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Thread: Merlin engine assembly stand

  1. #1
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    Merlin engine assembly stand

    Watching RR and Packard assemble Merlins via photos or film there are tantalizing glimpses of a rotating engine assembly stand. Various photos stolen from various sources are reproduced below showing this design. It seems to be a brilliant design, based on two large diameter rolled and machined rings that connect to the engine block feet. The rings break in two, allowing both full rotation and, by removing one half of the ring, easy access.
    The earlier RR Kestrel engine stand designs, both for factory assembly and field maintenance, are cumbersome and a poor ergonomic design. Somebody put a lot of thought into the Merlin assembly stand, and I think Packards evolved it even further.

    Your usual engine stand of today, which may accomodate a truck diesel of similar proportions to a Merlin, is suspended from one end, and won't allow the fitting of supercharger or reduction gear, so there is not much out there to do V12 aero engines. They seem to be built up on the bench. I have cast an eye over Allison fabrication techniques, and they did not seem to have something like the Merlin rotary stand.

    Does anybody have more detail or plans for the Merlin stand? - I would like to try and build one.

    Because I can't seem to insert images inline with text on key anymore I have numbered the attached images 1-3.

    The first two images show UK RR Merlin production, with the half rings removed, but they can be seen on the ground. When it is necessary to fully invert the block, the half rings are fixed back and the assembly rotated 180 degrees. I assume a pin was put in place to stop the block from auto rotating.
    Image 1 shows engine 'banks up' while image 2 shows engine 'banks down'. I assume there was a fitting on the block feet that engaged with the gusset feature on the rings, that allowed support by either the 'banks up' or 'banks down' half ring. It's nice to see everyone in a tie.

    The third image shows, I think, a Packard or Ford Merlin assembly line in the US. In this case, the block seems to be fixed to a small rectangular trolley, which makes its way down the line from left to right. The trolley enters a position with two fixed rings, that allows the cylinder banks to be lowered vertically down on the block. This assembly is then pushed out to the right. The principle of full assembly line production seems apparent, in comparison to the fixed station approach in the UK pictures, where the fitters 'build up' an engine in the one spot.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by powerandpassion; 1st February 2017 at 11:37.

  2. #2
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    I have seen this version in several photos here and there from several restorations. It seems simplified and would be easier to construct, and allows full rotation. Maybe split the hoops to remove half for more access when needed.

    Click image for larger version. 

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    Last edited by DoraNineFan; 1st February 2017 at 14:32.

  3. #3
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    Roll over stands, quite common in overhauling, now, if you want to see a piece of engineering excellence, you should have seen the Conway build stand in base hangar at Brize, designed to accommodate a Conway engine mounted vertically, it was in the engine bay................................. and never used, as it should have been buried in the floor when they built the hangar, but was wrongly bolted to the floor!!! resulting in the crane designed to lower the engine into it just clearing the top of the it, and that was without an engine on it..

    As for roll over stands see

    https://www.thesamba.com/vw/forum/vi...c.php?t=175412
    Last edited by TonyT; 1st February 2017 at 17:02.

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    Those roll-over Merlin stands were common by the end of WW2. Simple and effective.

    They'd probably be quite easy to make, too.

    Anon.

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    You should see the the stands used for R2800's & the like.... They make that Merlin stand look like Meccano.
    Last edited by ZRX61; 2nd February 2017 at 22:38.
    If anybody ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me: It's all balls. RJM.

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    PowerandPassion

    You probably know this, but there is a different type of stand that is used for Merlins, and probably other engines. This is a frame that pivots around the center at each end, and the crankcase mounting feet bolt to the frame. It's simpler because you don't have to build the rings that roll around on a track or set of bearings. I wish I had either type, since it would make rolling my Merlin crankcase 30 degrees left or right much easier, which would then make hoisting the cylinder blocks straight up much easier. Hoisting upward on an angle is a problem, I've found.

    I assume you're likely familiar with this type, but let me know if pictures would help.

    Tom.

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    Quote Originally Posted by Tom Kay View Post
    PowerandPassion

    You probably know this, but there is a different type of stand that is used for Merlins, and probably other engines. This is a frame that pivots around the center at each end, and the crankcase mounting feet bolt to the frame. It's simpler because you don't have to build the rings that roll around on a track or set of bearings. I wish I had either type, since it would make rolling my Merlin crankcase 30 degrees left or right much easier, which would then make hoisting the cylinder blocks straight up much easier. Hoisting upward on an angle is a problem, I've found.

    I assume you're likely familiar with this type, but let me know if pictures would help.

    Tom.
    We remove the cam etc & then bolt a spare center cam mount in place. With a strap around the inboard end of that mount it will hang the head/bang assembley at the correct angle to lift off or drop back in place.
    If anybody ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me: It's all balls. RJM.

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    I think Tom Kay was referring to the main crankcase being held at the correct angle, ZRX, so that the cylinder blocks could be raised or lowered down vertical studs.

    It doesn't sound much of a problem but, having done it myself on several occasions it really is a bug**r, especially with something so heavy. Half the problem is that, if the head is jacked off or lowered slightly more at one end the whole assembly jams on the studs and can be a swine to release - especially if, like in our case, it was being largely done by hand with limited mechanical lifting assistance.

    Anon.

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    ZRX61, Pictures speak a thousand words, so if you can show me what you mean, that would be great. Although I think I get it. By hanging the cylinder head and block on the inside edge, by a strap, the whole thing just happens to hang at about 30 degrees rolled outward?? I have done something like this, but it still is a case of "walking" the assembly off the long hold down studs, typically achieved by hammer taps at the front and back of the head as I hoist it up off the long studs. I really think it'd be easier if I were lifting purely vertically, as Anon mentioned.

    I broke a stud off the front coolant outlet face doing this once. I think the assembly swung a bit then rested on one of the studs. DOH ! Now I have to dig the little broken stud piece out of the cylinder head.

    Tom.

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    Quote Originally Posted by Tom Kay View Post
    ZRX61, Pictures speak a thousand words, so if you can show me what you mean, that would be great. Although I think I get it. By hanging the cylinder head and block on the inside edge, by a strap, the whole thing just happens to hang at about 30 degrees rolled outward?? I have done something like this, but it still is a case of "walking" the assembly off the long hold down studs, typically achieved by hammer taps at the front and back of the head as I hoist it up off the long studs. I really think it'd be easier if I were lifting purely vertically, as Anon mentioned.

    I broke a stud off the front coolant outlet face doing this once. I think the assembly swung a bit then rested on one of the studs. DOH ! Now I have to dig the little broken stud piece out of the cylinder head.

    Tom.
    Don't think I have any pics (I'll look), but you pretty much got the gist of it. Can't roll the Merlin over when it has a P51 attached to it.
    If anybody ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me: It's all balls. RJM.

  11. #11
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    ok, found some pics. They show the strap attached to the center mount with the head/bank resting on cylinder jacks. Don't have a pic of it "mid-dangle" as I was operating the forklift we were using. We don't employ hammer taps to install it, one person shakes the crap out of everything as another turns the jacks (made from a couple of pieces of billet & some threaded rod)





    If anybody ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me: It's all balls. RJM.

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    Next time I'm up at Mike Nixons I'll get some pics of what he uses for V12s & radials. The radial stands look like something you'd expert to find in a locomotive factory.
    If anybody ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me: It's all balls. RJM.

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    Radial stand, entire engine can be pivoted from vertical to horizontal..

    If anybody ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me: It's all balls. RJM.

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    Quote Originally Posted by DoraNineFan View Post
    I have seen this version in several photos here and there from several restorations. It seems simplified and would be easier to construct, and allows full rotation. Maybe split the hoops to remove half for more access when needed.

    Click image for larger version. 

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    DNF, thank you for that, yes, looks like a modern version, non splitting, most likely relies on its strength via being a unit. Your engine? I have some factory issue DB-600 spanners that came out with a migrant to Australia in the 50's, very light, well designed, expensive alloy. Who are the DB600 rebuilders out there?

  15. #15
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    Quote Originally Posted by TonyT View Post
    Thanks Tony, great article. Rollover for cars and fuselages is a fantastic idea, some set ups very elegant.

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    Quote Originally Posted by Tom Kay View Post
    PowerandPassion

    You probably know this... but let me know if pictures would help.Tom.
    Tom, I know nuffink, as Sergeant Schultz would say! Pictures always help. I wonder what happened to the orgiginal RR Merlin assembly stands, surely one or two must have crept out, even from field repair shops. I wonder what Packard supplied for field repair? I have found a Merlin Mosquito 'power egg' static stand here in Australia, turned upside down and used as a bench in a farmer's shed.

    What I am wondering is :

    a) there must of been a 'knuckle' that connected to the engine feet, that then allowed top or bottom ring to connect via the knuckle to the engine. I note one ring is, say 210 degrees and one is, say 150 degrees. Both rings have gussets that reach out to the knuckle.
    b) I figure the rings were rolled from mild steel channel, assembled as a ring, low temperature stress relieved, machined to perfect round, then disassembled. I figure if you dropped the ring on the ground too often it would not work. I wonder if the actual rings were cast steel. I can't get enough resolution from the photos to figure it out.
    c) Is there some friction damper that prevented auto rotation once you had it in the desired position, eg for bank A or B when lowering the banks.

  17. #17
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    Quote Originally Posted by ZRX61 View Post
    ok, found some pics.
    ZRX61, thanks for the pics and info. Everybody needs a pickup truck to get their Merlin bits around !

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    Quote Originally Posted by powerandpassion View Post
    DNF, thank you for that, yes, looks like a modern version, non splitting, most likely relies on its strength via being a unit. Your engine? I have some factory issue DB-600 spanners that came out with a migrant to Australia in the 50's, very light, well designed, expensive alloy. Who are the DB600 rebuilders out there?
    Not my engine. The photo is very old from Dirke Bende's shop in Germany. But I have seen versions of this engine stand from photos in other engine shops.

    Vintage V12s is handling a lot of the contract DB rebuilds (and starting on a few Jumo 2xx series now also.) I also have read comments that a gentleman named Sigi Knoll is a top expert on the DB series engines.
    Last edited by DoraNineFan; 14th February 2017 at 14:11.

  19. #19
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    Tell Siggi that I have some DB spanners that went to Russia and he can have them if he can help educate me about DB engines. Mainly interested in the Kawaskai licenced Ha140 DB 601 derivative and understanding why it coughed so much.

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    Quote Originally Posted by powerandpassion View Post
    Tell Siggi that I have some DB spanners that went to Russia and he can have them if he can help educate me about DB engines. Mainly interested in the Kawaskai licenced Ha140 DB 601 derivative and understanding why it coughed so much.
    You can probably contact Sigi through the Messerschmitt Museum in Germany.
    http://www.flugmuseum-messerschmitt....ian/index.html

    Also, here is another version of engine stand for a DB-6xx that allows top access and is strong enough for test runs (without a prop.) I love how this DB is purring.
    https://www.youtube.com/watch?v=_2gDVc46VNA&t=3s
    Last edited by DoraNineFan; 14th February 2017 at 14:25.

  21. #21
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    PowerandPassion;

    Here are a few pics of rolling Merlin stands that I've found. I don't know any of the rebuilders, but you can see how the crankcase mounting feet attach to the frame. Wish I had one.

    Tom.
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  22. #22
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    Quote Originally Posted by Tom Kay View Post
    PowerandPassion;

    Wish I had one.

    Tom.
    How's your welding skills?
    If anybody ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me: It's all balls. RJM.

  23. #23
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    Quote Originally Posted by Tom Kay View Post
    Here are a few pics of rolling Merlin stands that I've found. Tom.
    Tom, thank you for the selection of pictures, very informative. It seems that everybody goes for a 'universal' type stand that can handle truck diesels, which makes sense. A lot of air space is left for reduction gearbox and supercharger removal. The RR stand is a bit of a stradivarius in comparison, but allows you to 'get in' to the engine from all angles. In thinking about how you would do a RR stand today, you could laser cut the ring and arms connecting to the engine feet, with the outer diameter being standard. That way, you could have different rings for different v12s, but use the same base. The 'knuckle' engaging with the engine feet need be no more than a flat plate with a suitable number of holes in it. Hmmm...

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    Quote Originally Posted by powerandpassion View Post
    Tom, thank you for the selection of pictures, very informative. It seems that everybody goes for a 'universal' type stand that can handle truck diesels, which makes sense. A lot of air space is left for reduction gearbox and supercharger removal. The RR stand is a bit of a stradivarius in comparison, but allows you to 'get in' to the engine from all angles. In thinking about how you would do a RR stand today, you could laser cut the ring and arms connecting to the engine feet, with the outer diameter being standard. That way, you could have different rings for different v12s, but use the same base. The 'knuckle' engaging with the engine feet need be no more than a flat plate with a suitable number of holes in it. Hmmm...
    If your goal is to duplicate the original stand, perhaps you can ask Rolls Royce Heritage Trust for any information they may have in their archives? Or if they have an original stand in storage?
    https://www.rolls-royce.com/about/ou...age-trust.aspx

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    Good idea ! Thanks

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    Knuckle

    Here is another photo of the Merlin rolling stand stolen from the AWAL website in Australia. It shows more detail of the knuckle connecting to the engine foot and the intimation of some locking handles close to the base that would stop the engine - half circle assembly auto rotating. I imagine that the heads and block would be fairly easy to rotate around around a common centre of gravity designed around a bottom end dressed with crankshaft, conrods and blocks dressed with valve gear. It would be easy to rotate this by yourself but a second person was required to fix the locks that would stop subsequent auto or uncontrolled rotation.

    If you were to design this in CAD you might design a simple block model of the engine, weigh the separate components to determine the centre of gravity, understanding that when you just had the bottom end in it would auto rotate to present the block retaining studs/bolts to the sky.
    Attached Images Attached Images  

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    There are some DB and merlin tooling advertised in the current Aeroplane or Flypast.
    Last edited by TonyT; 18th March 2017 at 11:32.

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    This is my turnover stand, which works quite well. Long enough for a two speed engine, with adjustable feet positions and locks at set angles (zero and 30 deg either side is useful).

    DAI
    Attached Images Attached Images  

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    DAI, nice stand ! Is that an Anson U/C gearbox on the end !

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    Curtiss stand

    I was looking at a 1930 edition of Australia's Aircraft magazine that showed a Liberty engine being worked on in a US workshop with a DAI rollover stand. This got me into a Curtiss D12 workshop manual and there it popped out, in 1927. I have to say that the Curtiss D12 was a very, very, influential design on a whole range of levels. So until someone can post an earlier picture, I will say that Curtiss invented the familiar rollover stand.
    Certainly RR took it to another level, with the split ring design, getting rid of the awkward east -west cross bar.
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