Hi Paul and everybody
 Merry Christmas

 I finally dusted of the old VCR tapes and downloaded them onto my computer to make DVD's
 and have up loaded some parts to YouTube
 First Starts and First Flights ect.
 http://www.youtube.com/watch?v=I4Zm7zRU3vs
 http://www.youtube.com/watch?v=loEZcospzi8&feature=related
 http://www.youtube.com/watch?v=YpXFRisteek&feature=channel
 http://www.youtube.com/watch?v=cbxxTLtJZGM&feature=channel


 Mark Kirkpatrick

 MSK6 20B

 Great work Mark. OK everybody give him five stars.
 I am curious. How fast was the 13B? How fast was the 20B?
 Any cooling problems? The muffler seems to be working well.

 Paul Lamar

 I never got the speed or ROC out of the plane with the 13B I had hoped for, but I also
 never got around to cleaning up the airframe, nose wheel pant and intersection fairings or
 a paint job. I'm also not sure just how efficient the Ivo prop is because of the way the
 blade is twisted. With the 13B the cruise was 160 mph. I haven't gotten a good comparison
 with the 20B. The first time I fire walled it was 5 hours into the test flight period and
 that was when the re-drive broke, but the airspeed was flying passed the 160 mph mark.
 That was three years ago about the same time the shop I worked at for 28 years shut down.
 A lack of funds has slowed progress on getting the plane back in the air. I was quite
 happy with the cooling on the 20B. All the test flying was done is August with and air
 temp of 100 deg. plus, the worst I saw on the oil temp was 210 in a long climb and water
 temps around the same. In cruse they would run 180's. The plane is still uncomfortably
 loud. You have to fly with noise canceling headsets. The exhaust system consists of 3
 1-3/4 headers tube 21 long into a collector and then a 2 ¼ tube running to a Flowmaster
 muffler mounted under the co-pilots feet. I was thinking of trying a fish mouth exit on
 the back of the muffler to see if that helped.


 Mark Kirkpatrick

 MSK6 20B


 The 13B dynamic chamber was overrated for aircraft use. I tried to tell them but they did
 not understand it :)

 What broke on the Ross PSRU?

 The fish mouth will help but beef it up. Keep a close eye on the inside of the muffler
 with a Harbor Freight bore scope as something could melt in there and plug up the exit.
 It has happened. Best to use mufflers with nothing inside them. One of the tricks is to
 use a fairly large can with a air blast tube down the center to keep it cool.

 Paul Lamar

Paul, the conclusion I came to on the broken drive was I had put a bearing on the bell housing side of the drive just in front of the seal to center the shaft, but the hole that held the seal that I used to index the bearing on was about .030" off center. So I believe it was only driving one or two of the plant gears. See pic.


I like the idea of getting the muffler out from under the cowl. If you were going to build one that mounted in the same place, and were looking for noise reduction more then performance (I think I have plenty of power) what would you build? Also when I built the headers I was trying to tune the exhaust, how important is that on the three rotor? Would it make any difference in the noise level if done differently?



Mark Kirkpatrick

MSK6 20B

The best idea I can come up with for something under the airplane is a
coaxial type muffler. I'll do a quick 3D here. The outer shell is open
on both ends. The prop blast and the forward motion of the aircraft
will cause cooling air to flow through the muffler.

There is just enough sheet steel spacers to keep the outer shell
in alignment with the inner tube. Something like a 2.5 inch OD inner tube
with a 5 inch OD outer tube. 304 SS .035 thick outer tube and 304 SS .049
thick inner tube. Lots of 1/2 inch holes in the inner tube. The end
of the inner tube can be blocked or not blocked. Try it both ways.

Make it about 3 feet long.

I don't think tuning the exhaust will make much difference as far
as noise is concerned. The optimum length is around 32 inches
or more depending on your gear box ratio.

Paul Lamar