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Building Tips and technical articles. => Building techniques => Topic started by: kevin king on March 01, 2021, 01:39:36 PM
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What's the purpose of using ball links on non take apart stunt planes? With the bell crank in the center position, the flaps should be a level position. Once the plane is done, you would have to cut the plane open to adjust anything. Seems better to have it in the correct position the first time. Same question for the elevator, it should be neutral with the flaps and bellcrank neutral. Although I can see the adjustable elevator horn being beneficial to correct any bad flight characteristics. So what am I missing? Also, what kind of ball links are being used? Thanks
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What's the purpose of using ball links on non take apart stunt planes? With the bell crank in the center position, the flaps should be a level position. Once the plane is done, you would have to cut the plane open to adjust anything. Seems better to have it in the correct position the first time. Same question for the elevator, it should be neutral with the flaps and bellcrank neutral. Although I can see the adjustable elevator horn being beneficial to correct any bad flight characteristics. So what am I missing? Also, what kind of ball links are being used? Thanks
You need ball links for adjustments and trim. We had them on R/C models also.
You might want to contact Okkie Air in the vendor's corner. He has ALL the HDWE and he'll explain.
CB
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I like the smooth feel of the controls over time
and many flights
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I too like the smoothness. Adjustability is cool but the biggest smile I found when I started using them came from having no slop. I hate sloppy controls.
Ken
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What's the purpose of using ball links on non take apart stunt planes? With the bell crank in the center position, the flaps should be a level position. Once the plane is done, you would have to cut the plane open to adjust anything. Seems better to have it in the correct position the first time. Same question for the elevator, it should be neutral with the flaps and bellcrank neutral. Although I can see the adjustable elevator horn being beneficial to correct any bad flight characteristics. So what am I missing? Also, what kind of ball links are being used? Thanks
It's not about adjustments although that is a bonus, it's about handling the 3-dimensional motion without having to allow slop. They are also much more reliable than pushrods with soldered washers. I use them on both ends of the flap pushrod, and the front end of the elevator pushrod. I have a hatch at the elevator horn end, but it has a bent wire pushrod with a keeper since there it is essentially just 2-dimensional motion. I can reach in and turn the entire pushrod so it screws into the ball link at the front.
Brett
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I use ball links on both ends of the elevator pushrod. The couplers are cut from the tie rods from the RC car counter with left and right threads. Elevator trim is allowed without the need to disconnect the pushrod from the elevator horn. I have found that a quarter turn or less on the pushrod has helped in getting the airplane trimmed to turn equally insides and outsides. There is a locknut on the coupler next to the ball cup connector to keep the pushrod from any unwanted turning. All of this with with the bonus that + ball links = no slop.
Need to remember that the adjustments using these reverse thread couplers are twice as sensitive as a single coupler. One full turn with these is equivalent to two full turn using the same thread count on the couplers.
Another bonus is that those race car tie rods are much stronger (from steel or titanium) and less susceptible to fatigue which is a problem with smaller brass couplers sometimes used. (2-56 brass couplers are deadly on a stunt ship!).
Keith
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It's not about adjustments although that is a bonus, it's about handling the 3-dimensional motion without having to allow slop. They are also much more reliable than pushrods with soldered washers. I use them on both ends of the flap pushrod, and the front end of the elevator pushrod. I have a hatch at the elevator horn end, but it has a bent wire pushrod with a keeper since there it is essentially just 2-dimensional motion. I can reach in and turn the entire pushrod so it screws into the ball link at the front.
Brett
Using this setup for the elevator do you have any means for adjusting ratios?
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Using this setup for the elevator do you have any means for adjusting ratios?
Yes, the elevator horn has a slider in a slot, held by a separate screw. I would caution against using the screw holding the ball as the clamp for the slider in any case - I have seen several of them fail (including Uncle Jimby's 20-pointer) when the ball spread the slot open and then slid unexpectedly in flight. At least use a hardened washer between the ball and slider surface.
In fact, I did have to use the slider on this airplane (unlike any of its predecessors, aside from experiments). That is, until I did a more aggressive change involving a balsa stripper.
Brett
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I haven’t built a plane with an adjustable flap/elevator ratio. When you adjust flap/elevator ratio at the elevator horn, does that usually result in a change in handle line spacing?
I would think that ideally, the flap/elevator ratio would be best adjusted at the flap horn, keeping the elevator to control handle ratio the same (no change in elevator response) while adjusting flap travel for quality of turn. I understand that the adjustment is easier to build and adjust at the elevator horn. Does a typical flap/elevator ratio adjustment make significant elevator input changes? If so do you ever make a line spacing change at the same time or do you typically adjust the ratio, fly and then adjust line spacing? How big of a change in flap deflection do you typically see in the trimming process?
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I understand that the adjustment is easier to build and adjust at the elevator horn. Does a typical flap/elevator ratio adjustment make significant elevator input changes? If so do you ever make a line spacing change at the same time or do you typically adjust the ratio, fly and then adjust line spacing?
That's what I do on the rare occasions I have needed to change it (and when I change it instead of changing the size of the flaps). But, this is a *very sensitive* adjustment as far as control load and turn quality goes, so you only have to change it a tiny bit to get a big effect. Meaning it doesn't have drastic effects on the control speed.
I also think that most people are more responding to control pressure rather than deflection, so reducing the control pressure will make it seem more responsive than the actual geometric change would indicate.
Brett