alpinestar

Hey gang
I'm working on my first ziroli project; the big P-47. I'm at the point of planning/installing pushrods & was stumped for a while with the elevator. The plans show a pushrod exiting the side of the fuse & connecting to one elevator half with a normal horn, and the other elevator half is connected with a 1/4" piece of piano wire.

I'd really like to keep the linkage internal, and I like rigid pushrods versus flexible whenever possible. I thought of using the big nyrods (black & yellow ones) but am worried about flutter with these, as there is some slop & I will have plenty of speed with this plane thanks to a 3W-85xi.

here's my idea.. nothing new but I wanted opinions from those who have built big planes like this before. It's the usual horn-on-piano wire deal... I haven't yet brazed the two pieces together. It has a du-bro 4-40 ball joint and the threaded piece is a titanium end for the carbon pushrod I plan to use. It's a 5/32" rod, and I have an additional carbon tube which slides tight over the pushrod to "sleeve" it & really make it strong (will epoxy or slow CA the two together).

Will this be a good strong setup, or am i asking for trouble?? I plan to use a good digital servo, maybe a Hitec titanium gear so it's as strong & durable as possible. The plans show a single pushrod/single servo system.. Think she'll hold?? Let me know what you think!
Thanks!

bentwings

That very similar to what I use. I add a wheel collar on each side of the horn and braze or real silver solder it. You push rod sounds ok. Just guide it so it doesn't bend and rattle around.

pahtreek

My Feedback: (1)

Maybe I am over cautious, but I have always said...I can loose any channel but elevator. I would take it to a welding shop and have them weld it together (will probably charge you $5). You can take your 1/4" rod and make a small arm out of a much thicker piece of steel (dont butt weld it, drill a 1/4" hole in it and slide over the rod) so that it can be welded without any problems. grind down the end of the arm and drill a 1/16" hole in it and use a heavy duty 4-40 pin connector.
I have seen solder (ESPECIALLY when soldering a stress joint part) and even brazing fail (but they might just not know how to do it...). Again, if this was for ailerons or rudder, it would solder it no problem, but my elevator setup on my warbirds is the only thing I make bullet (bazooka) proof.
Just my humble opinion...
-Patrick
www.putfile.com/pahtreek

kvlasblom

Hi I'm stuck with exactly the same question, to use on my WACO SRE.
I was wondering how you got on; what you've decided to do.
Thanks in advance!

bentwings

The pickle fork arrangement as shown above and silver soldered with real silver solder is about as good as it gets. It's very heavy for the function and way out back so there is a weight penalty. About 4 to 1 on the war birds. In other words the approximte 2 oz it weighs needs 8 oz up front.

you could use titanium parts and have it welded. It would save about 1/2 of the weight and cost about $20 for materials. I am a professional welder now after 25 years of mech engineering and would think twice about welding this. I do TIG welding almost exclusively and this would be a challenge. It's not that it can't be welded, it is just very small and thin/thick material. I do this stuff and I can say that it is not a $5 job. I would guess that you wouldn't get away for less than $50 -75at most weld shops. Just a thought.
Try this for materials.
mcmaster.com

I'm going to experiment just for fun with a hand layup of carbon fiber and see if I can make something that is essentially one piece. It wil have to wait for winter however as there are already too many projects going.

kvlasblom

Thanks Bentwings.
I think I'll go for silver soldering then.

Another possible option might be to make the elevator joiner/fork from two pieces, and where they come together in the centre, bend them down at 90 degrees, towards the bottom of the fuselage, like you also see with ailerons where they share 1 servo.
Then these two could be fastened together to a ball-link or something. The disadvantage would be that one has to have more available space in the fuselage, and I also have a whole construction for the tailwheel which is also linked internally in the fus.

I'll have a bit more of a think, but will probably go for the option in the photo above, and silver solder it.

David Bathe

Don't for get this classic.
Driven by one push rod and ball clevis bolted between the two.
Or two push rods, two servos etc.
I've made them my self and bought them in 1/4 scale sizes.

AnthonyW

I did something similar. I took the 1/4 metal elevator connector and made two boomerang looking control horns and welded/silver soldered them with a ball link in between. The one elevator servo through the tail wheel opening with a push pull 4-40 rod over and under the Horzontal Stab. The only issue is I had to really hoolow out the rudder for clearance, but it came out GREAT. Attached is a link to thread in the Warbinrds section on the P-47. Mine is the Rozzi Geth II.
Good Luck.
http://www.rcuniverse.com/forum/m_23...NTHONYW/tm.htm

OldScaleGuy

My Feedback: (2)

I use 1/4" rod and 1/8" steel flat stock brazed together. Done right (good flux and proper heat) that holds up great. Always do a strength test before installing. For pushrods, i use solid wire with a 4-40 thread and ball link with a washer on the outside so if it would pop off it cannot come completely loose. Then at the servo arm, I put a 90 degree bend in the wire place that through the servo arm and retain it with a wheel collar.
Link to the push rods. Use the outer housing too and secure it ever 6-8" inside the fuse to eliminate any possible flex. http://www3.towerhobbies.com/cgi-bin...?&I=LXK060&P=7

kvlasblom

Thanks everyone!
I'm going for the sytem with two rods going into the fuselage after all.
I just placed an order for the ball link I need. Going to have to work on another part of the model until Monday now though as I won't receive it until then.

David Bathe

Also this one.
Carbon tube, alloy sleeve, 4mm bolt. All CA'd together and built into each elevator half.
Believe me, you'll break the elevators before loosening the rod or bolt.