Deltic engine origins surprised me

[JxJ Jr.]

Many thanks to you both.

[C2Red]

2xChevrons said:

alangla said:

As I understand it, there’s an oil catch drum in the exhaust system just before the roof port. When the engine runs at low load for a while (e.g. stopped in a station with the engine running & train heat on) then oil collects there. Rev the engine up and the oil ignites. IIRC, on the first preserved mainline run, something like this resulted in Berwick on Tweed’s station roof being set alight.

This is correct. Two-stroke uniflow diesels like the Deltic, by the nature of their design, pass a lot of oil into exhaust tract, so there are collector rings to gather it. Draining the collector ring(s) is part of the pre-start procedure. Once the engine is running under load and the exhaust is up to temperature, the tolerances in the engine close up (so there's less oil getting past the rings and through the exhaust ports) and the collected oil burns off near-invisibly. A Deltic that's been working properly for more than a few minutes should have a very clean exhaust - the smokescreens come when they've been idling or working light for a while.

Radial aircraft engines have the same design features, the same tendency to pass oil to the exhaust and the same tendency to cover the district with oily smoke when they're cold.

Q: is this a train peculiarity, as for the life of me, I can’t remember doing any of this on build or test. Albeit 40 years ago now..

Thanks

[Perseverant]

Lots of interesting stuff here! Napier seemed to have some considerable expertise in developing unusual engine formations, for example the "W" 12 cylinder "Lion" engine as in John Cobb's Napier- Railton and the more recent Napier-Bentley. There were various cruciform aero engines too - the "Dagger" and "Sabre" for example, with the added feature of sleeve valves for a bit of extra ingenuity. As a couple of contributors have said, they also produced the "Nomad". As something of an aside, Commer (the Rootes commercial brand) also made a most unusual 2-stroke horizontally opposed engine where the pistons drove the crank through levers. I read that this too was a German notion from the 1920s. I remember that the lorries had a very loud and distinctive engine noise!
As regards complexity, I'm amazed at the pictures of all those bits. My late father was a Navy air mechanic for nearly 20 years and had something of a soft spot for the Bristol "Centaurus" - a twin row radial sleeve valve as used latterly in the Hawker "Sea Fury". I remember him saying that inexperienced mechanics could manage quite a bit of assembly before realising that one connecting rod, for example, was out of sequence - learn the hard way!

[Wacky Racer]

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