1/18 Scale Blue Box F4U-1A Corsair Modification

[JayW]

OK, the prop governor (Hamilton Standard 4G10 series) .  Amazingly little technical data around, although I found a manual with parts lists for Hamilton Standard constant speed prop governors at Aircorps Library.  It has pictures like this:

 

 

Note the big pulley wheel - that is meant to be rotated by a cable attachment emanating from the cockpit, and it changes prop pitch depending on the rotation.  The manual speaks of single capacity and double capacity governors, which look a bit different.  Also there is a variety of bases that the governor is mounted on.  Lastly it appears that certain layers of the governor can be turned 90 deg or 180 deg to help with the integration with the engine.  All of this served to confuse the issue of what this thing looks like for Corsairs.  The propeller installation drawing VS-10375 offered even more confusion by showing two different versions of the governor control - one the pulley wheel that is commonly seen:

 

 

And two - a bracket and linkage arrangement (no wheel):

 

 

I could not find any point in the production run where the wheel arrangement took over, so I went to work looking at wartime pictures.  I have concluded that F4U-1's and 1A's had the linkage arrangement, and the wheel arrangement came a little later perhaps with the paddle bladed propeller or the pressurized ignition.  The F4U-1D has all that stuff, and I am making a 1A.  So my engine gets the linkage.

 

Here is a shot of the PITA prop governor, ready to be mounted onto the engine nose:

 

  

 

And on the engine:

 

 

And with the little bracket assembly (the linkage comes later):

 

 

Pan back and you see the full engine in its current state of completion - it is basically fully complete all the way back to the supercharger sections aft of the cylinders.  

 

 

Now, I believe I will start looking at the exhaust collectors.  Here is a picture of them from the parts catalog:

 

 

Talk about hand wringing.  The Vought drawing is very good, fully defining the pipes and their curves and shapes.  I will make the pipes from the .125 inch diameter silver solder I have used before.  Outside of that I just do not yet have a plan for how to accurately produce these.  Wish me luck.  

 

[brahman104]

Brilliant work on the prop governor Jay! Surely after everything you've done already, the remaining pipes should be pretty straightforward!

 

Craig

[JayW]

On 7/7/2020 at 2:11 PM, brahman104 said:

Brilliant work on the prop governor Jay! Surely after everything you've done already, the remaining pipes should be pretty straightforward!

 

Craig

 

Thank you Craig - no the pipes are going to be the biggest challenge yet. Sometimes I get surprised, both ways, but usually I can get a feel for what is straight forward, and what is problematic.  The pipes are definitely going to be problematic.  The exhaust pipes for the Thunderbolt, which you may recall,  were easier.  One, the ends of the pipes are unseen largely, instead travelling back inside the fuselage to the turbocharger.  And two, they collected into a large diameter pipe, one per side.  The Corsair will have three pipes per side each one nestled next to one another, with a distinctive 3-pipe exit at the cowl on each side.  Every plan I think of has huge flaws.  I think i might just dive in with both feet and see what happens - something you are good at!  I sure don't want a sloppy result after all this effort.      

[Anthony in NZ]

WOW....(sorry the feedback isnt more helpful) love it!

[Jeff T]

Jay, that engine looks absolutely superb!

 

Great work.

 

Cheer's,

Jeff.

[airscale]

ooof those exhausts look like fun...

 

no doubt you will be up to the challenge Jay

 

looking forward to seeing how you go about it

 

Peter

[JayW]

I have quit stalling and have begun work on the exhaust stacks.  Lots of trepidation, but geez - it's a model; it's supposed to be fun.  

 

My plan is to use a combination of .125 inch diameter aluminum tube and also .125 inch diameter solder.  If perfectly to scale the diameters would be about .14 inch.  But I could not find material that size that would suit this application.  I will use the solder where I can because it is easier to bend and form.  The aluminum tube will be used for the lower portions of the stacks where they exit the fuselage and the ends are exposed.  The stacks must be hollow there, obviously.  The aluminum tube must be bent and formed as well - and in order to prevent the walls from collapsing I have filled the ID with .093 plastic rod.  Then after forming, I can easily drill away the plastic rod from the ends to regain the hollow.  I have a variety of tools and fixtures in which to accomplish the bends and accurately locate the ends common to the cylinder exhaust ports - so far so good I guess.

 

There are three pairs of stacks, each one serving three cylinders.  I have started with the middle pair of stacks.  What I really need to do this is to mount the engine on the fuselage.  But it isn't time to do that yet (far from it), and I don't want to handle the engine a million times in the process (which is what would be required - lots and lots of trial and error here).  Also don't you know I would drop the engine on the floor doing untold damage to a 6+ month project.  So I made a fixture that simulates the rear portion of the engine and has all 18 exhaust ports accurately located.  Here it is with the two almost completed middle stacks:

 

 

This thing mounts onto the fuselage "bulkhead" that I am using to mount the engine:

 

 

That bulkhead kind of has a counterpart on the real aircraft, kinda doesn't.  The real aircraft has something called a diaphragm that provides an aerodynamic surface for air that enters the cowling and passes out the cowl flaps.  All radial engine aircraft have such a thing.  But it doesn't support the engine nor is it a firewall  - it is merely a thin sheet metal surface.  The real aircraft has six flexible "Lord" mounts (motor mounts) that attach the engine to a mount ring.  While I will model these "Lord" mounts later, they are too weak and fragile to hang onto that engine, so I had to modify the diaphragm and have it support the engine:

 

 

 

I did the same thing on the Thunderbolt.  You may also notice the aft fuselage and tail are gone.  I have done this on all my 1/18 efforts except the P-38.  One, the fuselage is very long and bumps into things.  That was painfully apparent while messing around with the exhaust stacks.  Two, a staggering amount of work must take place inside the fuselage - cockpit, engine compartment, aft landing gear and empennage.  This way all that work can be split up and joining the fuselage halves is easier.  I split it at the bulkhead where the pilot seat is hung - along a prominent panel line. 

 

Here is the LH middle stack:

 

 

 

Inspect it just a moment and you will see it has a long single tube, and two short pieces of solder bonded onto it (with copious amounts of 2-part epoxy and a little putty).  Those bends are exceedingly difficult to get just right, and were the reason for my trepidation.  Although it fits well to the cylinder exhaust ports, and seems to fit well to the fuselage, I still don't know for sure how it will fit with the upper stacks that kind of lay on top of it.  And that is going to be next.  Wish me luck - this is the most challenging part of the build to date.

Edited July 30, 2020 by JayW

[LSP_Kevin]

Incredible work, Jay! You could stay, it really stacks up...

 

Kev

[turbo]

Fantastic work on the engine and exhaust stacks Jay, looks very convincing to me!

 

Cheers, Kirby 

[chuck540z3]

Good Luck Jay, but nobody is worried you won't pull it off.  If anybody can analyze and solve a modeling problem- and clearly explain it, you can!

 

Cheers,

Chuck

[brahman104]

Every update you continue to amaze me with your unique fixtures and jigs! Super clever and necessary solution to your very complex engineering work. They alone are works of art, but the exhausts so far are just spectacular. I can't even fathom how you managed to bend those pipes with the precision you did Jay, except that I can understand when you say it wasn't easy, and that must be a massive understatement!

 

This is true model engineering, I love it!

 

Craig

[JayW]

Work progresses on the exhaust stacks.  Or manifolds, or pipes, or as Vought called them "collectors".  I have a tiger by the tail with these parts, as expected.  But I have some pretty decent results that I am kind of excited about.

 

The locating fixture I showed last post has worked quite well.  I can attach it to the front of the fuselage with masking tape, and I can leave the engine the heck alone so I don't break it.  Here it is with alot more parts:

 

 

 

The fixture's port locations are pretty close to the ports on the back of the engine's cylinders, which they are designed to simulate.  But of course not quite.  So the biggest frustration I have with this process is trying to fit a finished stack assembly to the engine and finding I have to bend or deflect one or two pipes just a bit to match the engine's exhaust ports.  And in that case as often as not, a pipe will break off, as it is only fixed with 2-part epoxy, which doesn't work real well on metallic surfaces.  I rough up the local surface pretty good, but it's still rather fragile.   

 

As you can see in the above photo, three of the pipes (per side) must pass through the fuselage.  And boy what a challenge that is.  Goofing around with that also breaks off pipes.  Sometimes I have to get up and just walk away in a huff, go do something else for a while.... 

 

Here is the fixture with all six stack assemblies mostly done:

 

  

 

The last step major step for the stack assemblies is to make that very Corsair-esque trim at the fuselage opening:

 

 

That step in the process was not nearly as tough as I thought, and notice I used the engine itself to temporarily fix the stacks in place (not the fixture).

 

Next post I will show you the completely finished and painted stack assemblies - a victory that was in doubt up until a day or so ago.  They will then be put away for quite a while as I do more engine stuff - complete the Station 54.125 diaphragm along with the engine mount ring, and the six engine (Lord) mounts, and teh very difficult "doghouses" behind the exhaust stacks at the fuselage openings.  After that I suspect it will be time to make the cowl flap ring and the fittings that afix the cowl flaps, and the nose cowl mount ring and it's fittings.  Those items are really important to get right because the engine cowling panels depend on it.  At the moment I don't have a good plan at all, so I fret about it (my MO).

Edited August 6, 2020 by JayW

[brahman104]

Every post raises the bar Jay! I still don't know how you do it... working with such fragile epoxy joints would drive me insane! I'm sure you mentioned it before, but was there any reason why you didn't make the pipework out of brass so you could solder it together? I take it this was much easier to form considering the complex curves? 

 

Even with the jigs I still don't know how you managed such a feat!

 

Each post is a feast for the eyes

 

Craig

[JayW]

Exhaust stacks are basically finished except final top coat of paint.  That will be down the road a bit.  Here:

 

  

 

 

 

While the stacks are not perfect, they are better than what I expected.  They are only temp installed onto the engine, and every time I take them off and put them back on, the orientation of the six scarfed ends seems to change a bit.  

 

 

On 8/6/2020 at 2:42 PM, brahman104 said:

but was there any reason why you didn't make the pipework out of brass so you could solder it together? I take it this was much easier to form considering the complex curves? 

 

You got it Craig.  Not sure, but I highly suspect copper or brass tubing would have been stiffer.  Even what I used (annealed aluminum and silver solder) was pretty stiff.    But in truth, I just didn't consider it at the time I committed to the materials I used.  

 

So what color to paint these, once it's time.  The drawing says the tubes are made of 18-8 stainless steel.  That stuff doesn't rust, and when new, it looks kind of like titanium - a dull darker shade of silver.  Have seen this stuff in my prior professional career.  But when subjected to high temperatures, I am pretty sure it discolors, and maybe more and more with time.  I know alot of modelling folks like to paint their exhaust stacks a rust color, but in this case I think that would not be right.  I have a "burnt iron" lacquer I could use, or I could use the titanium metalizer spray that I used on the s-shaped short stacks coming from the front row cylinders.  I am accepting ideas.

 

OK, it is on to the engine mount ring and "Lord" mounts.  Stay safe and healthy folks. 

[Landrotten Highlander]

Ho about using somthing like clear Tamiya yellow, red and blue to create the discoloration?  You can see this often on motorbikes' exhausts, partiulalry around the bends.