RunRyder RC Helicopter Topic - Cause or effect? - cracked A frame on Spectra G.

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Gasser Model RC Helicopters > Cause or effect? - cracked A frame on Spectra G.

gramey
Senior Heliman
Location: United Kingdom

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The last couple of times I've moved my heli around there's been a strange high picthed squeaking noise. I thought it was a loose bolt on the skid bows or such like but I checked every screw and bolt on the heli and couldn't find a single one loose.

I've flown it a few times since it started making this noise but today being garage bound by heavy rain I was determined to get to the bottom of it. It only squeaked when I lifted the heli up or put it down so I laid it on it's side and pulled on the rear skid bow and to my horror found the rear A frame was cracked right through.

On the last couple of flights I'd noticed foaming in the fuel tank so my question is could this be the cause of it?

I'm not sure what's caused this frame to crack, the heli's had one crash from about 8 feet and the noise and the foaming have only started some time after this. I'm wondering if it's using the rear mount Zimmerman that's caused this failure. Has anyone else had a similar issue with their A frames cracking?

Dumb thumb specialist

11-01-2009 07:36 PM

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xcellgasman101
Elite Veteran
Location: WOODWARD, OKLA....

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Just guessing here, but I would say that you damaged the rear frame support in the crash, then after rebuild, something didn't get back into place, and caused a vibe, probley high frequency vibe, that finished off the rear support,,,, I would fix the rear frame support, then check the engine alignment, fan, run out, and balanced, I'll bet you will find something out of wack!

XGM/VGM

John Crotts
www.soonerhelicamproductions.com

11-01-2009 08:14 PM

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Toadster25
Veteran
Location: Iowa

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yeah check the delrin ball for the clutch alignment. Make sure it is
still glued on tight and not showing signs of wear.

11-01-2009 09:17 PM

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AceBird
Elite Veteran
Location: Utica, NY USA

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Quote
On the last couple of flights I'd noticed foaming in the fuel tank so my question is could this be the cause of it?

Good possibility.

On the muffler though I would say no to the cause because other people have used the muffler without the problem. I would vote for the crash causing the A frame failure.

Ace
What could be more fun?

11-01-2009 11:48 PM

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jrockstuart
Elite Veteran
Location: Allen, Texas

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Raja attributed a cracked A-frame to the Zimmerman rear mount. But I can't imagine that could be the cause. There are many other ways the A-frame could break including just the overall stress on the airframe or the crash that you mentioned. Did it break right where there is the cutout for the spark plug boot?

MinAir Spectra-G
Trex 450Pro V-bar /Scorpion /JR
Wally Motors/New England Heli/DL Canopies

11-02-2009 12:30 AM

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rbort
Elite Veteran
Location: Franklin, MA - U.S.A.

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Get yourself a side mount zimmerman...

I already posted a while back that this rear zimmerman muffler doesn't work on the Spectra and that you guys should scrap the idea. I had issues with the muffler cracking as well as it cracked my rear A frame 2 to 3 times. There is too much weight hanging back there on the A frame it breaks it at the smallest point where its relieved for the spark plug.

But you guys wanted to continue with different couplers and such and I got a nasty PM from Alex for revealing the truth but as I've always said I say it how it is good or bad. Unfortunately the rear zimmerman is not a good choice but good news is that the side mount works excellent.

-=>Raja.

1005 Gasser, G26 3DMax++, 2205+ flights
Spectra-g, G26 3DMax, 870+ flights

11-02-2009 01:04 AM

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jrockstuart
Elite Veteran
Location: Allen, Texas

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You got a nastygram from Alex, huh?

MinAir Spectra-G
Trex 450Pro V-bar /Scorpion /JR
Wally Motors/New England Heli/DL Canopies

11-02-2009 01:06 AM

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xcellgasman101
Elite Veteran
Location: WOODWARD, OKLA....

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You got a nastygram from Alex, huh?

Yea.. inquiring minds want to know!!!

XGM/VGM

John Crotts
www.soonerhelicamproductions.com

11-02-2009 01:29 AM

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Excalibur
Veteran
Location: Destination: Earth

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Not unusual to get a nasty-gram from Alex. It happened to me last year about this time when we had that long drawn-out discussion about the rear mount muffler problems.

Raja, one thing I'm still in the process of proving out is the rear mount Zimmermann with the WIDE flange spacing that requires mounting to the side frames instead of the narrow flanges that mount to the A-frame. I had ordered and mounted this previous version before they narrowed up the mounting flanges and screwed the whole thing up.

I think you're right about too much weight on the back of the A-frame, but the version I have seems to be holding up quite well without affecting the A-frame. At this point, however, I think everybody's pretty much given up (for good reason) and gone with the side mount Zimmermann or another brand altogether.

I'm going to continue this experiment with my muffler just to see what results I get. I'll post every so often, as there may be some useful data come of it.

Xcal

Camper Fuel: It's Not Just for Breakfast Anymore

11-02-2009 04:36 AM

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Fixit
Elite Veteran
Location: UK

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If it’s proven that the exhaust is too heavy for the side frames is it possible to bring a bracket up from the base plate too the mounting point?

I think if the weight was still it wouldn’t crack the frames so I personally think it will be stress from vibrations that causes the frames to crack and not the weight.

I only like to fly gassed up

11-02-2009 12:37 PM

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AceBird
Elite Veteran
Location: Utica, NY USA

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Quote
I personally think it will be stress from vibrations that causes the frames to crack and not the weight.

I concur coupled with a stress concentration due to design of the A frame. I did not know there was an issue. Makes you wonder about the integrity of the A frame without the muffler.

Ace
What could be more fun?

11-02-2009 01:29 PM

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jrockstuart
Elite Veteran
Location: Allen, Texas

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I had ordered and mounted this previous version before they narrowed up the mounting flanges and screwed the whole thing up.

I'm not sure I agree with you. Besides, I'm not convinced about the link between the rear mount and the cracked A-frame.

Do I sound like one of those oil executives who disputes the link between greenhouse gasses and global warming?

MinAir Spectra-G
Trex 450Pro V-bar /Scorpion /JR
Wally Motors/New England Heli/DL Canopies

11-02-2009 01:29 PM

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rbort
Elite Veteran
Location: Franklin, MA - U.S.A.

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All I know is

Quote
Makes you wonder about the integrity of the A frame without the muffler.

The A-frame without the muffler is fine, over 800 flights say so.

With the muffler several A-frames have cracked that I know of -- mine a few times, chilibean's, and now gramey's that are reported.

Quote
If it’s proven that the exhaust is too heavy for the side frames is it possible to bring a bracket up from the base plate too the mounting point?

I thought about this, but decided to just get away from this muffler instead of sticking with it and trying to find a solution because I wanted to fly trouble-free. If you mount it from the base plate you may very well fine a solution for it to work.

Also, Excaliber's mounting of the wide version may work as well, he's still in test mode, needs to log more flights on it to confirm that it holds together. Remember he had issues of shearing the muffler bolts and then he went to bigger bolts. There is certainly more vibrations that transfer from the engine to that area due to the rigid mounting of the muffler to the exhaust port.

Good luck to you guys, I do hope you find a solution for it.

-=>Raja.

1005 Gasser, G26 3DMax++, 2205+ flights
Spectra-g, G26 3DMax, 870+ flights

11-02-2009 03:16 PM

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jrockstuart
Elite Veteran
Location: Allen, Texas

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You have to admit that the rear mount looks pretty good.

Gramey, Raja, Chilbean: Where exactly is the A-frame cracking? Does the A-frame crack all the way through from one side to the other such that the top half and bottom half are completely separate and the engine is just hanging on by the front A-frame?

Maybe using one of the thicker Stratus A-frames with a different kind of spark plug boot would be a solution? Do they make a spark plug boot which doesn't go in at 90 degrees? Or maybe one that gives more clearance such that a different A-frame could be substituted?

I just don't like all of that sh*t hanging off the side of my helicopter. I want a sleek helicopter. Not some sort of industrial machine.

MinAir Spectra-G
Trex 450Pro V-bar /Scorpion /JR
Wally Motors/New England Heli/DL Canopies

11-02-2009 04:01 PM

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rbort
Elite Veteran
Location: Franklin, MA - U.S.A.

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At the thinnest part where its relieved for the spark plug wire.

I did talk to Minair about this a while back and gave the feedback that they needed A frames with a smaller diameter spark plug hole thus leaving extra material so it will be stronger. As far as I was told it was in the works (new design on this part) on the next run of the parts, but I never checked back about this so Justin you may want to call and ask about it.

-=>Raja.

1005 Gasser, G26 3DMax++, 2205+ flights
Spectra-g, G26 3DMax, 870+ flights

11-02-2009 04:10 PM

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jrockstuart
Elite Veteran
Location: Allen, Texas

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Let me alert Brian to this thread and see if he can comment.

MinAir Spectra-G
Trex 450Pro V-bar /Scorpion /JR
Wally Motors/New England Heli/DL Canopies

11-02-2009 07:41 PM

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gramey
Senior Heliman
Location: United Kingdom

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The A frame cracked through both sides at the thinnest part right where the spark plug goes. Basically the tail boom supports were the only connection between base plate and the upper frames. The foaming in the fuel tank has only occurred since I've had the strange squeaking noise, I hadn't had any problems with vibration up to this point the engine had been running really smooth.
The crash may have weakened the A frame although I'd flown it several times since. My rear mount exhaust is mounted pretty damned rigid and I recall somebody mentioning their concern about this, although I can't remember who. I think the rear mount exhaust will be consigned to the junk box in my garage.
The only reason the heli won't be joining it is I shall sell it to help fund a Bergen replacement. I've now got to the stage where not only is the heli a PIA but the importers didn't even have the A frames in stock and told me it would be at least two weeks to get. I've had to order the parts from Ron's HeliPro's and pay a ridiculous amount of postage, minimum $30.00, for a couple of small pieces (I ordered 2 to be on the safe side). At least the Bergen importers over here are a big enough business that their service should be better.
jrockstuart whoever Brian is if he's anything to do with MinAir then you can tell him from me that the design of those A frames is ridicuously weak for the weight and size of the heli.

Dumb thumb specialist

11-02-2009 08:21 PM

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Fixit
Elite Veteran
Location: UK

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Quote

The only reason the heli won't be joining it is I shall sell it to help fund a Bergen replacement. I've now got to the stage where not only is the heli a PIA but the importers didn't even have the A frames in stock and told me it would be at least two weeks to get. I've had to order the parts from Ron's HeliPro's and pay a ridiculous amount of postage, minimum $30.00, for a couple of small pieces (I ordered 2 to be on the safe side). At least the Bergen importers over here are a big enough business that their service should be better.

I’m not having a dig but that’s why I sold My Predator and Spectra G, I just got fed up with waiting weeks for parts and having to pay outrages prises for them and that’s when I started doing the T-Rex conversions

I only like to fly gassed up

11-02-2009 08:44 PM

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TaleGunner
Elite Veteran
Location: Deer Park WA

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I’m not having a dig but that’s why I sold My Predator and Spectra G, I just got fed up with waiting weeks for parts and having to pay outrages prises for them and that’s when I started doing the T-Rex conversions

I’m not having a dig but have you ever got your trex conversion to run the way you want

Sorry I just couldn't resist.

I think most of us would be board to death if everything worked perfect and we couldn't tinker.

CRASH! GLUE! REPEAT!

11-02-2009 09:56 PM

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AceBird
Elite Veteran
Location: Utica, NY USA

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Quote
jrockstuart whoever Brian is if he's anything to do with MinAir then you can tell him from me that the design of those A frames is ridicuously weak for the weight and size of the heli.

What is weak is the fact that it is an "A" shaped frame. Strong enough I suppose for mild 3D like Raja does but not so strong for other things. As a frame design goes I prefer a box shape frame and preferable one that uses the engine case as a member.

Ace
What could be more fun?

11-02-2009 10:18 PM

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Gasser Model RC Helicopters > Cause or effect? - cracked A frame on Spectra G.

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