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Thread: Rolls Royce Merlin Engine-Rebuild by Roush

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    Registered User pepsi71ocean's Avatar
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    Rolls Royce Merlin Engine-Rebuild by Roush

    Does anyone know if that can be confirmed that Roush does indeed build Merlin engines. I heard about it but there isn't much on the web that i can find that details what Roush did to the engines.

    I know he owns a P-51D though.

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    Registered User Mac790's Avatar
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    Re: Rolls Royce Merlin Engine-Rebuild by Roush

    I don't have any info about it, but you might want to ask those guys.
    Historic Aviation - Key Publishing Ltd Aviation Forums

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    Re: Rolls Royce Merlin Engine-Rebuild by Roush

    Take a look at this place and/or post a question. There are guys who post there who would have the answer to your question for sure. Some really great Reno racing pics and warbird chat there too!
    Wally

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    Registered User pepsi71ocean's Avatar
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    Re: Rolls Royce Merlin Engine-Rebuild by Roush

    I took a look around and the second website looks promising, thanks for the info guys.

    It looks like a 1,000 HP V-12 is quite dooable now,

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    Re: Rolls Royce Merlin Engine-Rebuild by Roush

    Hi Pepsi;

    Yes, Jack Roush is into rebuilding Merlins. There was an article in a mag a few years ago about this. I went as far as calling their "Merlin guy" to talk to him about what they do. They make new pistons with a modified skirt, and I think they wanted to get into fabbing some of the oil plumbing parts that are hard to find. They do a fairly complete strip-down and rebuild, as far as I'm aware.

    Roush owns 2 nearly identical P51-D's unless he's sold one in the last couple years.

    I thought I had the guy's number to call about Merlins, but I can't find it in my files at work. I think his name is Paul Draper, in Livonia Michigan, although my fuzzy memory tells me that I talked at length to another guy who was pictured in the magazine. I typically collect every picture I can find about Merlins, and every rebuilder contact name and number that I can find. There have been a few changes in the last few years, and some of the big names in Merlins are no longer active (or alive). If I happen to find the contact info for Roush's rebuild team, I'll post it.

    Tom.
    Last edited by Tom Kay; March 19th, 2009 at 09:56 AM.

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    Registered User pepsi71ocean's Avatar
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    Re: Rolls Royce Merlin Engine-Rebuild by Roush

    We had a guy down at Cape May Airport who used to rebuild Merlin's, however no one knows where he went he just vanished after being there for 30 years, Im on the mission to find him.

    Any information you can find would be most helpful, I would like to learn anything and everything i can about them. Hopefully, i would like to find a rebuild in progress and learn the inner workings of the engine. More specifically the gearing between the cams the pumps, supercharger etic, what makes her run to say.

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    Re: Rolls Royce Merlin Engine-Rebuild by Roush

    Hi Pepsi;

    I'll keep working to find the contact that I talked to at Roush, but I might not be able to find it. However, you could call their Livonia office and just ask"Who is the Merlin guy?" like I did.

    There are ways you can learn about Merlins. Ebay doesn't have many parts anymore (they used to have whole engines once in a while) but they do have maintenance books. Also, you can find a fair bit on Google, at least about the basic description.

    The wheelcase gearbox is the heart of the engine in many ways, at least in terms of driving various systems. This delivers torque to many parts of the engine, camshafts, supercharger, accessories, etc. It also accepts torque from the starter. I have a wheelcase at home, and it sure is a box of spaghetti. Oodles of parts. A hoot to dismantle.

    My weakest area of knowledge of Merlins is boost control (carburetion). Otherwise I have a fair knowledge of the engine if you want to ask a few general questions. I've also never really understood the small vibration damping shaft which drives the gearbox from the crankshaft rear end, or how the speed-change mechanism works on the two-speed superchargers. At around 10,000 feet, the high speed drive kicks in with a hefty CLUNK, and the supercharger impeller(s) turn faster to crush more air into the cylinders. This feature, along with thoughtful supercharger design by Sir Stanley Hooker, was a big part of the Merlin's success, and the main reason it replaced the Allison V-1710 in the Mustang (P-51B, C, D, H, K). The Merlin 60 series and beyond were considered the "high output" engines that racers want today (especially if equipped with the beefier "transport heads, designed to last thousands of hours) because they were two-stage, two-speed superchargers with both intercooling and aftercooling.

    Do you want to contact other Merlin rebuilders in the US? Or elsewhere? I can provide you some contacts, but I'm not sure if that's the route you're looking to go.

    Also, I tend to be curious about what other people want to do with Merlins. Are you building a plane? Want to rebuild an engine to ground run for fun? (I'd like to). Or something else? Of course, you don't have to satisfy my or anyone's curiosity if you prefer not to. My area of interest was to study the parts and build a working 1/4 scale model. I progressed but didn't complete it. Maybe I'll come back to it when my house no longer dominates my spare time.

    Cheers, Tom.
    Last edited by Tom Kay; March 19th, 2009 at 11:10 AM.

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    Registered User pepsi71ocean's Avatar
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    Re: Rolls Royce Merlin Engine-Rebuild by Roush

    Withing 10 years i plan to build a P-51D, however i want to build a updated version of the Merlin. Specifically using things like Direct fuel injection, better lubrication, and better cooling. The Merlin was build for war, but i wanted to update the engine. This fascination started when i looked at the S-51 which was powered by a V-8. I didn't like the V-8 running such high rpm's so i tinkered with a V-10 design, which was designed heavily around the Merlin engine, especially the 620 transport banks as you talked about. However, i said why not spend the estra cash and go 1:1, and thus the V-12 was born. There is alot to talk about, but its all research and development so far.

    I'm happy i found someone who knows alot about the Merlins.

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    Re: Rolls Royce Merlin Engine-Rebuild by Roush

    Hi Pepsi;

    Quite a huge goal, but do it so we can all live vicariously through you ! Sort of kidding, but this is great. I hope you do it, but please keep us posted.

    I REALLY love the Stewart 51. The lines are beautiful, and it's all metal. I just had a good look at the Titan 51 today, and it's better looking than I thought it could possibly be, with an opposed engine. Beginner type flying and landing speeds, with reasonable performance. However, not beginner prices, although I admire their efforts in bringing this product to market. $80,000 isn't bad for a P-51 replica, but it's simply beyond me.

    About 25 years ago I was determined to make a full sized Mk IX Spitfire. I contacted everyone I could to ask for advice, including Larry Barnet of South Africa who had built one from scratch, in a mere 26,000 hours. Poor bugger, I first called him at 4 in the morning, his time, and claimed to be young and stupid, not realizing the time difference. That wasn't entirely true - I knew what time it was. I was just eager to get going. I even bought the right aluminum to machine the stub spars that bolt onto the firewall (called Frame 5). Then reality set in. It's a rich man's game, and I wasn't that guy.

    However, I am NOT trying to deter you at all. Your set of circumstances are, no doubt, completely different from mine. This would be great to see.

    Now, do you mean a full scale Merlin and Mustang, or did you mean 1:1 in terms of the number of cylinders? Like a 3/4 or 80% scale Merlin and airframe, or everything full scale? It would be awesome to make a slightly smaller Merlin because there are lots of scale aircraft in this world that could use it, although cost is the number one factor in the decision for most people. Obviously engine reliability would be right up there too in the thinking process. I have also done a bit of snooping to get engine parts made, such as a 4130 billet crankshaft cnc machined. I forget the US shop that does cranks, but they have a great reputation and do lots of cnc lathe work on new cranks. They shouldn't be hard to find on Google.

    Forged would cost a fortune, based on the dies, and I would not use cast crankshafts. Although I read once that the Packard Merlin crankshafts were cast, then shot-peined to add compressive strength to the surface. Don't know if that's true at all. Rolls forged all of theirs, and I think someone still owns the dies. I heard they were willing to do a run of 100 cranks at $10,000 apiece, say ten years ago. Ugh.

    See what happens when you get me started?

    The Merlin is a tremendous piece of aviation and engine development history. I know it had its early teething problems, but I feel it was the single most important aircraft engine ever built by a very wide margin. I'm Canadian, but I'll bet you could find a few Brits who'd agree with that. I know lots of US aviation guys will give the vote to some of the radials that powered the WildCats, HellCats, Flying Forts, etc. and from the American perspective, this would be understandable. It's just that it's too incomprehensible to think of what England would be like, had she lost The Battle.

    Anyway, back to the engine, hound me if I can help. It's a good hounding !

    Cheers, Tom.

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    Registered User pepsi71ocean's Avatar
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    Re: Rolls Royce Merlin Engine-Rebuild by Roush

    The Titan T-51 is a great airplane, and it was my first 51 replica i wanted to own. However my need for speed soon made the T-51 out dated with its low Vne speed. However, a Suzuki powered 2.6L V-6 is a great alternative engine, it will easily push the airplane to the Vne area without a problem. Infact its known as the Mini Merlin due to its similar sound to that of its full sized brethren.

    From the T-51 i moved to the Legendary Aircraft (AKA FEW-51) a fiberglass compost airplane hat is 75% scale, and was powered by a small block Chevy. once again the need for speed was the limiting factor. SO then i found the S-51.

    The S-51 is the ultimate 75% scale P-51 replica to own. I do believe a V-10 powered S-51 would be more reliable then a 572cid V-8 powered one. That was my original plan, i figured a 1,063cid V-10 stroker would help with a lower safer engine of choice. I don't and never will trust a big block to run 3,800+ RPM for hours on end, and so i figured with some modifications to the firewall forward i figured a V-10 would just about fit in there. After countless hours of design i came up with a 1,063cid V-10 that i felt could put out about 700-900 Block HP, and i was going to have a 2 stage centrifugal supercharger with 10lbs on the first and 14lbs on the second. This i figured should get me beyond the 1,100HP needed to push the S-51 at 400mph at a decent altitude. I wanted to get above 30,000 feet.

    The Falconer V-12 is a small Merlin that was tried but had a lot of reliability issues in the Thunder Mustangs, one more reason to go for it.

    I think there is a market for V-8 V-10 and V-12 aircraft engines, im sure alot of enthusiast would go for a low rpm high hp reliable engine.


    However i questioned the logic of all of those modifications, so then the last change was to a full sized 1:1 replica of the P-51D. In it i would add fake gun mounts on front, drop tanks and full sized wing fuel tanks, minus some room near the fuselage for baggage, i figure i could sneak a small jump seat in the rear for a passenger. I figured that i could get at least 800 or 1,000 block HP out of a new Merlin engine. Doing so would allow me to get up to 40,000 feet or better yet cruise at a good speed, i'll admit im a speed freak.

    But i like the Merlin design, and ive always wanted to think of new ways to update the Merlin to Direct Fuel injection, with 120lb injectors 4 valve, roller cam fingers SOHC design, and noticeably all gearing between everything no belts etic.

    Instead of cast, i was going to say forged and nitrized, however i would think nitrizing would be better then shot peeing, i think shot peeing the connecting rods would be better. Among other things i was curious to see how the Roush pistons differ from that of the normal stock pistons.

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    Registered User PTAirco's Avatar
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    Re: Rolls Royce Merlin Engine-Rebuild by Roush

    Quote Originally Posted by pepsi71ocean View Post




    But i like the Merlin design, and ive always wanted to think of new ways to update the Merlin to Direct Fuel injection, with 120lb injectors 4 valve, roller cam fingers SOHC design, and noticeably all gearing between everything no belts etic.
    Merlins never had a single belt-driven accessory and always were a SOHC , 4 valve design, no?
    "Aeronautical engineering is highly educated guessing, worked out to five decimal places. Fred Lindsley, Airspeed."

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    Registered User pepsi71ocean's Avatar
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    Re: Rolls Royce Merlin Engine-Rebuild by Roush

    Quote Originally Posted by PTAirco View Post
    Merlins never had a single belt-driven accessory and always were a SOHC , 4 valve design, no?
    Ahh, sorry i screwed up, i was half asleep when i wrote that. I was tired and i crossed my engine design and that of the Merlin into the same set of sentances.

    I meant to say my V-12 i want to build would be updated and still run SOCH with 4 valve, because no one does 4 valve on a SOCH design anymore, so if you run 4 valve usually its DOCH. This is mostly because its complicated, requires more time, and they have to use solid cam fingers which as ive been told wear out over time and degrade performance. I don't have any proof that thus is the case, and my Cummins 5.9L is proo that a 4valve system can work on a single camshaft.

    Thats why im going to use roller fingers and change the design to allow for better flow into and out of the engine.

    What sparked this thread was hearing that Roush is upgrading the Merlin engines, which brough up and interest to see what they have changed to the engine.


    I believe there is a Market for suped-up low rpm high horsepower air engines in the V-6, V-8, V-10, and V-12 arena. I think while Lycoming and contental are good companies its 60 year old technology, and i think better fuel eocnomly would help, in addition to this recent surge to auto engines. I think if i could get a company up and running this would be a good thing. I already have designs for a V-10 and V-12, And i think, wityh some design work i could turn a V-8 out that would be better then those used on the S-51 design. However, the reason i went to a V-10 in the S-51 was so i could get more CID into the engine.


    Tom Kay: do you know how long the fork and the knife rods were on the Merlin engines, and what the crank throw was?

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    Registered User PTAirco's Avatar
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    Re: Rolls Royce Merlin Engine-Rebuild by Roush

    Don't know the rod length, but the stroke was 6".

    You are bound to find something useful about the Merlin here:

    Aviation History - Browse the History of Flight from 1909
    There is so much on that subject that the search function "Merlin" will give you thousands of results, including adverts etc. This was a weekly magazine, after all. If you search year by year, you might narrow it down.
    "Aeronautical engineering is highly educated guessing, worked out to five decimal places. Fred Lindsley, Airspeed."

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    Re: Rolls Royce Merlin Engine-Rebuild by Roush

    Hi Boys;

    Yes the Merlin was a SOHC, but they cheated a bit by adding two "spindle shafts" per cyl head. So it's a bit more than just a standard SOHC. The spindle shaft rear ends also acted as a mounting place for additional drives/accessories. The British do have a knack for adding complication to designs, even though they end up working well. Napier Sabre or Rolls Eagle 22 anyone?

    There are other parts being fabbed anew these days. There was an outfit in Stratford Ontario called Merlin Fingers, that makes exactly that. (I just looked and couldn't find them on Google). They added a block of carbide to the cam fingers then ground it to the right shape. The chrome plating on the originals used to badly chew up the cam lobes. So new parts can certainly be made. Why not rollers, as you have mentioned? Could work.

    One thing I'd really like to see is a custom-designed crankcase with an integral gear reduction housing like the front end of a Merlin. I know there are PSRU's on the market for the Chevy LS-2's etc., but this is a separate bolt-on unit (typically $10,000 just for the gear box). There have been several failures of shafts and other critical parts in these reduction units, which wouldn't neccessarily be fixed if the PSRU and crankcase were one unit. Still it would seem a little more aircraft purpose-built. I've read a lot about vibration and its killer effect on props, crankshafts and gear box parts. So if you are to make an engine, this is one area that will really need some attention. Jack Kane at EPI is certainly one "guru" who believes in gears, and not Hyvo chain drives. On the other side of the coin, there's Jason Day of Vesta who is very into Hyvo chain drives, not gears. So, who's got the best approach?

    So, you've asked me some questions. I'm embarrassed to say that I can't tell you how long the rods are (bearing centre to bearing centre) because I think I left my rod notes at work, along with my actual parts. I'll have to locate them on Monday. I think it's 9.81 inches, but please don't trust that yet. I know Dwight Thorn (Mystery Aire) used to use Allison rods in Merlins, as they were heavier, stronger and 0.1" longer. This made the engines turn a tad slower, oddly an advantage because you could use a bigger prop. Who'd have guessed, huh?

    The crank throw is half of the stroke, and the Merlin had a 5.4" by 6.0" bore and stroke. So the throw was 3.0" off the central axis of the crankshaft. If you meant length, the crankpins were 2.7745" standard diameter, and 2.325 to 2.328" in length, but that includes 0.010" at each end of each crankpin that is useless radius (although neccessary). So the length of the forked rod, and any portion of the bearing sticking out proud of the rod would be 2.305" max, probably a few thou less.

    I'll try to remember to look for my connecting rod notes on Monday.

    Keep 'em coming !

    Tom.

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    Registered User pepsi71ocean's Avatar
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    Re: Rolls Royce Merlin Engine-Rebuild by Roush

    My engine (both the V-10 and V-12 designs) will have a cast in PRSU, using gearing instead of chains. In order to balance the two i plan to use needle pin bearings. and then im going to use a thick steel tube that will go inside the upper gear (the one that goes to the propeller), it will be filled with holes that would allow oil to shoot into the bearing at high pressure to help lubricate the needle bearings. The tube will be fixed into the back of the gearbox and a seperate oil pressure pump will drive the gearbox. I plan to use all the same oil between the two, however i want to add priming pumps to pump oil into the gearbox, and into the engine heads and other locations to help prevent engine wear. (Something i noticed on my Cummins engine.) I plan to use either a Bosch Rotary injection pump or one of my own design instead. And i want to run magnetos and spark ignition, dual spark plugs. The way i see it, the injector will be dead center, with dual spark plugs on both sides, and then 2 intake and 2 exhaust valves, both of which will be over sized to the most i can get. I will use a SOCH design using the spindle shafts to hold the cam fingers. There is a debate as to weather to use circleluar or oval valves. Oval valves would allow for bigger CFM and would complement the dual ignition and injector in the center. I want to use a circlip to prevent dropping a valve into the combustion chamber. Double springs and roller cam fingers. I would like to use low compression pistons (thus the interest in the roush design), enlarged wrist pins and the longest rods i can stuff in there, i think the V-10 was 8.5 inches or so. The V-10 had a crank throw of ~2.25 inches the stroke was 5.75. The crank would be nitrized, and the connecting rods would be enlarged at the crank side and shot peeined for durability, ide like to have both forged, but if i want to build all of this i might as well build a forge machine.

    So far im planning on .491:1 ratio in the gear box. The PRSU will be cast into a lower end peace that is from the banks down below the skirts. The banks will all be bolt on's. I plan to use aluminum for the lower end, and aluminum for the water jacket.

    However i want to increase the Steel cylinder liner to .20"inch from .10. I want to add .05" ripples to increase the cooling abilities of the cylinders. I still want to use the 3 ring gasket seals to seal the cylinder to the aluminum water jacket. I do want to use iron heads that are liquid cooled to help with cooling. This would allow me to run higher boost pressure.

    One of the current design issues facing me is if my fuel rail pressure is 55psi, then to produce 1,400HP i would need 124lb injectors, but to produce more then that say 1,700 hp i would need more like 150lb injectors, so the questions is should i raise the fuel rail pressure to say 60 or 70psi to help compensate for the injector size. If i used say 60lb injectors then i could get away with 135lb injectors instead of 150lbs. Something that RR never needed to figure out.

    According to my calculations my V-10 should put out 600 or so block HP at 3,300RPM, while the V-12 in development should be closer to 945ish. block HP.

    So Tom in your opinion what is the weakest link in the Merlin engine outside of lubrication and cooling. Also how was the gearbox lubricated and cooled? did it just use spray oil injectors or how was that lubricated? Another question is what exactly does a circlip look like, i have never scene one and from all of the searching i can't produce a good photo of this circlip.
    Last edited by pepsi71ocean; March 20th, 2009 at 11:37 PM.

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