SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Jul 16, 2013, 12:46 PM
Win=span\massXpractice+lu ck
webbsolution's Avatar
Joined Jul 2007
3,091 Posts
Alert
Bell Crank failure in HighEnd -

I purchased a used HighEnd as a trainer for my little girl last winter. She wanted to learn how to fly and maybe join her dad as a junior one day down the road at a WC event. The model was repaired on a wing tip from what appeared to be a minor ding. There was no other damage. I flew it 6 or 7 times to trim it out and test it on our mega bungees. It seemed to be an able aircraft - nice and stable. I spec'd it out on most of the occasions I flew it and put it through its paces. I had no issues.

A couple weeks ago I took it out with the hopes of teaching a friend how to throw f3J style overhand with some tension. I did a safety check which was a hand toss for trim checks. Then I launched with the mega bungee. The launch was stable and essentially everything I expected. I handed the model to my friend for his first J throw - he went back to a decent tension and then threw - the model rotated slightly - climbed about 120 feet and while still moving at an easy 70 KMH I lost elevator control. I had no time to react and the model piled in with full bungee tension - Everything was destroyed accept the fuse aft of the canopy and the stabs.

On inspection I saw that the bell crank had failed - the brass insert broke out of the plastic retainer. You can see daylight in the area where the brass retainer for the drive pin should be and you can clearly see the broken plastic ring in the picture supplied.


I contacted the distributor who felt the manufacturer would not be interested in this case since the model was not new - I dont feel like these components should be expiring before other pieces. I would have been fine if the spar failed or delamed but this is a major control point that should outlast the airframe in my opinion. So I am out a plane but lucky to have not injured or killed anyone.

I have only been flying F3J for 10 years - In that time frame I have flown roughly - 20 contest grade models and some of them were flown intensely for years. I have had components fail...I had an orca wing fail - Manufacturer replaced it due to an obvious production oversight - I had a X2 fuse fail - Nan replaced it free - these guys stand in the gap and it pays in the end. I was surprised not to even get a reply from the manufacturer in this recent scenario.

If you have this model in your shop I would strongly suggest you inspect it and possibly replace the bell crank. Its obviously not well designed and if yours fails like mine did - someone could get hurt.
webbsolution is online now Find More Posts by webbsolution
Reply With Quote
Sign up now
to remove ads between posts
Old Jul 16, 2013, 02:50 PM
Registered User
Tuomo's Avatar
Jyvaskyla, Finland
Joined Aug 2003
2,447 Posts
Auch Now you must give one of your Xplorers to your daughter

I have the ball link come out from bell crank come (push rod connection low in fin). It was an Aspire and the incidence happened probably because I had twisted the pushrod while adjusting servo kwik link.

Fortunately link came loose in landing, so no further damage to the plane. Repair job was a little fiddly. After some head scratching I flipped rudder 90 deg to side and hacked through rudder fin spar.

It is good to know that these parts, although reliable, are not bullet proof.
Tuomo is offline Find More Posts by Tuomo
Reply With Quote
Old Jul 17, 2013, 03:16 AM
F3B
satinet's Avatar
Warwickshire, England
Joined Sep 2006
5,541 Posts
I was once buy a model off a guy and he was demonstrating the model by assembling it and when he pushed the tails in the to fin the bell crank snapped
satinet is offline Find More Posts by satinet
Reply With Quote
Old Jul 17, 2013, 10:39 AM
Win=span\massXpractice+lu ck
webbsolution's Avatar
Joined Jul 2007
3,091 Posts
These are carbon kevlar lead filled projectiles without these parts properly functioning - I personally dont think they should ever fail without abuse- over driving a surface is within expected scenarios in my opinion.

My concern is two fold - 1) zero response from the manufacturer - regardless of the age of this design I am not sure I could endorse anything for contest use in the future - yes I know this design won a Euro tour in 07 but support is important when you are looking at 3-5 models.

2) safety - this could be a lethal scenario
webbsolution is online now Find More Posts by webbsolution
Reply With Quote
Old Jul 17, 2013, 11:45 AM
F3B
satinet's Avatar
Warwickshire, England
Joined Sep 2006
5,541 Posts
Quote:
Originally Posted by webbsolution View Post
These are carbon kevlar lead filled projectiles without these parts properly functioning - I personally dont think they should ever fail without abuse- over driving a surface is within expected scenarios in my opinion.

My concern is two fold - 1) zero response from the manufacturer - regardless of the age of this design I am not sure I could endorse anything for contest use in the future - yes I know this design won a Euro tour in 07 but support is important when you are looking at 3-5 models.

2) safety - this could be a lethal scenario
i know what you are saying but you could argue that a wing spar failure or other failure due to manufacturing defect is just as bad.

Quote:
I purchased a used HighEnd
I think that is the crux of the matter. You don't know what has happened to the model before you had it. People do crazy thigns. I heard about someone removing the foam from a spar on a slope model to run the servo wires down.

Yeah the bell crank going is a bad one because it doesn't slow the model down like other things, but anything can happen on a major failure. I feel for you really, but I think if you are telling the manufacturer about something that failed after you picked up a bag of bits you are on to a loser.

It's a huge sh*t sandwich no doubt.
satinet is offline Find More Posts by satinet
Reply With Quote
Old Jul 17, 2013, 01:04 PM
Challenge is rewarding
djklein21's Avatar
San Diego, CA
Joined Aug 2004
5,527 Posts
Quote:
Originally Posted by satinet View Post

It's a huge sh*t sandwich no doubt.
LOL, good quote
djklein21 is offline Find More Posts by djklein21
Reply With Quote
Old Jul 17, 2013, 01:15 PM
Registered User
MKSservosUSA.com's Avatar
Joined Feb 2011
91 Posts
Hey Dave,
Your bell crank failure occurred most likely from your elevator being over driven sometime over its life.
If your elevator down travel is more than the slot allows, it will place extra pressure on the plastic part of the ball link.

How do I know this?
I have broken them myself in my early years from over driving them during set up.
I was lucky I to see it and catch it on the ground.

Dave, I know you are a very talented builder and pilot but you need to understand, being a used aircraft the past owner could have caused this without knowing.
Whenever I buy a used aircraft, this is an item I check because of my past experience.

Cheers,
Thomas
MKSservosUSA.com is offline Find More Posts by MKSservosUSA.com
Site Sponsor
Reply With Quote
Old Jul 17, 2013, 01:42 PM
Win=span\massXpractice+lu ck
webbsolution's Avatar
Joined Jul 2007
3,091 Posts
Quote:
Originally Posted by satinet View Post
i know what you are saying but you could argue that a wing spar failure or other failure due to manufacturing defect is just as bad.



I think that is the crux of the matter. You don't know what has happened to the model before you had it. People do crazy thigns. I heard about someone removing the foam from a spar on a slope model to run the servo wires down.

Yeah the bell crank going is a bad one because it doesn't slow the model down like other things, but anything can happen on a major failure. I feel for you really, but I think if you are telling the manufacturer about something that failed after you picked up a bag of bits you are on to a loser.

It's a huge sh*t sandwich no doubt.
I agree that used birds have risk - If the spar had failed I would have chalked it up to "caveat emptor". I consider spars to be one of those components that will fail - launch a plane hard for a long time and its going to break. If the wing delamed I would as well just repair it and be happy that its still flying.

I just dont think this piece should be failing on a model that was not abused. This model was not abused. The stabs were perfect - the fuse was in great shape. The wing aside from a little ding was spotless.

Anyway "you pay your money, you take your chances" life is a gamble and I lost that one.

When my X2 3.5 fuse failed from obviously abusive wind at the F3J WC Nan sent me a new one with my requested customization (free). The wind in South africa was 40M second gusting to even higher once in a while. Nan was there too and could have said that these conditions were beyond the limits of what the models were intended to be flown at. They did not.

I get a lot of people asking me if I would consider switching to model ____ and then I remember moments like this and buy another Xplorer.
webbsolution is online now Find More Posts by webbsolution
Reply With Quote
Old Jul 17, 2013, 01:46 PM
Win=span\massXpractice+lu ck
webbsolution's Avatar
Joined Jul 2007
3,091 Posts
Quote:
Originally Posted by MKSservosUSA.com View Post
Hey Dave,
Your bell crank failure occurred most likely from your elevator being over driven sometime over its life.
If your elevator down travel is more than the slot allows, it will place extra pressure on the plastic part of the ball link.

How do I know this?
I have broken them myself in my early years from over driving them during set up.
I was lucky I to see it and catch it on the ground.

Dave, I know you are a very talented builder and pilot but you need to understand, being a used aircraft the past owner could have caused this without knowing.
Whenever I buy a used aircraft, this is an item I check because of my past experience.

Cheers,
Thomas
- yes it could have been done by the previous Owner - and yes I never overdrive anything but also have never seen this failure in 10 years of flying - maybe I have been lucky.
webbsolution is online now Find More Posts by webbsolution
Reply With Quote
Old Jul 17, 2013, 02:55 PM
Registered User
Brandon's Avatar
Riverside, California, United States
Joined Feb 2004
1,525 Posts
Just a thought.....

Could the age of the airframe have played a role in the failure of the bell crank?
What I am trying to get at, is maybe the material that the bell crank is made of was
not stored properly or stored in an environment where the elements made the material
brittle or weak?

B
Brandon is offline Find More Posts by Brandon
Reply With Quote
Old Jul 17, 2013, 03:11 PM
Registered User
R.M. Gellart's Avatar
Joined Nov 2005
3,589 Posts
David, the Tragi 801 early on had one circumstance that a bellcrank which was a carbon one, failed here in the USA. And to back up Thomas' comment, even on new Tragi's, I enlarge my alignment pin travel slot and actually open up a slot in the rudder drag spar to allow the stab pushrod more down throw travel aft in the fuse. Now, Heino did change to a glass, G10, style material for the bellcranks, and from what I know there has been no issues, and the slots eliminate the bind thing from happening.

Marc
R.M. Gellart is online now Find More Posts by R.M. Gellart
Reply With Quote
Old Jul 17, 2013, 03:22 PM
the flying is good
dephela's Avatar
USA, CT, Hamden
Joined Oct 2002
2,109 Posts
This bellcrank seems to be an injection molded plastic piece. It certainly doesn't look to have all the material around the hole that a laminate type has nor does it have a "flange" around the hole that would increase its strength. Lastly, if it is injection molded, the failure may have occurred at a "part line", the spot where material flowing in the mold comes together after going around a piece that would make the hole in the arm.

Dennis Phelan
dephela is online now Find More Posts by dephela
Reply With Quote
Old Jul 17, 2013, 04:02 PM
Win=span\massXpractice+lu ck
webbsolution's Avatar
Joined Jul 2007
3,091 Posts
Quote:
Originally Posted by R.M. Gellart View Post
David, the Tragi 801 early on had one circumstance that a bellcrank which was a carbon one, failed here in the USA. And to back up Thomas' comment, even on new Tragi's, I enlarge my alignment pin travel slot and actually open up a slot in the rudder drag spar to allow the stab pushrod more down throw travel aft in the fuse. Now, Heino did change to a glass, G10, style material for the bellcranks, and from what I know there has been no issues, and the slots eliminate the bind thing from happening.

Marc
Agreed I did this same mod to my 801 - but even when the slot was not allowing enough travel I never let the linkage bind - that's suicide.

More to the other post regarding injected molded pieces - possibly - its all done now - if anyone who owns a high end wants some stabs let me know -
webbsolution is online now Find More Posts by webbsolution
Reply With Quote
Old Jul 18, 2013, 07:58 AM
F3B and F3K
RetoF3X's Avatar
United States, TX, Dallas
Joined Mar 2009
1,638 Posts
Webbi

Sorry for the loss.

What seems to be broken on yours is the ball link. The High end has a small bell crank at the bottom of the fuse, then the elevator is actuated with a short pushrod with a ball link. Seems really odd that the ball link broke.

There are two details that were not too well solved on the production High end, can you please check on yours if they have been rectified:

-The balsa shear web of the spar is horizontal instead of vertical

-at the hinge line, inner and outer skin are not connected. Normally, a window is cut in the sandwich material prior to moulding, that way the inner and outer glass (or carbon) skins are connected (bonded) at the hinge line. In my High End (and others, even the ones Tobias Laemmlein got), the sandwich was moulded without cutting the rohacell window and the sandwich was opened afterwards to get the hingeline moving. You can see that if you deflect the flap down and if you see a tiny strip of exposed rohacell, then that is the case.

The detriment on doing a hingeline this way is that the sandwich is interupted at the hingeline and is prone to delamination. Just a shock (hard landing, midair) can cause the outer skin to delam and peel off the sandwich material.

All modern F3B and F3J planes have a hingeline where inner and outer skin are bonded together and greatly reduce delams of the outer skin.

Best,
Reto
RetoF3X is offline Find More Posts by RetoF3X
RCG Plus Member
Last edited by RetoF3X; Jul 18, 2013 at 08:04 AM.
Reply With Quote
Old Jul 18, 2013, 12:02 PM
Win=span\massXpractice+lu ck
webbsolution's Avatar
Joined Jul 2007
3,091 Posts
Quote:
Originally Posted by RetoF3X View Post
Webbi

Sorry for the loss.

What seems to be broken on yours is the ball link. The High end has a small bell crank at the bottom of the fuse, then the elevator is actuated with a short pushrod with a ball link. Seems really odd that the ball link broke.

There are two details that were not too well solved on the production High end, can you please check on yours if they have been rectified:

-The balsa shear web of the spar is horizontal instead of vertical

-at the hinge line, inner and outer skin are not connected. Normally, a window is cut in the sandwich material prior to moulding, that way the inner and outer glass (or carbon) skins are connected (bonded) at the hinge line. In my High End (and others, even the ones Tobias Laemmlein got), the sandwich was moulded without cutting the rohacell window and the sandwich was opened afterwards to get the hingeline moving. You can see that if you deflect the flap down and if you see a tiny strip of exposed rohacell, then that is the case.

The detriment on doing a hingeline this way is that the sandwich is interupted at the hingeline and is prone to delamination. Just a shock (hard landing, midair) can cause the outer skin to delam and peel off the sandwich material.

All modern F3B and F3J planes have a hingeline where inner and outer skin are bonded together and greatly reduce delams of the outer skin.

Best,
Reto
Yes its an odd failure at best. Thomas makes a good point about over driving being a potential for a root cause of this failure but I really have a hard time thinking that the drive system is not strong enough to stall a servo - even the venerable 3421 which was on this plane and cause the plastic to fail. Its just a bad component decision at the manufacturing level. Noted for future purchases...

Thats good information on the spar and hinge line to determine the age of the model - since on one side the spar is fully exposed it easy to see...(let me walk into my shop and check) - yup balsa spar - it looks like a continuous balsa spar and not a sheer web - but its horizontal and not vertical - Wow -

Hingline - well this wing is destroyed so that doesn't matter now but good to know if I ever have to identify another HighEnd.

Well its our team selects in a couple days - and the silver lining was that I was going to loan this model to a friend to fly at this contest - if I had not found this weak link before then he would have felt bad and we could have had an injury so its a blessing in disguise I say! I will be putting a few of my X2's through their paces today doing some landing practice. By Sunday we should know who the Canadian team is and or if we have a team Not many J pilots trying out this season for Canada.
webbsolution is online now Find More Posts by webbsolution
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Bag of Bell Cranks (6) TGKconnectors Non R/C Items (FS/W) 4 Apr 24, 2013 12:06 PM
Discussion Bell Cranks tigreflyer Control Line 6 Mar 02, 2013 09:35 PM
Discussion pull-pull crossed: how calculate bell crank? sroge The Builders Workshop 11 Feb 05, 2013 09:01 PM
For Sale HD Tiller Bars, Bell Cranks and Differential Bell cranks-Price to sell unclegeorge Aircraft - General - Miscellaneous (FS/W) 0 Jul 09, 2011 08:46 PM
warning elivator bell crank failure on nyx f3f charlieuk Slope 20 Sep 30, 2004 05:46 PM