engine servo
 

Can't connect servo to engine satisfactorily. Too many twists and turns, and can't relocate servo. Suggestions?

RE: engine servo
 

Jim,

We're going to need a little more info to help you. Which plane, which engine, etc.

RE: engine servo
 

OK.. This is a Tower Hobbies Uproar kit. I am using a TT .46 engine. The servo tray is positioned in line with the elevator and rudder, but is off line enough with the engine so the connection between servo and engine is in a bind. I have tried to connect with wire, but it doesn't work. I was thinking about using a cable inside a tube for more flexibility. Does that make sense?

RE: engine servo
 

Absolutely! You can get a flex-cable pushrod from DuBro or Great Planes that will work well in that situation.

RE: engine servo
 

What usually works quite well is to run your throttle push rod along the fuselage side and well out past the engine throttle connection then bend a U turn into the pushrod and bring it back to the throttle arm. I usually use a nyrod up to the firewall where I then thread in a long piece of metal rod to extend it past the throttle arm and them make the U bend and bring it back to mate up with the throttle arm. The use of a ball link on the throttle arm also simplifies the installation.

RE: engine servo
 

If I use a flex cable do I have to solder an attachment on the cable?

RE: engine servo
 

I guess I would- at least on the carburetor end- then you can use a clevis on the throttle arm. You could also just use a EZ connector on both ends. That would be a simple set-up too.

RE: engine servo
 

I'll probably go with the EZ connector since I don't solder.. at least not yet!

RE: engine servo
 

If you use the cable you may want to put a little solder on the ends of the cable. Use flux on the cable and just enough solder to harden up thearea were the set screw will be pressing on the cable. This will keep it from unravelling (sp?) when you tighten up the set screw with the EZ connectors.

RE: engine servo
 

Good point, stick. I forgot to mention that!

Make sure you measure and cut the cable to length before soldering the ends!

You will want to wick a bit of solder into the ends of the cable. Put some flux on the cable (I use plumber's flux in the red and white tin from the home-improvement store)- you can just stick the end of the cable in it. Then you'll heat the cable with a torch or soldering iron, and put a LITTLE solder on the end of the cable.

RE: engine servo
 

I built about 25 Uproars from scratch (5 at a time). The nose section of that design doesn't allow a ton of room for the fuel tank and the throttle connection. My version of the Uproar kit was much easier to buil than the original by planning out things better.

The recomendations made in this thread are good solutions. Let me add a couple of generic suggestions.

1) Always use a piece of nyrod between the engine servo and the throttle arm. The vibration transmitted back to the servo via a wire will wipe out the pot quickly.

2) Whenever using an EZ connector clamping onto a piece of music wire, anneal the steel rod so the screw will make a distinct impression into the steel. (Using rock hard music wire and an EZ connector will fail in time; soften the wire).

3) Always try to avoid using an EZ connector on any control surface linkage. You will regret it sooner or later.

RE: engine servo
 

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RE: engine servo
 

Ditto on EZ connector... EZ on... EZier Off.. especially where vibration is concerned.

I dont use servo trays for the throttle pushrod for precisely the issue you mention. Mount the servo to the side of the fuse that has the throttle arm and 95% of your routing will be solved. With flexible cable you'll need to support every bit of the way. Without full support you'll have issues getting minute adjustments to work properly for example between very low throttle and engine cutoff where a small arm movement wont be transmistted to the throttle amr due to bending.