throtle servo
 

I know your not supposed to use metal on your throttle servo but can you use carbon fiber?

RE: throtle servo
 

YES

RE: throtle servo
 

rc pilot. it is ok to use a metal rod just not metal clevises. No metal to metal contact.

RE: throtle servo
 

Wayne is right. You can use any type of linkage that works, IF you use a nylon clevis on the throttle arm (which is usually metal). The make/berak of metal parts causes EI that our radios don't like.

Dr.1

RE: throtle servo
 

Any ignition system on a model engine, be it magneto or electronic, will emit electronic noise (RF) while it is operating.

If you put a piece of metal wire, like a metal pushrod, in the vicinity of this RF interference, the wire will act as an antenna and radiate this "noise" along its length.

At the other end of this wire is usually a servo and that is connected electrically to the receiver.

See where I'm going?

Use plastic clevises at the engine and non-metallic pushrods back to the servo.

Just my opinion, but it seems to reduce or eliminate radio interference from ignition systems for me and a number of others too.

RE: throtle servo
 

I use teflon coated kevlar fishing line (Spiderwire) on a "pull" setup. The carb return spring takes care of the return side. The spring is not strong enough to put any adverse load on the throttle servo. I run mine through a tube with servo eyelets at each end. Since the line is teflon/kevlar it will not cut the tube. Sure makes setup and throttle control routing a lot simpler.

Works fine for me however; your mileage may vary.

Dan

RE: throtle servo
 

dant- so, with a pull system, there is constant tension on the throttle servo at any throttle advance position, and of course, no way to shut down the engine from the throttle? [sm=confused.gif]

RE: throtle servo
 

Jim:

yes, there is constant tension on the throttle servo in the "shut off" direction. Shutting down the engine from the throttle is the same as with a "push-pull" - simply lower the throttle stick and/or use your normal "throttle cut" on a computer radio. In addition, since I am using this setup with gas engines I have a computer activated "kill switch" setup.

I don't see a problem with this system shutting off the engine. The only times you could not shut off the engine would be if the battery(s) died or the throttle servo or throtte stuck. In those cases, you couldn't shut down the engine no matter what type of control you were using. In addition, if your throttle control breakes (servo arm, line, connectors. etc) then the engine automatically shuts down due to the throttle return spring.

As I said, this setup works fine for me. I have seen it used by others and haven't heard of any problems.

Dan

RE: throtle servo
 

Any type rod you want. Plastic clevis or ball link at both ends. It's not possible to obtain RfI through the rod this way.

RE: throtle servo
 

OK, I get it, now. The idle stop is still disabled, so the throttle servo can allow the spring to return enough to shut down the engine? Still, I will continue to use a push rod and eliminate the spring tension. It just makes me "feel better". ;)

RE: throtle servo
 

SilverSurfer: Sorry to disagree, but a metal throttle rod, even with plastic clevises, can act as an antenna and radiate RFI back to the radio equipment.

RE: throtle servo
 

could you clarify how this happens?
I have never been able to show that this occurs
Are you using older types of stuff with exterior (not the HV cable) grounding?
I have used early types of ignitions - a few years back but my current setups - (ZDZ) Falkon etc., - simply refuse to show this is happening
Some of the major ARF sellers ( H9 as an example) show servos mounted right up against the engines

RE: throtle servo
 

This is all good stuff people but that still does not answer my question will a carbon fiber rod work and not cause interference?

RE: throtle servo
 

I use a metal turnbuckle with plastic ball links on either end....never a glitch

RE: throtle servo
 

Yes, it can, but the metal rod would have to be very close to a multiple of 1/4 wavelength of the receiver operating frequency. The chances of this happening are very slight.
It also depends on the orientation of the antenna and the metal rod and the distance between them. This almost guarantees that there can be no coupling between the two.

RE: throtle servo
 

I use CF rods with ball links on both ends for the throttle and choke on my gas planes with no problems.

RE: throtle servo
 

Good Lord, you actually believe this?! This is a very old concept going back to the start of giant scale gassers during a period when magnetos were just about the only type of ignition to be had. Mostly prior to the use of carbon fiber for anything that was non military.

I fly aircraft that are constructed almost entirely carbon fiber. There is zero metal or wood anywhere in the structural components. One of the few pieces of moving metal in the things are the metal throttle linkage rods with plastic housed ball links at each end. Gas engines and electronic ignitions. At 100K a copy do you really think the RFI issue has not been fully and completely researched? BTW, the only "ground plane" is at antenna locations so let's rule out RFI elimination via grounding other that at the plug wire. Oh, yea, resistor plugs as well. BTW, this is the second type of brutally expensive aircraft that I have worked with that used a similar linkage arrangement.

On all my personal stuff I use only a metal or C/F rod with similar ball links at each end for two reasons. #1 is because it's rigid. #2 is because there is no RFI transmitted back through the rod. For something to transmit it must first be physically connected to something else that radiates. The C/F rod is not connected to anything electrically. Test the same type of installation with a continuity probe and tell us what you get.

Bottom line is that if properly connected with what amounts to an electrical isolater at each end it doesn't matter what you use for a throttle linkage rod.

However, that does not eliminate the possibility of interference caused by vibration induced electrical noise generated by physical contact with other metal components. As in any other component, a little care needs to be exercised by the builder to eliminate any metal to metal vibration anywhere on the aircraft.

Pat

RE: throtle servo
 

My good friend Al Deim walked me thru all of this years back - he made me some ignitions for special projects - the slick one -I wanted -was one with the coil mounted right next to the spark plug -just a few inches away -- and then a seperate box o electronics on the firewall - nary a glitch there either -
Some new cars are sorta the same - a coil for each spark plug then a basket of snakes to a computer

RE: throtle servo
 

Just remember that pettit is a redneck pizza slinger. Take what he writes with a grain of salt. He writes so much and builds and tests so many airplanes he doesn't have time to think about what he says. C&H has in their instructions that you should not use a metal throttle rod. Why, I don't know. Maybe they are afraid it may bang against something. Others including people like P. Reviers are convinced a metal rod can be a problem. Theroretically, there is little chance of that. I have used a metal cable for years

RE: throtle servo
 

If you want to get into the finer points and technicalities, the noise generated from the gears inside a full metal geared servo could also be considerd a noise source that may cause interference on a really bad day. They do radiate to some extent as well, but your system will have to be mighty uppity to have problems with them. Unless you have some really bad servos[:o] I have to admit there are some systems that require shielding a metal geared servo for just that reason, noise from the gears...

RE: throtle servo
 

Metal gear servos usually have at least one plastic gear. That helps a bit.
The sparks in the brushes of the servo can cause serious problems. Fortunately its easy to shield them. Just ground the motor case. There is usually a large value capacitor in parallel with the brushes to help eliminate the problem. If that gets broken off you have a noise source that can drive you nuts.

RE: throtle servo
 

I just purchased a Zenoah G38 and would like to know how to set up the throttle. The throttle butterfly runs east and west instead of the regular north south direction.

RE: throtle servo
 

Her are a few pictures./ Just use a bellcrank and a ballink.

Dave