Read the forum code of contact
By: - 12th November 2015 at 18:28 Permalink - Edited 1st January 1970 at 01:00
This is fascinating news, Tom. Question: can Merlins now be manufactured from scratch? If not, what is preventing this?
By: - 12th November 2015 at 18:57 Permalink - Edited 1st January 1970 at 01:00
Apparently, in the 1940s, the moulds for Merlin cylinder heads had to be assembled by women because the work was too delicate for the men in the foundries. Is this still the case one wonders?
By: - 12th November 2015 at 20:15 Permalink - Edited 1st January 1970 at 01:00
Hi SeaFuryFan;
No doubt, with the right will power and budget, Merlins could be produced today, but being practical, there would be a lot of components that are horribly costly. Crankshafts, gears, etc. I have no idea how Maurice Hammond is making these heads. Old fashioned methods or maybe some modern techniques, such as 3D printing the sand molds for casting?? I've written to him twice, indicating my interest in Merlins and his work, but no replies.
Using modern techniques would help. Once you have a CAD model of a cylinder skirt or head, you have lots of choices. Coming up with the model is the hard part. I've done a skirt, and am currently reverse engineering a port side head with the right software, but very fledgling software skills. Here's a pic of the skirt I modeled, and even that took a while. The head is much harder.
HP1111, I hadn't heard of this gender issue, but you might be right. I have seen pictures of men setting up the cores for casting the cylinder skirts, and that may have been in the Packard plant, Detroit. I can't seem to locate the pictures of that at the moment.
Cheers, Tom.
By: - 12th November 2015 at 21:38 Permalink - Edited 1st January 1970 at 01:00
Modern short run manufacturing is now eminently viable for almost any component, including cranks and cams heads and blocks. Its just a matter for the manufacturer to be certified by the CAA for airworthy purposes. I'm not sure how RR cast all the Merlin cylinder heads, but with an original and todays materials and methods any replacement would no doubt be better than the original war-time product. I'm picking that any "new heads" would be of the same material as the original and cast in a way to give the new head the same properties as the original so as not to introduce any unintended changes to the engines that could result in an inflight failure.
By: - 12th November 2015 at 22:06 Permalink - Edited 1st January 1970 at 01:00
Hi Tom
It is Retro Track & Air, not Maurice Hammond who is casting these heads.
Pete
By: - 13th November 2015 at 02:17 Permalink - Edited 1st January 1970 at 01:00
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.
I'd like to see more parts of the Merlin made with whatever modern method is advantageous. When you consider the total number of parts in these engines, it would still be a horrendous cost to build a full engine. But, I'd buy a front seat ticket to watch the action.
Any more pics of Retro's new heads?
Tom.
By: - 13th November 2015 at 02:22 Permalink - Edited 1st January 1970 at 01:00
Merlin experts...what parts does Roush make?
By: - 13th November 2015 at 04:47 Permalink - Edited 1st January 1970 at 01:00
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.
By: - 13th November 2015 at 09:05 Permalink - Edited 1st January 1970 at 01:00
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.
By: - 13th November 2015 at 10:21 Permalink - Edited 1st January 1970 at 01:00
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.
By: - 13th November 2015 at 10:47 Permalink - Edited 1st January 1970 at 01:00
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.
By: - 13th November 2015 at 12:32 Permalink - Edited 1st January 1970 at 01:00
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.
By: - 13th November 2015 at 16:52 Permalink - Edited 1st January 1970 at 01:00
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!
By: - 13th November 2015 at 18:01 Permalink - Edited 1st January 1970 at 01:00
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?.
By: - 13th November 2015 at 19:10 Permalink - Edited 1st January 1970 at 01:00
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.
By: - 13th November 2015 at 20:32 Permalink - Edited 1st January 1970 at 01:00
I rang Maurice Hammond up a few weeks ago (it was to do with the Mustang fin) and he was very helpful.
By: - 13th November 2015 at 20:52 Permalink - Edited 1st January 1970 at 01:00
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.
By: - 13th November 2015 at 20:55 Permalink - Edited 1st January 1970 at 01:00
Thank you Tom.
By: - 13th November 2015 at 23:09 Permalink - Edited 1st January 1970 at 01:00
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.
By: - 15th November 2015 at 10:13 Permalink - Edited 1st January 1970 at 01:00
Its retro track and air making the new cylinder heads for merlin engines.
Posts: 146
By: Tom Kay - 12th November 2015 at 17:29 - Edited 2nd October 2019 at 11:40
Hello;
I've seen a couple pictures of the newly cast Merlin Engine cylinder heads at Retro Track and Air, and attached them to this thread. (I hope they show up, not sure if I did it right).
Does anyone have any more pics of these heads, or any other large castings made by Retro? I am quite fascinated by these new large Merlin castings.
Thanks, Tom Kay.