

This is how the conrods connect to the crankshaft – curved pads on the big ends fit into concentric grooves in two discs on the crank.

The clean, clean cylinder on the outside…

… and the beautiful bore on the inside. You can see the exhaust valve on the right of the picture which opens into fresh air.

And finally, a close-up of the finish on the cylinder bores. the cylinder wall is 1.5mm (1/16in) thick, with a cast iron liner about the same thickness. No wonder it’s a bit flexible!

 

 

 

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3 Comments
  1. Ted Timberlake permalink

    What a wonderful piece of engineering. Makes one aware of the standards achieved all those years ago. Really great to see the parts and the assembling on going. Look forward to seeing , and hearing, the day that it fires up, as no doubt you do too. Good luck.

  2. Ted Timberlake permalink

    Take two… I had meant to request a photo(s) of a piston with and without rings. What material were the original pistons made of and what will you use now?

  3. The originals were steel, and probably came with the original (American made). Apparently all the licence-builders designed their own pistons. The American ones are flat topped. Our new ones look like copies of the Swedish examples which are aluminium and have a domed top. the British-built ones had a concave top!

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