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HomeAircraftHelicopterHelicopter Main Discussion › Strange engine noise - Align/OS 50 hyper
04-25-2009 04:11 PM  9 years agoPost 1
MattHarper

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Lancashire, UK

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Well, today was supposed to be the maiden flight of my Align 600NSP. All the planets were in alignment, the weather was good so I headed off to the club for a day of setting up and running in. I started the new engine and immediately felt uneasy. There was a strange metalic rattling noise coming from the engine, a bit like a loose nut in the crank case. Back at base I removed the engine and backplate in order to track down the noise. It appears that the conrod is a very loose fit onto the crank gudgeon pin and at BDC rattles and taps against the backplate when shaking the engine. Is the normal for these engines ? Ideas ?

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04-25-2009 04:35 PM  9 years agoPost 2
duceduc

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Saitama-Ken, Japan

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Do you see any metal debris inside.

Duc S
Do It! Do It!™
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04-25-2009 05:14 PM  9 years agoPost 3
Riq

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ND

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How good at autos are you?

Sorry, thats no help.
Ive had a couple hypers rattles when shaken, and they left score marks on the backplate. If its new, and you have the time, or an extra, send it in.

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04-25-2009 06:01 PM  9 years agoPost 4
Andy from Sandy

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Bedfordshire, UK

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The fan hub pulls the crankshaft forward and holds it in place. If with the hub on the crankshaft big end pin can touch the backplate then you may not have fitted the hub properly.

The big end is just a push on fit and so will be able to move. It is a mixture of the back plate and the groove in the crankcase that holds the con-rod in place.

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04-25-2009 06:45 PM  9 years agoPost 5
MattHarper

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Lancashire, UK

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Thanks for the replies.

duceduc No debris whatsoever
Riq Autos ? what are autos
Andy from Sandy It's like you describe, it's not the backplate so much as it rattling around in the groove in the crankcase. I'll try backing off the fan hub to see if it makes a difference but I suspect not. I've never experienced this with any engine i've owned, even a 30 year old one which I've recently refurbed.

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05-14-2009 06:28 PM  9 years agoPost 6
MattHarper

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Lancashire, UK

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Follow up:

Well, I sent the engine back to the shop for them to inspect.
They stripped it down and found nothing untoward. They then put it into a model, put four tanks of fuel through it and said it was initially way too rich but it's now adjusted and runs really well. Does this stack up with you guys ? Would running an over rich engine at idle result in the noise observed ?

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05-14-2009 10:32 PM  9 years agoPost 7
w.pasman

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Netherlands

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There was a strange metalic rattling noise coming from the engine, a bit like a loose nut in the crank case.
First I think of with an OS50 is a bad rear bearing.
If that is left unattended metal may come off that bearing damaging the rest of the engine.
If you hear a light coffee grinder sound during idle it's the rear bearing. the louder the worse the rear bearing.
It appears that the conrod is a very loose fit onto the crank gudgeon pin and at BDC rattles and taps against the backplate when shaking the engine.
Mmm not with my engines but it does not sound too disturbing.
Is your fan tightly on the crank, if the fan is loose you may get rattling sounds as well. Also notice that the raptor fans are of aluminum and dig themselves into the front bearing of the OS, causing it to get loose after a while even if it was originally tight. I don't know what the align fan is but I would not be surprised if the construction is the same as the raptor.

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05-14-2009 10:35 PM  9 years agoPost 8
w.pasman

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Netherlands

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Would running an over rich engine at idle result in the noise observed ?
Not a rattling noise I think, mostly a sputtering engine that does not respond properly to throttle.
It might be a combination of factors, for instance if you are too rich but also had a small leak in muffler or carb, or a loose muffler etc, this might cause rattling sounds (and a very inconsistent running engine).

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05-15-2009 12:54 AM  9 years agoPost 9
rcjon

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Macon, GA

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Baffle loose in muffler? Align mufflers are bad about that.

Ask your doctor if your heart is healthy enough for Radio Control Helicoptering.

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05-15-2009 01:02 AM  9 years agoPost 10
Yug

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UK. Herts

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+1 on fan installation

Vegetable rights and Peace

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05-15-2009 02:02 AM  9 years agoPost 11
2LTime

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Walworth,NY

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I would start the engine, if the noise is there, loosen the four fan shroud screws and wiggle the shroud around. This will tell you where the problem is. The shroud rubbing does sound like an engine problem.

Jeff

If you can't learn to do it well, learn to enjoy doing it badly.

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05-15-2009 08:28 PM  9 years agoPost 12
MattHarper

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Lancashire, UK

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Thanks all and 2LTime, you may have confirmed my suspisions. The shop put four flights on the engine with no fault found. I've just installed the alloy fan on to the engine and dry assembled it in the heli to check for clearance between the governor sensor and fan. Needless to say that there is loads of clearance. So it can only be the muffler (baffles seem OK, no rattles when shaken) or the fan shroud. Thinking aloud, the metal fan chimes like a bell when tapped so if it hits the shroud it may create the noise which I heard. Is it worth turning the engine over on the starter whilst adjusting the shroud ?

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