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Engine basics => Four strokes only => Topic started by: Dane Martin on October 05, 2015, 11:43:39 AM
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First full fuse big plane I've had. Built by the treasurer of our club. It will be powered by a Magnum 70fs. The Magnum and OS 70 is identical. I'll get it done and try it out this weekend. I'll get the carb off and see what i can do.
Any suggestions for a starting point on the prop? Like a 14 inch? Thanks guys
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Hi Dane, let me know which field you'll be at and I'll meet up with you. Good to hear the 70 fits. I'll grab a bunch of props for you to experiment with too. Bill
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Hey Bill!
Yep, it seems like a great idea to me to use that 70! I'll just go out to Bennett. I'm hauling @$$ on some 1/2A combat planes too. So we might have a lot to fly!
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14" 14x6 good for Strega, you must load the 4 stroke also.
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Thanks Walter. Bill is the one who gave me the plane, so I'll have him figure it out! Lol
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Ok, so Rueben told me it had an ST60 originally, but they felt it didn't have enough stank on it. They switched to a rojet 76re and said it did real good. I'm thinking the four stroker will be great when set up properly. It's a brodak kit. I'll weigh it after the engine install ~^
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I was wrong. I thought the engine was all the way down. The case under the lugs is too fat. The engine won't slip down into the engine bearers without a big modification. I'd rather get a different engine.
Bill, i might wanna borrow that saito. Then I'll know if it's the right power before i buy one. Thanks
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You bet Dane, I'll send you a pm with info.
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Ok! I got a sweet saito 72 and some experimenting props! Thanks Walter! I got the engine fit into the mount. I'm making some different clamp plates at work today. My choice is to use the UHP manifold set up, or send the rc carb over to mr Lee and get it situated. Decisions! If i use the UHP manifold, I'll have to turn the intake manifold tube down. The inlet of the UHP block is 7mm and the tube is 8mm
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Humm.. That tube is pretty thin, doubtful you will have enough meat to be able to reduce it by much. Surprised by your findings, always thought the 56/62 and 72 all used the same carb and same size intake tube.
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You are correct in your concern with the thickness of the tube. I'll have to post pics. But the intake tube is turned down where it enters the head. It's turned down to 7mm. If it were turned down on both ends, I'd be golden. The other option of course, would be to drill the UHP manifold block out to 8mm but then the problem is the o-ring seal inside of the block.
Not sure what's the best option n~
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Ok. I took it over to a close by machine shop and they said they can't turn down the pipe because it's bent and they have no way to hold it. We talked a little and measured the id of the block. I drilled the block to 11/32 and with that, the o-ring groove is now the same dimensions as the oem carb. I was able to take the o-ring out of the carb and put it in the block. Now the tube fits nice and snug. I'm thinking this is the ticket for now! Oh, and I took an o-ring from an os carb for the venturi.
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sorry Dane, I do not remember what size engine possible Saito 56 that the Ultra Hobbies carb adapter came from. Please note that
the supplied venture is probably too large and may yield too much rpm for your needs. If so try some pantie hose with o rings to choke it
down until you get the RPM you want.
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Not a problem Walter. The venturi set i have from the OS52fs fits. So i have three more to test.
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When I started playing with a 40 using the UHP intake I ended up with 7 or 8 layers of panty hose which became a chore to deal with. Drill and tap a hole through the side of the insert and put a 10-32 nylon screw in the hole. Then you can adjust the intake area by how much area the screw closes off. This is what I ended up doing with the 40 and it worked out OK. Not the greatest photos but will give you an idea of what I ended up with on the 40.
Reason I ended up abandoning the UHP intake in favor of modifying the carb was the OS needle valve. The clicks were not fine enough and it's loose in the threads. On the couple I had, just touching the needle would change the RPM and it was difficult to set properly.
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I like the screw method you have. If you'll recall, that's what i did on my os40 four strokes. I'm hoping this will be a little different, because it's the same NVA from the os fp series. It goes all the way through and has a spray bar. I've had very good luck using them on my LA series engines. Fingers crossed!
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Dane,
Just seen your Thread. Informative! H^^
I don't do 4S for CL but you make it tempting.
Good Thread.
Charles
Dane,
I'm adding to this because I've been thinking about the NVA issue.
If you welded a flange on the intake tube, you could bolt the old FOX cast NVA to that flange.
Plenty of them available.
Could this work?
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Hey Charles,
Sorry i missed your reply. That would infact work. I like using the os or saito sizes because of how easy it is to interchange venturi sizes. Plus, os parts are cheap and i get them next day from reno when i order from tower.
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How's the Four Cycle engine running for stunt, Dane?
Greetings from SoCal.
R,
Chris
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Hey Chris! I keep missing you in cali!
So this project actually turned into
http://stunthanger.com/smf/engine-set-up-tips/ro-jett-61-prop-advice/
After some digging, I found that a ro-Jett 61 was in this plane first. So I got one for myself so I could just drop it in the plane. Then I decided it was too loud, and figured why not go for the gusto and pipe it. So the plane underwent huge modifications any way.....
Indecisiveness struck big time on this "little" project.
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I see I see....