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Old Aug 26, 2012, 09:23 PM
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I have been racking up some time and flights on the Walbro equipped NGH 9cc engine. I usually get at least five flights a day on the weekends, Approximately 8 to ten minutes or so a flight. I have done 25 flights so far with the Walbro carb mod, and the engine has been working pretty well like that. I am running it to see how well the engine holds up actually being used. I had something like 15 flights on the engine before the rod let go because it ran a little too lean once on me. I had a hour of bench running before then as well. Then it got the Walbro carb modifcation done to it.

I have another plane in the works for my other NGH 9cc engine. As soon as I get it finished and setup, I'll try running my other engine using the NGH carb and pump with the larger crankcase pressure fittings and see how that goes. I am expecting it to work out pretty well too as the engine never ran that good on the test stand before. It is my physical test of my theory on why the engine was having problems in a plane. Anyway, that is what I have been up to.

I didn't do any bench running of engines this weekend as we had some rain recently and the mosquitoes didn't waste anytime at all taking advantage of it. There were swarms of the little buggers all over outside. Even in the daylight in the shade the pesky devils would go after you. We have the little tiny ankle biters that stay close to the ground in the grass. The regular annoying buzzers that fly around too. Then the big Tiger mosquitoes that will bite your through your clothing too. You can't just spray repellant on your arms and face with those big ones, as they can bite through the clothing too. Those big ones leave large welts on me, like a bee sting, but they itch like crazy instead of hurt. Plus we have people getting West Nile virus infections out here too. Fortunately our flying field is fairly far from the lake, so we don't have a lot of mosquito problems there, unless you have to go and retrieve your plane from the trees and bushes nearby. But I haven't tried night flying yet and it probably gets bad at night though.

I have rebuilt a number of engines that other people would have tossed in the trash. In the past I used to have people give me their Fox engines when they couldn't get them to work and grew frustrated with them. I would readjust the carb and use the engine in a plane for the next weekend. That was the good times as I went like ten years without having to buy any new engines to fly with. Of course if the Fox engine wasn't damaged, they tend to never wear out either. So sometimes I swap out to a different brand engine for a change of pace.

A little while back I saved a SV 17cc gas engine from the junk bin and got it working good too. I now have it on a airplane and I am flying it around too. I remember reading about when a number of people claimed they were junk, bad, no power and gutless. So you never know until to try it. I'll see how long it goes before something happens to it.

Yeah, I guess I sometimes like the challenge to get something to work. Besides it isn't like we have a lot of gasoline spark ignition engine choices to choose from in the 7.5cc to 9cc range for .40-.45 size airplanes. So it was something I was going to do anyway, if I had to convert a engine myself to do it.
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Old Aug 26, 2012, 11:35 PM
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Australia, NSW, Ashby
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Yes some of us when the motor does not work or work well ask the question 'Why' and then start examining which of course leads us down the ever slippery slope of tinkering with engines . Personally would have it no other way as I myself have learnt so much and enjoyed it as well.
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Old Aug 27, 2012, 11:18 AM
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I had stuck a small keychain camera on the Ugly stick to see what would happen.
Obviously the speed makes it hard to see things, plus the engine vibration doesn't do anything for it either. So here is a really bad video of me flying the Ugly stick with the NGH 9cc engine on it. It was somewhat breezy and the temperature was 105 degrees F too.

Here is a attempt at putting a video camera on my Ugly stick using a NGH 9cc gas engine (6 min 41 sec)
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Old Aug 27, 2012, 08:43 PM
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Results from larger pulse fittings

I installed the 8/32 threaded fittings to the back plate and pump on my engine, following earlwb's suggestion. Before, the engine would sag if the throttle was opened more than about 80 percent.

With the new fittings and a short 1/8 inch id pulse line, the engine now runs fine wide open. I attached a long line to the fuel tank and found that when I moved the tank down so that the fuel level was 32 inches below the needle or if I raised it 32 inches above it made no difference. I imagin I could have lowered the tank even more, but was limited by my test stand and the tube I had handy.

In addition, the idle was better. I could get it down to 2.2k rpm without surging with a 12x4 APC prop.

Excellent work!
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Old Aug 27, 2012, 09:17 PM
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That is great news. Thanks for telling us about it.
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Old Aug 28, 2012, 04:52 AM
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I hope Mr.Chow also reading it.It seems obviously nipples need a change.
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Old Aug 28, 2012, 05:00 AM
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Originally Posted by turk1 View Post
I hope Mr.Chow also reading it.It seems obviously nipples need a change.
They need to be pierced larger
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Old Aug 28, 2012, 07:22 AM
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Please ... I am on a pun free diet
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Old Aug 28, 2012, 01:24 PM
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I suspect that the video by NGH showing an engine running with the fuel supply on the floor may have been a pre-production version that happened to have larger pulse fittings. Maybe the fittings were changed when it went into production without further testing.
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Old Aug 28, 2012, 04:40 PM
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Friends don't let friends fly with small nipples .
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Old Aug 28, 2012, 06:56 PM
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Quote:
Originally Posted by sbs70 View Post
I suspect that the video by NGH showing an engine running with the fuel supply on the floor may have been a pre-production version that happened to have larger pulse fittings. Maybe the fittings were changed when it went into production without further testing.
I don't understand the relationship of larger fittings = better carburetion??


Bill M.
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Old Aug 28, 2012, 08:03 PM
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Quote:
Originally Posted by Capt. Quirk View Post
I don't understand the relationship of larger fittings = better carburetion??


Bill M.
Starts at about post 797 & on. Not better carbination but better fuel pump action feeding the carbinator!
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Old Aug 28, 2012, 08:37 PM
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Originally Posted by Capt. Quirk View Post
I don't understand the relationship of larger fittings = better carburetion??
Bill M.
it is better fuel pump action or performance. With the small fittings with a tiny hole in them, there wasn't enough of the crankcase pulses getting to the pump diaphragm to allow it to pump good. With the larger fittings and bigger holes, the pulses are stronger and the pump now pumps really good and then the carburetor works good.

So the carb is actually not bad, it works well when it gets a good fuel supply.

I think what happens is as the engine displacement gets smaller and smaller, the crankcase pressure pulses become more and more weak. So what might work OK on a larger engine doesn't work well when the engine is smaller. So the fittings need larger holes in them to allow for more of the pressure pulses to get to the pump diaphragm, so the pump will pump fuel better.

It just took me longer to figure it all out and come up with a fix for it on the 9cc engine.
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Old Aug 28, 2012, 08:47 PM
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I do really admire your vast thoughts and excelent skills. engine is a little thing, but the most important is attitude to everything. I think this is why USA is standing No.1 and Why do humans science and technology so advanced reason, because of you all are GREAT EARTH PEOPLE. I must learn from you all not just tech.

Each pump tested with a 1000mm lower tank before is ok with stock smaller nipples , but I am not sure its size is most suitable, bigger might be, so I will test it with a bigger nipple . and please let me know if your test is just on bench or made a flight?

pay attention on the flip of HSN, might need clasp HSN tightly.

Please accept my respect!

zhou wei
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Old Aug 28, 2012, 09:06 PM
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I will be flight testing one of my 9cc engines like this on this weekend coming up.

One thought is how did you test the pump? Did you use a running engine or did you use a simulator where you have a device provide pulses to the pump to test it? I can see someone using a electric motor coupled to a cam operating a diaphragm to provide pulses. Or a electroc motor coupled to a engine without a glow plug in it, and it uses the crankcase pulses to test a pump with too.

There also could be some odd relationship or issue with you using metric sized fuel tubing where we use SAE sized fuel tubing here in the USA. I haven't studied that part, but maybe that is a issue too.
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Last edited by earlwb; Aug 28, 2012 at 09:24 PM.
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