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Engine basics => Four strokes only => Topic started by: Martin Quartim on September 23, 2011, 04:35:45 PM
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Here is a video of my 4S engine in action
It is an OS 70 Ultimate with .285" venturi, Enya S Pro NVA (.158"), fuel tank Sullivan 4.0Oz RST, Prop JXF 14x6 Wood Electric and Byron 20/20 is all this engine has ever seen. I built this model in 2008 and it went to Brodaks 2008 with it. It burns only 3.0Oz of fuel. Never misses a bit and always repeat same results. I start and go fly, very very rarely I touch the needle.
http://www.youtube.com/watch?v=p4Z9PlAQBTo
Martin
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Can't understand a word of Portuguese but who cares!! The engine run was killer-the cat at the handle was a great flyer-the quality of the video was outstanding. H^^
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Nice flight Martin, and a rock-solid engine run, indeed. 8)
What's the price of the JXF prop you're using here?
Regards,
Claudio.
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Thank you Claudio!
Here they cost R$24,00 or about U$ 13
Martin
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Can't understand a word of Portuguese but who cares!! The engine run was killer-the cat at the handle was a great flyer-the quality of the video was outstanding. H^^
Thank you Milton,
Martin
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Really cool, sounds just like my Saitos y1
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Martin , hi from France !
Great video and fantastic engine run.
May I ask please what was your launch RPM ?
Bom dia .....That's the extent of my Portuguese , sorry.
Kind regards ,
Robin.
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Hi Robin,
I never use a tach. I guess anywhere from 8000 to 8300rpms. 4S is very easy to tune, you close the needle until peak and then turn the needle back a bit, that is it no need to measure RPMs and once the needle is set hardly it needs to be changed, even if climate changes. The only thing I change is the propeller. In very hot days with no wind I use prop with as much as 8 in true pitch and cold and windy days 5.5 pitch.
Warmest regards from Brazil
Martin
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<snip> The only thing I change is the propeller. In very hot days with no wind I use prop with as much as 8 in true pitch and cold and windy days 5.5 pitch.
Warmest regards from Brazil
Martin
Interesting!
Here in Oklahoma our temps vary wildy in the spring and fall, summer temps. can hit 100*F + for weeks on end.
I need to remember this trick.
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People may think that more pitch will load the engine more and in the heat you want to go the other way around, well that would be true if the air density was kept the same. But in hot days air is less dense and it requires more pitch to load the engine the same way.
One feature I love about this engine is that it does not change much with climate and if I use the same prop it will work well. As matter of fact I did that for one whole season. But then I noticed that using more pitch I would get better line tension in those hot days and no wind, and it would wind up less in cold and windy days with less pitch.
The nice thing about wood prop is that in a bag of props we get all sorts of pitch. I have a set of TopFlite 14x6 from 5" to 8" in real pitch.
The JXF vary less in pitch and I have been buying 14x6 and 14x7 and I have a set of props with pitch from 5.4 to 7.6. The hard thing is to find two props with the same pitch. They also vary pitch from one blade to another . I guess this is old news, but I thought I would mention it again in case some one does not know how wood props really are.
So if you use a wood prop and it dos not work well, dont give it up so fast, try another one and check the real pitch.
Martin