Merlin Engine Cylinder Heads, Newly Cast at Retro Track and Air.

We already use non-original items here in Europe, such as camshafts and aftermarket modified followers…and, of course, ultimately, Retro cylinder heads

Hello Pete,
I believe only Roush Aviation in the USA manufactures the mentioned parts under PMA FAA approval. These parts are reversed engineered and are not manufactured under license/permission of Rolls Royce.
American PMA FAA parts are accepted replacement in the USA by the FAA but are only accepted without approval of EASA if they are non-critical flight items. I don’t think that Camshafts , Followers, Mayor engine castings are under this category.

If my memory serves me well, the Vickers Vimy replica original had Mercedes engines installed. When it flew to the USA, Mercedes started a lawsuit to prevent their engine being used as such over American soil. They re-engined it with American V-8’s.

Same for Boeing replicas of the Peashooter for which the Boeing Company forbid to use their name.

I can already see the Rolls Royce lawyers thinking of an accident caused by an Rolls Royce Merlin engine failure which could be traced back to an aftermarket part.

Ofcourse I am not an expert and could be wrong, so if you know such a Merlin flying around in Europe I would be more then interested, so I could see under which provisions they got their approval.

Pim

Early Birds Foundation Netherlands
Mustang P-51D, 44-74923

I know under American Experimental Category almost any modification is possible.

But here in Europe a Rolls Royce Engine needs a original Rolls Royce Cylinder head with Rolls Royce papers.

Don’t forget data plate restorations are done as a repair, not a rebuild……..

Not so Pim. We already use non-original items here in Europe, such as camshafts and aftermarket modified followers…and, of course, ultimately, Retro cylinder heads.
Also, a Merlin doesn`t require paperwork prior to rebuild, only after.

Pete

I know under American Experimental Category almost any modification is possible.

But here in Europe a Rolls Royce Engine needs a original Rolls Royce Cylinder head with Rolls Royce papers.

Don’t forget data plate restorations are done as a repair, not a rebuild……..

Richw
I wasn’t aware of C & G making castings.

They offer all sorts of new castings such as Coventry-Climax race engine block castings and head castings etc., so if they aren’t cast in-house, they certainly get them done somewhere……

And yes, I don’t think they are CAA certified.

“New build Merlins are not a pipe dream.”

This is something I’ve wanted to see for ages, so I’m all for it. Truthfully though, I can’t see it happening very soon, or even at all. And this is after seeing lots of new parts, including Retro’s new cylinder heads. This sounds counter-intuitive, but there are thousands of parts in a Merlin (I’ve heard 11,000 parts, but can’t verify).

Also, despite appearances, I think there is still a ton of inventory, if it could only be accessed a little more easily. Take 51 Factory in California for example. Their Merlin inventory is staggering. Here’s a glimpse of some of their spare parts. http://51-factory.com/inventory.htm If you look at just one of the pictures, you’ll see dozens of cylinder heads on a single shelf. All of this came from Paul Szendroi, former operator of Universal Airmotive in Chicago. Looking at 51 Factory’s inventory pictures kinda reminds me of the last scene in the Indiana Jones movie, where the Ark of the Covenant is stored in some endless warehouse, with row-on-row of shelves.

This doesn’t even include what Dwight Thorne claimed was enough parts to build 200 complete Merlins, and another collection of major parts to make 200 more without all the tiny seals and small parts. Mike Barrow, who used to work with Dwight Thorne (of Mystery Aire) mentioned that Dwight’s widow is just sitting on this inventory, and won’t sell it. I have no idea what her current status is, but that’s the last info I have on the late Dwight’s Merlin stock. This was 10+ years ago.

I have no idea what Mike Nixon’s inventory is either, but they are still very active in Merlin restoration.

Despite buying a crankcase from Mike Barrow last year, I really don’t know how much usable stock he owns. Or Jack Roush.

As I see it, it’s a pretty tough sell to go into limited production to make all new Merlin engines. I’d heard the crankshaft dies exist, but I suspect that a machined billet crank would be much easier for low production numbers.

I would love to see new production happen. I just have my ongoing doubts, based on cost, demand, and existing inventory. Of course, it would be foolish to assume that we have seen our last new Merlin part, minor or major, as this is happening all around us.

Cheers, Tom.

New build Merlins are not a pipe dream, the number of available usable original parts is dwindling rapidly, and more newly manufactured items are made for them every year, at some point, nearly every part will be being produced for the more common marks as well as quite a few for the rarer ones. It won’t all happen at once, but bit by bit as each new type of part is reproduced, the funds raised from the sale of these will probably be plowed back into making other parts. Cylinder heads now, cranks and crankcases next year, complete engines some time after that.

By the way if I recall correctly, aren’t there some original crankshaft etc dies still around, I’m sure there is one in the Industrial museum in Sheffield ?.

Bob T.

Its retro track and air making the new cylinder heads for merlin engines.

I can imagine all sorts of problems cropping up with any complex engine rebuild. Tight tolerances would be one of a whole shopping list…

That depends what we mean by ‘tight tolerances’; strictly speaking a ‘tolerance’ is a measure of the acceptable variance of a measurable dimension of a single engine component.

No matter how ‘tight’ the tolerance of any newly manufactured part, even down to (impossible) zero tolerance, that new part will fit any existing engine, and (all other things being equal) will run without any problem whatsoever.

Thank you Tom.

J Boyle, Roush makes a fair number of Merlin parts, but not any of the larger castings. Here’s a list of what they do; https://www.roushaviation.com/parts-inventory just click on the individual parts in the list that appears.

SeaFuryFan, I can imagine all sorts of problems cropping up with any complex engine rebuild. Tight tolerances would be one of a whole shopping list. I seem to recall Rolls Royce using an alloy called hydaminium (plus a number) but Pete would know more about this than I do. I wonder if the Merlin would be better with some modern alloy of aluminum.

Sopwith, I’m pretty sure it’s Retro Track and Air that is making the new Merlin heads, not Maurice Hammond. Having not been within 3000 miles of either, I got it wrong.

Oxcart, I may have wrongly written to Retro and started with “Dear Maurice Hammond” which would have warranted a speedy deposit into the email junk basket. I suspect now that I never actually did write to Mr. Hammond, just to Retro.

So, nobody has the elusive additional pics of Retro’s new cylinder heads? Cheers, Tom.

I rang Maurice Hammond up a few weeks ago (it was to do with the Mustang fin) and he was very helpful.

To be honest, I can’t understand why the bore wouldn’t have been honed to finish it anyway; why wouldn’t that have produced a surface that retained the oil?

I think the original quote is somewhat misleading. CAD / CAM production of cylinders with ‘tighter tolerances’ will not produce less clearance between the piston and cylinder; if fact ‘slacker tolerances’ produced by ‘manual’ methods is far more likely to produce less clearance between piston and cylinder.

It is an interesting example, but it isn’t strictly a case of ‘tolerance’…..more one of surface finish.

I can understand exactly how such a ‘failure’ in an air-cooled cylinder could occur if the surface finish is ‘too good’ and has no imperfections to retain lubricating oil and that leads to increased wear, overheating and, ultimately, to a piston seizure.

At one time ‘cylinder honing’ was done to remove imperfections; now honing is mainly used to introduce them!

I take your point Creaking Door, but if the bore was that perfect, you would glaze bust it before service, for the rings to bed in?.

That was interesting…..but at the same time the tolerances should be there to account for heat expansion.

It is an interesting example, but it isn’t strictly a case of ‘tolerance’…..more one of surface finish.

I can understand exactly how such a ‘failure’ in an air-cooled cylinder could occur if the surface finish is ‘too good’ and has no imperfections to retain lubricating oil and that leads to increased wear, overheating and, ultimately, to a piston seizure.

At one time ‘cylinder honing’ was done to remove imperfections; now honing is mainly used to introduce them!

That was interesting Seafuryfan, that would make sense with air cooled engine but at the same time the tolerances should be there to account for heat expansion.
Tom still unclear whether you mean Retro Track and Air or Maurice Hammond who is casting new heads.

Richw
I wasn’t aware of C & G making castings. I would have thought they would use Grainger & Worrall of Wolverhampton .. But not sure if they are CAA approved.

Thanks for your reply Tom. Here’s an account of manual vs CAD tolerances that affected 60 Sqn Pembroke Leonides engines in the early 1980s:

“Engine problems increased during the year, and in Sep 81, a director of Alvis visited, and Squadron engineers spent a week at the factory, but without finding a solution to the failures. Lengthy inspections of components meant loss of aircraft for flying. After more failures in 1982, it eventually transpired that local overheating of one cylinder was leading to piston seizure. Alvis concluded the cause was computer-controlled clearances being much finer than the former manual method, and oil retention properties of the cylinder walls were being degraded. By Jan 83, six modified engines had been received, but it was not until April 83 that all engine modifications had been completed.”

An interesting example of modern technology causing unforseen problems.

Those cylinder heads look gorgeous. Do Retro manufacture them in house, or farm them out to another company? I know in the historic racing car world people like Crosthwaite and Gardiner have been casting new engine blocks, cylinder heads and all sorts for all manner of exotic machinery, so its surprising that its taken as long to filter into the historic aircraft world.

Hmmm, I had it in my mind that Maurice Hammond was with Retro, or even the owner. I see that I’m wrong. He appears to be with a company called Eye Tech.

Tom, Maurice IS Eye Tech.

Merlin experts…what parts does Roush make?