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Very Hot Topic (More than 25 Replies) Pratt & Whitney "Wasp" R-1340 (Read 3391 times)
Craig 3
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Re: Pratt & Whitney "Wasp" R-1340
Reply #26 - Apr 17th, 2018 at 3:18pm
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It's a pretty time-consuming way to build an engine (I've assembled race car engines about as quickly!) but hey, it's all about the instant gratification, right? One glue joint at a time Smiley

It's a pretty easy way to get a fairly realistic looking engine with stuff laying on the back of the building table, really. For instance, the spark pugs are 1/32" slices of 1/16" aluminum tubing, sliced with a piece of wire stuck in it to catch them, shoved over the end of a round wooden toothpick, then dipped up to the ring in white paint & sliced off after they dry. Make sure to have a backstop to catch 'em!
  
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Re: Pratt & Whitney "Wasp" R-1340
Reply #25 - Apr 17th, 2018 at 6:17am
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An amazingly great result and an effort I will need to replicate, hopefully as well as you did for my Marcoux Bromberg. Well done and will be a great addition to your model.
Mike
  

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bigrip74
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Re: Pratt & Whitney "Wasp" R-1340
Reply #24 - Apr 16th, 2018 at 10:24am
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Craig, ive never spent this much time on a radial, but you are making step up my game now Wink

Bob
  

IF IT AINT BROKE DONT FIX IT!
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Spliffsecond
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Re: Pratt & Whitney "Wasp" R-1340
Reply #23 - Apr 15th, 2018 at 10:01am
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Incredible scratch building.
Looks like a real one
Grt free
  
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Craig 3
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Re: Pratt & Whitney "Wasp" R-1340
Reply #22 - Apr 15th, 2018 at 8:43am
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Time to start adding some detail...
  

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Craig 3
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Re: Pratt & Whitney "Wasp" R-1340
Reply #21 - Apr 14th, 2018 at 2:38pm
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I gotta admit, these took a few minutrs...
  

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bigrip74
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Re: Pratt & Whitney "Wasp" R-1340
Reply #20 - Apr 14th, 2018 at 12:27pm
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Craig, thanks for the photos of how you assembled the radial and I would have never thought of using folder material. Now I am thinking of all the uses it would be good for.

Bob
  

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Craig 3
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Re: Pratt & Whitney "Wasp" R-1340
Reply #19 - Apr 12th, 2018 at 7:54pm
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Using Tom’s “slow and steady” method of cutting the discs with the Olfa leaves a very small hole in the center- a bit smaller than the common straight pin on this lovely building jig. This makes for a snug fit, so as the stack is getting glued up each cylinder disc needs to be pushed home- I use a deep-well 1/4” socket. This makes the setup self-clamping and self-centering.

Since everything is built on the pin, the holes in the upper and lower cylinders can be mated for alignment. Just pull the pin before it sets up too good :)
  

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Craig 3
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Re: Pratt & Whitney "Wasp" R-1340
Reply #18 - Apr 12th, 2018 at 7:31pm
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Came home from the shop this evening and cut & assembled the upper cylinders. Each consists of 7 “fin plates” and 8 “cylinder discs”- the fins cut from manila folder and the discs cut from Guillows box. There are three different fin plates graduated in size, with the the stack comprising disc, small fin, disc, intermediate fin, discs and three large fins with notches for the spark plug boss (cut back to be flush with the cylinder discs), then tapering back down, finishing with a cylinder disc. Next up, the rocker boxes and covers.
  

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Craig 3
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Re: Pratt & Whitney "Wasp" R-1340
Reply #17 - Apr 11th, 2018 at 6:27pm
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Prototype #2. This is pretty close to what I’m shooting for.  It’s rough-hewn and stuck together with gluestick, and has toothpicks standing in for pushrod tubes, so use your imagination!  I’ll blow it apart now and make patterns for the assembly line. It does fit the plan- assuming a cowling of scale thickness. As I figured, the rocker arm covers may just be on long enough for a photo-shoot.
  

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Craig 3
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Re: Pratt & Whitney "Wasp" R-1340
Reply #16 - Apr 11th, 2018 at 7:05am
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The sad thing is, I’ll probably have to slice the rocker covers off in order to get the speed ring around it- unless I hammer said ring out of aluminum. Those engines were pretty well shrink wrapped. I think everything up to the upper end of the pushrod will fit under balsa. Oh, well/ the rocker arm covers are the easy part.
  
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Re: Pratt & Whitney "Wasp" R-1340
Reply #15 - Apr 11th, 2018 at 6:22am
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Mock you? Not a chance, I applaud you for your effort. My firm belief is that success is built on the shoulders of failure. I'm scratching the covering over the gray matter to try to remember where I saw a similar project doing this same thing but remember they made a long piece of the rocker assembly and then sliced off what was needed for each cylinder. I'm on the hunt now.
Mike
  

"Skill comes by the constant repetition of familiar feats rather than by a few overbold attempts for which the performer is yet poorly prepared." Wilbur Wright
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Craig 3
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Re: Pratt & Whitney "Wasp" R-1340
Reply #14 - Apr 10th, 2018 at 7:48pm
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I'm liking the new improved cylinders better. I'm trying to figure out the head & rocker boxes. I didn't realize how asymmetrical these things were until I started this- there's a lot more going on on the exhaust side as far as fins go, so I started there. Don't mock me-yet. This is just a hands-on thought experiment at this point Smiley
  

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Re: Pratt & Whitney "Wasp" R-1340
Reply #13 - Apr 9th, 2018 at 10:27pm
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Hint for the Olfa circle cutter and balsa... I start a whole in the center and then put a couple drops of thin Cya glue to harden the hole.  When it's dry I then cut the circle.  Helps the center hole from elongating.  Another trick is to not use pressure on the blade while cutting, but just spin the handle between your fingers making  lots of passes around the circle.  Takes a bit longer but turns out more concentric circles and sharper edges, especially through the grain.
tom
  

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Craig 3
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Re: Pratt & Whitney "Wasp" R-1340
Reply #12 - Apr 9th, 2018 at 8:08pm
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Tom, I've used a card as a flexible straightedge, but the masking tape stop is brilliant. I've overshot or dropped off a corner more than once!
  
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