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Engine basics => Engine set up tips => Topic started by: Ken Culbertson on February 09, 2018, 01:43:52 PM
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I have been talked out of using my OS 46 in an ARF Nobler by those here of vast knowledge and experience. So help me with my current delema. My trusty OS 35 is an older model that used the bolt on muffler that bolts on from inside the muffler instead of through the side mounts like the newer OS mufflers. It does not have a uniflow fitting. What I want to know is can a muffler like this be fitted for muffler pressure and if so does it matter where it goes since the muffler does not have a baffle. Those of you using the Max 35 in the late 70's will know what I am talking about.
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Hi Ken
You can tap and install a pressure fitting near the middle of the chamber, do not tap it on the exhaust stack, I would however caution you to not use muffler pressure unless you are forced to, Pressure makes everything more critical, delays the beak making the motor "dumb" and fills the fuel tank with a huge amount of air bubbles, carbon, sand dirt or anything else that can get into the tubing
Randy
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I have been talked out of using my OS 46 in an ARF Nobler by those here of vast knowledge and experience. So help me with my current delema. My trusty OS 35 is an older model that used the bolt on muffler that bolts on from inside the muffler instead of through the side mounts like the newer OS mufflers. It does not have a uniflow fitting. What I want to know is can a muffler like this be fitted for muffler pressure and if so does it matter where it goes since the muffler does not have a baffle. Those of you using the Max 35 in the late 70's will know what I am talking about.
Ken, I hope I'm no to late with my comments.
I had an ARF Nobler with an LA 46 and it was a GREAT combination. I would highly recommend that you reconsider the LA 46. Mine died when the pilot had a brain phart! To bad because it was my best flying ship.
I had an LA 25 venturi/OS NVA (6 mm) and an OS 762 muffler (No you don't need to open up the outlet) an 11 x 4 zoar prop and 10-22 fuel. I also extended the landing gear 1" as that is the length in the green box Nobler.
Good luck, Jerry
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Thanks for the responses. I will hold off on the muffler until I see how the tank works without it. Never used a square plastic clunk before but I have always used uniflow on the metal ones.
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These OS 703 mufflers , from the 30, 35, & 40 Strap On & have a pressure nipple std .
Id used a large OS 20 intake in the 30 , & maybe 35s , which they say 1/4 in. is the go for .
(https://static.rcgroups.net/forums/attachments/3/3/2/3/5/8/t3981366-76-thumb-os703%20002.jpg?d=1304211647)
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The venturi to use for the 703 muffler is a 290 to 300, because of the TINY hole in the muffler and all of the restriction
If you use the Jet Stream muffler then use a 265 ti 275 venturi
If you use a tongue muffler a 265 to 280 is the range
No Muffler use the 265 venturi
Randy
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Randy: Thank you a bunch for the tips. I am amazed how far the sport has come technology wise in the past 25 years. Where does one go to find these ventui? One last question. If you are familiar with the tank that comes with the Top Flight Nobler ARF I need to know #1 where to put it, other than in the trash, and can I route the fuel line to the inside of the circle. The drop from center tank to the needle valve is nearly 1/2". It is a clunk and it will have pressure but this just violates so many of the "old" rules about tanks that I need to ask someone that knows the new rules! But then I ask myself, why would Top Flight include this tank if it won't work?
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Never hurts to fit a filter in the pressure line to keep the crap out. I'll have to find one of those old OS mufflers for my 35S I have sitting on the shelf along with a back plate, and all of the little items that fit on the end of the crankshaft of a OS 20 I alos have sitting there. I do not recall the 20 coming with a muffler, but it was such a long time ago.
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Thanks for the responses. I will hold off on the muffler until I see how the tank works without it. Never used a square plastic clunk before but I have always used uniflow on the metal ones.
I always use plastic clunk tanks. No pressure. Full fuse or profile. On my borrowed nobler arf, it was an os 40 la with a plastic tank and no pressure. Ran good after I got a smaller venturi.
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I always use plastic clunk tanks. No pressure. Full fuse or profile. On my borrowed nobler arf, it was an os 40 la with a plastic tank and no pressure. Ran good after I got a smaller venturi.
Thanks for the pictures. I too have nearly always used clunk but they were always round. I have never used a square one and I was concerned that it would get weird near the end of the pattern. You convinced me that it is OK. Still plan to use pressure.
Ken
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If any of y'all come across one of these I'd be interested.
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Hi all.
Peter, it is almost identical to the old Merco unit.
Kind regards.
Manuel.
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Bolt Spacings differant .
The Merco matches Super Tigre 46 / 60 etc . And Mercos . :o
The OS Silentflow fits the 64-74 etc 29,30,35 & 40 etc . Andll nail on the FP with a big hammer or little bolts . as its only a mm out . >:(
inc. Magnum 25 GP .
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Thanks for clarify that Matt.
Kind Regards.
Manuel.