dual elevator bell crank question
09-15-2008, 06:50 AM
#1
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dual elevator bell crank question
Please see the following link:
http://www.centralhobbies.com/contro.../Bellcrnk.html
I plan on putting together a Venus II ARF, however, due to CG considerations there is a setup for externally mounted dual elevator servos near the back. I've had the headaches of matching dual elevator servos before. Yes I have a computer radio, linkages correct, matchbox installed. I wanted a system whereby one servo could control both halves. This looks to be the answer, however, I'm unsure of how this works. I will not be using the D.E.P.S. system as I need the stuff in the back for CG.
http://www.centralhobbies.com/contro.../Bellcrnk.html
I plan on putting together a Venus II ARF, however, due to CG considerations there is a setup for externally mounted dual elevator servos near the back. I've had the headaches of matching dual elevator servos before. Yes I have a computer radio, linkages correct, matchbox installed. I wanted a system whereby one servo could control both halves. This looks to be the answer, however, I'm unsure of how this works. I will not be using the D.E.P.S. system as I need the stuff in the back for CG.
09-15-2008, 07:08 AM
#2
Senior Member
RE: dual elevator bell crank question
Whenever you introduce bellcranks into a system, they add additional connections and connections allow slop. Ain't a big deal if you know about it and can rig connections with minimal slop. And of course you have to keep an eye out for wear. whatever..........
The bellcrank shown works ok, but actually isn't as good a solution as a Y pushrod from one servo. You've got to do significant work to place the bellcrank. Do the same or less shaping a custom Y pushrod and you've got the same functionality with no added connections and very slightly less weight.
If that bellcrank does not have a way to change it's shaft length it won't be easy at all to place in your aft fuselage. It will need to go where the plates match up very closely to the width of the fuselage. And if the two attaching plates are rigidly parallel to each other they're not going to fit most fuselages. Most are tapered. So there are a couple of issues to face as for an easy installation. I'm not going into every possibility and solution, but am going to suggest you think about how that sucker could be installed in YOUR airplane.
And then consider how much less work it'd be to create a Y connector.
The bellcrank shown works ok, but actually isn't as good a solution as a Y pushrod from one servo. You've got to do significant work to place the bellcrank. Do the same or less shaping a custom Y pushrod and you've got the same functionality with no added connections and very slightly less weight.
If that bellcrank does not have a way to change it's shaft length it won't be easy at all to place in your aft fuselage. It will need to go where the plates match up very closely to the width of the fuselage. And if the two attaching plates are rigidly parallel to each other they're not going to fit most fuselages. Most are tapered. So there are a couple of issues to face as for an easy installation. I'm not going into every possibility and solution, but am going to suggest you think about how that sucker could be installed in YOUR airplane.
And then consider how much less work it'd be to create a Y connector.
09-15-2008, 07:12 AM
#3
Senior Member
RE: dual elevator bell crank question
Next thing to think about is how easy it is to create an elevator half connector.
You can easily bend a length of piano wire for a connector. You'll need to figure out when to install it, but they work perfectly. And they can also serve as an additional elevator hinge with a close fitting tube on their center.
Dead simple to make and very easy to install in some designs and only moderately easy in others.
You can easily bend a length of piano wire for a connector. You'll need to figure out when to install it, but they work perfectly. And they can also serve as an additional elevator hinge with a close fitting tube on their center.
Dead simple to make and very easy to install in some designs and only moderately easy in others.
09-15-2008, 09:59 AM
#4
RE: dual elevator bell crank question
I agree with Da Rock coupled elevators wth a stiff tie are a good way to go in many cases.
Now if you want to use two aft fuselage surface mounted elevator servos with a Y cord its very easy to do without a matchbox and you certainly do not need a reversing Y or reversed servo. All you have to do is position them with the pushrod on one side below the servo and the one on the other side above the servo.
Very easy cost nothing and is just as good as complicating matters with a layering on of uneeded electronics such as a reversing Y or matchbox. The only time those electronic methods would be needed is when a rarely used taileron mix was being used.
John
Now if you want to use two aft fuselage surface mounted elevator servos with a Y cord its very easy to do without a matchbox and you certainly do not need a reversing Y or reversed servo. All you have to do is position them with the pushrod on one side below the servo and the one on the other side above the servo.
Very easy cost nothing and is just as good as complicating matters with a layering on of uneeded electronics such as a reversing Y or matchbox. The only time those electronic methods would be needed is when a rarely used taileron mix was being used.
John
