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  • September 22, 2018, 03:31:21 PM

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Author Topic: Horn Sizing  (Read 303 times)

Offline Curare

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Horn Sizing
« on: June 21, 2018, 05:45:57 PM »
Just another hypothetical - which may lead to future real world experimentation...

OK, so since the dawn of time, and store bought horns and bellcranks there seems to have been a tacit standard in control horn heights (and geometries). Fast forward 50 years and the aircraft are larger, we're using bigger bellcranks, 1/8" horn wire. and carbon pushrods, and of course, ball links all over the place.

I know everyone loves ball links, and I see their place in stunt, but having seen aircraft die because of a broken ball link, and having my own issues with 'sticky' links in humid weather I'm not 'entirely' sold on the status quo.

From my limited understanding - would we be better off having the tallest horns we can fit inside a fuselage to lessen the loads, and reduce 'apparent' friction in the system, but also reduce compressive loads on the pushrod as well?  Am I missing something?

Furthermore, if we can make the horns tall enough, could we not revert to bushed connections, and even with a few thousanths slop, that could me reduce at the trailing edge to an acceptable limit by having overly tall horns?

Greg Kowalski
AUS 36694


Online Tim Wescott

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Re: Horn Sizing
« Reply #1 on: June 21, 2018, 06:10:37 PM »
From my limited understanding - would we be better off having the tallest horns we can fit inside a fuselage to lessen the loads, and reduce 'apparent' friction in the system, but also reduce compressive loads on the pushrod as well?  Am I missing something?

I make things as long as I can and have them still fit.  I think you may be causing more geometrical problems between the bellcrank and flap horn, because the arc traveled by those is bigger with respect to the distance between them, but I don't think it's a big deal for practical planes.  Yes, you'll reduce compressive loads, and forces on the pushrod.  Any friction at a ball link or whatnot will still reflect back to the handle just the same.

Furthermore, if we can make the horns tall enough, could we not revert to bushed connections, and even with a few thousanths slop, that could me reduce at the trailing edge to an acceptable limit by having overly tall horns?

In theory, yes.  But you may be better off trying to find an industrial source of miniature ball links, or learn how to build them and then sell them to us.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online Tim Wescott

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Re: Horn Sizing
« Reply #2 on: June 21, 2018, 06:14:38 PM »
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Curare

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Re: Horn Sizing
« Reply #3 on: June 21, 2018, 06:32:13 PM »
Tim, having messed with those things (known as Rose joints in motor racing) they're a consumable item. Expect to get one season's racing out of them, and the throw them away. Less than ideal for a enclosed stunter!

Also, are you sure about the friction being the same using large horns instead of small? I would have though you'd have a greater moment arm to overcome the friction, which could correspond to 'less' feel of it, no?

I hear you on the bellcrank - unless of course you go for a huge bell, which I don't know whether that will help or hinder or be indifferent to 'stock' geometry  ???
'
Greg Kowalski
AUS 36694


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