RE: Hi guys, need opinion  
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RE: Hi guys, need opinion - 9/14/2008 1:25:02 AM   
jeffie8696



Posts: 1283
Joined: 5/10/2007
From: coralville, IA, USA
Status: offline 		Personally I think the 6X3 prop is a winner. I believe you may have a fuel starvation or even an overheating problem. Perhaps a bit richer on the ground?

_____________________________

Castor, its like Vitamin C for glow engines. I am not Dom from Airwolf but I do resemble him.......Unfortunately

(in reply to steve111)
       Post #: 26

RE: Hi guys, need opinion - 9/18/2008 3:46:09 AM   
mikeainia


 

Posts: 20
Joined: 12/24/2007
From: Madrid, IA, USA
Status: offline 		One trait that has shown itself often here is for some of the Norvel's to have the crank fit too tight - it feels fine when cold but as the engine heats up it acts like it is leaning out, when it fact the crank is starting to grab in the bearing (it's actually the aluminum bearing that is the culprit). We lap the cranks to the case when a new one shows up with this. Sometimes it takes two or even three teardowns and lapping to get this symptom under control. I don't recommend too much lapping of the piston to the sleeve - they are fit very tight but after a run or two, they generally feel much better and you don't want to get the piston too sloppy in the sleeve. This could have caused the sudden shutdown, especially since it ran through the same maneuvers earlier.

Mike A.

(in reply to jeffie8696)
       Post #: 27

RE: Hi guys, need opinion - 9/18/2008 4:25:46 AM   
jeffie8696



Posts: 1283
Joined: 5/10/2007
From: coralville, IA, USA
Status: offline 		Will this show up on the test stand?

_____________________________

Castor, its like Vitamin C for glow engines. I am not Dom from Airwolf but I do resemble him.......Unfortunately

(in reply to mikeainia)
       Post #: 28

RE: Hi guys, need opinion - 9/18/2008 1:12:00 PM   
gcb



Posts: 2473
Joined: 10/24/2002
From: Port Ewen, NY, USA
Status: offline 		Steve,

Suggestion 1: I think, as others have mentioned, that you are starving the engine. You might try adjusting the needle while holding the outboard wing down. Adjust for the rich side of peak since it will unload somewhat in the air.

Suggestion 2: You are asking an engine with marginal fuel draw to pull fuel from the end of the pickup in the tank to the needle valve. To increase RPM (thus fuel draw), you might drop down to an APC 6x2 or 5.7x3. I think I see a pressure nipple on the muffler. Hook a pressure line from the muffler nipple to the fuel fill line and cap the vent so it will accept the pressure.

George

(in reply to jeffie8696)
       Post #: 29

RE: Hi guys, need opinion - 9/19/2008 1:01:04 AM   
steve111


 

Posts: 38
Joined: 4/30/2007
From: Wollongong, AUSTRALIA
Status: offline
Thanks guys.

quote:

Suggestion 1: I think, as others have mentioned, that you are starving the engine. You might try adjusting the needle while holding the outboard wing down. Adjust for the rich side of peak since it will unload somewhat in the air.



Uh, yeah, been doing that since I started messing about with CL models about 30 years ago . In this case the needle was set on the ground so the motor was just on the verge of 4-stroking. Oddly enough, holding it on either wingtip or nose-up made no appreciable difference to rpm, which surprised me given the distance the fuel has to be drawn inboard. In the air it unwound nicely and held strong revs regardless of what attitude it was in - prior to cutting abruptly. In other words, this was not like any excessively lean run I've seen, so I don't believe the problem was caused by being set too lean prior to launch.

quote:

Suggestion 2: You are asking an engine with marginal fuel draw to pull fuel from the end of the pickup in the tank to the needle valve. To increase RPM (thus fuel draw), you might drop down to an APC 6x2 or 5.7x3. I think I see a pressure nipple on the muffler. Hook a pressure line from the muffler nipple to the fuel fill line and cap the vent so it will accept the pressure.


I'm inclined to agree. I'm getting a smaller tank made up so I can mount the engine outboard rather than inboard, and will also hook up the muffler pressure line. (Muffler was off for the flight in question due to the two bits of it coming loose - apparently not uncommon.) I'm also wondering if I should use thinner fuel line to assist with fuel draw - I'm sure that what came with the integral tank was thinner than the medium-size stuff I used on this model.

Mike A. - I've been reading a bit about the tight-crankshaft issue, and wondering if that might be the problem. (I'm hoping it's not!) Previously the motor had only been run with the integral plastic tank, and I experienced no problems. Perhaps this was because the plastic tank doesn't let the engine run long enough for the crank to grab, or maybe we're back to the fuel-draw issue.

The other thing is that this motor came attached to the front end of a Skybaby, which was sorely and entertainingly abused by a number of people (myself included...). Maybe a bit of dirt found its way past the screen or something.

Cheers
Steve

(in reply to gcb)
       Post #: 30

RE: Hi guys, need opinion - 9/19/2008 1:30:22 AM   
gcb



Posts: 2473
Joined: 10/24/2002
From: Port Ewen, NY, USA
Status: offline 		The tight crankshaft problem can be easily diagnosed. It should occur when being bench run. As soon as it stops, feel the bottom of the crankcase near the crankshaft. If it is running tight, it will be hot. IMHO with as much time as you seem to have on that engine, I doubt that it is the problem...but worth a check.

Next time you don't have room for the tank, you might try mounting the engine outboard and the tank inboard. That should add a little fuel pressure.

Good luck.

George

(in reply to steve111)
       Post #: 31

RE: Hi guys, need opinion - 9/19/2008 2:25:01 AM   
steve111


 

Posts: 38
Joined: 4/30/2007
From: Wollongong, AUSTRALIA
Status: offline 		Thanks George, I'll give it a go.

Stev

(in reply to gcb)
       Post #: 32

RE: Hi guys, need opinion - 9/29/2008 7:59:42 PM   
jeffie8696



Posts: 1283
Joined: 5/10/2007
From: coralville, IA, USA
Status: offline 		Like the commercial says. "That was easy"

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_____________________________

Castor, its like Vitamin C for glow engines. I am not Dom from Airwolf but I do resemble him.......Unfortunately

(in reply to steve111)
       Post #: 33

RE: Hi guys, need opinion - 10/3/2008 4:39:42 PM   
jeffie8696



Posts: 1283
Joined: 5/10/2007
From: coralville, IA, USA
Status: offline 		Slowly but surely. Designing as I go.

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_____________________________

Castor, its like Vitamin C for glow engines. I am not Dom from Airwolf but I do resemble him.......Unfortunately

(in reply to jeffie8696)
       Post #: 34

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