Hello,
my plane is suffering from elevator deflection; the side of the elevator with the control horn is more precise than the side with nothing, causing my plane to roll with elevator input. There are cutouts for push rods on both sides of the plane, so I'd like to add a control horn to the opposite side of the elevator. What is the best way to link the two push rods together? (I just realized I could run one full length rod, and splice a second piece on to it, or I could form a Y-shaped device, and run a 3/4 length push rod to a connector, and have two pieces (1/4 length) to each half of the elevator.

Any suggestions?

Thanks.

So the wire between the two halves has come unjoined? I'd try to get the two halves rejoined before I'd go to a Y setup.

what sort of plane? -
Is it the dolphin that is the subject of your other post?
If so - the easiest way is to splice a second wire to the other side of the wooden pushrod so that one wire comes out each side - a little fiddly but it works.

I agree with aussiesteve. Two rods connected to a common wood pushrod exiting both sides near the elevator.

Another way but a little more complicated is to run a pull/pull cable for both sides of the elevator.

It's a bit of work with the four wires but once you get it set up it works great.

Yes, it's the Dolphin. I think your idea is right on the money, thanks.

Pumba, the wire between the halves is still joined, but you can easily bend one half up and one half down with very little pressure; the wire is not very strong or something. When I use elevator, especially for outside loops, the plane rolls out. This seems to be a likely cause.

Poboy, dual pull-pull does sound nice. Will consider this too, though there is little room or material to work with above the stab.

Thanks guys.

you mentioned elsewhere that you needed to have some sharp bends in the pushrod to clear things.
A number of manufacturers use "Y'd" rods these days. - they simply bend the two wires into a gentle Y shape instead of using z bends. - Knagke are one of the suppliers that do it that way - maybe have a look on their website at the manual for the Monocoupe or the 25% CAP and you will see what I mean. To install that method - bend the and of the Y to the correct width for the control horns then use some cotton to tie them together until the rod is sinstalled down the fuse. Once they are in line with the exit slots - use a knive to cut the cotton and the wires will spring out of the slots.

If hitting formers etc is a big issue, the other alternative is to run 2 x nyrods (flexible pushrods) down the fuselage with a connector at the servo end (Or solder the wires together) Make sure the outers are very well glued in place though.

If you picture a wooden push rod with a wire at either end, there is a 45 degree bend in the wire, at both ends, and then a 45 degree bend back near the servo horn and near the control horn.

Thanks for the tips, I'll look into this stuff.

How are things for you in China? OK I hope.

Did you epoxy the rod between the elevators into their respective holes? If it has become loose you need to glue the rod in their holes...thats a simpler fix than push/pull or y pushrod
there are a number of issues that can cause you to roll out of loops...not enough airspeed, laterail balance, CG, thrust angle...

No, it was/is an ARF. The tail is all epoxied together, so accessing that rod now would be pretty tough. I will be checking for other things over the next week or two before I start changing the push rod setup. While there is definitely some flex, I haven't heard anyone else complain about this plane, so I'm thinking there might be some other setup issues going on.

Thanks.

Check out Central Hobbies. They sell a Dual Elevator Pushrod System (DEPS) that will do what you're looking for. Here's the link: http://centralhobbies.com/control_linkage/deps1.html

A pushrod that is forked at the back end of the plane can lead to trouble. It allows too much flex and can allow flutter. I lost a Goldberg Extra this way. A much better method is to run two full length pushrods and attach them near the servo. This is exactly what the DEPS that Jon mentions is. The DEPS is carbon fiber pushrods but the same thing can be done with standard steel pushrods. Use two full length 4-40 steel pushrods and run them as straight as possible and solder one to the other just short of the servo end clevis. Be sure to brace the pushrod guides. This is the way I set up all my old school pattern planes. Here's a picture of the pushrod I made yesterday.

Dave

Back to that picture and A 1000 words thing. This is A really old scratch built plane I did about 10 or more years ago. There are A lot of ways to end up doing the same thing but this is the only plane I had handy with this old system in it. I have also made up Ys by soldering and bending 4-40 rod to custom fit A plane.
In this case I used A carbon Fiber arrow shaft, I used to have them in all sizes because I lived in the country and deer hunting came early for archers. During practice they tend to robin hood arrows and destroy them so I had my friends save them for me. The tip I used on this one you can buy, they even have kits to do this but free is better.
When using A Y I don't use the wire between the two elevator halfs. The Y can be used to trim each side as needed just like using two elevator servos and/or adjust for any warp.
Remember too that elevator rolling can be caused by too much elevator throw too, well, that and A few other things but this is A Y system.

Are you sure it's not your thumb pulling a little aileron in while you are using the elevator?