Author Topic: Tip for the day: Dont use substandard parts (Read 4178 times)

Randy Powell · « **on:** June 07, 2009, 07:27:15 PM »

Well, in building my profile, I used a POS bellcrank. Seemed like it would be OK, but today it must have cracked. I'm looking at it right now and it's split at the pivot. So, the nice new profile went into the pavement. Pretty much exploded on impact. Sigh... The moral of the story is, just because it's a profile, that's no excuse to use substandard parts. To bad, too. It was flying really, really well.

Mark Scarborough · « **Reply #1 on:** June 07, 2009, 07:38:46 PM »

CRAP!!!!!

Steve Helmick · « **Reply #2 on:** June 07, 2009, 07:39:56 PM »

I'm very sorry to hear that, Randy. I gotta ask: What brand POS bellcrank was it? I won't tell!

Steve

Greg L Bahrman · « **Reply #3 on:** June 07, 2009, 08:24:44 PM »

sorry, sorry, sorry.......It was really cool

Shultzie · « **Reply #4 on:** June 07, 2009, 08:39:36 PM »

RANDY!!!
This afternoon I didn't see any divit's in the tarmac at the Narrows???
Here is the photos for the memories...if it isn't repairable?

My deepest condolences....

Randy Powell · « **Reply #5 on:** June 07, 2009, 09:15:01 PM »

Steve,

The bellcrank was a cut down version of my own CF unit. I cut it too thin and the thing split at the pivot. Stupid on my part. I should have just taken the time and laid a new one up, but I was, of course, in a hurry. Man, and it was really fly well.

Shultzie,

Uh, no. Not repairable. I suppose anything is repairable, but it would be much easier to build another. And as well as the thing flew, I probably will.

Edit: Typo

Mark Scarborough · « **Reply #6 on:** June 07, 2009, 10:55:13 PM »

Randy,
you have till saturday at one I think is when profile starts in puyallup,, better get cracking
or maybe this is the chance to change the nose length, and proof the plans Pat did for you, he could hack out the laser short kit for you in post haste most likely. Ok so maybe not by saturday,,

Randy Powell · « **Reply #7 on:** June 08, 2009, 10:33:26 AM »

Well, I'm mad at myself because I knew it was a bad decision at the time, but talked myself into it. Oh, I'm worrying about nothing. It will be fine. Hmmm...

Well, it has the benefit that I will never make that particular mistake again. I'm sure I'll find others, but not that one.

Claudio Chacon · « **Reply #8 on:** June 08, 2009, 10:37:37 AM »

Sorry for my ignorance but, what is a POS bellcrank, Randy?
And of course, very sorry to know that your plane was lost...

Best regards,
Claudio.

Randy Powell · « **Reply #9 on:** June 08, 2009, 01:24:46 PM »

Claudio,

Sorry, an American idiom. POS: Piece of, uh, excrement. Non-functional for it's intended purpose. Junk.

As Ty notes, never take your own advice at 11:30pm on a Saturday night. It's usually something you'll regret in the light of day.

Claudio Chacon · « **Reply #10 on:** June 08, 2009, 03:59:13 PM »

Quote from: Randy Powell on June 08, 2009, 01:24:46 PM

Claudio,

Sorry, an American idiom. POS: Piece of, uh, excrement. Non-functional for it's intended purpose. Junk.

As Ty notes, never take your own advice at 11:30pm on a Saturday night. It's usually something you'll regret in the light of day.

Oh, I think I get it. Does it mean "PIECE OF SH##"?

Mark Scarborough · « **Reply #11 on:** June 08, 2009, 04:07:35 PM »

that is EXACTLY what it means

Randy Powell · « **Reply #12 on:** June 08, 2009, 04:25:19 PM »

I forgot sometimes that not everyone on here is a local.

Yea, Claudo, that's pretty much it. Amazing how a bad decision can come back to bite you occasionally. The good news is, a plane I thought lost has returned to be a good flier shockingly. I flew a plane I had given up for a hanger queen last weekend after some substantial modification. For once, what I thought was wrong was, in fact, wrong and after correction it seems that the thing may turn out of be a good one. So something good came out of it.

Claudio Chacon · « **Reply #13 on:** June 08, 2009, 05:15:42 PM »

Quote from: Randy Powell on June 08, 2009, 04:25:19 PM

I forgot sometimes that not everyone on here is a local.

Yea, Claudo, that's pretty much it. Amazing how a bad decision can come back to bite you occasionally. The good news is, a plane I thought lost has returned to be a good flier shockingly. I flew a plane I had given up for a hanger queen last weekend after some substantial modification. For once, what I thought was wrong was, in fact, wrong and after correction it seems that the thing may turn out of be a good one. So something good came out of it.

OK. Now I have a new acronym to add to my list. I hear that expression in the movies quite frequently, mostly when the guy/lady refers to someone he/she dislikes badly.
My all time favorite: K.I.S.S. !

Concerning your plane, I'm sure the next one will be lighter-shinier-prettier, if that can be at all possible.
Could you save the engine/header/pipe?

Thanks,
Claudio.

Paul Allen · « **Reply #14 on:** June 09, 2009, 06:31:05 AM »

Randy
Sorry to read of your bad luck,I have learnt that if you have any doubt, at any stage of model building,
re do it! I have just started a Brodak Smoothie kit to replace my Brodak Nobler that failed a ball link, after
10 flights,I used a 1/4 scale R/C ball link, purpose made for large scale R/C and it failed,I had some doubts but
pressed on, my mistake.You never stop learning!
Paul Allen
Australia

Randy Powell · « **Reply #15 on:** June 09, 2009, 09:23:39 AM »

Claudio,

Yea, surprisingly, the engine, header and pipe seem to have survived. Engine needs a new head, unfortunately.

Claudio Chacon · « **Reply #16 on:** June 09, 2009, 09:47:35 AM »

Quote from: Randy Powell on June 09, 2009, 09:23:39 AM

Claudio,

Yea, surprisingly, the engine, header and pipe seem to have survived. Engine needs a new head, unfortunately.

That's good news Randy! You saved quite a bunch of money there....

Matt Colan · « **Reply #17 on:** June 09, 2009, 10:52:30 AM »

That Sucks Randy!!! But even standard parts fail too. My grandfather's Big Job crashed due to a leadout break at the bellcrank, a simple pull test would've saved it. Now he cut the controls out of a black tiger and put new stuff in because back when he built it, he was just getting back into stunt and put some crap horns that weren't even the same length in. Now he has to cut into the wing to keep the controls from binding, which would be a good reason why it absolutely would not turn an outside loop.

Good thing the engine is okay

Randy Powell · « **Reply #18 on:** June 09, 2009, 04:04:49 PM »

Matt,

It's one thing to put in a system that wears out. Even somewhat prematurely. This is particularly egregious to me because I'm usually kidded about my belt and suspenders approach to building control systems. I'm always figuring out what the maximum load that could possibly be needed then doubling or even tripling the specs. My usual bellcrank is 3/8" thick and this is the first time I've had a control system part fail. The fact that I knew it was questionable when I put it in just makes it worse.

But hey, lesson learned.

Richard Grogan · « **Reply #19 on:** June 09, 2009, 04:50:05 PM »

Daaaannggg! A new Deluxe RM on the board again? Sorry to hear of your loss. It's a great new design, go fer it!!

Dennis Adamisin · « **Reply #20 on:** June 09, 2009, 04:56:28 PM »

Been staying away form this thread - hurts too much. I do no think I have evr heard of THIS kind of failure before. Damned shame to lose a good airplane (heck, ANY airplane) to a preventable cause like that.

I did not see - were there any special contributing causes? did the airplane go slack then hit the end of the lines? recent hard pull test or anything like that?

Guess this is just another reminder to the rest of us to pay attention to all the control system components...

Robert McHam · « **Reply #21 on:** June 09, 2009, 05:22:43 PM »

This is a good lesson for all of us.
I believe the same thing applies with using the correct tool for the job and using quality tools as much as possible.
How often do we try to short cut situations and materials by grabbing the first convenient thing we can get our hands on?
I know I know I am guilty of this from time to time. Just because you get away with no mishap this time does not mean it was a good idea...

Robert

Randy Powell · « **Reply #22 on:** June 09, 2009, 09:33:58 PM »

>>I did not see - were there any special contributing causes? did the airplane go slack then hit the end of the lines? recent hard pull test or anything like that?<<

Well Dennis, the answer is yes. The flight before I felt a little click in the handle on hard down control. I thought there was a bind in the handle or something. I kept playing with the handle (while flying - not usually a good idea). So, I knew something was wrong. In looking at the bellcrank (now sitting here on my desk as an object lesson - I may mount it), I can see exactly what happened. The thing is split right at the pivot. When I gave it hard down control, the bellcrank sort of twisted. Enough of that and it split. Then it was only a matter of time until air pressure on the control surfaces broke the center support. As it happened, that took place as I was exiting the vertical 8.

Ward Van Duzer · « **Reply #23 on:** June 22, 2009, 08:22:15 AM »

Someone once commented to me that one of those wire horns with the plastic upright was "good enough" for a Nobler.

Guess what?

W.

Randy Powell · « **Reply #24 on:** June 22, 2009, 09:49:31 AM »

Ward,

Yea, I'm currently machining up a new plug for a mold to make another carbon bellcrank. Different design that should be a bit more stout (and put the down line in front without flipping it over). The original was fine when it was done correctly, but splitting it in half and using the cut down version was just stupid. The new one will be somewhat lighter and certainly rigid enough.

Jim Pollock · « **Reply #25 on:** July 07, 2009, 01:40:39 PM »

I think the bellcrank in my Twister will be O.K. - It's a Morris 4" and is mounted with the suspension system used in larger stunt planes.

Jim Pollock

Matt Colan · « **Reply #26 on:** July 07, 2009, 07:52:36 PM »

Randy how is Dangerous coming along? You said it had promise and that was it

Randy Powell · « **Reply #27 on:** July 08, 2009, 12:51:37 PM »

Hi Matt,

Well, the challenge is to see if I can get it to fly a decent pattern. Bottom line is, it's too heavy. But there are some things you can do to mitigate that. I managed to break the tail wheel mount last weekend and so, it went into the rack for now so I can get some other stuff done. I'll get back to it later.

Thanks for asking.

jim gilmore · « **Reply #28 on:** July 12, 2009, 09:12:13 PM »

Who is Dangerous.. Pictures we need pictures