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HelicopterThunder TigerOther › First series of flights....first crash of the year
03-15-2003 08:34 PM  14 years agoPost 1
Kurt64

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Salladasburg, PA

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Well, I finally got my new Rap50 out for a spin today. The fix for the auto hub was working very well...in case any of you were wondering. After getting the curves set to where I wanted, I started playing around by jacking the throttle/collective to check the climbout, which by the way, is incredible! Anyway, on the 4th hard climbout, it happened. The clutch broke which made the engine scream and the heli slam into the ground from about 20 ft. I hit the throttle hold, but it was too late. Broken skids, fins, fiberglass blades, radio tray, and bent boom, main shaft, feathering shaft, etc....
I thought that the clutch problems were fixed. Mine didnt last an hour!

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03-16-2003 04:11 PM  14 years agoPost 2
Kurt64

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Salladasburg, PA

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The autopsy will reveal the true cause.
The auto hub was working as smooth as silk. If the hub failed, the machine would have either gone into a pirro, or I would only have lost tail control in an auto.
The other possibility is that the auto unit one-way bearing was slipping. I dont know of any way to test that though.
I am really ticked....it is going to hit 60 degrees today!

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03-16-2003 05:04 PM  14 years agoPost 3
Sillyness

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Little Rock AR

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That happened to a a guy I know... we never did figure out what happened. His clutch was good and his liner glued in tight. As far as we could figure it was the auto hub slipping. I moved out of the state before he got it running again, so I never got a follow-up diagnosis. Did you say you machined out some of the auto hub bearing iteself?

As for your project, I guess boca sells some one-way bearing units. I don't know much about them, but they may be a place to start for a totally new auto-hub unit.

Cheers, and happy loctiting.

Jason

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03-16-2003 05:21 PM  14 years agoPost 4
Kurt64

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Salladasburg, PA

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I just finished the Autopsy......
The clutch and liner are in perfect condition. The auto hub is in perfect condition as well as the aluminum auto bearing housing that I machined off a couple thousandths of a inch. The only things that could cause the engine to "free-wheel" would be:

broken clutch
bad clutch liner (extreme)
broken Jesus bolt
bad one-way (sprag) bearing in the auto unit
aluminum fan spinning on engine crank (almost impossible to happen)
stripped main gear
stripped drive gear

My main gear does have teeth missing, but I dont know if that was pre or post mortum (sp?). In other words, before or after the crash. It is making me wonder though....right before the crash, the engine reved up once, but then was ok for a split second .....then it just screamed. I hit the throttle hold, so the engine was at idle before it hit the ground.

Does it sound like the main gear stripped in flight or could the gears have stripped from the crash? So far that is the only evidence that leads to the engine over-speeding.

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03-16-2003 05:42 PM  14 years agoPost 5
jvsjvs

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Auto bearing problem

Hi Kurt,

I had this problem before. It is the one-way bearing that is slipping (in the wrong direction).

When it slips for a second and then grips again it is likely to rip some teeth of the main gear since the engine revs up quite badly in that split second.

I had this happen exactly like that although mine slipped for seconds at most, it never kept on slipping. I cleaned the one way bearing thoroughly. This resolved the problem for a couple of weeks. After that it started to slip again. After that I replaced the one-way bearing and the auto hub. I did not have any problem since. Note that you should not grease the auto bearing! Even if you want to oil it, the oil should be very thin! If not, it starts to slip. When I replaced mine, I did not oil it at all, it came lightly oiled from the factory.

So replace the whole auto gear and it will probably be ok.
Sorry that it has caused so much damage for you.

Best regards,

John

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03-16-2003 07:26 PM  14 years agoPost 6
Kurt64

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Salladasburg, PA

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That must be it John. I greased that one way bearing. It happened just like you said.....only the last time it slipped, I lost all head speed and couldnt auto softly. I guess I will have to order another one.
Thanks a million for that info....it was a great help!

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03-17-2003 08:41 PM  14 years agoPost 7
jvsjvs

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You are welcome Kurt.

This is what these discussion forums are for right

Good luck with rebuilding

Best regards,

John

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03-17-2003 11:54 PM  14 years agoPost 8
corey11

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Bay Area, California

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its your main gear....same thing happened to me. but i was lucky enough not to crash. heard a click and them engine started to scream. droped the throttle and then landed in throttle hold.

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03-18-2003 04:57 PM  14 years agoPost 9
Kurt64

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Salladasburg, PA

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I just finished ordering all of the parts. $200 in damage.....There goes my "crash budget" for the year!

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HelicopterThunder TigerOther › First series of flights....first crash of the year
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