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Author Topic: Elevator horn/pushrod connection  (Read 890 times)

Offline Matt Brown

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Elevator horn/pushrod connection
« on: April 29, 2024, 01:19:03 PM »
I posted the topic of unequal turning on my Pathfinder LE a day or so ago. In it I mentioned that there wasnít room for a hatch in the rear. I had cut out for the hatch but that was necessary for clearance on the ball link and bolt for the pushrod. Iím curious what others are using to connect the pushrod to the elevator horn.  Iím using an M3 x 10mm button head socket screw, Dubro 4-40 ball link and a nylok nut. That takes up about 7/16Ē width. That is exactly how much width I have in the tail of my new Legacy Iím working on. Moving the pushrod backwards like giving up elevator is starting to bind on the fuse sides. Iíll have to cut out the fuse side just to have sufficient space for operation. Iíve seen enough planes at the Nats that are as narrow or even more so than mine. Iím wondering what people are using to connect the horn and pushrod in that narrow space and still have the ability to adjust it.

Thanks, Matt

Online Ken Culbertson

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Re: Elevator horn/pushrod connection
« Reply #1 on: April 29, 2024, 01:40:30 PM »
I do mine similar to yours.  I have replaced the socket head 4-40 with a flat head Phillips used for countersinking.  That gives you about an extra 1/16".  Best answer is to widen the fuselage (My Endgame IV is 3/4" inside width at the hinge point)  or make your hatch a blister.  The wider aft fuselage gives the stab considerably more rigidity.  Leaving it fixed is not an option.

Ken
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Offline Steve Helmick

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Re: Elevator horn/pushrod connection
« Reply #2 on: April 29, 2024, 02:13:37 PM »
You could cut a rectangular hole in both sides of the fuselage and cover the holes with 1/64" plywood, fair in with 1/32" sheet balsa all around & apply sandpaper.

Or, you could do what Paul does and angle the aft end of the fuselage from the hingeline forward to give access to the elevator horn...the stab and fin/rudder all come off. I think it's a great idea, because then if your stab needs some incidence change, is skewed or tilted, it's easy to fix.  y1 Steve
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Offline Matt Colan

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Re: Elevator horn/pushrod connection
« Reply #3 on: April 29, 2024, 07:17:29 PM »
If itís not too late you could cut and widen the rear fuselage. Split the fuselage sides and add 1/8Ē between them. All you need is just enough to clear. You can also sand down the inside of the fuselage where the horn travels and give you extra room as well. My new plane I purposely made wider for this reason
Matt Colan

Offline Dave_Trible

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Re: Elevator horn/pushrod connection
« Reply #4 on: April 29, 2024, 08:14:44 PM »
I have just cut open holes in the fuselage sides where the gadgetry needs clearance-then covered the holes with silkspan in the finishing process.

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Offline Matt Brown

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Re: Elevator horn/pushrod connection
« Reply #5 on: April 29, 2024, 08:17:28 PM »
I have just cut open holes in the fuselage sides where the gadgetry needs clearance-then covered the holes with silkspan in the finishing process.

Dave

Thatís what I did on my Pathfinder. Downside is the refinishing after adjusting.

Offline Air Ministry .

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Re: Elevator horn/pushrod connection
« Reply #6 on: April 29, 2024, 09:14:51 PM »
Mutter Fume ! .

NARROW , Chisels ! 60 Wt. sandpaper strip - shiift to full up after putting paper vertical & saw away ! up'n'down ' , To get sandpaper widths clearance thru travel .
But theres a easier way . Make it WIDER . ( Ive a few where the inner groove to clear the rod ends flush / open . Domed Solder on washer protrudesfor a way , near full travel . very artistic !  ;D   LL~

Look at the wing T E to Stab L E as a Tourque Tube , neccesary to stop twist , working hard in a blow . If its anchored well there .
Cut cardboard slabs inner to match the wing T E , horn arm bush . then get srtistic . Say  1/2 in deep ' V ' Arms  .  2 1/4 long or so .

Rear the bulkhead as a L E saddle , with maybe a strip of 1 / 32 ply as per above thru under the stab and aft  away past the horn .

If thats say 3/4 deep - and a clean close joint affixed both surfaces ( Pre Glue BOTH so ne DRY SPOTS . it should stay on .

A bulkhead AT the Stab T E / Hinge Line normally whittled out to clear control movement .

My Horn , if good wire - Brass tube & washer Ea side , paper under & vasaline . 80 watt , stick solder ( plumbers bar  60 40 is hard , 50 50 is soft ) and ACID . phosphoric . Then boiled in BAKING SODA .
That Neutralisation , flushing with acetone etc . Chainsaw Bar Oil or m'Cylce chain lube .

The PUSHROD . 3/32 min . usually 1/8th wire now . But 3 mm is lighter ! good wire . Hammer Over square in VICE . wriggle to check it didnt crack ! ! ! . Some Does . or aneal bend reaneal !
A Washer . Or if not - for narrowness - file round diameter into curve inner face to wire shaft flank . for maximumum narrowness off FIT . fit , put on a thin washer , use a shaft hacksaw narrow blade
to get a cut on opposite flanks of arm - or cut circumferance 1/2 m.m. groove . So 1 m.m. pre tinned ! copper wire Half Engages pushrod wire arm & retains washer ! . Paper under washer 9 for a few thou. end float
AND NON STICK .
Solder bloddy well whilst NOT heating Bush !  :P
a squirt or two of coolant if you dont catch ' the melt ' instant like .

THEN file , or Cut & File down narrow . As youd left the Arm Long to ensure it was square / parrallel - to Hinge Line . By now its midnight & your dinners cold . So starty early . Its NOT a five minute job .

Timber ( BASS ) Pushrods get equal barometric expansion to timber fuse & negate necessity for length adjustment . So They say !  But Adj at flap horn or telescopic joint maybe .
But Two wire pushrods into brass tube joiner ! / youd never know if the inner tube was fully tinned or would part . Plus its a failure point if you kinked the tube wall , maybe .

SO 1 in or 1 1/4 in at the stab L E is about it for a 46/60 flat side ship . taper in a bit to hinge , then taper away more to rudder post or aft edge . Perhaps .    H^^

a liight ply circumferance to any hatches & Super glue ' hardening ' of  balsa & ply ' edges ' . PLUS dope thrown inside so as LUBE dont soak into structure . As In Dope Inside ! too . MATE .

Offline Air Ministry .

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Re: Elevator horn/pushrod connection
« Reply #7 on: April 29, 2024, 11:48:35 PM »


There , the hard brass tube , washer each side , thru the horn , isnt yet filed back to working length . One you can see is longer . Like that with wire through to align , or cut AFTER fitting to the horn .
Here , the hardware store brass ( chinese ) washers , sometimes theres smaller lighter thinner ones , rather than the 3 x ? ( or so ) bolt diameter . i.e. 1/8 in. hole 3/8 in O.D. . Theyre say 2 x hole size O.D.
if you want to save by the gramme . BUT adequate solder fillets are are a necessity .

The Brass Bushes are best left say 1/4 in. long .

The Pushrod Wire end , left long ( a few inches ) despite best laid plans , usually gets a final teak , so the bush rotates free on the pushrod end & in the horn . fitted . or just about .

For weight , the wire pushrod ends ussually only a few inches long . Lapping the carbon pushrod say 1 1/2 inch   . Hole or slot if Zer Zero is got after all else is secured .
Use a bike spoke end to pull thread binding up & push down / around .  :( Try looping on the rod , fitting wire , sliding the bundle aft & taughtening off , but usually thats a tangle .

The holes in the horn there are often ' tap fit ' , deburr & maybe chamfer a wire end , push firmly , or tap thru  . Firm sliding Fit . Sometimes the ' keeper wire ' has a FLAT .
So the holes overlap . Pilot drill . Drill half thru from both sides , then finish drill . . Tricky but o.k. if you get it right , say - 1/32 on the centers .

Its essential you pre solder - TIN  - all the wire bits where they join , beforehand . After sanding wire bare first ! and dressing most off the solder OFF so it'll go together .
But Then , when you heat it , the 60 / 40 Bar Solder flows nicely . Saves three applications of acid and head ' to take ' and less liable to capture acid residue .

After thorougly cleaning the assembly , best to hit it with a spray can of engine enamel or something . Etch Primer . as inevitably if you oppen up a old ship , the surface rusts
on it , HOW I couldnt tell you . So they get the horn arm hit with dope or whatevers handy . That'd b e why good comercial ones are plated  .

If its NARROW aft , the tubes filled flush with the washers . When the pushrod wire arm ends filed back , youve got to pre measure to see you dont remove the ( then ) lip to the retaining copper wire groove .
So , it'll be say 1/16 th or 1/32 left . sometimes THEN soldered , hopefully you get a dome , and file flat to wire end .

Offline Tim Wescott

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Re: Elevator horn/pushrod connection
« Reply #8 on: May 04, 2024, 09:10:30 AM »
I just widened the fuselage in the back.  Widen it more than you think you need -- I widened mine, got it looking nice on the outside, checked fit, then widened it again because I was too timid the first time.  Mine is going to look -- awkward.
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