1/18 Scale P-51B 3D Print Build

[monthebiff]

This is an epic build Jay, love each an every update! What you have done with the clear canopy parts is just incredible!

 

Regards. Andy 

[JayW]

I have for the better part of the day been studying pictures of cockpits with the Malcolm hood modification.  As you are probably aware by now, the hood travels on rollers that are attached to a rather prominent rail on either side of the fuselage exterior.  To drive the hood back and forth, there are two sets of chains and sprockets in the inside of the cockpit, nested between flanges on the upper longerons.  And driven by a hand crank handle.  Like so:

 

 

What a challenge to properly represent all that clap trap.  Already I have learned that the recongition light switch box must be relocated to clear the handle crank on the RH side.  Now, I have discovered something else very curious.  Take a look at these two pictures.

 

One - 

 

  

 

Those are outlet ducts for the pilots' heating system, right at the pilot's shoulders peaking out from behind teh armor plate (armor plate and seat not in this picture).  They are attached to the upper longerons and the sta 146 frame.  This is taken from the Lope's Hope P-51C resto - which does NOT have a Malcolm hood. 

 

Two -  

 

  

 

This shows the aft end of the Malcolm hood chain drive, with a small sprocket and a connector shaft to the other side and teh other chain.  The support fitting is mounted on the upper longeron, and is directly in front of the sta 146 frame.  This is taken from a resto with a Malcolm hood, and in process.

 

Both items are in the same place!   What gives?  Were these ducts relocated in some fashion?  Anybody know?  Some of my period pictures suggest maybe they were just removed and the holes plugged.   If so - what a penalty.  Cold pilots.     

Edited April 15 by JayW

[SwissFighters]

Regarding heating outlets or chain drive, I wonder what do the drawings show?

[Azgaron]

Excellent work so far Jay! Looks great!

 

Håkan

 

[JayW]

8 hours ago, SwissFighters said:

Regarding heating outlets or chain drive, I wonder what do the drawings show?

 

The heater outlets are defined on drawings - they are part of the production airplane.  The Malcolm hood mod however is just that - a mod.  And no drawings are available. 

 

But wait!  I think I have it solved, and the solution was in my pictures all along:

 

 

 

 

LH side, the flex tube is attached to a convenient fuselage frame further forward.  RH side, the flex tube is routed under the map case forward to an empty spot on a radio mounting bracket.  I can do that! 

 

This is from a modern resto, so I am going to have to hope it fairly well represents what was actually done back when.  I am going to declare the mystery solved though.

Edited April 16 by JayW

[Antonio Argudo]

superb job Jay, just saw this cool pic and wanted to share, keep the great work, cheers

[Paulpk]

Jay, great work. I am very suspect of restored equipment in private use as being totally accurately restored. So I’d stick to period photos myself. I find this so true with armor vehicle restorations.

 

I knew of the Malcom hood but not the details of usage or installation. I find the cranking system to close and open questionable. I hope there was an over ride when you needed to escape fast 

 

I searched today for an answer to your question and probably came up with the same answers you have. There must be a set of instructions for installation somewhere in a British museum.  Have you contacted any museum?

[JayW]

15 hours ago, Antonio Argudo said:

superb job Jay, just saw this cool pic and wanted to share, keep the great work, cheers

 

 

Oh cool pic indeed!  Thank you Antonio.  Some things to notice:

 

1.  Relocated recognition light electrical box (a few inches forward) seen through the side window windshield glass (with what appears to be a natural metal finish bracket)

2.  Some dark colored strip of putty or something along the periphery of the aft enclosure cutout - clearly meant to seal the gap between the hood and the fuselage crown when hood is closed.  First I have seen that - I wonder if that was common...

3.  There are five sets of rollers exposed with the hood open.  All other pictures I have seen either period or modern have six sets.  Mine too.  Hmmm...  Is the hood in this pic not fully open?  Or, were more rollers added at some point to address a service issue.....

4.  You can see a portion of the round outboard end of the crank handle / forward sprocket support bracket peaking out from behind the roller rail just aft of the windshield.  You'll see that on mine too pretty soon.

4.  The girl is very hot. 

 

14 hours ago, Paulpk said:

Jay, great work. I am very suspect of restored equipment in private use as being totally accurately restored. So I’d stick to period photos myself. I find this so true with armor vehicle restorations.

 

I knew of the Malcom hood but not the details of usage or installation. I find the cranking system to close and open questionable. I hope there was an over ride when you needed to escape fast 

 

I searched today for an answer to your question and probably came up with the same answers you have. There must be a set of instructions for installation somewhere in a British museum.  Have you contacted any museum?

 

I hear you on modern restos.  However I am very confident that the cranking system is accurately represented.  All are consistent, and anything that can be gleaned from period photos seem to be in acordance.   

 

As for escape - the Malcolm has an emergency jettison mechanism, including a red pull handle not unlike what we see on all production Mustangs whether greenhouse or bubble top canopy.  You will see that on mine soon.   

 

Upon your suggestion, I sent in a querie to the Imperial War Museum in GB, since the British back in the day modified practically every one of their many P-51B's (or Mustang Mk 3's as they called them), to have the Malcolm hood.  We'll see if they respond or have anything.  Hope they hurry - I am not waiting.

Edited April 17 by JayW

[Oldbaldguy]

Additionally, the driver is either a major or light colonel, the first row of fasteners below the canopy rail is not rivets but countersunk screws, and while the girl is wearing finger nail polish and what looks like a leather flight jacket, she appears to have mislaid her hair brush.

[Kaeone57]

9 hours ago, Oldbaldguy said:

Additionally, the driver is either a major or light colonel, the first row of fasteners below the canopy rail is not rivets but countersunk screws, and while the girl is wearing finger nail polish and what looks like a leather flight jacket, she appears to have mislaid her hair brush.

OBG -  Ii looks as if her hair is "gone with the wind"! LoL!

 

Gorgeous work Jay!!

 

Alfonso

Edited April 18 by Kaeone57

[JayW]

Getting back onto the subject at hand - the Malcolm Hood drive and emergency release mechanisms, I have finally got Rhino 3D representations of the parts (13 in all) that I will 3D print.  It was a bit of an integration nightmare, as alot of stuff gets crammed in between the flanges of the upper longerons.  And my longeron flanges are thicker than the real thing by a good bit (scaled of course).  Also my longerons are not quite as wide as the real thing, to account for my skin gages, which are also thicker than the real thing (scaled).  This all works against me shrinking the space to work with.  Neverthless here are some hard won details that I hope will look representative once painted and assembled (assuming they print up OK):

 

 

 

Yup - you are looking at a 3D printed chain (with sprockets).  I measure, from the pictures I have, a 1/2 inch pitch and about 1/2 inch wide.  Scale to 1/18, and the links are much smaller than I could scratch build (something I managed to do on the Corsair tail wheel door mechanism a while back - but the chain was a bit larger).  It is alot to ask of my printer - we shall see.  You also see other details that have had a whole lot of artistic license applied to them.  

 

Shortly I hope to show you the actual parts installed into the fuselage side panels.  Stay tuned!

 

 

 

 

Edited April 20 by JayW

[Jim Barry]

Oh boy, that’s an easier way to do the chain! Beautiful.  the rear wheel chain in the Corsair is legend, still. 

[Kaeone57]

Ok now, Mr Fancy pants!!! LoL 

 

Gorgeous work Bro!

 

Alfonso

[scvrobeson]

Wonderful 3D details. Here I was going to suggest one of those PE chain sets from a motorcycle kit, but your idea is much better

 

 

 

Matt 

[JayW]

It was quite a ride, but I have a Malcolm Hood mechanism to show you.  This is what I am trying to represent:

 

 

The chains, the emergency release pushrods, the sprocket support fittings, the crank handle, the emergency release handle, and the black cover plates.  Not the cross-tube.  That comes later.

 

First, just as what happened so many times back in the 1940's when -B's and -C's were getting their hoods, I had to relocate the recognition light switch box on the windshield frame.  From here:

 

 

 

To here:

 

 

Had to be done to clear the new crank handle.

 

All the parts printed up pretty well.  There is alot of small detail, especially the chain itself, so I went with the 30 micron thickness setting on the printer (I normally use 50 micron).   After careful removal of supports, and carefully painting, I got this collection of details:

 

 

 

And I had to be exceedingly careful at all stages of preparation - the long thin parts are so very fragile.  The black plates are not 3D printed - just old fashion scratch build with styrene sheet and Meng nuts.

 

Ok that was the easy part.  Installing these details into the airplane was the hard part - a most stressful and "stimulating" experience, trying to pry into a small space all these parts without breaking anything.  I broke one of the chains, but had a spare and used it.   Everything else worked out OK, sort of.  Pictures:

 

 

 

 

 

The 3D printed chains are a success, I am happy to announce.

 

Let's see the finished mechanism in the fuselage jig:

 

 

 

 

 

I need to do a better job painting up the rollers - I know.  But that comes later.  Glad to put this sub-project in the rear view mirror!

 

Next I believe is a bit of miscellaneous clean-up chores, and then the lower radio floor and the fuselage tank.  I've been waiting forever to get started on that.  Hope you like the chain drive!  Later.

Edited April 23 by JayW