Cox Black Widow "Sqeal?"  
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Cox Black Widow "Sqeal?" - 7/7/2008 1:58:34 AM   
franklin_m


 

Posts: 117
Joined: 11/17/2005
From: Lemoore, CA, USA
Status: offline 		Hi,

I've got a Cox black widow that's relatively new, but is acting very strangely. Specifically, while running, it sounds as if there's a squeal / whistling sound. Don't know if it's related or not, but it hunts around a lot in rpm.

I've also noticed what seems to be a fair amount of play in the crankshaft (a three sheets of paper or so gap between the case and the drive nut), and some black looking residue just to the rear of that after a run.

I've taken it apart and put it back together several times and I'm stumped..

Thanks,
Frank
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RE: Cox Black Widow "Sqeal?" - 7/7/2008 2:26:50 AM   
build light


 

Posts: 1359
Joined: 11/30/2005
From: Crete, NE, USA
Status: online 		A sound like that would likely to be hard to hear over the firing and prop noise generated. I would look first at the prop and use another type, style or brand and see if it persists.
Still, it could be coming from the shaft.
The gap between the drive washer and the front of the case sounds normal.

Hopefully someone else can provide better info.

Robert


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RE: Cox Black Widow "Sqeal?" - 7/7/2008 3:27:52 AM   
franklin_m


 

Posts: 117
Joined: 11/17/2005
From: Lemoore, CA, USA
Status: offline 		I've tried two different props on it thus far, same sound with both. Does that help?


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RE: Cox Black Widow "Sqeal?" - 7/7/2008 5:20:44 AM   
MJD


 

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quote:

ORIGINAL: franklin_m

I've tried two different props on it thus far, same sound with both. Does that help?




Black gunk = metal scrubbing = trouble somewhere!

It's running forward, not backwards, right?

Are you bench running it?

What prop, what fuel, etc.?

How rich/lean are you running it?

Is the plug snug, and has the gasket in place (hey, I had to ask..)?

Does the crank spin freely in the case when the engine is disassembled, conrod disconnected from crank etc.? End play sounds reasonable, but what about clearance, i.e. radial fit?

Can't think of any other questions at the moment..

MJD



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RE: Cox Black Widow "Sqeal?" - 7/7/2008 5:24:20 AM   
lildiesel


 

Posts: 459
Joined: 11/18/2005
From: Cincinnati, OH, USA
Status: offline 		I've measured the gap between prop drive plate and the nose of the crankcase on a couple of NIB Bee engines as tight as 0.008 inch (0.203 mm) with a brass feeler. That's 2 sheets of 20lb copier bond. The feeler will actually turn the drive plate with the slight drag of the tight fit. But I think your 3 sheets is within norms.

If the engine made this sound from new and it's a mechanical squeal then I'd suspect something in the fit of the crankshaft and the lower end of the con rod in the crankcase. Look for signs of galling on the surfaces where steel meets aluminum. The black at the nose of the crankcase has to be from the aluminum crankcase wearing against steel.

The only experience I've had anywhere near like this was an AE 1cc diesel that hunted all the time even after careful break in. No mechanical squeal that I could hear, though. I spent a lot of time turning just the crankshaft in the case with small amounts of jeweler's rouge (powdered ferric oxide) between the mating surfaces and the when the crank spun effortlessly the hunting was gone on the next test run on the bench.

Hope this helps.

< Message edited by lildiesel -- 7/7/2008 5:26:28 AM >

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RE: Cox Black Widow "Sqeal?" - 7/7/2008 5:36:54 AM   
skaliwag



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Joined: 1/9/2003
From: santa cruz, CA, USA
Status: offline 		If you PM or Email me you address I can send you a new crankcase to try.

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RE: Cox Black Widow "Sqeal?" - 7/7/2008 8:05:18 AM   
Tee Bee


 

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From: Angleton, TX, USA
Status: offline 		I've got a Black Widow that made a squealing sound for the 1st couple of hours of runtime. It seemed to originate in the intake(If I spun it thru with my finger over the intake port, it wouldn't squeal.) and eventually went away after lots of flying. It never seemed to affect performance either way. It's the only .049 I've had do that. FWIW, mine was a new late model(Estes) Black Widow that came in the clear plastic package and wasn't anodized black. I still run it fairly regularly. Good luck.

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RE: Cox Black Widow "Sqeal?" - 7/7/2008 12:24:44 PM   
Larry Driskill



Posts: 683
Joined: 6/2/2003
From: Lubbock, TX, USA
Status: offline 		I'm thinking that the shaft / crankcase fit is too tight, or that there is a bind there.

The evidence is the black residue and the RPM changes. Does the case get hot too?

I would take the engine apart again and examine the shaft for signs of galling. Have you had the shaft out?

Does the shaft feel tight when you get the cylinder and piston off?

If there is aluminum on the steel shaft surface, that will be clear evidence of the problem.

....and that is a problem that can be easily fixed.





< Message edited by Larry Driskill -- 7/7/2008 9:44:42 PM >


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RE: Cox Black Widow "Sqeal?" - 7/7/2008 8:38:15 PM   
Remby


 

Posts: 610
Joined: 11/2/2002
From: Russell, PA, USA
Status: offline 		I think Larry D. has the trouble on target here.

I had a .049 Tee Dee, the drive plate spacer was so close that it ran fine when started, but two/three minutes of run time and the washer started rubbing, and the engine started dying in flight. It would loosen the glow head in flight, about every flight, and it was the frequency of the harmonic caused by the expansion and rubbing, it made the glow heads come loose in flight.

Is there any end play of the drive plate up and down in the crankcase? Has this engine been subject to a crash? Dirt in the crankcase may have wore the surface, mabye even a bent shaft from a hit could cause/effect the trouble you are seeing.

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RE: Cox Black Widow "Sqeal?" - 7/8/2008 2:10:26 AM   
BMatthews



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From: Burnaby, BC, CANADA
Status: offline 		The residue should not be black.

Two things I can think off. One is the case is tight and binding. The other is that it's too loose and it's rattling at the "squeal" frequency.

Try pushing lightly on the prop screw to hold the crank fully back in the case. Then wiggle the prop front to back at the tip. Does it move other then flexing? If so how much?


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RE: Cox Black Widow "Sqeal?" - 7/8/2008 3:24:03 AM   
combatpigg



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Status: offline 		Keep adding nitro until the squeal sound goes away.

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RE: Cox Black Widow "Sqeal?" - 7/8/2008 3:31:26 AM   
jetpack



Posts: 1516
Joined: 10/2/2002
From: Portage, IN, USA
Status: offline 		I would guess the crankshaft fit and the black anodizing which is also hard untill it galls in, doesn't like each other yet.

Black anodizing has harder qualities than all the other colors I hear.

It will probably squeel like that untill it wears it's own metal spots without anodizing. Either way, it is anodized, and that means a harder surface finish than natural aluminum.

I think the crankshaft is floating around on top of the anodizing and has to break through it to bed in and not make noise anymore.

< Message edited by jetpack -- 7/8/2008 3:37:28 AM >

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RE: Cox Black Widow "Sqeal?" - 7/8/2008 3:31:49 AM   
Larry Driskill



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From: Lubbock, TX, USA
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quote:

ORIGINAL: combatpigg

Keep adding nitro until the squeal sound goes away.



I may need to reconsider my earlier analysis of the problem. . .

. . . does that squeal sound like a Pigg?


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RE: Cox Black Widow "Sqeal?" - 7/8/2008 3:33:16 AM   
injunnut1


 

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From: Cocoa, FL, USA
Status: offline 		A wee tiny leak at the reed valve / reed seat is likely causing the "squeal".

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RE: Cox Black Widow "Sqeal?" - 7/8/2008 3:43:42 AM   
proptop



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Joined: 10/18/2002
From: Rome, NY, USA
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quote:

ORIGINAL: injunnut1

A wee tiny leak at the reed valve / reed seat is likely causing the "squeal".



I was just thinking the same thing...had one that did it...sounded a bit like an off key Clarinet or something.
That doesn't explain the dark oily residue though?
Maybe a little bit of both...the reed and a slightly snug fit of the case/crank?

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