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Old Jun 20, 2012, 06:12 PM
Precision Aerobatics Team
demonGti's Avatar
South Africa, GP, Randburg
Joined Dec 2006
2,020 Posts
How did the prop break
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Old Jun 20, 2012, 06:30 PM
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United States, CA, Palos Verdes Peninsula
Joined Dec 2011
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Have you tried turning your motor - maybe one of your bearings seized up?
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Old Jun 20, 2012, 08:05 PM
They Call him Dead!
YellowJacketsRC's Avatar
United States, SC, Pawleys Island
Joined Jul 2003
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First of all, Dang I am sorry to see that!

Second, this seems quite strange. The only way I know of the motor box breaking due to MF problems is when the front mounting plate breaks out. I am not aware of them breaking in this way. Am I wrong? Have others seen this before?

It is interesting to see that it broke aft of the CF reinforcement. I just wonder what went wrong? Were you doing something radical when it happened? Did you hear any shuttering prior to failure?

More info please?
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Old Jun 20, 2012, 08:45 PM
The Earth got in the way!
kuczy's Avatar
United States, OH, Canal Winchester
Joined Feb 2007
6,282 Posts
Oh man!! I was going to finally order one tonight and the motor box has had me on the fence now to see this.

The poor blue one that was to be mine may have to wait for further explanation of what happened.......
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Old Jun 20, 2012, 10:16 PM
I'm torquing to you!
Mr Kamikaze's Avatar
Wattle Grove NSW Australia
Joined Nov 2006
7,394 Posts
Quote:
Originally Posted by Dead View Post
First of all, Dang I am sorry to see that!

Second, this seems quite strange. The only way I know of the motor box breaking due to MF problems is when the front mounting plate breaks out. I am not aware of them breaking in this way. Am I wrong? Have others seen this before?

It is interesting to see that it broke aft of the CF reinforcement. I just wonder what went wrong? Were you doing something radical when it happened? Did you hear any shuttering prior to failure?

More info please?
Yeah I agree. I have seen a few pics of failures before but don't recall seeing one where the front inch and a half of the motor box broke off?
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Old Jun 20, 2012, 10:52 PM
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United States, CA, Palos Verdes Peninsula
Joined Dec 2011
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Quote:
Originally Posted by JetPlaneFlyer View Post
PS.. there is an alternative explanation. The hacker motor could have broken in flight and the flailing rotor may have ripped up the box.. it's kinda hard to be sure what went first.
I think the alternative explanation is a definite possibility. If a motor stops spinning suddenly (magnet coming loose and jamming into the stator or a bearing seizing), it could break off it's mount and swing wildly. The prop's momentum could also break the shaft off of the motor like in the picture and the prop would then be loose to strike something like the landing gear legs.
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Old Jun 21, 2012, 12:06 AM
If it's to be, it's up to me.
subsonic's Avatar
Sydney, Australia
Joined Jan 2007
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Quote:
Originally Posted by Jboy90277 View Post
I think the alternative explanation is a definite possibility. If a motor stops spinning suddenly (magnet coming loose and jamming into the stator or a bearing seizing), it could break off it's mount and swing wildly. The prop's momentum could also break the shaft off of the motor like in the picture and the prop would then be loose to strike something like the landing gear legs.
Something as simple as a broken motor wire or poor solder connection can also cause the motor to suddenly stop and lock up. I has happened many times that a simple failed bullet can lock the motor and shear the mount bolts clean off the motor, but I've only ever seen it in heli's.

Sub.
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Old Jun 21, 2012, 12:13 AM
how'd I do that....oh
chop stiX's Avatar
South Africa, GP, Pretoria
Joined May 2011
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Steve.did this maybe happen during a KE spin at WOT? sorry to see,but by looking at your pic the most damage looks like the motor is toast?any other damage to the airframe?
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Old Jun 21, 2012, 12:21 AM
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cepheus's Avatar
Canada, BC, Vancouver
Joined Feb 2009
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Quote:
Originally Posted by kuczy View Post
Oh man!! I was going to finally order one tonight and the motor box has had me on the fence now to see this.

The poor blue one that was to be mine may have to wait for further explanation of what happened.......
Don't worry, it's still worth it. If you do a few mods it will keep you smiling. The Mark 2 version will be perfect. When's that coming out? Surviving Mark 1s will be collectable.Mine's 9 mths old and is now bullet proof.Name: 021.jpg
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Old Jun 21, 2012, 01:28 AM
The Earth got in the way!
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United States, OH, Canal Winchester
Joined Feb 2007
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I went ahead and ordered it.
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Old Jun 21, 2012, 01:42 AM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
Aberdeen
Joined Mar 2006
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Thaks for the voices of support guys, worse thing is the useless UK importer has virtually no spares but thankfully I've got someone in the USA who kindly offered to forward parts to me.

Ok he
rre is the full story:

Previous flight I'd been practising hovering and harriering and I plopped it down from an inverted harrier very gently onto it's top wing. This obviously did cause a prop strike but it just gently settled on it's top wing and I cut the motor as it touched so it was nothing major. I gave the prop a good tug around to check for damage and all looked fine, there was no damage at all anywhere else.

The flight it broke it had any just took off and was flying straight and level. I opened the throttle and the motor pretty much instantly ripped out of the nose and flew away forward by 50yds or more before coming to earth.

I'm sure that the shaft and prop blade broke on impact because the prop/spinner and the motor were right next to each other, the prop would have flew away from the motor if it had broke in flight and if the prop had been on it's own I don't think there would have been enough momentum to break the blade.
As for the bullets coming loose.. I gave the plane a good inspection less than two weeks back and all was fine then. The motor leads were tight and held in place with a zip tie. In the cases where I've heard of bullets coming loose at WOT there is a lot of electrical damage, the ESC usually burns up and the wires fry, there is no sign of that at all.

The motor bearings are all perfect, the rotor still turns smoothly, the break is where the mounting plate joins to the stator/bearing tube, on the Hacker there is very little metal in this location. I pulled the stator out and there is no sign of any contact between the stator and the magnets. I've not tried but I'm sure that the motor would actually run fine if I held it by the broken stub of the bearing tube.

Having had time to think about it and examine the motor closely I'm now pretty sure that the motor went first. a lifetime of WOT KE spins must have caused fatigue damage and the inverted harrier 'landing' must have been the final straw.

Looking at the break closely is think I can see where fatigue cracks have been growing through the metal. I'll see if I can get a real close up photo.

The only damage to the airframe is de-laminated c/f on the l/g legs as landing without the motor up front wasn't the best!

Steve
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Old Jun 21, 2012, 03:10 AM
how'd I do that....oh
chop stiX's Avatar
South Africa, GP, Pretoria
Joined May 2011
2,260 Posts
lol now Steve havn't you learnt from snapping your SK3 on you slick in half with WOT KE spinsI'm g;ad ther airframe is ok though.I can't imagine toasting my AMR
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Old Jun 21, 2012, 05:44 PM
They Call him Dead!
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United States, SC, Pawleys Island
Joined Jul 2003
6,952 Posts
Well,
It sounds like you have definitely gotten some use out of that set up!!
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Old Jun 22, 2012, 04:17 PM
Registered User
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United States, PA, Wrightsville
Joined Nov 2002
267 Posts
yoooo hoo my red came in today.
guess i have some work to do now.

Craig
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Old Jun 22, 2012, 04:30 PM
The Earth got in the way!
kuczy's Avatar
United States, OH, Canal Winchester
Joined Feb 2007
6,282 Posts
Blue one should be here next week. Can't wait!
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