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HelicopterHIROBOOther › Blade grips splitting?
10-23-2004 07:23 AM  13 years agoPost 1
JCadwell

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Richland WA/ Morro​Bay, CA

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I've got a new set of plastic blade grips on my Sceadu 50, running Thunder Tiger 600 carbon blades. These grips have never been in a crash or any hard bounce of any kind. They are new because I had a tail rotor failure about two months ago, and I replaced both grips after one broke.

The grips are both splitting where the metal ball link threads into the grip, on the outside. There is a plastic molding line down the middle of the grip, and it runs right into the hole that the ball threads into, and the split is propagating along that line. The ball links are plenty long, and sink deep into the grip, so I don't think it is coming out, but the split is forming.

Has anybody else seen this? I noticed it about a week ago, and kept flying, checking it regularly, and it doesn't seem to get worse. I'm looking at new grips just for retentive sake, though I don't think it is dangerous as is for the time being. The split is perhaps 2-3 millimeters long.

Thanks, John Cadwell

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10-23-2004 06:32 PM  13 years agoPost 2
I3DM

rrProfessor

Israel

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Hey John.

1. did you pre thread the holes with a 3mm bolt before threading in the balls ?

2. PM MRC-Hirobo (Jeff Green of Altech MRC) - he will take care you i am sure, he always does.

with that being said, never heard of this kind of problem, maybe you got a set with a bad mold.

www.liorzahavi.com

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10-23-2004 10:21 PM  13 years agoPost 3
marc8090

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Long Island, N.Y.

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I saw this once and it was caused by over tightening the balls into the grips. Screw them in until they just touch and maybe 1/8 turn more. Too tight and they will crack.

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10-23-2004 10:29 PM  13 years agoPost 4
raptorv2

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Deerfield Beach,​Florida

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Yes Call the guy, I read somewhere I can't remember now... (I think it was some kind of review) that Hirobo had some production problems and some parts came out bad..something about the plastic being "brittle" out of the mold. I remove yesterday a part from my EVO shaft and the part crack and split in my hands... I'm replacing it with a metal one.. mine crack also along the mold line...

Mr. Hover

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10-24-2004 02:54 AM  13 years agoPost 5
JCadwell

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Richland WA/ Morro​Bay, CA

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Did not prethread with a bolt. Perhaps I should have. I did use the ball link and threaded it once, removed it, and then put a drop of thick CA on the end and threaded it in again. Didn't over tighten that I know of. They were not cracked when I installed them. The crack developed on both grips over time, but it seems to have stopped at a certain point.

I'll PM Jeff. Not really a complaint as I love my sceadu, perhaps just an FYI. I changed the damping a bit to make it tighter and have had no problems. Was shooting inverted autos today with pirouettes and roll outs. Great flying ship.

Thanks, John Cadwell

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10-24-2004 01:07 PM  13 years agoPost 6
HobbyHomee

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Beale AFB California

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Yea I noticed both of mine split as soon as I put the screw in. Ive been keeping an eye on them and the crack hasnt gotten any worse. The screw goes in pretty far so it would have to crack a bit more before I will start to worry about mine. I think the problem is that the predrilled holes arent quite big enough. I had a hard time getting the screw to bottom out they were so tight going in.

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10-27-2004 05:11 AM  13 years agoPost 7
Erick Wipf

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Reno Nevada

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how clean is the plastic split?

I'm not sure exactly where all the "gates" are for the injection molded blade grip are, but it is quite possible that there is a "weld-line" near the hole where the plastic is splitting. The path of the plastic as it flows through the mold can create visible flow lines in the plastic, and where the plastic has connected after flowing around a hole(like a blade grip, or hole for ball link) is the weld line. This is not to be confused with the parting line which is the line created where the tool clamps together. temperature and set-up of the injection molding machine can affect how well the plastic bonds at the weld line.

I guess what I am saying is that it could be a manufacturing defect. I've seen it on Injection molded parts at my job. If it was a super clean break along the grip, I would bank on a defect.

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10-27-2004 06:25 AM  13 years agoPost 8
GordoSH-3

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Birmingham, Alabama ​ (USA)

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Hi to everyone:

Not to bust anyone's chops, but I hope all reading and commenting on this post would refrain from/reconsider flying any bird with a crack in the blade grips, no matter where in/on the grip or how large or small. The potential for serious damage/harm/injury is just too great.

I know from the original post that JCadwell has considered the safety angle (
I noticed it about a week ago, and kept flying, checking it regularly, and it doesn't seem to get worse. I'm looking at new grips just for retentive sake, though I don't think it is dangerous as is for the time being.
) and feels comfortable with his inspections, etc. But . . . I have numerous concerns: 1) Without sophisticated inspection equipment and techniques, I don't believe any R/C pilot can guarantee that the crack will not propagate to the point of failure during a flight; 2) I don't believe that a mere visual inspection between flights, no matter how frequent, will catch a potentially increasing propagation rate that may lead to an in-flight failure; 3) There is no standard for how large a crack the grip will absorb before it fails (i.e., consider the 2-3mm split described in the post; is 2-3 mm O.K. or can the grip withstand 4-5 mm??); 4) Finally, newer or inexperienced pilots may read this and come away with the idea that its O.K. to fly around with any number of items cracked or broken (YIKES!!! - has anyone not read a post from a new guy asking if it is O.K. to use epoxy to repair a broken/crashed rotor head or blades?).

Personally, I'd be really P.O. if some guy was flying at my club field with cracks in any critical flight component. I'd be double, secret P.O. if the pilot experienced an in-flight failure and someone was hurt. The $15-$20 bucks for the replacement parts (and a bit of patience until the parts arrive) is just too inexpensive to warrant exposing anyone around you to the potential risks.

BUT ON THE OTHER HAND . . . If you fly on a private, ten acre field with no one around you, then the only life/injury/property at risk is yours.

Gordo

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10-27-2004 08:43 AM  13 years agoPost 9
JCadwell

rrKey Veteran

Richland WA/ Morro​Bay, CA

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15 Acre backyard at home. Club Field at school. New grips are on the way. It's been raining for days, so no flying anyway. I acknowledge your concern. I looked at both grips, the screw is huge going into it. I made a judgement call. I've seen plenty of helicopters with scary chafing wiring, cracked all kinds of things, re-epoxied blades. Doesn't make flying with bad parts a viable solution, but they are out there and do fly.

Thanks, John Cadwell

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