Posted by earlwb |
Nov 11, 2012 @ 06:59 PM | 6,915 Views
Many years ago, circa 1990, my best friend at attempted a business venture, where he would have some planes made as ARF's that used foam core wings with 1/64 inch plywood sheeting, balsa, ply fuselage and tail. But the best part was they were all hand painted very nicely. Well the batch of prototype planes all worked out great. I built up six of them for my friend and had used Saito engines for three of them and Fox engines for the other three. He had three models, designed for .45 two stroke glow engines, a high wing trainer like plane, a high wing sport plane and a low wing sport plane built more like a pattern plane.
But unfortunately things didn't work out so well for the container load that came in. The planes were produced during the monsoon season and loaded into a container, which was shipped to Arizona. The dry heat in Arizona dried the wood out too much and the paint all cracked and peeled around the edges of the planes. Some planes turned out much worse than others though. But he couldn't sell them as new, high quality ARF's though.
Anyway, I have been building and flying some of the planes for years now. A while back I accidentally crashed a low wing plane. But I dug another one out of the storage shed and put it together. I almost lost it when some high winds caused it to pancake into the ground when it lost lift at the flying field. But it wasn't damaged much, so I fixed it back up to fly again.
I accidentally deleted the entire thread by mistake. So I recreated it here again. Sorry.
A while back I had acquired a SV-17cc engine. At the time the reviews weren't all that good for it either. But the price was right, so I couldn't resist.
When I first ran the engine, I found that I couldn't lean it out enough to run at its top speed. It stayed blubbery rich even with the needle valve all the way out, ready to fall out even. So when I looked at the carb I found that it had a Walbro WT-694 carb on it with a 12.7mm venturi bore, which I thought was way too big for a 17cc engine. As I have seen them a carb with around a 9mm venturi is about right. A 12.7mm carb is big enough to run a 35cc engine or even some 50cc engines too. So I rummaged around and found a WT-520 carb with a 9.53mm venturi and I put it on the engine. Now the engine ran great, easy to adjust, throttle response good, nice RPMs and I could lean it out good too.
At that point I didn't see any reason to not use the engine as it was performing good now.
Posted by earlwb |
Sep 03, 2012 @ 08:12 AM | 6,847 Views
I had put my second NGH 9cc engine in a Great Planes Escapade 40 size plane.
The only modification done to the engine was to use 8x32 fittings for the crankcase to fuel pump diaphragm and 1/8 inch Tygon fuel tubing instead of the smaller 3/32 inch fuel tubing. Previously I showed a video clip of how well the engine ran like that so I was motivated to fly the engine to be sure it was working in the air too.
Also the carb should have the low speed needle set to about 6 turns out and the high speed needle set to about 1 and a half turns out. The LSN setting on my case was about right and I didn't need to change it from 6 turns out. Also the carb does spit fuel out, so it is not running too rich, it is just the nature of the beast, so to speak.
Posted by earlwb |
Aug 05, 2012 @ 09:49 PM | 8,507 Views
I had modified my NGH 9cc engine to use a Walbro carburetor. After getting it all setup I do realize I had several other ways I could have done it. But I wasn't sure what the effects would be or how successful it might be either. So I sort of took a more simple approach to it. This carb I used is a WT-298-1 carb and it has a 7.14mm intake venturi in it, but the carb has no choke, so you have a harder time warming up the engine before it runs good like that. There are several other carb models that ought to work fine as well, and also some carbs with about a 8mm venturi size that might maybe work better too, but I haven't tried one myself.
All in all after getting the carb dialed in some, the engine was running pretty good, much better than how it behaved with the OEM two piece carb and pump/regulator. The Walbro carb exhibited no vibration sensitivity and was reasonably linear in its throttle opening from low to high speed. Now if you rapidly chopped the throttle from WOT to low, the engine had a tendency to flood out and die, but if you more gradually went to low throttle it allowed the regulator to work better and the engine would idle fine then. The engine temperatures I measured were about what measured with the stock unmodified NGH 9cc engine. I don't think it was running much more hot in temperature as the measurements were around the same at 376 degrees on the ground in a static engine run scenario. I assume the engine would run more cool up in the air flying around...Continue Reading
Today I got to test run my poor SV 17cc engine which has some problems. One problem was it ran way too rich and the needle valves were essentially useless at dialing it in. But when I examined it more closely I found that it had a Walbro WT694 carburetor on it, which has a 12.7mm venturi in it. So I don't know if someone had swapped out the carb earlier or that was the carb that came with it. But in anycase I think the intake bore of 12.7mm is way too large for a 17cc engine. I think that a carb with a 9mm bore would be better for the engine.
So I rummaged around in my parts boxes and found a Walbro WT520 carb, which has a 9.53mm venturi bore in it. But when I tried the carb on the engine, it would barely pump any fuel at all. So when I checked it has a stupid blue plastic pump diaphragm on it. So I visited out local small engine repair shop and bought a rebuild kit and put in a black rubber pump diaphragm instead. Now when I test ran the engine the carb started working like it should work. Now the engine had a more linear throttle response and the high speed needle would actually adjust the mixture too. The previous big bore carb was at full throttle way before the carb throttle was at full open. But now with the smaller bore carb the engine was at full throttle when the throttle plate was fully open.
So now the performance was a lot better as I got almost s 1,000 RPM improvement over what it was doing slobbering rich with the oversize carb on it.
With a 13x6 Master...Continue Reading
One of our forum members "Gary Cee" was kind enough to make me a couple of Fox carburetor adapters for some other brand engines. I think he did a really excellent job as the adapter fit perfectly too. Thank you very much Gary Cee, I really appreciate it a lot too. This allows me to use the really good Fox carb on a engine that doesn't quite have as good of a carburetor on it. In this example it is a adapter for a ASP .61 engine. The OEM carb on the engine actually works OK, but the bore is too large. Thus you have to let the engine turn higher RPMs (smaller props) and use a more restrictive muffler, that provides extra back pressure for the fuel tank, in order to get good fuel draw out of the engine. Quite a few people ran afoul of the problem of a carb bore being a little too large for the engine when they used a Pitts muffler that had a lot less muffler back pressure for the pressurizing the fuel tank. They usually had to block off one of the exhaust outlets to increase the muffler pressure for the fuel tank, but even then it may have been somewhat marginal. But by using a carburetor with a little smaller bore to it, I can get good fuel draw for the engine, and it is much less sensitive to fuel tank location and also to needing extra muffler pressure. So I have more versatility and better all around performance with the engine. Besides the Fox carburetors are really good carburetors and well worth using on engines other than Fox engines too. The cost for a Fox carburetor isn't all that bad and quite attractive cost-wise when you compare the cost to some of the other brand name carbs as well. The flange design of the carb does work really well, in that it prevents warps from causing the carb to bind when you attach the carb using clamps or screws. But the flange makes it more difficult to adapt the carb to other brand engines though.
Comparing the larger bore of the ASP carb to the smaller bore of the Fox carb.
Posted by earlwb |
Jun 25, 2012 @ 10:41 AM | 7,416 Views
Here are pic of my huge Aeroworks Profile Extra plane with a 80 inch wingspan. I can just barely get it into my car to take it to the flying field. I am using a ASP 1.80 engine on the plane. At present I am running a 20x6 prop on the engine. I might have to go larger on the fuel tank, but at this time the 16 ounce tank is doing OK for flight time, as I don't fly the plane WOT all the time.
I also tried out the Futaba S.Bus system with this plane, I used S.Bus servos on all the control surfaces with a conventional throttle servo. A 5 cell NMH 2000 mah pack supplies the power. The receiver is a newer dual S.Bus channel RX.
I flew the plane several times and it flies great. I love the buzz saw roll rate too. One would think with a plane this big that it wouldn't roll fast or perform tight loops, but this plane does them anyway.
The ASP 1.80 engine works OK, but it is too rich through the mid range, so I'll probably have to do some mods to the carb, if I figure out what the problem is. I suspect the spray bar is too short and needs to be a bit longer.
Posted by earlwb |
Aug 19, 2011 @ 01:27 PM | 7,800 Views
I managed to kill my old pattern plane that i had built way back circa 1991.
I had been flying it all this time since then. But I was doing some manuevers a little too close to the ground and I did a Split S and lacked about 6 inches of making it OK. but I have two more like it in the storage shed so I'll have one of its brothers going again shortly.
A picture of it before:
and of course afterwards, the wing is way back there in the backgorund, the horizonatal stab and other parts in between and the battery pack is where I stood to take the picture.
Posted by earlwb |
Aug 09, 2011 @ 10:14 PM | 9,599 Views
I recently acquired a WOHM 10cc radial diesel engine. I am in love with it too. These are hand made by Wolfgang in Germany, and he does some really wonderful craftsmanship in making the engines. My engine is #22 of the series he has made so far. The engine is very smooth running. if you look at the fuel jar in the video, you can see that the fuel inside the jar isn't moving or jiggling around any. The jar is just sitting in the test stand loose, it isn't tied down or glued down.
Posted by earlwb |
May 04, 2009 @ 05:57 AM | 10,718 Views
It was storming all weekend, so while thunder, lightning and rain was pouring down Saturday, I decided to build a big 36 inch Nutball. 1017 square inches of wingspan, 1kg AUW, and long landing gear too. I need to get a more powerful motor though, the biggest motor I have at the moment is a Komodo KH2413-11 and it can swing a big 12x6 prop, but only at like 3600 rpm. Which gives the big Nutball about a 20mph speed.
So I now have a big 36 inch Nutball, a 20 incher, a 12 incher, a 8 incher and a tiny 6 inch Pico-Nutball.
Here is a pic of my tiny Pico-Nutball with 6 inch wingspan. it uses throttle and rudder only control. ...Continue Reading