Deltic

[sideshowbob9]

Hi all! I've been playing with the idea of a Napier Deltic diesel engined aircraft for some time now but wasn't sure how to go about it. Today it hit me. 00 Gauge is roughly 1/72 scale, so why not use one of Dapol's Class 55 Deltic models to act as a fuselage? Not the whole thing mind, just a section.

I envisage an A-1E to make up the rest of the aircraft (wings, tail etc.). Obviously the engine would be mid-mounted and connected to a shaft-driven prop.

Have I lost my marbles or does this sound like a vaguely credible idea?

An alternate idea involves some A-31 Vengeance wings I have spare, which would be somewhat appropriate, given Convair's association with Napier with the Convairliners.

[PR19_Kit]

A DELTIC engine?

Ye gods, you better look for a 1/48 scale A-1E for the wings then. While the Deltic engine was termed a 'lightweight engine' that was in railway terms and they call anything less than 5 tons 'light'!

It sounds a great idea visually though, the mind BOGGLES at the final look. Don't forget that Deltic locos had TWO engines though, even more weight......

[Hobbes]

PR19 is right. A Deltic engine weighs about 4000 kg and produces 1650 bhp. A Merlin weighs 750 kg for about the same power.

[Jeffry Fontaine]

The Napier Deltic is one the few engines that I find interesting.  Though, not as an aircraft engine but for what it evolved into for marine and rail use, more specificially, as the propulsion engines for the Tjeld, Nasty, and Osprey class patrol boats among others.  

I have been trying to come up with a 3D model of the Deltic for my boat model project in SketchUp which has managed to elude me so far.

Napier Deltic Engines (ptfnasty.com)

[Caveman]

PR19 is right. A Deltic engine weighs about 4000 kg and produces 1650 bhp. A Merlin weighs 750 kg for about the same power.

A Deltic is a 2 stroke diesel though...

[Jeffry Fontaine]

1/4th scale model Deltic Diesel built by Quarter scale model Deltic engine built by Clennell Tomlinson


1/4th Napier Deltic and 1/8th scale Napier Sabre models

[sideshowbob9]

Good point about the weight but who said this had to be a successful experiment?!!  

The 18-cylinder railway variant indeed produced 1650-odd hp but that doesn't mean that an "aero-ised" variant wouldn't be lighter, have more cylinders, take advantage of super/turbochargers or even be a turbo-compound (it isn't much heavier than the Napier Nomad and a trialled turbo-compound Deltic was apparently good for 5000+hp!!!).

In this WHIF, I see the Deltic as more of an economic engine for larger aircraft (much like the Nomad was meant to be) but being put through its paces on a Skyraider-like testbed. At least the engine is mid-mounted, so aerodynamic and CofG issues should be minimised and the engine could probably be mounted directly to the main wing spar! If any aircraft can take that kind of abuse, its the Skyraider!  

Thanks for the input so far guys. My next question is: what, if anything, would you do to lighten the engine?

As for those models...   yikes!!!

[Hobbes]

Having read some more, I suspect the 1650 bhp is with minimal supercharger pressure. this page states that the same engine could develop 3000 bhp, and that the loco engines were derated to 1650 bhp to increase service life.

The engine was built from light alloys, so I doubt you could decrease its weight very much. With 88 litres of displacement, it's 3.2 times larger than the Merlin and 5.3 times heavier, which sounds about right for the weight penalty a diesel inevitably incurs (due to higher compression ratio, the engine has to be built stronger than a petrol engine).

For an aero variant, I'd go with 18 cylinders and half the displacement, crank up the supercharger pressure and add turbocompounding. You could end up with 3000 bhp from 40-odd litres, which isn't too bad.

[PR19_Kit]

There was a half-size version of the Deltic engine too, a 9 cylinder which developed 1100 bhp in its railway application and was designated a T9-29.

They were fitted to the 10 EE Class 23 'Baby Deltics' but always suffered cooling system problems, which wasn't part of Napier's remit. The last Class 23, D5901, was at the Railway Technical Centre at the same time as me in the mid-70s, and was used for the Tribometer Train duties.

When D5901 was scrapped in 1977 the engine was saved and still survives. Not only that, it's been re-built and installed in a Class 37, but that hasn't been seen in public yet.

[sideshowbob9]

When D5901 was scrapped in 1977 the engine was saved and still survives. Not only that, it's been re-built and installed in a Class 37, but that hasn't been seen in public yet.

Ironic, considering that one of the proposals, to "save" the Class 23 was to fit D5901 with a single D18-25 Deltic of 1650hp, putting it right into the Class 37's ballywick. The other proposal was EE's 12 CSUT engine, which showed great promise and would have made the Class 23 quite competitive against the Class 31. Had the Class 23s been more numerically significant (or the backbone of the ECML like the Class 55s) I feel much greater effort would have been made in fixing them but BR's bias against non-standard locomotives (the diesel-hydraulics also come to mind) worked against them.

For an aero variant, I'd go with 18 cylinders and half the displacement, crank up the supercharger pressure and add turbocompounding. You could end up with 3000 bhp from 40-odd litres, which isn't too bad.

I've been wondering if the aero variant wouldn't use Sabre proportioned cylinders (same bore but effectively twice the stroke, as the Deltic cylinders are double-ended). This may be over-simplistic but that way, you would get the equivalent of 36 "Sabre cylinders" into the same six rows as the Sabre's 24 cylinders. As you say, a diesel will be heavier but after adding supercharger and turbo-coumpounding, I can't believe it will be THAT far behind the Napier Nomad or a turbo-compounded R-3350! At least not to be worthy of a single testbed!