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General control line discussion => Open Forum => Topic started by: Mike Griffin on October 03, 2023, 08:56:50 AM
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I guess we take things for granted sometimes. I was reading a post on a facebook control line forum, and some asked what a suspended bellcrank was. We have new people to the hobby who ask good questions and we sometimes assume they know things that they really don't. I made this video 8 years ago for Eric Rule and he had it posted on his website. I dug it up and posted it on the facebook forum for the gentleman who asked the question and thought I would post here in case there are individuals monitoring the forum and wondered the same thing. If so, I hope this helps.
Here is the link to my You Tube video.
https://youtu.be/Vo6rVtyv78I
Mike
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I guess we take things for granted sometimes. I was reading a post on a facebook control line forum, and some asked what a suspended bellcrank was. We have new people to the hobby who ask good questions and we sometimes assume they know things that they really don't.
I had never heard the phrase "suspended bellcrank" until someone asked about it here, even though I had been using it for 25 years. There are a lot of these terms people use as if they were common, and in fact, they aren't. Same with "reversed bellcrank", I correctly guessed on that one.
This is part of why it is so difficult to have general technical discussions, because we have no standards or baseline assumed knowledge, and so you have to start from first principles every time - which is tedious to write, tedious to read for those who already know, and is hard to follow for those who don't. Add this to the things that are "common knowledge" that are 99% wrong or at least universally misunderstood, and it becomes a very difficult task.
Brett
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Gee I thought a suspended bellcrank was for Navy Carrier- the three line J Roberts job.
Dave
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Gee I thought a suspended bellcrank was for Navy Carrier- the three line J Roberts job.
That's exactly what I thought when I heard it, but the context was stunt, so I guessed what they meant.
Brett
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Gee I thought a suspended bellcrank was for Navy Carrier- the three line J Roberts job.
Dave
It's been a while since I have seen one in the box, but isn't that what they are called on the package? Because that is kind of how they work? This is one thing I have noticed on the FB groups, is that there are a lot of people that have never participated in the hobby, are just getting back into it and not used to the modern vernacular, or just have their own way of doing and saying things.
Type at you later,
Dan McEntee
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I had never heard the phrase "suspended bellcrank" until someone asked about it here, even though I had been using it for 25 years. There are a lot of these terms people use as if they were common, and in fact, they aren't. Same with "reversed bellcrank", I correctly guessed on that one.
This is part of why it is so difficult to have general technical discussions, because we have no standards or baseline assumed knowledge, and so you have to start from first principles every time - which is tedious to write, tedious to read for those who already know, and is hard to follow for those who don't. Add this to the things that are "common knowledge" that are 99% wrong or at least universally misunderstood, and it becomes a very difficult task.
Brett
Brett,
That is one of the best points that has been made in a long time. This particular item has been referred to as "suspended bellcrank" and "floating bellcrank" and maybe other nomenclatures as well. I do not know how to solve the problem you bring up but I certainly don't mind helping someone who is seeking knowledge. Again, great point you make.
Mike
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For those that plan on using a suspended bell crank remember to make sure the rod does not move up down in the mounting platforms. My Sheeks Spitfire bought the dust when the rod moved down out of the top side ply wood mount. For some reason I for got to add a ply plate on the ply mounts top and bottom. Seems the wheel collars set screws were not in the notches I had put in the wire. So now I make sure I have ply caps over the end of the bell crank posts(wire). D>K
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For those that plan on using a suspended bell crank remember to make sure the rod does not move up down in the mounting platforms.
I used this method for years until one pulled out during a pull test. Same way as Doc's only mine had bent the wire enough from some rough air antics that it slipped out of the holes, even with caps. Caps are useless if the wire bends. Since then, I have been using a brass tube with washers soldered on each side of the bellcrank and mounting the whole mess to the spar doubler, then boxing it in. I add all kinds to angled supports to help transfer the load to the entire wing. Sort of a modified I-Beam mount. Never had one fail. Amount of hardwood is about the same. It is mounted behind the main spar and 1/16"ply spar joiner. Cool part is that the bellcrank becomes removable by sliding the center wire out. I hope the pictures aren't confusing, they are from an old build. By the way, this one is *Suspended*, the one in the video is *Floating*. The difference being............. I too had never heard the term "Suspended" till I read it here years ago. It was always, as it should be, "Floating".
Ken