Norvel fuel draw - no muffler pressure
#1
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Norvel fuel draw - no muffler pressure
Unfortunately, I had a bad 'incident' (landing) with my DNU in the weekend. The TD 051 that was mounted now has a badly split plastic venturi mount. The rest of the plane in fine (I would have preferred to break the plane instead of this engine). In the meantime, I am thinking of mounting my Norvel Big Mig .061 in place of the Cox. With the Cox, I was using a 'pitot tube' (brass tube stuck out into the propwash connected back to the tank) to pressurise the tank. The tube is right where the muffler for the Norvel would be and because the tube is a fairly permanent installation, I would like to keep it there, which means running the Norvel with no muffler, which means no muffler pressure for the tank. The Norvel has an RC carb, which I plan to jam open (don't want to increase weight with a throttle servo) with a piece of wire or something. Will it have enough draw at WOT to run properly (remember - there is still the tube providing some pressure to the tank) or am I wasting my time trying to run a Big Mig without muffler pressure.
#2
Senior Member
RE: Norvel fuel draw - no muffler pressure
I have more experience with AME's than Big Migs, but the two I had drew better (this was 10 years ago) than any T.D. that I can remember.
#4
RE: Norvel fuel draw - no muffler pressure
If you need preasure, you used to be able to get a back plate with a preasure nipple on it. You can make your own if you want but you'll have to drill, tap and then mount a preasure nipple and regulate the flow from it. I believe it's about the same size hole in it that the Teedee nipple on the crank is (#60?) Just heat your nipple and sick a little solder inside to seal it and then drill the solder. Make sure that tap is even with the back plate and you're set. I have one somewhere that I had on my first Norvel that I bought for 1/2A racing in DesMoines. Man, that was 10 years ago? Wowsers! Anyways, you won't have any problem getting fuel to the engine after that.
#5
RE: Norvel fuel draw - no muffler pressure
Some folks used to have fuel draw problems, especially CL flyers. If you have problems, try using a smaller prop to increase intake velocity.
Many used a 6x3 on a TD but found that a 6x2 or 5.7x3 APC worked best for the Big Mig .061. Note we are talking smaller prop on larger engine.
The Big Mig AND the AME like to rev...and you don't have to reset a ball socket. I like both the TD and the Big Mig.
Of course this is only one opinion, individual results DO vary.
George
Many used a 6x3 on a TD but found that a 6x2 or 5.7x3 APC worked best for the Big Mig .061. Note we are talking smaller prop on larger engine.
The Big Mig AND the AME like to rev...and you don't have to reset a ball socket. I like both the TD and the Big Mig.
Of course this is only one opinion, individual results DO vary.
George
#6
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RE: Norvel fuel draw - no muffler pressure
I too like the TD and the Big Mig. I'm still kicking myself after I practically gave away a Big Mig c/l engine that had about 10 minutes total run time on it AND a spare glow head with it [:@]
#8
RE: Norvel fuel draw - no muffler pressure
All complaints I've read about were somewhat early ones with the muffler without pressure fittings. Perhaps they decreased intake size along the way or perhaps when they went to the courser needle valve it decreased intake area.
George
George
#9
RE: Norvel fuel draw - no muffler pressure
Sometimes I've removed the muffler from an engine that was being difficult to start just so I could either prime directly or blow out the cylinder if it seemed to be too wet. Once started, fuel delivery seemed just fine.
I have had a muffler cap pop loose in mid-flight causing it to lean out a bit and it seemed to run forever; I wasn't aware that I had lost pressure until it finally quit. I have found most of the NVs to be course and have a broad range so fine tuning is sometimes limited to several clicks (may just be me).
The early C/L NORVELs shipped with three different venturis - a high performance, a mid-range and one labeled EZ Start. The high performance required either a pressure bladder or crankcase pressure. Mid-range also ran better if muffler pressure was used rather than none at all. I think that the early combat guys probably needed pressure more than the RC sport flyer simply to help overcome fuel pooling in the lines due to fairly constant G forces. While we also have fuel pooling in RC flight, the G forces usually vary more and come from different directions.
I have had a muffler cap pop loose in mid-flight causing it to lean out a bit and it seemed to run forever; I wasn't aware that I had lost pressure until it finally quit. I have found most of the NVs to be course and have a broad range so fine tuning is sometimes limited to several clicks (may just be me).
The early C/L NORVELs shipped with three different venturis - a high performance, a mid-range and one labeled EZ Start. The high performance required either a pressure bladder or crankcase pressure. Mid-range also ran better if muffler pressure was used rather than none at all. I think that the early combat guys probably needed pressure more than the RC sport flyer simply to help overcome fuel pooling in the lines due to fairly constant G forces. While we also have fuel pooling in RC flight, the G forces usually vary more and come from different directions.
#10
RE: Norvel fuel draw - no muffler pressure
Dan,
The Kamdax ducted fans use Norvel .061's with no
muffler. The have a piece of fuel tubing in the prop
wash for pressure. I run 40% in them & they have
been very reliable on my 1/2A Warthog.
Good Luck!
Johnny C!
The Kamdax ducted fans use Norvel .061's with no
muffler. The have a piece of fuel tubing in the prop
wash for pressure. I run 40% in them & they have
been very reliable on my 1/2A Warthog.
Good Luck!
Johnny C!