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New CARF P-51D Project

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Old 10-03-2017, 08:15 AM
  #101
bentwings
 
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Scale exhaust

ive made a number of scale exhaust systems for my Ziroli Corsair, P 51 and the 118" B 25.
ive used Stainless steel, 4130 steel tubing, copper tube fittings and totally fabricated from sheet Stainlees steel. All are relatively time consuming to build.

I like your P 51 system and the heat wrap. It sounds really cool.

With the two cylinder system as you have even though yours runs very well, I found that the multi engine (twin like yours) needed equal length pipes for each cylinder. Not really as " tuned pipes" but to provide equal exhaust flow for each motor/cylinder. It was quite pronounced on the big bomber. Even though I had to add a full 180 deg turn to equalize the length on the short side it improved performance of that motor so we could balance the speeds.

While yours seems to run very well it may help equalize temps on both cylinders to balance the pipe lengths. Just a thought.

The single cylinder P 51 had a 5.8 cu in 2 stroke motor. On this one I split the manifold at the exhaust port into two ports then and made two individual equal length pipes to the exit manifolds. This worked pretty well but we felt that it was a bit too heavy as we had to insulate both pipes as you did. It's very difficult to get tight bends in SS or steel so I made a single pipe to a smooth flowing " Y " and fabricated SS manifolds. This was all done with .028" sheet SS. I do TIG welding on hotrod stuff as well as for work but even so it was really difficult to weld this as it had to be back purged to make good welds. This system worked very well and was much lighter even with the heat wrap.

The Corsair was much easier as it needed considerable balance weight in the nose so weight wasn't an issue. I simply used copper tube fittings and for the " Y " pipe I sectioned a pair of elbows and welded them together. This gave a smooth and equal flow to both pipes. I never did add the smaller pipes as the radial has but that was the next step. This plane flew for 13 years without exhaust problems.

byron
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Old 10-04-2017, 12:38 PM
  #102
Chris Nicastro
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I've been thinking of a design for a three into one header that's pretty basic. From each head up to a common larger tube then a flexible connection out to each side of the nose. Scale pipes optional but at least two working, one per side.
Like car manufacturers it would be great to tune the sound to get as much bass and rumble possible.
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Old 10-04-2017, 01:20 PM
  #103
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That would be ok too. The hard part is getting flex tubing that fits the header close enough for a good weld. TIG welding flex tubing is very difficult as it is usually really thin. .015-.. 020". Fit has to be nearly ..0 It takes a very small electrode and .020 -.035 SS wire. It can be silicone bronze welded....TIG braised but even that is very tricky.
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Old 10-07-2017, 07:53 AM
  #104
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@Flypilot
How much vibration did you experience when running your engine?
Are you planning to use the supplied dampening mounts?
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Old 10-07-2017, 02:56 PM
  #105
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We tried the dampening mounts but the motor simply moved around too much. It worked best to just solid mount it. I made aluminum replacements for the urathane soft mounts. I still used a slip joint in the headers however.

we also tried them on the B 25 but there was just too much moving around. So we solid mounted the motors. They actually ran smoother however I think there was just a different sound. The rpm remained the same.

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Old 10-08-2017, 02:37 PM
  #106
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Quote:
Originally Posted by Chris Nicastro View Post
@Flypilot
How much vibration did you experience when running your engine?
Are you planning to use the supplied dampening mounts?
There is some vibration but not excessive I would say. I will hardmount it directly to the fuse in my plane..

I also found the engine to be very easy to start so I will not be using the starter, that way I will save about 1.5kg on the flying weight...maybe add it later when I get to know the plane..

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