Rookie Mistake. Screwed up Bellcrank location

[Marty Hammersmith]

     I'm building a Sig Akromaster from templates and memory. Somehow I managed to glue the bellcrank assembly in the right bay instead of the left. Can I leave it like this or do I have to cut it all out and get on the left side of the fuselage?

[Dennis Toth]

Marty,
From the photo it looks like you could simply remove the top brace, then take the bellcrank out and flip it around. This will put the pushrod close to the fuse side but on the outboard side of the fuse. If it is to close just redrill the mount a bit further out so it clears.

Best,   DennisT

[Peter in Fairfax, VA]

You might just unglue it with the hot knife method. 

Heat a knife blade red hot with a torch, then bring it to the glue, which will melt away.  Works great for epoxy and titebond, probably OK for CA, too.  I've disassembled doublers and motor bearers with this method and enjoyed the results.

[David_Ruff]

If you used CA glue you can  use CA debonder.

[Marty Hammersmith]

Thanks for the advice guys but I can get it apart. I can do that.....if I have to. What I am asking is, do I have to take it apart and move it? What sort of problems have I created by mounting the bellcrank in the bay outboard of the center instead of inside the center? From what I read I can probably leave the bellcrank where it is. That it's the leadout locations that is critical. I'm hoping to lean on some experience in that regard.

[Dave_Trible]

I won't make any difference as long as the pushrod exits fairly close to the fuselage either side to align with the elevator horn.  No flying difference whatsoever.  You can even reverse the crank -front line 'up' if need be to get there.  From what I see that's your easy fix.  Just flip the crank over making sure the leadout and pushrod clear each other.  Then the pushrod will be in close proximity to the fuse, albeit on the outside rather than inside.  Locate the control horn on the same side.

Dave

[Jim Svitko]

Maybe you have another problem--it is hard to see for sure, but did you simply loop the stranded leadout cable thru the bellcrank, then wrap and cover them?

Others might disagree with me, but I am not a fan of doing that.  I have heard of the cable eventually fraying, even when rubbing on nylon like that.  Another issue with that method is fatigue.  That loop of cable will "flatten out then spring back" (if you know what I mean) when load is applied then relieved.  This movement might be very slight but this fatigue could lead to a failure.

It might last long enough and it will not matter but it is something to consider for next time.

[Doug Moisuk]

I would use solid lead outs with that bell crank.

[Dave_Trible]

I hadn't noticed that Jim.  In this case I can't see it ever being a problem.  This is a .15-.19 powered airplane that weighs and pulls little.  Even if it did it would take 500 flights to saw though that heavy nylon.  I doubt the ship will live half that long.  It is a good lesson though for later on. 

Dave

[Jim Svitko]

Yes, Dave, on such a small plane, it probably makes little difference.  But on anything larger, a different method is needed for control system longevity.

You have been around this a long time, like me.  We have seen some bizarre failures.  When it comes to the control system, I want it so that I never worry about it.

[Marty Hammersmith]

     I am highly confident .027" braided stainless wire is going to need YEARS to saw through the Zytel bellcrank on a .15 size model.

   

[Dan McEntee]

     I am highly confident .027" braided stainless wire is going to need YEARS to saw through the Zytel bellcrank on a .15 size model.

   

    The old adage with controls was, for metal bell cranks use solid wire and for plastic bell cranks, use cable. These days , in either case, I think we have found that bushing either method is best. My son lost a model with about 100 flights on it when the up lead out broke at the bell crank. I was initially shocked to see that. This happened during an official flight at the NATS in in 2002 I think. it was a SIG plastic bell crank using Sullivan/Perfect large diameter cable lead outs. In thinking about this through the years and such, I think the root cause was that he made the loops through the bell crank too tight and the result was the lead outs had no slack, and no room to flex, except at one specific point and then the cable work hardened and broke. Even a bushing in the plastic would not have helped in this case. Since then I pretty much have used to cable through small copper tubing to attach lead outs to any bell crank, and keep the loops long and lean. I don't use music wire any more just because I hate the twanging sound when you catch the ends on something!!

     Type at you later and HAPPY HOLIDAYS!!!!!
   Dan McEntee

[BillLee]

And then there is the infamous 'laced bellcrank' that was described on the Skat Rat plans many years ago. Surely, NOBODY would make a bellcrank like that! 

[Dave_Trible]

Solid leadoffs too easily get banged and bent at the tip.  Then you bend it back but may still feel a rough spot in the controls.  Do that a few times and the wire is damaged and may break there.  If you don't fly much then maybe not an issue.  If you fly a lot,  loading and unloading into the car then solids can be a pain.  On full size airplanes I use .027 cable double wrapped-two loops going through the bell crank and the loops outside the airplane.  This way if one loop should ever break (never have) there is a backup.  I make most of my bell cranks from 3/16 Delrin which requires NO bushing and is a bearing material itself.  Even after umpteen flights there is no visible sign of wear on cranks or cable.  I find on some classics like I beams the bell crank needs to be pretty thin to keep the spar cut out minimal.  Here I use the old Veco aluminum type.  I JB Weld pieces of brass tubing into the crank for pushrod bushings.  For the leadouts I do the double wrap cable and JB steel #4 washers on the bell crank where the leadouts pass through.  The cable won't saw through that in my life time anyway.

Dave

[Steve Helmick]

Solid leadoffs too easily get banged and bent at the tip.  Then you bend it back but may still feel a rough spot in the controls.  Do that a few times and the wire is damaged and may break there.  If you don't fly much then maybe not an issue.  If you fly a lot,  loading and unloading into the car then solids can be a pain.  On full size airplanes I use .027 cable double wrapped-two loops going through the bell crank and the loops outside the airplane.  This way if one loop should ever break (never have) there is a backup.  I make most of my bell cranks from 3/16 Delrin which requires NO bushing and is a bearing material itself.  Even after umpteen flights there is no visible sign of wear on cranks or cable.  I find on some classics like I beams the bell crank needs to be pretty thin to keep the spar cut out minimal.  Here I use the old Veco aluminum type.  I JB Weld pieces of brass tubing into the crank for pushrod bushings.  For the leadouts I do the double wrap cable and JB steel #4 washers on the bell crank where the leadouts pass through.  The cable won't saw through that in my life time anyway.

Dave

Solid "piano wire" isn't what it once was, either. I think it was Pylon/Sullivan that used to be the good stuff, and K&N was the dull finished wire that I found nearly useless. The difference is the shiny surfaced Pylon/Sullivan (and SIG?) wire was double drawn through the dies that form it. The second trip work hardens the surface and gives the shiny finish.

Frankly, I would flip the bellcrank, to get the pushrod closer to the fuselage. I would also suggest moving the pushrod closer to the pivot, and bush the leadouts as previously mentioned. IMO, it's best to build the controls with the idea that the model will last for 2,000 flights. It might not, but what if it does?    Steve

[Jim Svitko]

And then there is the infamous 'laced bellcrank' that was described on the Skat Rat plans many years ago. Surely, NOBODY would make a bellcrank like that! 

I had never seen that set up before.  I wonder how long that method held up.

[944_Jim]

I fly small...I don't fly to compete...I fly alone. All mentioned to indicate why/where I'm going with what follows:

Mr. Marty,

How long do you hope the model will last? That is, how many actual flights do you hope to make before you call the model "used enough?" Since you are scratch-building this one, do you plan on building another one upon this one's demise?

I ask that last one as I enjoyed one of my prior planes. I'be learned things since that I want to apply to the next copy of this plane.

How much effort would be involved in cutting another bellcrank shelf and glueing it where is should be? Or, how about flip the wing over? Is is a symmetrical wing after all.



Regarding. Mr. Steve's statement...2k flights? I would never build another model if I kept it/them that long since I don't have an aircraft hanger. Do competitive pilots actually get to fly the same plane that many times? I'm not trying to be a smart-aleck, I'm just amazed!

[Jim Svitko]

For quite some time, I used solid leadouts.  Usually 0.031 diameter.  It was easier to terminate the ends, but I always worried about the leadouts being bent and thus causing another problem.  I finally went to stranded leadouts, and making my own bellcranks and teardrop fittings.

This is probably unnecessary for smaller planes, but it is how I do things now:

I slip the cable thru some brass tubing, then bend that tubing around the teardrop fitting.  The teardrop fitting has a groove filed in it for the tubing to rest in.  I then wrap the cable like I would the lines.  I can't think of another way to do this so that it can last a long time without worry.

[Dave_Trible]

I fly small...I don't fly to compete...I fly alone. All mentioned to indicate why/where I'm going with what follows:

Mr. Marty,

How long do you hope the model will last? That is, how many actual flights do you hope to make before you call the model "used enough?" Since you are scratch-building this one, do you plan on building another one upon this one's demise?

I ask that last one as I enjoyed one of my prior planes. I'be learned things since that I want to apply to the next copy of this plane.

How much effort would be involved in cutting another bellcrank shelf and glueing it where is should be? Or, how about flip the wing over? Is is a symmetrical wing after all.



Regarding. Mr. Steve's statement...2k flights? I would never build another model if I kept it/them that long since I don't have an aircraft hanger. Do competitive pilots actually get to fly the same plane that many times? I'm not trying to be a smart-aleck, I'm just amazed!

Well yes sometimes they do.  Two drivers of that;  1.  a few fly many hundreds of practice flights in a year.   2.  some just don't build new ones very often.   I can fly quite a bit although my flying weather season is only about 1/2-2/3 the year where some live in much better climates where year-round flying is possible.  I also like to build a lot so I move on to newer airplanes more often.  Some build a new one every 3-4 years.  I build a new one every three to four months so it's doubtful I get more than 250 to 300 flights on any one airplane.  After that they are passed on to others or scrapped out for parts except in rare cases where I think the ship is really outstanding and I MAY use it to compete in the future again.

Dave

[Jim Svitko]

As far as the 2,000 flights go, I think that number gives a good safety margin.  So, it is a good idea to incorporate long-lasting features in the control system because you never know.

Competitive fliers will put in many flights just to get the plane trimmed to their liking.  Then, practice with that same plane, over and over.  It is good to have a robust control system.  The loads on the larger planes are far beyond what the smaller planes have to endure.  Even smaller planes, such as Classic era, can be expected to take a beating.

I have seen too many failures with components that were thought to be "good enough."

[Marty Hammersmith]

      Do you think maybe we've gotten too far away from the original question? I asked about the bellcrank position of my scratch built .15 size Sig Akromaster. We've gone off into solid leadouts, how I apparently poorly attached the leadouts (good enough for Sig and Brodak) and now we're talking about competition practice. It's a Sig Akromaster. Anyway, I've sheeted the wing now and have moved on. I think we can close this thread. I'll report back if my leadouts fail. Thanks for all the comments.

[pmackenzie]

     I am highly confident .027" braided stainless wire is going to need YEARS to saw through the Zytel bellcrank on a .15 size model.

   

The problem is not sawing through the nylon, it is the cables fraying from flexing where they go though it.
I had them fail like this on a Gieseke Nobler, totaled the model. Lots of flight on it, but if that had not failed I would have gotten lots more
It could have been the quality of the cable that came with the kit that led to it, but why take a chance?

[Ken Culbertson]

Do competitive pilots actually get to fly the same plane that many times? I'm not trying to be a smart-aleck, I'm just amazed!

Short answer - yes.  Some more than others but I know a few that definitely did.  When you say the "plane" what you really mean is the wing.  A really good wing will likely end up in several planes.

ken

[Ken Culbertson]

      Do you think maybe we've gotten too far away from the original question? I asked about the bellcrank position of my scratch built .15 size Sig Akromaster. We've gone off into solid leadouts, how I apparently poorly attached the leadouts (good enough for Sig and Brodak) and now we're talking about competition practice. It's a Sig Akromaster. Anyway, I've sheeted the wing now and have moved on. I think we can close this thread. I'll report back if my leadouts fail. Thanks for all the comments.

Sorry about that.  My advice was going to be to just leave it as is and maybe move the fuselage over just a bit so that the left edge is over the center rib.  At least yours was just in the wrong bay.  I once put the whole controls, leadouts and all in the wrong wing, but hasn't everybody done that at least one time?

ken

[Marty Hammersmith]

Sorry about that.  My advice was going to be to just leave it as is and maybe move the fuselage over just a bit so that the left edge is over the center rib.  At least yours was just in the wrong bay.  I once put the whole controls, leadouts and all in the wrong wing, but hasn't everybody done that at least one time?

ken

Oh Ken THAT is an interesting idea. I'm open to a little more thread drift if we can talk about sliding the fuselage outboard a bit. How far? How does one determine that?

I have caught my breath a couple times fearing I'd put everything in the wrong direction. Then I remembered I had flipped the wing upside down. Whew!

[Ken Culbertson]

 

Oh Ken THAT is an interesting idea. I'm open to a little more thread drift if we can talk about sliding the fuselage outboard a bit. How far? How does one determine that?

I have caught my breath a couple times fearing I'd put everything in the wrong direction. Then I remembered I had flipped the wing upside down. Whew!

My brain fart came the same way.  I forgot I had flipped the wing on the jig and finished it upside down.  Luckily for me it had a floating bellcrank mounted at the center joint.  I just flipped it over.  Had to swap tips since I had already mounted the leadout guide.  Now I write Top and Bottom on the TE center.

You don't want to go too far or you have the fuselage attached to the wing where there is no support.  An extra 1/4" on the inboard of a profile is a simple tip weight adjustment, you will need a hair less.  At least that gets the pushrod closer to the fuselage.  If you are using ball links I would not (others probably will disagree here) mount the elevator horn further out to keep the pushrod straight but I would put the ball link on the outside of the elevator horn to keep it as straight as possible.  Just check it periodically to make sure it is not wearing out, they routinely outlast the plane.  You should use a ball link on both ends. I would consider using some fillets on the wing joint as well.  Most profiles don't use then but it will add a lot of strength to the wing joint.

Good luck - I hope others add their ideas.  I love learning the many ways to skin our cats! 

Let me add a PS - most of us here are competition fliers at one level or another.  If there is anything wrong with the control system of a competition bound plane FIX IT.  No exceptions.  Once the finish is on the temptation is to leave it and hope for the best.  I am fighting that urge right now with a stab that has the wrong incidence - and loosing.

[Marty Hammersmith]

Thanks Ken. I flew IMAC R/C precision aerobatics competition for 3 years. I won 28 contests and 3 regional championships. It nearly ruined the hobby for me. I became a jerk treating sport fliers as inferior. when people start talking about competition, I can’t get away fast enough. I will never get involved in competition again. All of my control line activity is strictly for fun.

I think just for fun I will scoot the fuselage outboard a smidge when I get that far.

[David_Ruff]

Thanks Ken. I flew IMAC R/C precision aerobatics competition for 3 years. I won 28 contests and 3 regional championships. It nearly ruined the hobby for me. I became a jerk treating sport fliers as inferior. when people start talking about competition, I can’t get away fast enough. I will never get involved in competition again. All of my control line activity is strictly for fun.

I think just for fun I will scoot the fuselage outboard a smidge when I get that far.

I am just a sport flyer and fun flyer and fun crasher.  I like to build.  I will never compete; too old and don't care.  My perfection days were when I was an Explosive Ordnance Disposal Tech.  You know; when a mistake kills people.

[Dennis Toth]

Marty,
Moving the fuse a bit is a good solution, just add a rib doubler to have some additional strength under the fuse and it will be fine. What ship is it?

As to competition, maybe consider Old Time Stunt. If is a fun event with fun flying being more the thing then serious competition and is a simple pattern to learn and fly.

Best,   DennisT

[Ken Culbertson]

My perfection days were when I was an Explosive Ordnance Disposal Tech.  You know; when a mistake kills people.

I can relate to that.  I was in fighter weapons in the USAF and was trained in EOD as part of my job.  I had to disarm hung weapons when they returned with armed fuses.  I only had to do it once for real.  I was 29 when I started and 33 when I finished 15 minutes later.  My hat's off to you!

Ken