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Building Tips and technical articles. => Building techniques => Topic started by: Leester on September 10, 2006, 10:59:05 AM
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On a standard Brodak or Sig bellcrank you have a selection of holes for your pushrod. Which one do you use for a flapless plane? and is it a different hole for one with flaps? Is there a set measurement from the pivot that works best? I am refering to a 3" BC. Thanks
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I've always used the middle hole for both flapped & unflapped airplanes.
Walter
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Hi Ty & Leester,
I use 5/8 from the pivot, but that dimension is based on the control horns used. Also 5/8 is whats recommended when using Tom Morris hardware. So 7/16 may be good for you and the horns your using but the actual dimension should be based on the total system and the dimensions of the horn pivots etc. I find that the 5/8 dimension produces controls that are not considered fast (good for this old guy) but speed can be increased by wider handle spacing. Anyway it works for me and it also keeps me from overcontroling as in the often seen bobble at the 5 ft. pullout from a wingover. This is all based on a 4 inch bellcrank.
y1
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Thanks guys, it looks like the middle hole is the closest to the measurements given and what Walter said. So does moving the pushrod farther away from the pivot slow down the controls?
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Thanks guys, it looks like the middle hole is the closest to the measurements given and what Walter said. So does moving the pushrod farther away from the pivot slow down the controls?
NO! ;D
Moving the rod further out gives MORE control, closer in gives less, on the bellcrank.
Opposite for the horns.
Bill <><
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While moving the push rod in or out on the bellcrank does obviously increase the total distance the push rod is going to travel, I think it is more important to think in terms of SPEED of the controls as Greg said. I personally use nearly all Windy's 4 inch bellcranks with the hole 8/10th of an inch from pivot. Bob Hunt uses 9/10th. that works for me too. I almost never use 3 inch BC's any more. But when I did Dixon told me to redrill sig BC's to 7/16. That worked for me. Those Old time control systems were toooooooo fast!
To describe it better, It's personal choice!
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While moving the push rod in or out on the bellcrank does obviously increase the total distance the push rod is going to travel, I think it is more important to think in terms of SPEED of the controls as Greg said. I personally use nearly all Windy's 4 inch bellcranks with the hole 8/10th of an inch from pivot. Bob Hunt uses 9/10th. that works for me too. I almost never use 3 inch BC's any more. But when I did Dixon told me to redrill sig BC's to 7/16. That worked for me. Those Old time control systems were toooooooo fast!
To describe it better, It's personal choice!
Hi Ward,
I equate more travel per input to "speed" of the controls. If the horn moves more given the same deflection of the bellcrank, it is "faster".
I believe that one of the great trimming tools we have readily available these days is adjustable line spacing on our handles. y1
Bill <><
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Absolutely...I just recently became aware of this. Had a model with an annoying "searching" habit in level flight; had to "fly" it all the time. I didn't want to move the CG forward as I liked its handling in maneuvers, so as an experiment II set the lines about an inch and a half narrower at the handle and it sat in a groove perfectly; like it was a different plane. I was impressed with the effect, and intend to use it freely.
--Ray