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norvel engines

Old 02-03-2008, 02:05 AM
  #1  
billym8228
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Default norvel engines

Im currently building an A-10 warthog twin ducted fan.it is fron rc modeler plans.It has 54 1/2 inch wingspan flat bottom airfoil ,the fuselage is 45 inches,it called for tee dee .020 engines with cut down 5x3 props.i have added a little extra weight it now weight dry and no electronics a tad over 2 lbs.so i have opted for a pair of norvel .061 engines rc. i have recently bought 2 new norvell .061 engines with carbs. my question or questions are will the 2 .061 engines with 5x3 cut props pull it?are there any differences in the .061s,power wise i need to watch for?ie porting?the reason i ask is because someone told me that some norvel engines have 3 ports plus exhaust and some have 5 ports plus exhaust,is this true? this is the first twin ive ever built and it is from plans so if you dont mind i could use the help.also does anyone know what i could use for the ducts for the engines,the plans stated to use 2 liter pop bottles cut down.is there anything better?
Old 02-03-2008, 02:18 AM
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Andrew
 
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Default RE: norvel engines

NORVELs were manufactured in two versions, the AME which had 3 oblong intake ports and the Big Mig which had 5 basically round ports. The AME was the high performance engine - a little less user friendly; did not throttle quite as well on the low end and it tended to turn a higher RPM.

Both are ported for higher RPM and each model should not be over propped -- the 5x3 works well. You will probably want to run 20 to 35% nitro and around 20 to 22% oil with a good portion castor.
Old 02-03-2008, 02:38 AM
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billym8228
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Default RE: norvel engines

the 2 i have are the big mig .061s one was a vent valve but i have a new carb for it.how can i tell the diff?
Old 02-03-2008, 05:10 AM
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ffkiwi
 
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Default RE: norvel engines

If you remove the glowhead from your Big Mig 061's, and look down into the cylinder, with the piston at bottom dead centre you will be able to see five transfer ports feeding the cylinder-plus the single exhaust port on the right hand side. As you look from above the five will appear in an arc from the front to the rear on the left side of the cylinder. The AME version has only three transfers-two large ones at the front and rear of the cylinder, and a smaller one directly opposite the exhaust. The Big Mig has all 5 transfers the same size. The speed difference on the same prop ranges from about 1000 rpm on larger props to 2000 rpm on smaller props-with the AME version being the fastest. There used to be a section on the Norvel website which not only explained the differences in detail but also gave an rpm table for different fuels and prop for both versions. If the original plan was for two 020s then you will have no trouble with two 061s-other than perhaps TOO MUCH power-the 061s produce about 4 times the power of a TD 020. Be aware that ducted fans require a very close fit of the fan to the duct to operate efficiently-and your workmanship and alignment within the ducts will have to be spot on.
For ducted fan use, it would have been better if you had purchased the higher revving AME versions, as on larger ducted fans, the engines are ported to run a lot faster with fans, than with props-typically around 23,000-25,000 rpm even with 90 sized engines. They (the larger DF units) tend to be hard on plugs, and like plenty of nitro as well.

'ffkiwi'
Old 02-03-2008, 09:20 AM
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billym8228
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Default RE: norvel engines

Hey ffkiwi thank you very much,youre info is very helpful altho i do not have a matched pair as i thought i had lol,one has 5 ports and the other has 3.so I guess its back to the drawing board so to say. I found a place that has norvel heads ill ck with them and see if they have a 3 or 5 port head,that should maybe fix my problem i hope.i hope the extra power will help because the engines are equiped with carbs and ill have to have a hitec hss 55 servo on each for throttle control,then 2 of the same on the wing for alerons and i think ill run a big servo on the elevator it can go in the nose along with my batt and reciever that should help out on my balance.
Do you think that the wing should be fully sheeted? i have sheeted the center section.Im worried if it will be strong enough. The fuselage has 1 wrap of 1/2 oz epoxy glass cloth and will be painted,should i do this to the wing,or just the center or should i leave it off the wing? thanks Billy
Old 02-05-2008, 11:06 PM
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ffkiwi
 
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Default RE: norvel engines

Without seeing the plans for your A-10, and seeing what the airframe structure is, I can't adequately comment on whether the structure would benefit from beefing up with more sheeting and/or more glass. Either way you're adding weight as well as strength-which can be a dangerous spiral to get into.

'ffkiwi'

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