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Giant scale propellor failure
Bought one of these because of the attractive price and wanted to try different props:
https://hobbyking.com/en_us/aerostar...24x10-1pc.html Used it on an EME 60 a couple of times but it loaded the engine too much. About a year later I loaned it to a buddy to try on his DJ 72. He had a few flights on it and when doing some maintenance on his plane he noticed that it was de-laminating. Needless to say the prop has been promoted to paint stirrer. I'll post a picture as soon as possible. And yes, I got what I paid for.... |
Thank-you for the heads up! I bought four of those props that are labeled as 24x12 for my FG90R3, unfortunately the RPM was too high. I got the same RPM on a Falcon 24x10; turns out the 24X12 props are actually 24x10 props that are labeled wrong. Yes, I got what I paid cheaply for, lesson learned!
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Really scary. No ground contact, just about 10 or 12 flights.
My preferred props are Mejzlik, followed by Xoar and Sail props. I'll be sticking with them. |
Yipes!
I'll stick with name brand props. In over 30 years of crashing planes, I've never seen a prop delaminate like that. The closest I've heard about are the old white nylon props that would break pretty easy but that was from many years ago. carl |
Hopefully the message will get out. I'd hate to see somebody hurt by these things.
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Was it balanced or checked for balance before use? I have a new Xoar 23x10 that had soft wood in the hub section and it compressed much like your prop did on the back. Although the prop was balanced the soft wood allowed the hub to shift when tightened causing a lot of vibration. I could see the runout on the spinner as a result of the situation. Now it’s a paint stick... Xoar has been my #1 prop of choice for the past many years of RC flight and this was the first one I’ve had a problem with. So, always check your props even if it’s a trusted brand or not and pay attention to how it runs every time you use it. I watch the tips and how they track and look for vibration that’s out of the norm each time I fire up to go fly. Good catch before that prop hurt someone. Personally I don’t loan out props. I’ll give one away or ask for a replacement because you just can’t trust a used prop unless you know exactly how it was installed and used. |
Always checked for balance and runout.
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Looks like the prop bolts were tightened unevenly which could cause the prop hub to deform. I have had failures over the years with even the most expensive carbon fiber props so price is not a surefire test of quality. With wood props I always check the grain and make sure it looks OK. I have run into some funky wood props that looked like they were cut out cross grained at the hub, those are stir sticks.
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I like to give a wood prop a twist at each tip. If there is a hairline crack, it will show up much better.
carl |
Some interesting theories(?) but my take is that they used wood blocks made up from laminations rather than a solid piece. As well, the glue was either insufficient in strength or quantity. In any event, the message stands; avoid buying these props!
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I'm thinking that the over tightening had a part in the delam/failure. How much torque was applied to the bolts? |
Don't know for sure how much torque was used, but the hub isn't deformed so I question that line of reasoning. I use as much as necessary to be absolutely certain it is tight. In all my years of using wood props, I have never seen this before.
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When we first started flying indoor I was introduced to Hobby King as a cheap way to finance indoor models. Within the first year it became obvious that Hobby Klunk made inferior products prone to a higher failure/manufacturing error rate than anyone else. I stopped using Hobby Klunk because of this and thank goodness the junk they produce never made it to anything large I own. I fail to understand how one pays bottom line price point and then is surprised when the stuff turns out to be junk. What do you expect?
Dennis |
I do have to agree that buying cheap usually does not work out in the long run. I do see a prop hub that has been compressed quite a bit. I don't know if the prop was made from wood that is too soft or if it was done from over tightening. IMO the cause is of secondary concern. What concerns me the most is that the amount of compression at the hub was overlooked and the prop was used. I'm glad that the fracture was noticed and I hope that it still would have been caught if the prop had not been painted. |
In looking at the hub again it looks like individual washers for each bolt were used instead of a std prop washer, if that was the case that's a real no no. I have a couple of that brand prop and can see no obvious issues with the wood on them with close examination.
Larry |
I have used these props a lot on my aerobatic planes and I also use them on some of my larger ARF's and I have never had any problems, and I have abused some of them before. I think if there were a 'slew' of complaints regarding them, I would be inclined to be more aware of them. For now though, the do a good job for me, and I always use a hub washer and never individual washers, as per this example.
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https://cimg3.ibsrv.net/gimg/www.rcu...c3cc5b1dcc.jpg
No individual washers were used. The standard DLE prop clamp was only used along with the 4 standard bolts. Solid wood props always compress a little when the bolts tighten. Got the prop back from my friend and I cut it in half at the hub. It appears to be made from 24, 1mm laminations. I stand by my belief that the glue was lacking in either quality or quantity. In any event, I hope people avoid these Hobbyking props! |
The proper term is HOBBYKLUNK The noise they make when they hit the trash can LOL!!!!!!!
Within one indoor season the box of HOBBYKLUNK JUNK was bigger than all the stuff that worked. Lots of it was junk right out of the box. 24 indoor props in a single order so out of balance they could not be corrected or used BIG KLUNK no more junk for me LOL!!!!
Originally Posted by Lifer
(Post 12558269)
https://cimg3.ibsrv.net/gimg/www.rcu...c3cc5b1dcc.jpg
No individual washers were used. The standard DLE prop clamp was only used along with the 4 standard bolts. Solid wood props always compress a little when the bolts tighten. Got the prop back from my friend and I cut it in half at the hub. It appears to be made from 24, 1mm laminations. I stand by my belief that the glue was lacking in either quality or quantity. In any event, I hope people avoid these Hobbyking props! |
I just hope nobody gets hurt by one of these things.
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