Brilliant Mate !!.........Harv
Posted 29 December 2016 - 03:14 PM
- JayW likes this
There's a fine line between cuddling and holding someone down so they can't get away
working on: Tamiya F4U-2 Night Fighter
Trump P-38M BACK ON BENCH FINISHED!!!
Posted 29 December 2016 - 10:07 PM
Jeez man, I thought something happened to you. Don't disappear like that.
Anyway..Glad you're back! Looking forward to more of your wizardry and thoughtful methodologies...
Looking good already.
Happy New Year to you and yours.
- harvey, Shawn M and JayW like this
Posted 29 December 2016 - 10:17 PM
Thanks for those links. Just what I'm looking for. Have you used those guys?
- harvey likes this
Posted 30 December 2016 - 02:21 AM
Hi Geoff - long time no hear from! I just relinked to the P-51 SIG (you reminded me), and your P-51 re-skinning looks wonderful! Keep up the great work. Oh, and if you have not seen my 8-part article on P-38 Lucky Lady - google it and tell me what you think.
At the beginning of this thread I stated I would basically reserve judgment on the new engine, and fall back on the toy part if need be.
Now I am committed:
I sawed the engine away from its mount, and ground the firewall down flat to accept the new engine block. I did this for a good reason - I needed to assure myself the new engine would fit within the confines of the cowling, and the new engine block is designed to attach to a flat firewall. The cylinders are taller than I calculated mostly due to the glue thickness between the umpteen layers of plastic sheet they are made from. And I was not sure if it would fit. But it does! Success.
Also, I am pretty confident the new engine will be a success. So it's off to the races!
- harvey and Shaka HI like this
Posted 07 January 2017 - 04:10 AM
I have a new development to share with you. I scored a partially complete 21CT bubble top P-47 on E-bay for a price I could not resist:
This is from the E-bay pictures, the model has not yet arrived. It was my preference originally to do a bubble top in lieu of the razorback, but at the time only the razorback was available. Missing parts can be supplied by the razorback, as the molds are identical where it counts. The engine work, so far, is compatible with either one. The ignition system is what is different, which is visible mounted on the reduction gearbox in front of the cylinders. I have not started that yet. I am super pumped about this.
However, one problem looms large. One of the four prop blades is missing, and the model has a Curtis Electric paddlebladed prop, which is appropriate. The razorback has the older style symmetrical thin prop blades.
So I have to get a fourth prop blade. It seems I have two options - scratch build a TE extension on one of the razorback prop blades and try to get it to the same profile as the paddleblades, or mold a new paddleblade using one of the existing ones as a master. I am experienced in the former, but not the latter.
I will pay a visit to the local hobby shop in the next few days to see what kind of resin molding kits they might have or can order.
I am all ears on suggestions. Meanwhile the assembly line for the R-2800 cylinders is humming along. I hope to report out in the next couple of weeks.
- harvey, NavyF4s and TorbenD like this
Posted 14 January 2017 - 04:05 AM
I have a bit of an update. Recall that this new bubbletop P-47 is missing a prop blade. Here is a shot of the existing prop, minus the missing blade, and also minus another one that I would use as a master for a new resin blade:
This is just about the best prop I have ever seen on a 21CT toy. I believe the blades are quite accurate for a Curtis asymmetrical paddleblade prop, and beautifully done. The hub isn't as nice, but I will fix that. It's a shame the prop was damaged, but that is partly why I got the big jug on the cheap. So now I will take you through my adventures making a new blade.
I purchased an Alumilite resin kit from Hobby Lobby:
I have never molded anything before, so please indulge me as I describe my first experience. All I knew was that a guy from FineScaleModeler made a couple of tutorial u-tubes using this stuff, so I thought that would be good enough. Even with the 40% off coupon, this kit was not cheap. Resin work takes money.
First to do was to prepare the "master". I cut a blade off the prop, added some putty material to the root above the cuff (to assure full coverage by the resin), and mounted it on a short stalk and a base, so that it could stand in the middle of the mold container.
Second was to make the mold out of silicone rubber compound, included in the kit. To do this one must pour this stuff (prior to setting up of course) into some appropriately sized container. This mold container is a clear plastic container I happened to have that was about the right size. Here is a shot of the container, filled with two-part mold material poured over the master which is being held in the middle of the container, and in the process of curing:
It took many hours to completely cure, but it came out great.
This shot shows the mold removed from the plastic container (I split the container with an x-acto knife):
I also split the mold part way down in order to extract the master blade, which is lying on the table. To make the mold ready to accept a resin pour, I used several rubber bands to close up the split.
This shot shows the (messy) resin pour.
If it looks like it leaked out the bottom, it did - through the hole provided by the mounting stalk. And that was on purpose because it assured no bubbles at the tip. The resin is two part, 50-50 proportions. Its work time before it starts to set is only a couple of minutes. So I had to mix thoroughly and quickly, and pour quickly. Cure time is less than an hour (so I thought). Despite the instruction's recommendation to preheat the mold, I ignored that, and that was a mistake.
Here is the first attempt resin casting, fresh out of the mold about an hour after the pour:
This part is a failure. The thin edges of the blade never did cure properly, MOF the entire part never got really hard, was sticky over most of its surface, and seemed too flexy. The thin edges never survived pulling the part out of the mold. It is possible I didn't mix the two parts of the resin thoroughly enough. But I suspected I needed to preheat the mold. Also, some web research told me that thin sections do not cure as quickly as thick sections for reasons not very clear to me.
At any rate, my second attempt involved a mold preheated to about 140 deg, and a much longer wait before demolding the part. The result was far better:
I can work with this. A little putty here and there, and it will be perfect. Hip hip hooray! BTW - that is one expensive part! But I feel a whole lot better about this project.
Meanwhile, here is the cowling of this beast:
The paint job is stunning, although a little messy in places. I am going to try to use it rather than a complete new paint job. If it doesn't work, then a new paint job..... Skull and crossbones - very cool. This paint job has special significance for me - it is a P-47 from the 354th FG, 353rd squadron, 9th AF. That is the squadron my late uncle was in, and this airplane is the personal mount of his CO Glenn Eagleston. Some of you may know that the 354th was the "Pioneer Mustang" group in Europe. But there was a short time where they flew the P-47, in support of the invasion. So I would love to use it.
While taking a break from the prop work and the very grueling engine work, I proceeded to behead the beast:
Why? Two reasons. One, it will receive new cowling outlet flaps, in a partly open position, and two, I intend to add the preheater bulkhead just aft of the flaps, because you will be able to see it with flaps open. Relax - it will look great.
Now it's back to work on R-2800 cylinders. It is possible I can resin cast them or parts of them. But I am not real confident. Maybe the back row..... I will report on all that next post. Take care.
I would like to thank Jerry Rutman for giving me some great pointers on resin molds. He should know, right?
Edited by JayW, 14 January 2017 - 04:12 AM.
- harvey likes this
Posted 14 January 2017 - 11:51 PM
Another winner coming along here Jay! Congratulations on entering the dark world of resin casting, where there's no assurances of anything, but you look like you had a win on the second one
Love your engine work too, looking forward to seeing more of that
- harvey and JayW like this
Posted 20 January 2017 - 05:51 PM
I purchased a book called "R-2800 Pratt & Whitney's Dependable Masterpiece", a 700-page tome that is apparently the definitive authority on all things R-2800. I have learned much. That, plus P-47 drawings and various manuals from the wonderful website "aircorpslibrary.com", have affected how I want this engine to look. You should visit that site - for a small sum you are provided with access to engineering drawings, and all sorts of manuals for many WW2 fighters and bombers. Anyway my engine will be authentic for a P-47D-30, equipped with the Curtiss Electric asymmetrical prop and the GE ignition system with "turtleback" distributor/magnetos. That's all important because it greatly affects all the (very visible) equipment that hangs off the big reduction gearbox housing on the nose of the engine.
Recall I made a "prototype" cylinder a while back, and thought i might just use it as is:
Well for various reasons I will not use it. Instead, I will improve the look and detail of the rocker arm covers, and double the quantity of the cooling fins on the lower half of the cylinder barrel, while halving their thickness. It is tough to see in the picture above, but the R-2800 (and alot of other radials) is actually this way - with thinner more closely spaced cooling fins on the lower part of each cylinder, and thicker fins on the upper portion and the cylinder head.
So I have been at work creating the "production" cylinders and it is tedious work indeed. My plan is to build maybe six of them and see if I can resin cast the rest (two pourings of six each makes 18 total including the originals). I don't think the mold could handle much more than two pourings because the cooling fins and gaps between are pretty tough on the mold. Here are three of them:
What you see are the three new cylinder barrels on the left , where I used liquid glue between layers. I used .005 inch thick sheet for the lower portion, and .010 plastic sheet for the upper portion. Just to the right is another barrel, only glued with regular cement from a squeeze tube. It came out several hundredths of an inch taller - no good. Call it another "prototype". Each barrel takes a half day to make, under powerful magnification, so it is indeed tedious work. And then on the right are the original prototype for comparison, and a resin mold I made of it just to see if I could (it's not too bad).
Here, you see the cylinder head assembly line:
All 18 cylinder heads are shown, and they are not very far along, obviously. You also see various flat patterns scribed into plastic sheet for the cooling fins and spacers between them. The round ones are for the cylinder barrel, the oblong ones for the cylinder head. One of y'all said I was crazy to do this, and you were right. Much work remains. But the result is going to knock your socks off - guaranteed.
But wait! I have been up to other things too. Here is the most welcome resin-cast fourth prop blade resplendent with a coat of primer:
Its three companions were summarily lopped off the prop hub, and will be re-attached in very realistic fashion. Also, I chopped off the bullet fairing that covers the pitch transmission (it desperately needed a thin flange underneath it that is there on the real thing):
So what is that bushing shaped lathe turning? Well, the Curtis props had a housing just aft of the prop hub and forward of the engine reduction housing, where an electrical brush assembly is mounted, with a wire bundle that goes from it to an electrical box in the cowling. It is associated with the prop governor, and possibly the prop pitch unit on the hub. I have not seen this feature on existing P-47 models (but haven't looked very hard). The Hamilton Standard prop has no such animal, as it is hydraulically actuated (not electrically). Note also the aluminum tube I added to the prop shaft. This obviously is to help the prop sit true on the airplane and be turned and spun to my whims.
And that's not all. My trusty mini-lathe came in handy for producing the reduction transmission housing. Here it is still in the process of being machined:
This was not a very difficult turning. What will be difficult is adding on the various mounting bosses for the distributors, governor, and sump drain, and the unused mounting plane for the magneto (it gets a "blanking" plate). That involves machining holes and slots into that pretty housing. You will see that dangerous work soon (dangerous in that I could ruin the turned part).
Put them together and it looks like this:
OK all for now. You may have noticed that I am not concentrating solely on the engine cylinders like I should. That is because one can go insane doing all that tedious work and so little immediate satisfaction. So I am eating that elephant one bite at a time. And it will take time. Stay tuned.
Edited by JayW, 20 January 2017 - 10:56 PM.
- harvey, Out2gtcha, Shawn M and 1 other like this
Posted 20 January 2017 - 06:59 PM
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