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Other › My Bent Metalhead Is Ready to Go!
11-20-2006 04:35 PM  11 years agoPost 21
vic20owner

rrApprentice

St. Pete, FL

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I have to admit, I find it a bit humerous that people jump up and down and scream about safety this and safety that. They warn that these things could fly apart at any minute and kill someone (which they can), yet these same people are astoundingly quiet when they see the "pros" do inverted funnels with something as big as a lawnmower 10-20 feet from spectators. I've seen video where the helis came so close to the camera that *I* ducked... even while sitting behind a computer screen!

btw, it's true that aluminum does crack when worked. Chances are your head is fine if bent back only a very small amount one time, but any more bending and it's likely to crack and fall apart. You knew that though.

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11-20-2006 05:23 PM  11 years agoPost 22
monts

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San Diego Ca

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One thing I was trying to accomplish with these tests was to confirm my instincts. My instincts tell me that there are weaker links in the safety chain that would fail before a plastic head, a metal head, or a metal head bent by a few hundredths. While it would be informative and fun to test these assumptions, as you guys point out, the tests are easier said than done.

Even the simple torque wrench rotational sheer test would not adequately represent real-world conditions. This slow motion twisting force may actually favor the slightly forgiving plastic head while a metal head may actually start to twist first.

To really prove anything, you guys are correct in that it would be a fairly extensive procedure. I was hoping that someone would take the contrary position to my initial basic assumptions; being so confident in their position that they would help with the tests and videotaping and such. The test would determine who covers the cost of parts. Initially, it seemed that there were plenty of strong and contrary opinions that we could have some fun with this, but I am not inclined to underwrite the parts and all the tests on my own.

With the 600, one would have to be even more conservative. Fortunately, it appears that these parts are of higher quality and I would guess, with a larger built-in margin of safety. I have not read as many parts failure issues with the 600.

The 600 question is much like my previous battery question. Would you guys use a lithium battery with a small ding?

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11-20-2006 05:26 PM  11 years agoPost 23
caseyjholmes

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Portland, Oregon

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I do use dinged up lipos, but I take extensive precaution before doing so. Which is Why I stated, if you honestly feel the head is safe to use, then use it! If I felt a headblock I bent was safe to use still, I would still use it. It boils down to personal opinion again, as it did in the original thread

Any accurate test would be quite extensive for the average joe who doesn't have 6-8 headblocks on hand to play around with. This is one of the reasons I can't help you out here. I have 3 metal headblocks, and two are in use (#3 has some slight modifications done to it for my own tests and modifications already)

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11-20-2006 05:50 PM  11 years agoPost 24
Jon the Rooster

rrElite Veteran

Johns Island, Charleston, SC

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Alot of Shenanigans?
Bending of a metal part is simple to fix, Replace it!
Murphy has a way of letting you think it's ok until, CrasH!!!
I replaced both Blade grips cause I didn't like the creases I saw!
Better Safe than So Sorry!
If it was on a car go for it, but in the Air Not worth the Risk!

and one more thing "DON'T BE AFRAID!"

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11-20-2006 06:01 PM  11 years agoPost 25
monts

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San Diego Ca

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I think these decisions should be based on considered thought which gets down to personal opinion. The flavor of the original thread led me to believe that I was way out of my mind for even considering tweaking a metal head a few hundreds like I did. I took it as a challenge figuring someone would take the other side and also put their money where their mouths were.

Whether a head block or a lipo, a 450, 600 or full scale, decisions are made like this every day, fortunately most of them are not way out there!

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11-20-2006 06:04 PM  11 years agoPost 26
monts

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San Diego Ca

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jontherooster

Creases in blade grips are not good, hard to fix too!

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11-21-2006 03:51 AM  11 years agoPost 27
spames

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Wayland, Ma USA

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i think you should go for it. test and retest and let all of us know. finally somethig to read thats quite interesting to say the least... i have been reading all this drab with interest. and would even help fund the project come on anyone else want a piece of the action??? let us know where to send parts or funds. after all i would like to know what the safest parts are...

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11-21-2006 04:01 AM  11 years agoPost 28
caseyjholmes

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Portland, Oregon

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figuring someone would take the other side and also put their money where their mouths were
Well, shell out the dough and set it up then. You're the one who wants to spend the time to do it, not me. If I said I would do it, you can bet I would be putting my money where my mouth is, but this is YOUR experiment here.. and I won't be paying for it

No need to get offensive because I won't fund your project. Sorry, testing part failure is not my cup of tea. I replace the part if I think it's a bad one, and don't beat the dead horse untill it comes back to life. No real need to find the breaking point of the part once it's replaced. A whole lot cheaper too.. than conducting a scientific experiment requiring the breakage of more than one headblock.

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11-21-2006 05:50 AM  11 years agoPost 29
monts

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San Diego Ca

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That's the spirit spames!

I took a lot of ridicule defending my assumption about the structural integrity and safety of my opinion. There seemed to be plenty of opposing views, (not only you, casey). I always said I would put up the parts as long as someone was there to assist (and verify).

Actually, I looked up my original statement:

"If anyone is interested in helping conduct the test, I am willing to buy them a T. Rex if I am wrong if they are willing to buy me the metal heads if my hunch is correct".

From the sounds of all those posts, I would have thought that this was a sure bet to many of you.

Without any assistance it wouldn't be as meaningful, and certainly less fun. Believe me, I don't relish the thought of spending the time to conduct the tests and coughing up the money for a new bird plus a bunch of metal heads. Since I didn't get deluged with requests for the new T. Rex, maybe my assumptions were somewhat reasonable after all.

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11-21-2006 06:19 AM  11 years agoPost 30
caseyjholmes

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Portland, Oregon

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It's all good. We all know the original reason you started this second post is because you were offended of our response in the original post, and felt you needed to prove your point. You shouldn't require our assistance to prove the point, and I don't need another heli to crash and fix. Buy me the headblocks, and I will do a test for you on video. I don't care if you are wrong or wright, as it does nothing to change my opinion.

I don't need the free trex, don't care who is wrong or right, and frankly don't give a crap if the head fails or not. Nor do I care to know the results. My opinion still stands. Aluminum DOES weaken on the second bend, weather or not it breaks. Flying with knowingly weakened parts is irresponsible. RC helicopters are not toys, and even a trex 450 can be quite deadly. I would NEVER chance anything as stupid as a $40 headblock to risk an eyeball or possibly my life.

That said, I believe we all use our best judgment to decide when a part is faulty. Appearantly, You have decided your headblock is not faulty. Why go make a big stink about it trying to prove everyone wrong? What is it that you are going to achieve by being right that your headblock won't fail at say 5,000 rpm, fully loaded?

You gonna walk around strutting your stuff that you were correct? Is that going to change my opinion? NO! I'm still not going to fly with a weakened headblock. Which brings me to state that my original opinion was simply that, and not a commitment to help you prove me wrong.

But I will do so anyways. Regardless of if the headblock would fail in real life conditions, you will not change my thinking on the subject.

Send me 4 metal headblocks (the original bent headblock as one of them) and 4 sets of align 325 CF blades. I Will do the rest on video in a controlled invironment, and make some headblocks fail. Hows that? Saves you buying a trex. happy now? Get busy on ordering, and pm me for my address.

How are you even going to prove one of the headblocks is THE headblock you bent back?!

You crash it on video, get it to warp, bend it back and use it for the test or what? Starting to sound like a waste of time/money to you yet?
I'll call your bluff

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11-21-2006 08:04 AM  11 years agoPost 31
TrexRookie

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San Francisco, CA

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monts, I would've been happy to help you with your testing, but I'm unfortunately 8 hours north of you and I'm not about to burn that much gas, nor am I about to spend that much on a plane ticket down there... if you wanna come up to the Bay Area, I'd be more than happy to tho... won't pay for your expenses though... and I do agree with Casey... I was pretty ademant about replacing weakened parts. same flight characteristics or not, bent aluminum parts ARE weaker, and is an unneccessary risk in an already potentially dangerous hobby.

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11-21-2006 04:29 PM  11 years agoPost 32
monts

rrApprentice

San Diego Ca

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I guess we can beat this thing to death.

You are correct in the sense that I started the second thread, to prove my point. My point though, is not really whether my actions were correct, but whether or not my sense of the materials I am working with have some semblance to reality.

Casey, you may feel comfortable using a lithium battery that has been dented even though damaged lithium polymer batteries can cause an even greater catastrophic result (far more catastrophic battery failures than T-Rex head failures). I, too, could have gone on about the safety risks that this practice entails, subjecting you and others to unnecessary hazards.

But after reading many of your posts I figured you knew what you're doing and didn't have a cavalier approach making these kinds of decisions.

I did take many of the responses from the first thread as that I had a blatant disregard for the safety of myself and others. So, I figured if I was risking my fully blinged SE, not to mention my own personal safety and that of others, the least I could do is put up the cost of another T-Rex to someone who could prove my lack of judgment while satisfying my own curiosity.

So how about this, the next time either of you are in San Diego I would be happy to meet with you guys. You can show me some of your flying skills and if you're up for it we could put some heads to the test. If my assumptions were wrong I'll throw in your trip down here.

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11-21-2006 07:18 PM  11 years agoPost 33
ChristianM

rrVeteran

Oslo, Norway

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As Casey has stated, aluminum will weaken when plastically deformed (permanent deformation). Aluminum has a much higher tendency to crack compared to steel. The failure mechanism that will eventually destroy the head block is fatigue so and torque test would be completely meaningless. Also spinning it up to X rpm is meaningless as this puts a constant load on the head as long as the head speed is constant. If you spin it up until something fails then it will most likely be either the blade or the bolt holding the blade grip.

The best test for this that I can think of is to run the head up to let say 3000 rpm and start pitch pumping +- 10 degrees repeatedly. After you have done this many thousand of times something will fail. Now you will have to do this with the bent head (ideally several identically bent heads) and then at least 5 or 6 new heads to achieve statistical significance and then compare the number of pitch pumping cycles it can handle. It should only take you about a year or two to complete the test

Having said all this I think you can use the head block if you inspect it for cracks regularly. Use the WD-40 technique as described in an earlier post and replace the head if you see any cracks develop.

Be safe.

Christian

Burn fuel, be happy

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11-21-2006 09:27 PM  11 years agoPost 34
TrexRookie

rrKey Veteran

San Francisco, CA

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Mind you, I'm not saying that this part will fail immediately. It could fail months, maybe years down the line when you least expect it. After someone fixes something, they tend to forget about it over time. And disaster strikes when you least expect it.
Casey, you may feel comfortable using a lithium battery that has been dented even though damaged lithium polymer batteries can cause an even greater catastrophic result (far more catastrophic battery failures than T-Rex head failures). I, too, could have gone on about the safety risks that this practice entails, subjecting you and others to unnecessary hazards.
Actually, not necessarily true. Although your heli might burst into flames and melt down, it's not going to send rotor blades hurtling at 3000rpm at any person's head. Also, LiPos that are dented WILL show signs that the battery is failing, given that the damage is significant enough... (ie. swelling of the cells, or severe inability to hold a charge) It isn't the physical characteristics we're worried about when it comes to LiPos. It's the chemical stability. Even a LiPo that looks perfectly good may explode because someone didn't charge or store it properly. A dented LiPo and a rotor head that's been bent once out of shape, and bent again back into shape, are not the same thing.

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11-21-2006 10:23 PM  11 years agoPost 35
monts

rrApprentice

San Diego Ca

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This may be getting a little a little theoretical but,

"Although your heli might burst into flames and melt down, it's not going to send rotor blades hurtling at 3000rpm at any person's head."

Explain to me how a heli that has burst into flames and is melting is precluded from sending the rotors into someone's head?

I would think that the lithium polymer battery is far more delicate than the SE metal heads in queston and has caused far more damage aloft as well as considerable damage and life threatening destruction on the ground.

"It isn't the physical characteristics we're worried about when it comes to LiPos"

I would hazard to guess that the greater the physical defects the greater the chance for internal shorts (those can happen anytime) and is always catastrophic.

Using your logic, if even a LiPo that looks perfectly good can fail, why risk using a damaged one with all the hundreds, if not thousands of posts regarding lipo failure?

I have yet to read any posts about Trex Head failures. The only failure I have heard about or witnessed with T-Rex heads is with the plastic ones. And even those appear to fail only on severe impact.

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11-21-2006 10:44 PM  11 years agoPost 36
TrexRookie

rrKey Veteran

San Francisco, CA

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Using your logic, if even a LiPo that looks perfectly can fail, why risk using a damaged one with all the hundreds, if not thousands of posts regarding lipo failure?
A lipo that LOOKS perfect may be ill-treated when charging, or may be stored in undesirable conditions. If a battery swells after a crash, then you know that it is unflyable as well. But if not, you are supposed to observe whether it still holds a charge, or if it begins to swell for any reason. At which point, the LiPo is deemed unsafe. There have been numerous TRex600s that have gone up in smoke and flames due to bad ESCs but did not burn down the field... Probably because somebody did something to prevent the flames from spreading.. For one thing, it takes some time for a fire to spread out of control, and if you just stand there while your heli is going up in flames (as opposed to calling for help and/or trying to put it out), then yea, you pose a threat of burning down a large area. In the case of rotor head flying off the heli, you have a split second to react. And even then, it might be useless.
I would think that the lithium polymer battery is far more delicate than the SE metal heads in queston and has caused far more damage aloft as well as considerable damage and life threatening destruction off the field.
Yes, LiPos are delicate, but they're designed to withstand some abuse. Do you honestly think ThunderPower would design a LiPo that wasn't able to withstand violent heli crashes? Metal heads, however, are NOT designed to bend out of shape and back into shape. And of course LiPos would cause more damage off the field. It is a battery capable of exploding. But the chances of that happening are correlated with how the LiPos are treated.

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11-21-2006 11:39 PM  11 years agoPost 37
spames

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Wayland, Ma USA

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I know...Someone should call in MITH BUSTERS

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11-21-2006 11:41 PM  11 years agoPost 38
monts

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San Diego Ca

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Perfect!

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11-21-2006 11:43 PM  11 years agoPost 39
monts

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San Diego Ca

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I guess I got to hand it to you TrexRookie, you almost had me convinced that a flaming, melting heli is not one that would be out of control and could potentially hit someone in the head.

I guess were not really making any new progress here, but I still like the odds though, of thousands of posts with some serious lipo accidents to none with the heads?

In a perfect world we could fly fully trimmed out new helicopters every flight. No worn-out parts, much less damaged ones. Face it, neither one of us is going to make many points defending the use of damaged helicopter parts.

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