Technology To Make New Merlin Engines…?

Really what you need to use this tecnology for is a Napier Sabre! I think also the layout
of a Sabre lends itself to this process as basically they appear to be a series of rectangular blocks [ roughly ] in layout that are bolted together.
Imagine getting these accepted! You would have to register the aircraft in France and then fly over to Duxford only at the Air shows!!

Graham

…these are made up of layers of CNC machined material then fused together.

Can’t see why a similar arrangement couldn’t be used to form the internal waterways of an engine block.

Yes, I think that’s the only way you could CNC machine a Merlin cylinder-block from solid; make it in two (or more) parts and weld them together (somehow). I very much doubt you could make one from a single billet.

I’m not sure that there wouldn’t be problems with such a cylinder-block and it’d probably be cheaper to cast them anyway.

Well if that isn’t clever, I’d like to know what is!

The thing is though, it is all down to money, because if you had enough, you could get Rolls-Royce to restart production; in this instance CNC machines are to be used to produce a component from solid that was previously cast, and as such the water ways were easily created by that process.

Is it really that cost effective when you consider the wastage in machining from solid, and as is the way with these machines, a tool breaking right at the end of the process, rendering the almost complete part scrap, yes you will get failures in casting, but they are put back in the pot.

I think where the process has merit is producing crankshafts, con rods and reduction gears etc.

The CAA do accept different manufacturing methods, and also modern material equivilents; specifically they allow machining from solid components, that would have originally been forged, (stamped) provided that they are to the original drgs, and material spec, but as you say it would be a very clever CNC machine that was able to machine internal waterways.

Not really that clever….

We use robotic arms at work made by a company called Schilling. They are made out of Titanium and were originally intended for use in nuclear reactors. The hydraulic oil paths go through solid blocks – known as galleries. I gather these are made up of layers of CNC machined material then fused together. Expensive, but good for about 4200psi, and use up to 10,000 metres of seawater.

Can’t see why a similar arrangement couldn’t be used to form the internal waterways of an engine block.

Kind regards,
Scotty

Yes, and they are FAA certified parts as well. Not sure what RR think about it though.

Roush Merlin Parts listing here…

http://www.roushaviation.com/parts-inventory.aspx#

As I said in my post above, Rolls Royce have zero interest in this as its an STC mod raised by Roush and approved by the FAA.

Rolls Royce only have a legal responsiblity for engines assembled in line with their own build instructions and that will not include these parts.

Anyone know the status of Merlin blocks out there? Are there still plenty to meet demand?

Local engine shop has a warehouse full of them… & another warehouse next door full of Allisons..

Doesn’t Jack Roush build many improved Merlin parts now?

I wonder what RR (and the FAA/CAA) thinks of that?

omnomnomnom… 😉

Roush Merlin Parts listing here…

http://www.roushaviation.com/parts-inventory.aspx#

An impressive parts supply. Good to see they’re FAA approved. (Sorry I don’t know, haven’t had to buy spares for my Mustang lately…:) )

It says they have a selection of rebuildable cores.

Anyone know the status of Merlin blocks out there? Are there still plenty to meet demand?
They may not be a need for new-build engines if there are still plenty of blocks around (after all, they made 100,000 of them).

Anyone know if Roush sells many parts in the UK?

Doesn’t Jack Roush build many improved Merlin parts now?

Yes, and they are FAA certified parts as well. Not sure what RR think about it though.

Roush Merlin Parts listing here…

http://www.roushaviation.com/parts-inventory.aspx#

The CAA and EASA regulations (CAP,& IR 21) do not require that the OEM is involved in a Mod application and/or approval i.e. an STC mod …….. But the mod must be supported by a safety justification for approval. The latter for a major mod e.g change of a block from a casting to a machining, will be a very significant undertaking. Not only will the justification cover every design detail, its testing, its qualifications (known as cert compliance), its quality & process control (known as POA) but it will also have to demonstrate that people who wrote the justification are a competent set of individuals to under take such a task(know as DOA). In general this is only cost effect for the OEM, but if you have somebody who will keep signing cheques anything is possible. The mod itself, if classed as major and the supporting approval applications, often running to thousands of pages, will have to be independently checked at the AA charging rate (£70++/hrs).

I play these games daily.

(Would not recommend a forging is ever replaced by a machining, due to the unfavourable grain properties in the latter (-30% in strength i.e. longitudinal to short transverse), and no, believe it or not, steels/al alloys are not much stronger than they were 50 years ago, …a few % maybe)

Getting back to the basics, surely if you are recreating, or building from new, major Merlin engine componants, then you wouldn’t be entertaining the idea of putting old smaller parts in it.
Therefore we are essentially discussing here the use of new technology in building a new engine, all be it very similar to a RR Merlin (or Vulture etc), that new engine could be subject to CAA testing and acceptable use regulations as any new aero engine would be – so if successful it could in theory be certified for use.

I spoke to Euro CAA about this a few years ago. Asked what I’d have to do to get a new design 27.1 Litre V12 certified.

Simple answer was complete history of the process from design to manufacture and one destructive test (crankshaft failure to see if it stayed reasonably well contained).

Not that daunting really.

Ford did in fact question the tolerances on the merlin, and spent a huge amount of time redrawing it!

Companies usually have their own ‘style’ of drawing so I could see how Ford would want to redraw the Rolls-Royce components plus it would be very difficult for, say, a drawing of a large casting to completely describe that component (unlike today with CAD drawings) so some ‘interpretation’ probably went on in the Rolls-Royce foundry. One pattern makes identical(ish) castings; two or more patterns don’t but they can still be interchangeable (and of course will be machined within tolerance where necessary).

What Ford wouldn’t have wanted was any ‘selective fitting’ of components (although they were still doing this themselves up to the 1970s I believe); every component of every Merlin should be completely interchangeable without having to machine (or select) any part to fit its neighbour.

I think there is a common misunderstanding that ‘tighter tolerances’ will lead to an engine being ‘tight’ or seized 😀

Along the same lines, have you seen this…a 3D scanner and printer that makes parts out of plastic? You then use that plastic part as a mold for casting. It saves time from having a machinest make a prototype.

Fantastic technology; what I wouldn’t give (unfortunately I don’t have $18,000 :o) to have one of those!

One problem with using such a system to make sand-casting patterns is that again you couldn’t scan the internals of a cylinder head. Also, many complex casting patterns have to be made in several pieces so that you can remove the pattern from the moulding sand; simply scanning the desired component wouldn’t allow you to produce a pattern (although it would help) and for some many castings the pattern has to be slightly bigger than the finished casting to allow for shrinkage as the molten metal cools. I guess adding this feature to the software wouldn’t be that much of a problem.

One way to avoid complex patterns is to have the patterns made in a light foam (even polystyrene); there is no need to remove such a pattern, it simply melts away as the molten metal reaches it!

Ford did in fact question the tolerances on the merlin, and spent a huge amount of time redrawing it!

I believe it was little more than “flexing of the muscles” having been effectively forced to build another rival companies product, at any rate they produced merlins that are exactly the same as Rolls-Royce, and Packard, all are interchangeable; (I think they only built the 20 series engines)

Post war,one has to ask the question what did they learn from the experience, going back to sidevalve engines with white metal bigends, right up to the ’60’s.

Don’t the FAA and the CAA have different views on many things; an Avro Shackleton flew for many years in the US (and there is a Sea Harrier flying there now) while I understand there was never any chance of a Shackleton flying in the UK without the support of the Design Authority (BEA Systems).

I imagine that the same is true of ‘unauthorised’ Rolls-Royce (Packard?) Merlin modifications and spares.

Doesn’t Jack Roush build many improved Merlin parts now?

I wonder what RR (and the FAA/CAA) thinks of that?

Remember the story of Ford’s horror at Rolls Royce’s large tolerences when asked to produce the Merlin at their Trafford Park works (For mass production Ford required tighter tolerences than Rolls Royce did for their ‘hand built’ production methods).

I think there has been some confusion over the details of this story; and I’m not saying that there isn’t some truth in it.

If Ford produced Merlin parts to ‘tighter tolerances’ than Rolls-Royce did then there would be absolutely no problems with them; they would be completely interchangeable with any Rolls-Royce part or engine.

Yes, it seems from some of the other posts that the CAA would accept new-build parts (or complete engines) so long as they were satisfied as you say. I think the real issue here is one of cost; the cost of manufacture but also the cost of satisfying the CAA (and Rolls-Royce) that the parts (or engines) were in fact satisfactory.

It does open-up some interesting possibilities; maybe not Merlin engines but what about earlier, simpler, engines?

Only a couple of problems I can see; you can’t make a Rolls-Royce Merlin (or a Peregrine) like this, and if you could, it would not be certified to fly (in the UK anyway).

Surely if it was satisfactorily built, tested, and demonstrated within regulations, and production examples built to the same guidelines then the engines could be certifiable by the CAA as new engines?