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Re: Internal Elivartor Linkage using a Bellcrank

I require an internal linkage system for my elivator that needs to run

> through the fin. The stab sits just over half way up the fin so the > linkage needs to come into the fin at the bottom, onto a bellcrank and > up to an arm connected to the elivator itself. All within the fin > itself. Ive build a test fin and it seems to work ok but theres a little > slop. Does anyone know of any articles or pics of something or weather > this is a common method to link up a higher up the fin elivator?? > > Cheers Grant > >

You can use a very flexible snake to do the same sort of thing without a bellcrank.

Bellcranks always introduce SOME play. Make the bellcrank and horns as big as possible to reduce this.

Another possibility is a pull-pull system with thin wires running over pulleys.

The best way is probably a tail mounted servo and an extension wire :-)

Reply to
The Natural Philosopher
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Hi there, thanks for your reply. Ive tried the snake method, but the stab is to high and it requires the plastic flexi cable to bend to much which creats real stiff movment. The fin is 10mm at its thickest so I dont have room for a server. Slop is the main problem im having with a bell crank at the moment. If anyone has any ideas or pictures of how they have mounted a stab high on the fin that would be great? Surly there is a good way of doing this otherwise how do they go about the linkages witin a tTail?

Cheers Grant

The Natural Philos>

Reply to
Grant

Get with the glider guiders. They do this all the time. A couple of questions though, is this a flying stab or a conventional fixed stab with elevator hinged to it? Can make a difference.

If a flying stab, use the flex cable aka Sullivan. I've used this for this very purpose and it works well. If a powered plane or large glider (over 2 metre) I'd go with the larger Sullivan cable. The trick then is to secure the outer tube to the frame work in as many places as possible. Leaving as little as possible unsecured at the end for flex.

Another option depends on how wide the fuselage is at the tail? If it's wide enough to house a low profile servo, you may be able to mount one back there and run a pushrod up to the stab. But remember, an extra ounce in the tail means several more in the nose.

Reply to
Fly Higher

Thanks for all the replys, some good suggestions. Ok, ill shed a little more light on this.

The plane intended is a 2m (Ail/Ele/Flap) plane optimised for DS'ing. The entire setup NEEDS to be strong.

The fin is built of solid 5mm balsa sandwiched between two peices of 2mm balsa and then glassed for strengt. There is really only 5mm where the cable or wire can run up to the elivator. The elivator is hinged to a stabilizer. Also the fin doesent get glued ontop of the fuse, the fuse sides actualy get glued directly to the fin sides so the fuse and fin are practacly one peice, no room for a servo bellow the stab.

Ill try to post a plan of the tail up soon. The main thing is I cant use any light cable setup as this thing is being built to go fast so there will be a fair bit of pressure on this spot.

One good point with the bell crank is that you can set it up so that when the servo pulls it makes the elivator move up, this is ideal for DS'ing as that would pull any slop it had out. Just a thought.

Anyway, Ill post soon let you know where you can see a drawing of my tail. Many thanks.

Cheers Grant

Fly Higher wrote:

Reply to
Grant

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