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Broken gear in 120 SP

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Old 09-12-2011, 05:40 PM
  #1
andym817
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Default Broken gear in 120 SP

I have a 120 SP that I finally got around to breaking in after several years of sitting. I ran 1 gallon of Byron 10% and 1/2 gallon of Cool Power 10% before installing it in my new ESM Stuka. It still had the 20x12 breakin prop on it for the maiden flight and flew very slow but it did fly it. On my landing approach the engine died and I deadsticked it in with no damage. (I have video if you like) When I returned the plane to the bench I noticed metal coming from the crankcase vent (more so than during break-in) I disassembledd the engine and found a broken gear on the crankshaft. I don't expect it to be covered by warranty, I just want to know if it is worth fixing. I know I will need new bearings as they are full of metal, do I need a new cylinder as well? The piston and rod are not scored so they should be fine. My serial # is 04-1-338

Your help is greatly appreciated,
Andy
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Old 09-12-2011, 06:05 PM
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Default RE: Broken gear in 120 SP

Thought you might like to see the set up, there is a cooling duct that scoops air from the cowl chin and directs it to the engine. My Eagle Tree temp sensor shows it running at 225 degrees F next to the exhaust elbow. I'm guessing that is pretty close to what it should be.
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Old 09-12-2011, 08:04 PM
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Default RE: Broken gear in 120 SP

Andy,
You might want to call Bill Jensen at B.J. Model Engine Service. He is an authorized servicecenter in theUS for RCV engines. Bill is a nice guy and he can answer allyour questions. Here is thelink to his site.


http://www.bj-model-engines.com/home.html
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Old 09-12-2011, 10:24 PM
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Default RE: Broken gear in 120 SP

To be able to maintain the clean look of the nose without engine parts sticking out, I would say it would be worth repairing! Let us know how it goes.

Scott
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Old 09-13-2011, 06:25 AM
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Default RE: Broken gear in 120 SP

Talk to RCV (your US agent or in the UK I think it is Weston now) as this is not an uncommon event with these motors.

I had 3 go this way (well 2 failed and 1 was on the way).
Unfortunately the solution was to send all motors back for a refund, which was happily offered.
I say unfortunately because I really liked them, despite the problems, and they haul like a freight train.

I am sure it was a fuel related issue but that will remain a mystery.
If Weston are as good as RCV were they are just the best to deal with.
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Old 09-13-2011, 05:44 PM
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Default RE: Broken gear in 120 SP

I spoke to Bill today and ordered the parts for my 120. He seemed to think the damage was caused by a prop strike. I know this was not the case as the plane only has one flight and the landing was dead stick due to the piece of gear lodged between the housing and the gear itself. No worries, it is still only around $100 bucks to replace the damaged parts. I have begun break in on my two 90 sp engines and they are much smoother and quieter than my 120 ever was. I think they will be fine once they are broken in. I'll let you guys know how the rebuild goes.
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Old 09-21-2011, 05:39 PM
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Default RE: Broken gear in 120 SP

The rebuild is complete and after another two tanks on the test stand she sounds better than when I first fired her up. Thanks for the help Bill!!!!!!
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Old 09-21-2011, 05:43 PM
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Default RE: Broken gear in 120 SP

Good deal. Glad it worked out for you....

Quote:
ORIGINAL: andym817

The rebuild is complete and after another two tanks on the test stand she sounds better than when I first fired her up. Thanks for the help Bill!!!!!!
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Old 09-21-2011, 10:33 PM
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Default RE: Broken gear in 120 SP

Great to here the good news.

Scott
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