DeviousDave

Hey guys,


I test flew my first .074 powered airplane today. I have a bunch of them but never actually flew any because I had been saving them for some kind of 'special project' because they are, well, special. In the past I had run one but didn't play with props or tach it-this was back when they came out, so things are fuzzy. At any rate, the motor on this airplane has about 12 minutes on it. I figured that being a clean airplane I would want a 6-4 to start with and had a choice of an APC skinny electric prop or a Cox Grey with it's fat, wide blades. Figuring that the wide blades would be better for test flights, I went with the Cox prop. The airplane will almost support it's weight when held vertically on this prop, and the speed seems pretty good. It was really windy today, but averaging in my head I'm pretty happy with the performance.

The motor holds a needle setting well, idles very low, and while the transition from idle to full throttle could be better, it is very linear. It pretty much runs like a motor that is broken in already, but I'm not too impressed with the tach numbers I am seeing: 14500-14700 on this prop with 35% Norvel fuel, temps in the low 90's at sea level. I was hoping for 2-2500 more than that, given what the motor is supposed to turn a 7-3 at and how well it responds to smaller props based on the posts I dug up here.

How does this stack up with your experience? Are the .074's undercompressed like the 1/2A and 1cc motors? can I expect it to get better with time?

Mr Cox

Yes, those number are too low, I think you are running overcompressed. How many shims do you have?
Not all 1/2A engines are undercompressed, I have a few that are overcompressed, it also depends on the prop you're running and the fuel of coarse.

I'm running two shims and 10% Nitro, getting 17400 on an APC 6.3x4. If I take one shim out it drops 200rpm on that and I think I can even go back to three shims again. I haven't tached mine on the cox 6x4 gray but it sounded similar when I ran it. My engine has probably picked up around 500rpm from the first few runs, and I don't think you should expect much more than that.

RocketRob

My Feedback: (1)

I recall setteling on the APC 6.3x4 on mine also.
Don't have my engine spreadsheet out here with me though.
Can let you know in a couple of days.
I'd be curious to see what a drop in nitro would do for you?

combatpigg

My Feedback: (3)

DD ...Instead of waiting for the engine to loosen itself up, I'd polish the crank and test fit till it passes the flick test. Your numbers sound low and this is most likely why. A few seconds with 1000 grit paper is usually all it takes.

somiss1

My Feedback: (5)

Please DO NOT use that electric prop!!!!!!!!! They are made for electrics only!

gkamysz

My Feedback: (19)

Is that the airplane you picked up at the swap out here?

Mr Cox

Which prop are you referring to?
The APC 6.3x4 is a combat .15 prop and it has a proper strong hub like the other glow sport props from APC.

DeviousDave

It's a Cheap Trills (P-51 Penetrator with short wings) from John Fotiu.

DeviousDave

I think I may have found the problem-the head was loose. I put the spanner wrench on to loosen it and as gripped the handle to 'put a little Dave on it', the head unscrewed. The engine has two gaskets in it. In my haste to test fly yesterday I left my tach on and it's dead now, but I just took the plane outside and ran it. Sounds a little stronger, maybe 16,500, and has a little better vertical pull. Still doesn't sound 'happy', but closer to it. The needle setting near peak shows signs of a tight engine, it is peaking but then looses some RPM, then I back off the needle a few clicks and it speeds back up. It's getting there though. I may just pull it apart after all and polish the crank, maybe put an air bleed screw on the carb to improve throttling, will definitely try adding gaskets.

The engine went rich on the first flight as the motor loosened up and cooled off-second flight was much livelier. Gotta say, this engine has a very reliable slow idle.. After not being able to land at the 5k idle I set on my radio with the first flight, I set the idle reeeally low, and waited to do my flat spin later in the flight so I could dictate when/where the flight terminated if it died. This airplane spins *really* fast, I thought for sure it would kill the engine by the time I recovered but it was still running. I'm pretty pleased so far-it's going to be a great motor.

DeviousDave

If I can run an APC electric prop on a Cyclon, they are fine for a Norvel. You just have to apply some common sense and not use a prop that has been stressed on a landing and check the roots and hubs for signs of stress. A glow motor may have torque impulses as the piston fires, but compared to bolting one of these props on an F5D electric motor they are very low stress. At double the RPM of the .074, the Cyclon will put 4 times the centrifugal force on the blades.

DeviousDave

I understand they make fuel that has a lower content than 30%, but it won't run in this motor without a special head. IIRC, the fuel is a little different, it still has castor in it, but you have to replace the alcohol with kerosene and add a bunch of ether until it starts easily. Greg and Andy would love to tell you all about them!

Mr Cox

Oh, I see, you have a Nitro engine...

DeviousDave

Well, nitro for now....

(Feel free to post a picture Greg)

ChicaWolverina

I've also one of these, and it certainly is a glow engine!

DeviousDave

We're just funnin' each other, though this particular .074 will be converted to diesel eventually.

hllywdb

Hi Dave,
I get my best balance between thrust/speed with the APC 6.3 X 4. I also notice that the motor keeps running better the longer it runs. The second quart of fuel is much better than the first, by the 3rd it is really stating to run. I notice my verticals just keep getting stronger and stronger.

DeviousDave

Thanks, I'll be trying that prop once I find one. The local shops are really hurting for prop choices, even the smaller E-props are not in stock-people don't have money for hobbies. Might have to suck it up and mail order a few.

I'm pretty happy with the vertical it has now, a little more would be better but the main thing I am after is the get the engine to where it's 'happy'.

(typed while flipping a random engine over on my desk-sometimes being a bachelor isn't all bad...)

flyinrog

My Feedback: (1)

I have twice had my norvels break in while in flight..you can just hear it,,flying along, I ususally run a small tank so I deadstick in, but I'd say about an hour of run time and the throttle just jumped about 1k rpm and the .074 doesnt like a big prop ....and as soon as its broken in, it feels like theres no compression, but it starts like a light switch....Rog

RocketRob

My Feedback: (1)

Dave,
Checked my spread sheet to find I didn't log any numbers for my .74 and my use of the 6.3x4 apc was on the AME .15 at 18,800 rpm.

We need to talk, am I going to have to head out there[X(]

airraptor

My Feedback: (66)

that number seems very week for a 15???

Mr Cox

What do you get on a stock .15 and the same prop?

hllywdb

I think my Enya 09 will spin that prop close to 17k, that seems real low for a 15

DeviousDave

Looking at some older posts, my engine was way down on power compared to other folks-I'll be going to the Dollar Store this afternoon to pick up a 9v battery before the weekend so I can get a tach on it again. My hope is that with the tightened head and a prop with less blade area an thinner sections I'll get the engine up to where it is supposed to be.

DeviousDave

ETA: You better see your way out here, I'm holding your new diesel hostage! Speaking of which, David Owen emailed today to say the Schlosser shipment arrived safe in Oz.... (ohboyohboyohboyohboyohboy!)

DeviousDave

I just realized I made a Gaffe in my original post. This is not my first .074 powered plane, that dubious honor when to an Aerocraft Snapper with a Queen Bee on it back in 1993 or so. It barely balanced with a ton of weight, and on most days around here would just hold up in the wind at full throttle. Later versions with the OS .10FP were much better... I'm saving one last kit for a piped MDS .15[X(]