# 1" bore Merlin Plans



## cds4byu (Oct 3, 2021)

Dear members,

I've been looking for Merlin plans, and it appears that the quarter-scale Merlin has headed off into the internet graveyard.

I've found some Merlin overhaul/maintenance manuals that appear to give enough detail to create a model that, while not perfect, is probably good enough for a small-scale model.

I'm thinking about embarking on a project to create a solid model of the Merlin in Onshape, which could eventually result in drawings.  If I do so, I'll probably make it 1" bore, compared to the approximately 5.5 inch bore in the real engine.

As I try to decide whether or not to jump in on this project, I'd like to gauge the interest of members of this forum.

Would you be excited, happy, or indifferent to having such a model/plans available?

Are you interested in participating in the creation of the model?

Thanks,

Carl


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## lohring (Oct 3, 2021)

Excellent CAD drawings are available on grabcad.  I recommend John Fall's models starting on page 2 and running to page 6.  There is also Rob McClune's Packard Merlin crankcase model.  The only missing area is the intercooler for the Packard Merlin.  Lots of pictures are available on the internet.

Lohring Miller


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## cds4byu (Oct 5, 2021)

Thanks for pointing me to John Fall's models.  They appear to be complete and will form an excellent starting point for my work.

THanks,

Carl


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## CF-EKM (Oct 6, 2021)

Hi,
i'm working on something similar but far away from a scale engine.
Mine will be 30.4 mm bore and 27,5 mm stroke from practical reasons. And cylinders are offset left to right column. However it is liquid cooled and with reduction gear. Purpose is to power my 22% size P51.
Design is a mix of good ideas from Schillings, using high quality pistons & sleeves and valves from O.S.

This design is all about weight and practical running characteristics. Power will be plenty enough to turn the 30" scale 4 blade prop.
Speed is obviously higher than fullsize Merlin, it's planned with 5500 max rpm and 3000 for 'scale' flying.

Weight is currently aiming 8 kgs including cooling system but I'll reduce it some more.

I'm planning to make the first chips on the housing before christmas.

Kind greetings,
Christian


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## Bentwings (Aug 22, 2022)

cds4byu said:


> Dear members,
> I most certainly would be interested in participating. I may have come off as bay sayer but that’s not the case at all
> My thought would be to look toward a 3D printable model or set of plans capable of this. It wold give many the opportunity to have a desk top model as well as possibility of an actual operating model if you had ability to machine parts .  Having something like a visible Merlin would be cool . The nice thing is that 3 d printing would allow you see just what you are getting into .  Just think of the crankshaft. Conley had piles of  machined parts that were out of spec that he sold as  “look at this” parts    You could possibly start with a set of Hogson 18 cyl radial he won’t let you mass produce the engines but you could make 3D models and print them . You can 3D print more than one mating part and make them shake and break sub assemblies .
> I've been looking for Merlin plans, and it appears that the quarter-scale Merlin has headed off into the internet graveyard.
> ...


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## Bentwings (Aug 24, 2022)

As I noted above, I’d like to participate. Bending into Rc scale warbirds I think it would be a neat project . There are only a few V  engines in approximate 1/5 or 1/4 scale they are extremely expensive  well made but the cost is jut way to high . I wish I could see well enough to do precision TIG welding so I could help with the exhaust . I’ve done a number using single flinders engines ant it is very tough to weld thin stainless u have a double regulator system that allows bak purging so the welds don’t get sugary on the inside . Even single scale stacks will be an issue. I don’t know if they could be 3 d metal printed . The wall thickness might be an issue   The last set I made had.015 3 “ wall tubing . It might be possible to make wood or even 3d printed plastic bucks or forms an form annealed copper or brass then silver braze  even that is tricky on a good day  if you coumetal ld live with round tube it’s possible to bend  using cero bend bismuth metall making small bending equipment isn’t easy either . Weight is an issue too the thinner wall you can work with the better . Remember ex gas  in a gas engine can get close to 1000 deg f very close to silver braze temp multiple stacks can dissipate heat better but it’s still hot.

I don’t know what the intake looks like but I’d guess it could be printed  car intakes are plastic so it acceptable 

Making the aluminum parts out of magnesium could save a third in weight but it’s a dangerous material in the shop I saw a big lathe chip pan burn and we had a brand new belt sander burn up mixing mag and steel  filings. It’s also expensive . Many metal parts can be printed now but I don’t know costs  you could print connecting rods then  finish machining an make bearing shells . Any gears can be plastic or metal printed so I Think  that would be the way I’d go  if the crankshaft has enough bearings it to could be printed then final finished  you could easily do s nice dry dump oil pump. On our race cars we just use an oil tank with scavenge returns. There is no real provision for de aeration  scaling that would be really hard it’s hard enough on rod cars . My father in law flew corsairs during the war he said they had very little oil left returning from missions . As for super charging or turbo I forget the turbo except for scale appearance . There have been numerous model turbos built but I’ve yet to see one capable of inflating plastic bag.  There have been a number of positive displacement blower or super chargers that really worked. The roots type seems best . I’ve GSD a number of street rods with them an lots of racers .  Very little trouble. These exist on grab cad


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## William May (Aug 25, 2022)

Yes, the large radial engines,, such as the 28 cylinder "4360"'s that were used on Corsairs had oil tanks that carried many gallons of oil, and the oil consumption was measured in gallons of oil per hour flown.


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## Bentwings (Aug 25, 2022)

William May said:


> actually only a few F2g corsairs were built with the R 4360.All others had R 2800 18 cylinder engines
> Yes, the large radial engines,, such as the 28 cylinder "4360"'s that were used on Corsairs had oil tanks that carried many gallons of oil, and the oil consumption was measured in gallons of oil per hour flown.


 actually tcorsairs had r 4360 engines
Hard to believe how much oil they used and leaked  the top center cowl flaps had to be closed and sealed to prevent leaked oil from getting on the wind screen  . If you ever get to see Fifi  the above 29 try snd look in the Bombay . They carry many barrel of engine oil.  They usually put drain pans under the engines  to keep the oil mess down


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