Talk:Napier Nomad

This a "compound cycle diesel engine" I believe.

Is there a museum in the US or UK where I can see this engine on display?

homebuilding207.178.98.48 01:00, 21 May 2007 (UTC)

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A small mistake in the specification I think: the engine is described as "Horizontally Opposed" but the original Culverin was based on the very different Junkers "Opposed Piston" engine.

I am sure that this is just a simple mistake.

http://en.wikipedia.org/wiki/Junkers_Jumo_205

DesmondW (talk) —Preceding comment was added at 15:31, 5 December 2007 (UTC)

My correction withdrawn - the Nomad was indeed 12 cyliner horizontally opposed

DesmondW (talk) —Preceding comment was added at 16:46, 27 December 2007 (UTC)

A tricky one!

I've tried to clarify this article as it is a very complex engine, what has just occured to me is that the Naiad engine appears to have no combustion chambers, so it is no more than a giant supercharger. Need to come back and fix the text to confirm/clarify this as it is slightly wrong if this is the case. Nimbus (Cumulus nimbus floats by) 23:27, 22 August 2009 (UTC)

Nomad 1

As the article is now: < the axial compressor also drove the supercharger impeller >

but page 544 of reference 8 states, and the diagram clearly shows, that the impeller was driven by the crankshaft.

86.152.190.173 (talk) 00:36, 27 September 2011 (UTC)

Yes, this is one of several problems with this article. I've re-worded it a bit. The illustrations here aren't great either. The Flight article is very good, but remember that there were many variants of the Nomade during its development and even Flight were only allowed to see a couple of them, at the time. It's risky to make definitive statements about details of how the Nomad worked, because the chance is that there was always another version that had done it the other way. Andy Dingley (talk) 14:38, 27 September 2011 (UTC)

Nomad II hydraulic clutch

This was much more than a mere clutch. It was a variable-ratio transmission, namely, a Beier variable-ratio gear. 86.3.108.41 (talk) 13:41, 30 September 2011 (UTC)

180° Vee

User Aaa3-other wanted to classify this engine as a 180° Vee. Even if I appreciate the seems like reserve, I have some difficulty in imagining a 180 degrees V - and reverted immediately. Or what have I missed? Is it one more USA <==> Europe semantic issue? Jan olieslagers (talk) 20:59, 24 February 2012 (UTC)

There is no agreement on wiki as to what a "flat" engine is. However there is a general acceptance of 180 V and that "boxer" is only appropriate for those with the right crankshaft layout, which I don't believe includes the Nomad. Andy Dingley (talk) 21:02, 24 February 2012 (UTC)

Thanks for prompt and positive reply. I am however afraid it doesn't even begin to make sense with me... Flat was never in the discussion, I can see no use in entering this term. And what do you mean by the right crankshaft layout? I still fail to imagine a layout termed "180 degrees Vee", a letter V never having a 180 degrees angle in my (probably over-simple) view. ((after consulting the V engine article I can see that SOME people make a distinction, based on the sharing of crank pins by several pistons, but I have difficulty in accepting an edit war over a semantic issue)) Jan olieslagers (talk) 21:13, 24 February 2012 (UTC)

After more consultation, couldn't we agree to classify it as "horizontally opposed", avoiding any idle semantic argument? Jan olieslagers (talk) 21:30, 24 February 2012 (UTC)

hi, sry for being late, didnt expect so prompt activity. i can make all this clear: flat is every one in 180 degree bank layout where all two banks are in one plane, including vee, boxer and opposed. the broadest category. a vee is, any one where the conrods share a crankpin (angle diff=zero), regardless of bank degree, usually 60 90 180, less common 45 135 etc. a boxer is special, such a flat (180deg banks) with separate pins for every conrod AND they (pins) must be exactly 180deg apart! this makes every opposed piston move symmetrically in and out. and finally, a horizontally opposed is like this Opposed-piston engine, 2 pistons sharing a cylinder. disregarding crankshaft arrangement this is like the inside-out mirror of a boxer, both same for the purpose of balance. (rare, a VR engine is where the bank angle is usually very small (so width is much the same as an inline), and the separate crankpins' angle is the same as it would be on an inline one. made by lancia and volkswagen. comes from german V and R(eihe), for it is actually a deformed (take every second cylinder into a new, second, cylinder bank, like a V) inline made shorter, very superficially resembling a vee. but theoretically of course this can be any bank angle, and then a boxer is just a case when the bank angle is 180, that is, a flat variant of this.)

so seeing the above, the diff between a 180deg V and a boxer is, that on a vee, the cyl pairs are moving in unison first both left then both right, while in a boxer they cancel out each other's inertia. this intra-opposed-pair balancing is not realizable on a vee, but it can, with adequate number of pistons, can be balanced intra-bank and-or intra-block just like any inline engine. the napier nomad is an example of this. just check the image i linked File:NapierNomadCross-Section,Flight1954p1217or545.png in the article history, uploaded just this night - 2 conrods on common crankpin, 0 deg difference, ergo vee type engine. on the nomad picture, one can imagine if you rotate the shaft in your fantasy to a direction; both the pistons will move that direction as well. characteristic of the v layout. the boxer, on the other hand: File:Boxerengineanimation.gif--Aaa3-other | Talk | Contribs 23:01, 24 February 2012 (UTC)

re: well im not into edit war over this, but this is clearly a mechanical (balancing) (engineering coice) (etc) issue, not alinguistical/categorical... of course im avare that regardless of language or continent most people are blurring all these always, but...--Aaa3-other | Talk | Contribs 23:05, 24 February 2012 (UTC)

oh and dont wast too much time, imo, on reading over here on wiki, iirc last time i saw there was much chaos and incosistency over this and cant know which articles are getting it right and which arent :( on diesels for example i read orbital stupidities i planned to correct since a few weeks. the stuff is simple, only it is not cleaned up here on wiki across the whole topic. someone somewhen will do this, i hope, preferable after writing up his plan to some project page notifying others to get a consensus or whatever--Aaa3-other | Talk | Contribs 23:12, 24 February 2012 (UTC)

Sorry, but I'd disagree with many of your points here:

• There is no requirement for V engines to share a crankpin. Some do, but this isn't required or implicit in the V layout itself. It's done with twins for simplicity (allowing a much simpler crankshaft), it's done with high cylinder counts to make a shorter engine with a stiffer crankcase. It's the usual choice for eight and above, it's unusual for four, and six can go either way.
• "Opposed engines" have one cylinder per piston, with these cylinders opposite each other. These are common, especially for twins. If two pistons share a cylinder, then that's specifically termed an "opposed piston engine".

There are four terms for "180° V" engines: "180° V", "opposed", "flat" and "boxer". As "V engine" implies no more about an engine layout than having two cylinder banks, and "180° V" is accepted for a V at that angle, it's an acceptable term for the whole lot, including those covered by the other three terms.

There is much less agreement about the meaning of the other terms, whether they apply to any 180° V, or only to layouts with specific crankshaft layouts or firing orders. There is no agreement on WP about this, and not even much competent discussion of the issue by those who know any more than reading a few copies of Hot Car. They're also terms that are surprisingly hard to find good sources that explain them in a canonical form. I did the obvious thing and opened my drynamics textbooks on engine balancing, but even in these (although authoritative) there's no need felt to define their terms clearly before use - they're assumed to be clear already.

"Flat" sometimes (which I don't support) has implicit connotations added about the crankshaft layout being flat, not cross plane. That would then include four cylinders, but would imply that there are no flat sixes!

"Boxer" has a generally accepted meaning (amongst those who think it means anything more) related to piston balance by pistons moving as opposed pairs. There is argument though beyond this: do the pairs have to be in opposing cylinders? (this rules out shared crankpins). Is an engine where their pairs of balanced pistons are not in the cylinders directly opposite still boxers? I've also seen it claimed for four strokes that the pistons must not only be opposite, but must fire simultaneously - tending to a rather lumpy firing order.

"Opposed" is generally seen as the same as "180° V", whatever the piston and crankshaft layout, but on this page we see it being conflated with the quite distinct "opposed piston".

Andy Dingley (talk) 10:33, 25 February 2012 (UTC)

Certainly the air-cooled piston engines of Continental, Lycoming etc are usually decribed as horizontally opposed, including by sources such as Jane's All The World's Aircraft. What do the sources say about the format of the Nomad?Nigel Ish (talk) 11:44, 25 February 2012 (UTC)

The Nomad is described as "horizontally-opposed" in Lumsden, Caxton's "Modern High-Speed Oil Engines" and Gunston's 1954 Flight article, although in Gunston's later World Encyclopedia he terms it a flat-12. I think there's a big piece in one of Ricardo's books too, but I can't find that just at the moment. Andy Dingley (talk) 12:37, 25 February 2012 (UTC)

well, ok i concede to the aboves (at least as far as wiki goes) but i must then argue that the term opposed engine is at least unfortunate as it (at least in me) invariably raises the opposed piston stuff. wow ricardo wrote books? i must get them!

anyway, i propose the two following alts. 1)simple and safe, lets remove the cat 'boxer' and every other specials, and create 'flat', - which is then absolutely equivalent to 'opposed' (no mutter how i dont like the latter, seems really prevalent) - , which would include all 180° layouts regardless of absolutely everything else. or 2)this seems the 'right thing' but can lead to tug wars and trouble with 'hot car types' (maybe including me?, tho i wish better ;), is to create flat, and within that, create boxer and 180vee[ok no, as you say it is also 100%eq] for spec, and leave others which are either disputed or the catter just cant decide, in the root. perhaps o-pistons could get in there too as a third 2nd subcat. and for a case like this, we probably should dualput 'em in both v-12 engines and flat engines, and avoid creating numberred subcats for flats, boxers and o-pistons. or for all cases.

in both cases we should put the text to the flat catpage that it is also known as horizontally opposed. maybe, though i wouldnt like, the names could be switched and it (the main cat) could be called h.o. and text would mention f.--Aaa3-other | Talk | Contribs 00:18, 26 February 2012 (UTC)

(cat creations & edits) done. (decided to) avoided creation of numbered subcats for all cases. probably this is conclusion. --Aaa3-other | Talk | Contribs 10:35, 9 March 2012 (UTC)

Why have you now categorized Category:Opposed piston engines as Category:Flat engines? This is quite wrong. Andy Dingley (talk) 11:27, 9 March 2012 (UTC)

err... because it seemed to me flat... i mean, its 180 degree, and sor-of two banks of erm... pistons. if i cut a "real" flat in the centreline and turn the two halves inside out, it will become an o-p. but, im not at all sure or insistent on keeping it this way, just seemed a neat categorisation to me. first step. if you and/or others disagree and its wrong then of course correct it. well.... i hope some others too react; if no one then just do it in a few days, fine with me.--Aaa3-other | Talk | Contribs 12:30, 9 March 2012 (UTC)

p.s., only now i noticed that as the flat is - imo correctly - within the V now, the inclusion of opposed pistons is truly unfortunate.--Aaa3-other | Talk | Contribs 13:17, 9 March 2012 (UTC)

"Flat engine" doesn't just mean, "an engine that is flat". It carries more implicit meaning than this. Regarding opposed-piston engines as such is just plain wrong (and if you want that in wiki-bollocks-speak, then it's "uncited"). Andy Dingley (talk) 01:03, 10 March 2012 (UTC)

ok something else. i noticed you are creating very detailed subcats (inv v12 aero), including numbered subs for cyl layouts. i earlier came to the result that itd be better to avoid this as if the no-subcat way somebody navigates to the category page, he will see (thanks to the alphabethical order, and naming consistency of article titles) many relevant engines together, which would be more and more impossible, the more we do specialise the categories... the more interesting links he can found there, the better. for example, i dont want to find the royce car v12-s in a different subcat than the aero ones, and perhaps not their v8s either. also not nice if the whole german inv-v12 lineup gets unnoticed hiding away from the upright ones, on the other hand its nice to see them together. though this is obviously a question of where do we draw the line, as if the cat would grow too big... --Aaa3-other | Talk | Contribs 13:01, 9 March 2012 (UTC)

Then categorize them into both (or more) categories where there is some value to having them in that category. This is yet another situation where WikiMedia's slavish and simplistic assumption "Never simultaneously categorize into an ancestor category!!!" is just wrong. Andy Dingley (talk) 01:03, 10 March 2012 (UTC)

"ok", for both sub-thread -- Aaa3-other | Talk | Contribs 18:25, 10 March 2012 (UTC)

Efficiency

The article states, in a paragraph devoid of citations, that:

Thermal efficiency is given by 1-(Tx/Tp), where Tx is the exhaust temperature (any absolute scale) and Tp is the peak combustion temperature

Indeed it is, but what about Tx, and, in particular, the fraction Tx/Tp? The ratio of Tx to Tp is driven by the pressure ratio available for expansion, and this in turn is dependent on the pressure ratio on the compressor side of the engine. The Nomad was intended for economical long-range cruising (hence its name, we dare say) and had the form it did in order to achieve a high value of pressure ratio at cruise at altitude. Here the ambient pressure is low, so that high pressure ratios can be used without attaining high pressures. It was entirely beyond the state of the gas turbine art at the time to use similarly high pressure ratios. 195.194.10.62 (talk) 18:57, 4 April 2013 (UTC)

Original motivation

Thanks to 220.244.88.237 for adding this. It would be nice to improve the sourcing of this (the fuel numbers are in Ricardo, AFAIR). Any ideas on sources? There's not many for the Nomad. If only RRHT had one of their little monographs on Napier engines too!

Also the Nomad can be considered as either of two engines: as described here, a gas turbine prefixed with a high pressure ratio piston engine, or else a highly supercharged piston engine suffixed by a turbine as a turbo-compound engine. Both are contemporary themes of development around this period. There's also the 1930s work on free piston diesel engines with power output turbines.

I think we also need to expand this section to explain why the Nomad was eventually never used. The comparison with "gas turbines" is actually a comparison across a couple of generations of gas turbine, and also turboprops or turbofans. Although the low turbine inlet temperature of thee early jets was indeed a limit (and it's the effect of creep at high temperature on the turbine blades that was the early limit, not the combustor temperature), this improved a lot during the Nomad's development lifetime, such that their efficiency improved and removed the Nomad's advantage. Also the turboprop (or in practice, the Conway's turbofan) improved efficiency of gas turbine aircraft loitering at lower speeds. The Nomad's advantages over the jets just didn't last into the next generation of jets. Andy Dingley (talk) 13:45, 21 May 2013 (UTC)

< Why was the Nomad eventually never used? > What is the evidence that it came anywhere near certification, without which it wasn't going anywhere? (What (do we suppose) was the airframers' view of the engine's prospects?) 86.184.154.118 (talk) 00:25, 9 October 2013 (UTC)

The original motivation was very long range economical flight such as for maritime reconnaissance - the name 'Nomad' says it all. The engine was designed for aircraft such as the Avro Shackleton and what later became the Canadair Argus - at the time referred-to as the 'Britannia Maritime Reconnaissance'. The engine was also thought to be desirable for civilian usage where extremely long range and fuel economy was required. The Nomad could run on the cheapest fuels such as diesel - which was then, unlike today, a very cheap fuel, and so operating costs would have been - all other things being equal - much lower than for comparable engines running on 100 octane petrol - the only engines then available with the fuel economy required for transatlantic flight.

At the time, c1950 the then-new turboprop and turbojet had miserable fuel economy compared to piston engines, and the Nomad was developed to fill in the gap between the conventional piston engine and these types.

The reason for its lack of use and cancellation is simply that the airframe application's designers either chose alternative engines - such as for the Argus - or the aircraft applications themselves were cancelled - the Shackleton IV. In addition, Napier's became more interested in gas turbines such as the Nymph, Naiad, and Eland. The Nomad's chief designer BTW, was Ernest Chatterton. The E.145 Nomad gave 4,095 ehp with water injection.

The Nomad's problem was that it was five years too late. If it had been developed earlier it might have filled in a gap until the more economical turbojets such as the Rolls-Royce Avon came into airline service in the Comet 4. The Shackleton would also probably have been designed around it from the start, rather than the Griffon.

... an article by Chatterton in a 1954 issue of Flight; [1] quotes some 1954 UK aviation fuel prices which are; Avtur at 1 shilling & 10 pence per-gallon (pre decimalisation), 100/130 grade avgas at 2 shillings, 7 & 1/4 pence per-gal, and 115/145 grade avgas at 2 shillings and 9 pence per-gal. In contrast, diesel was 1 shilling and 8 pence per-gal.

A Napier Nomad 2 mounted in the outboard nacelle of a Shackleton in a 1961 issue of Flight