[NSRCA-discussion] Hatori Short Pipe O-Rings

[Troy A. Newman]

Jim,

the NMP replacement viton o-ring is sized to accept the NMP header NOT the Hatori header. The Hatori is 15mm and the NMP is 5/8" the difference between the or-rings is about 3.5-4 thousands on the ID. This will be enough to cause it to leak.

If you are using the Hatori header you need to replace the o-ring with the Hatori original o-rings. And yes 50-75 flights is normal replacement time frame. The Hatori original replacements are available from Central Hobbies.

Proper cooling on your engine and exhaust system will extend the life of the o-ring, improper cooling and abuse will eat the o-ring in as little as 5-10 flights.

The NMP o-ring replacement for the NMP header is a much more robust material than the Hatori Original. The Viton material on the NMP will tend to last quite a bit longer than the Hatori originals.  I have models using both the NMP header with the replacement o-ring to fit that header and the Hatori header-and o-ring versions. I can get about 50% better life out of the NMP header/NMP o-ring version. I think it has to do with the cooling properties of the NMP header. 

I have been running the replacement o-rings for several years.

Troy Newman



  ----- Original Message ----- 
  From: Woodward, Jim 
  To: NSRCA Mailing List 
  Sent: Tuesday, December 11, 2007 11:49 AM
  Subject: [NSRCA-discussion] Hatori Short Pipe O-Rings


  Hi Guys,



  What is the final verdict on these O-rings?  Will a warm run "melt" the O-ring?  Does the viton replacement fit tight enough over the header?  Recently my plane is getting really messy, where as before there wasn't a drop of burnt fuel ahead of the exhaust stinger.  I replaced the o-ring but still had the mess.  I pull the motor last night and checked out everything and the motor looks great, bolts were tight, with no indication of any leakage from the motor or header to motor/flange attachment.  



  I am using the Nishioka spring clamp mount.  All things considered and experienced, I think I prefer the stock Hatori mount that comes with the pipe.  The Nishioka seems to allow for more fore and aft pipe slippage during running due to the thin vertical white plastic supports (checked while running the plane upside down to try and determine spray pattern and such -  in which I didn't find one, which leads me to believe that it starts to happen maybe later in the flight or heat cycle, versus the small amount of running I did as a cursory check.



  Thanks,

  Jim




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