Heavy Mod - 1/18 21st Century Toys P-47D Razorback

[Menelaos]

wow....

[JayW]

Let me provide you with a minor update.  First, main LG tire/wheel assemblies are done:

 

 

That's a big milestone for me, and it's a success.  Here is my customary shot showing old versus new:

 

 

 

It's certain the tire/wheels combo's needed improvement....        I applied some weathering in the form of water paint.  Think I'll apply some more.

 

Meanwhile, the design of my lower struts are very linked with the design of the brake drums and outer rims.  And the lower struts are complicated.  In order to not have to resurrect all that work, I thought I would go ahead and do the lower struts now instead of later.  Then, back to the fuselage.

 

The lower struts have about a 3 degree kink to them resulting in a bow-legged stance to the LG (87 degrees, or 93 degrees if you will).  Most lower struts are straight up 90 degrees; not the Thunderbolt:

 

, 

 

So I have to capture that for sure.  I would cut these pieces out of .25 thick plastic stock.  Here are the scribe marks for both the LH and RH parts:

 

 

From there it was off to the drill press to drill holes for the oleo tubes and the axles.  Then dremmeling and filing away at the outlines.  And I get this:

 

 

Bonding in the oleo tubes and axles I get this:

 

 

Note the non-perpendicular relationship of the oleos and axles.  The tubes are .125 inch diameter alum.  Those are not final diameters - the axles will be .156 inch diameter, and the oleo tubes will be .218 inch diameter.  I will just slide tubes over tubes.  Final diameter holes in the struts would be nearly as large as the thickness of the struts, resulting in very weak struts.  So I used the smaller diameter material.

 

So far, so good.  Stay tuned, next post will be completed lower struts.

Edited March 25, 2018 by JayW

[brahman104]

Oh man Jay,

 

Those wheels have come out perfectly! Good on you for having another go, the results were clearly worth the effort! Every little improvement you're making on this is an engineering marvel in its own right.

 

Looks like you're off to a flying start on the landing gear legs.

 

Craig

[speedgraflex]

Jay,

 

I am following along quietly for a little while now. Your work is really impressive, and inspiring, and kind of... challenging... in a very good way. Thank you for being so persistent and patient with your approach. I am really glad you are here doing what you do.

 

Warm Regards,

 

Bruce

[Thunnus]

Thank you for taking the time to explain the process.  Your scratch-building, especially the metal work, is way beyond me but it is definitely inspirational to follow.  Knocking back the shine of the tires with some flat might give it some wear.

[JayW]

OK - the subject is lower landing gear struts.  Last post I had dremmeled and filed them into rough shapes.  Now was to file and sand them round, into final shape,slip on and bond the final diameter oleo and axle tubes, and add the various bosses and lugs for the torque links and door attachment.  No machine work - just plane old fashioned hand work.  Also, the lower brake line needed to be created.  Here you go:

 

 

 

Several things to note:  The wheel mounting plate is made from .010 thick plastic, with Meng nuts added.  It's a little flimsy, although to scale it is about the right thickness.  If I could do it over again, I would make it .015 instead of .010, and decrease the width of the lower strut locally to suit.  Man - am I getting picky?  Note also I have bonded the brake drum to the mounting plate.  That allowed me to mount a rigid brake line between the brake drum brake line fitting and a clamp-bracket on the strut leg.  Truth be told - these details will be nearly if not entirely unseen, because they will be between the tire and the door.  But also note on the other side of the bracket is the black flex hose that will attach to the lower torque link later on.  That line is definitely going to be visible.  The two big clunky looking bosses at the axle are the lower mounting surfaces for the lower LG door.  The forked looking plate on top of the strut is also a mounting point for the door. 

 

I made a minor mistake a while back on the left hand wheel in that I bonded the brake drum to the wheel.  There is supposed to be rotation between the brake drum housing and the wheel, and lack of same between the brake drum housing and the strut.  That will not be the case for the left hand wheel, but will be the case for the right hand wheel.  That error prevents me from running that rigid brake line to the brake drum, as I was able to do on the right hand wheel.  But, like I said, the details will be practically invisible, so no fuss, no muss.

 

Here - I think this is kinda cool - the back of the wheel where the brake drum is inserted:

 

     

 

By the way - The lugs you see there at the top of the strut are for the torque link (the solid one), and also for the "shrink link" (the crooked clevis one).  Shrink link you ask?   The P-47 main gear, with oleos fully extended, and when retracted into the wing, do not fit in the space provided in the wing and lower fuselage.  Why?  As I understand it, The large propeller sizes the length of the landing gear, to provide adequate ground clearance during take-off.   Also, given the wing airfoil selected and its thickness and taper ratio, the four machine guns are mounted as far outboard as they can without requiring blisters or other deviations from contour.  The landing gear attach points are as close to the MG's as they can be and still integrate properly.  But there just isn't enough wing span to fit the long LG in the wing (with oleo's extended) given those constraints.  So, there is a fixed length rod that attaches to the lower strut and the wing, which kinematically forces the LG to compress as it retracts into the wing.  And that provides enough clearance for the gear to fit in the wing when retracted.  Here is the landing gear installation drawing with a view showing the shrink link:    

 

 

It's going to be quite a while until the shrink link shows up on this model, but the lower link attach lugs are ready and waiting for it.

 

Here is a picture showing what the lower strut looks like with the wheel:

 

 

The lower LG door will cover very much of this, but not all.

 

Lastly for this post, an end view showing the 3-degree cant of the oleo:

 

 

I am not sure what I will do next.  Should be the fuselage as I have been promising.  But I really want to try to make the lower LG doors and perhaps the torque links.  It will be an arbitrary decision!  Stay tuned.

Edited March 31, 2018 by JayW

[Guest]

!!!!!!WOW!!!!!!. Just amazing........Harv

[TorbenD]

Very clever stuff - love it!

 

Torben

[Gazzas]

Those struts look way too good!

 

Gaz

[JayW]

Hey out there.  Still on the landing gear; I cannot seem to tear myself away from it.  What I think I want to do is keep going on them until it comes time to do the upper tube with it's attachment features to the gear bay structure and stop short of that.  That work needs to be integrated with the gear bay work which I am not ready to do yet.  Fuselage comes first.  But until then, more work can be done to the LG below that.

 

Here is a neat picture taken from the parts catalog:

 

 

In real life the P-47 LG looks like this:

 

 

And this:

 

 

That last one is actually from a P-47N, a later version with differences (like an eight-spoke wheel instead of a six-spoke wheel). 

 

The aim, of course, is to duplicate that stuff as accurately as possible in the desired scale.  That's what we do! 

 

The "link" between the lower strut and the upper cylinder are the torque links.  These little tuffies are just that - little, and tough:

 

 

After studying up on what they look like and their size and rough dimensions, I just cut them out of .10 thick plastic.  Pockets were done on the mini-lathe/end mill.  That's the hard part - unlike more expensive machine equipment I have no good way to closely control depth of cut.  I just turn a lever as you would on a drill press.  Anyway the rough parts look like that and they look better after fooling around with them for a few hours with sanding sticks, etc.

 

To fix the torque links to the gear struts, I had to make the lower fitting of the upper strut.  I have no shots of this very complicated detail; you see it instead on the completed item here:

 

 

I thought about machining the torque link attachment to the cylinder, but could not bring myself to do it.  Instead I layered it.  Middle layer was cut out of .10 thick plastic, and it has the attachment lug.  Upper and lower layers are lathe turned acrylic.  Also there is a spanner nut (very large in real life) that you see just under the lug.  That part is apparent in the real-life photos, and in the exploded view from the parts catalog.  You can also see the flexible hose for the brake line, which was quite difficult to get right (made from solder; wiring insulator would have worked better I think if I could find the right diameter).  Note the truncated lower fixed portion.  As I tried to explain in my last post, that is due to my erroneously attaching the brake housing to the wheel instead of the strut, on this wheel only.  I didn't make that mistake on the other, as you can see in the pictures below.  It is here also that I fixed the extension of the oleo - what you see is just a bit more extended than the normal full gross weight static extension as shown on the drawing. 

 

Some more shots of the completed lower landing gear:

 

 

 

 

Next I shall fabricate the lower gear doors which attach directly to the lower gear struts without any mechanism.  That will be fun!  Until then.... 

Edited April 10, 2018 by JayW

[Guest Maxim]

Man that's some really nice gear! Splendid workmanship.

[Gerhard]

MInd blown, superb work.

[brahman104]

Hi Jay,

 

Those scissor links are a seriously nice piece of machining work! I know what you mean about not being able to control depth of cut.... my stuff always seems to creep down even when I lock it in.

 

How did you manage to clean the styrene up so well and not have machining marks or "fuzz?" I though brass might have worked better for a piece like that but clearly you have proved me wrong!

 

Brilliant mate.

 

Craig

[JayW]

Thanks Craig - I didn't go with brass on the scissor links for three reasons.  One, all I have in brass is round rod, and my .10 thick plastic stock was so much more convenient.  Two, drilling the small (.025 inch) bolt holes in brass would have been problematic - the holes need to be very square and how many drill bits would I have broken...  And three - dremmeling and filing the part exterior profiles was much easier than cutting them with the end mill.

 

Getting past that, I would have loved to do them out of brass.  I could control the cut profile better.  Like you said - the "fuzz" on the cut made it difficult to know where the cut was relative to the part edges. 

Edited April 11, 2018 by JayW

[JayW]

The last project I committed to on the landing gear (for now) is the "wheel fork fairing".  That is the official name of the lower main landing gear door.  This component is fixed to the lower oleo strut, in three places (bottom, mid, and top).  It should look very familiar to you.  My 21CT model came to me missing the "wheel fork fairings", but I would have replaced them anyway.  I studied the drawing for a long time, and devised a way to make new doors, much as they were manufactured anyway:

 

 

You see a 4 x size layout, with the inner and outer skin panels already scribed onto .015 inch thick plastic sheet, and cut out.  So far so good.

 

I then added some frames and ribs:

 

 

Note there are two thicknesses with a tapered section in between.  That complicated things a bit, but that's the kind of things we do right?

 

Further along, with inner close-out skins.  Note the many many drill starts to simulate rivet heads. 

 

 

Actually on this side, the rivet heads should be protruding, but I don't know how one would do that.

 

Add lots of little knick-knacks like bulb seals, skin flange doublers, and a latch fitting, paint, home-made decals, weathering, and voila!  

 

 

 

The actual drawing is in the background.  I tell you - it is pretty gratifying to take a drawing like this, scale everything you want to make to 1/18 scale (or whatever scale you want), make it (the hard part of course), and it looks like a miniature of the real thing.  No guesswork required.  I recommend it highly!

 

Here is what the fairing will look like installed:

 

 

 

That's the LH fairing.  The RH fairing is in for paint, so will be done very soon.

 

Then it is time for the fuselage once again.  It has been almost a two month hiatus.  I will start with the back where the supercharger is:

 

 

You may be wondering why I cut off the tail.  Well - because there is so very much work to be done in the fuselage proper some of which complicates bonding the two halves together, and there is also much work in the empennage that will also complicate bonding the two halves together (like the tail gear), that I felt they were best done separately.  I did this with the Mustang years ago, and it was a good thing.  You can see the scratch built bulkhead laying there.  The empennage will get one two.

 

All right.  Next post you will see some fuselage work.  Enough scratch building for a while.   Take care, see y'all later.

Edited April 16, 2018 by JayW