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1/18 P51C Mustang "Lopes Hope the 3rd"

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Damn, that is some nice stuff right there!

 

Peter, for them oleo's you may want to try this site for those shiny parts. Pure Stainless steel at it's best and sizes to do most everything.

 

https://www.mcmaster.com/hypodermic-tubing

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This just gets better and better. As other have said previously it’s a often a struggle to determine what’s real and what’s model. 
 

Will this beauty be coming to Telford for you to show her off in all her current glory?

 

Looking forward to catching up as always next week. 
 

Tom

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thanks chaps :)

 

5 hours ago, tomprobert said:

Will this beauty be coming to Telford for you to show her off in all her current glory?

 

Looking forward to catching up as always next week. 
 

Tom

 

 

Hi Tom - no, it is too near completion really, so I am going to save it for next year when it is finished...

 

this one will be though :)

 

18_zps1zjktzt3.jpg

 

Looking forward to a good natter at the weekend :)

 

Peter

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Peter - your efforts on the MLG have yielded another shrink ray component(s).  Honestly - I have seen so very many efforts by so many model manufacturers in 1/72, 1/48, 1/32, or 1/24 to represent the P-51 MLG struts, and nearly all fail to get the shape just right.  Tamiya 1/32 seems the best.  When I did my struts on Miss Velma in 1/18,  I scribed the shape on blocks of plastic stock straight from the drawing (and I was thrilled to discover those drawings).  So there was literally no guess work - all I had to do was accurately carve it out based on the scribe lines.  But you have somehow arrived at what looks to be a dead-on accurate shape using formed metal parts brazed together.  Amazing.  I am also extremely impressed with the torque links.  Those are very small parts even at 1/18 - I struggled with mine and didn't do a very good job.  However even mine are way better than what one will find in a mass manufactured kit.  Yours look wonderful.  You will find the torque links lurk in the shadow of the wings and are not easily seen - but we know they are there, don't we?  

 

Also I am blown away by the wheel/tire assemblies.  Those parts seem tailor made for 3d printing, and that is apparently the key.  Congratulations.

 

Now - in addition to the all important gear rake angle which we have discussed already, and which seems right to me based on your pictures, the relationship between the gear struts and the doors, IMO, is critical.  Here again - most of the manufacturers get it wrong.  It's a matter of length mostly.  The problem, if there is one, usually arises when the wing thickness is inaccurate.  This was an issue with both my 1/18 P-47 and my 1/18 P-51, and I had to take care to tweak the gear door length as required so that the lower edge of the door had the correct relationship with the wheel/tire. 

 

Of course, strut extension affects this relationship.  Drawing 102-33001 defines three gear extension values - 44.727 inch fully compressed, 46.227 inch "static", and 52.727 inch fully extended.  If one (correctly) assumes fully compressed has the lower and upper struts slammed down against one another, then fully extended exposes 8.0 inches of lower strut.  And "static" position exposes 1.5 inches of lower strut.  In 1/18 that is .44 inch and .08 inch.  For Miss Velma I exposed about .18 to .20 inch, to depict an aircraft at something less than full gross weight.  Wartime pics of P-51's show many aircraft with something like that extension.    Your extension appears similar.  Is it?

 

Oh BTW - the lower extremity of the brake line attaches to a fitting on the brake drum.  Lots of pics available.  I am not sure it is defined on drawings though. 

Edited by JayW

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Peter - check the two little lugs on the upper strut which are the attach points for the gear door links.  They need to be 180 deg around (on the inboard side of the strut, not the outboard).

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17 hours ago, JayW said:

Peter - check the two little lugs on the upper strut which are the attach points for the gear door links.  They need to be 180 deg around (on the inboard side of the strut, not the outboard).

 

 

Hi Jay - thanks for all that info - I did actually spot those door mount lugs were the wrong side when I was offering up the door to get the door / wheel relationship right, which as you say is critical for the sit of the model..

 

they have been reversed now - though close up some of the welding I tried to imitate looks a bit rough!

 

WIP1069_zpsqfroa6r8.jpg

 

the spigots in the wing that the gear plugs into are pretty solid and were done a looooong time ago so with a tight fit into holes in the gear legs they pretty much define how the model sits and would be hard to change - I think in length they are ok - the compression strut showing is 5.89mm and 0.2 inches os 5.09mm so its ballpark - the forward rake is perhaps a degree or two off, but I took this pic & transposed it onto side pics of real 'C's' and everything looks to be right enough - I can pull a degree or two of rake back when I cement them..

 

WIP1068_zpssop1yyzd.jpg

 

thanks for the brake info too - I have the bit that line goes into as part of the wheel hub, not the leg hub so will have to wait until the wheels are on to connect it..

 

its so good to have an expert with an encyclopedic knowledge of the drawings on my wing :)

 

Peter

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Well done.  As a reminder main gear strut rake angle from vertical is supposed to be 11 deg.  From the picture above (a stunning picture BTW - another one that looks like an actual aircraft), I measure 13 deg to that piece of thread, so if I measure right and the pic isn't distorted and the thread is indeed horizontal, then yeah - when gear are permanently installed, pull back on them a bit.  As for door length - do enough arithmetic with dimensions provided on the drawings, and you can figure out the real life relationship between the door lower edge and the wheel hub in any one of the three defined extensions.  From there, easy to define the relationship to your own extension (which is a good bit more than "static").     

Edited by JayW

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Sorry Peter - I have to make a correction.  Further inspection of drawing 73-33102 (LG strut assembly) show that under full compression, there is 1 29/32 inch of exposed compression strut oleo (not slammed down as I previously said).  If you want to see this dimension, see zone A4.  

 

"... I think in length they are ok - the compression strut showing is 5.89mm and 0.2 inches os 5.09mm so its ballpark."  you say.

 

So if "static" extension is 1.5 inches from fully compressed, then static extension has 1.5 + 1.906 = 3.406 inches exposed oleo.  Or in 1/18 scale - .189 inch.  That equates to .189/.039 = 4.85 mm.  That puts your 5.89 mm much closer to static.  

 

 

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I might be hurting rather than helping.  I closely studied drawing 91-33106 Support Assembly - Landing Gear Pivot.  That drawing puts the gear pivot point (intersection of gear pivot axis and centerline of gear oleo) at Wing Sta 69.346, dist above wing ref plane 0.9325 inch, dist forward of wing 1/4 chord 13.3125 inch.  That drawing also shows local wing contour ordinates where I was able to determine (with the above ordinates) that the lower wing loft at the point where the gear strut protrudes is about 4.25 inches below the gear pivot point.   Account for the 11 deg rake angle and you get 4.25 / (cos 11 deg) = 4.33 inches.  From here, I can take drawing dimensions of the gear strut to arrive at the proper gear strut protrusion from the lower wing skin:

 

Kl3i7l6l.jpg

 

Miss Velma has 1.07 inch protrusion of the upper strut to the lower wing skin (very close).  Peter - I suggest you check Lopes Hope for gear upper strut protrusion relative to the lower wing skin.  Should be 1.08 inch per above.  If it is close, and if your gear door is an exact scale-down from the drawing (73-33302), then you can be assured the relationship between the gear strut and the door will be right.  If not, then you will need to make some adjustment to the gear door length or strut length.  

 

Also note the 2.625 inch dimension above (from upper strut lower edge to door lug centerline).  Scaled down to 1/18 and that is .146 inch.  Check your door lug locations to that dimension.  That way, assuming you have an accurate gear door,  you can assure the orientation of the door links is right.  So many Mustang efforts get this wrong. 

 

I will shut up now.   

Edited by JayW

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7 hours ago, JayW said:

assuming you have an accurate gear door,

 

Peter has an accurate gear door. If there is any discrepancy, it will be the full size version that is wrong.

 

Stunning stuff and I am enjoying all the details being swapped between experts.

 

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