Throttle control question
 

Have a question...is it OK to use a metal throttle control wire (supplied with my ARF)? The wire has a "Z" bend for the throttle link...I thought this has to be plastic to avoid possible interference. Thank you.

RE: Throttle control question
 

the rod is fine... just make sure to use a plastic clevis

RE: Throttle control question
 

According to the instructions the "Z" bend part connects to the engine. I have the EZ connectors for the servo. Not sure where to use the plastic clevis.

RE: Throttle control question
 

Interference, MAY be caused by the metal-to-metal contact of the "z" bend to the throttle arm (If indeed your engine HAS a metal throttle arm - If it's plastic, don't worry about it) If it's metal, and you DO indeed get some radio glitches (it doesn't ALWAYS happen), you may want to replace the "z" bend with a nylon clevis - thos, of course, will mean replacing the exisiting pushrod, or cutting off the "z" bend and soldering a threaded end on in it's place.

As for a metal rod transferring engine interference back to the radio compartment, that only happens in Gasoline engines that use a Spark Plug instead of a Glow Plug

RE: Throttle control question
 

Thank you for the info, I'll see how it goes with the metal pushrod.

RE: Throttle control question
 

Also can I use an EZ connector on the throttle arm when using flex-cable?
The firewall and the engine throttle arm are very close and using a plastic clevis will get in the way.

RE: Throttle control question
 

I've used them on a couple 4 strokes with no problem... as always, do a good range check, with the engine running

RE: Throttle control question
 

Sounds good, thank you. This as well is for a 4 stroke.

RE: Throttle control question
 

Metal to metal on a throttle arm is an incipient time bomb. A simple range check on a new installation is of no help. What happens is the throttle arm hole with a metal clevis and particularly an 'S' bend while when first installed may be resonably tight. However that arm hole will wear bigger to the point that the amplitude gets into the range where the stray RF noise will happen.

Do it right. It makes no sense to install a built in problem on a new airplane. I don,t care what the ARF provides with the airplane, Heck its just more product for those Pacific Rim countries to pump out.

I am flight testing for folks almost on a daily basis and will always refuse one untill its fixed that shows up with metal on metal throttles. I think this is a frequent culprit in many of those so called mysterious interferance hits.

John

RE: Throttle control question
 

Any ideas what to do if the throttle arm and the firewall are close together?

RE: Throttle control question
 

Do you have enough room for a ball connector? If you have half an inch between the firewall and throttle arm hole at its rearmost position, consider replacing the cable with nyrod and connecting a 2-56 ball connector to the nyrod where it exits the firewall (using a short length of threaded rod). Screw the ball through the hole in the throttle arm, then pop the connector over the ball and you've got your linkage. You can even shorten the ball connector a bit for a little more clearance if needed.

RE: Throttle control question
 

I have to take a better look at how much space I have. I appreciate the suggestion.

RE: Throttle control question
 

On may of my 4 strokes, I run the throttle pushrod out past the throttle arm by as much as 3 inches then bend a U shape and bring it back to the throttle arm. This also lets you run the throttle pushrod well off to the side of the tank then the U bend brings it back in line with the throttle arm. That way you can use just about any type of clevis or ball joint with no problem with interferance with the firewall.

RE: Throttle control question
 

Nickj and Rodney both have offered possible good solutions and here is yet another way to skin the cat. First be aware almost all engines have a way to make small adjustments in the throttle arm on the rotating barrel itself, either by a set screw or a lock nut. Sometimes a slight adjustment here will do the job.

For those times when its a must to get the engine back as far as possible (a common situation with todays propensity to use oversize engines) and the four stroke throttle arm is directly aginst the firewall allowing no reward swing. A simple and effective method is to make an oversize hole behind the arm to allow it to swing. Instead of anchoring the pushrod housing in the fire wall it can be anchored inside the compartment several inchs aft of the firewall with a simple wood standoff. This avoids the binding that always occurs when the throttle arm swings through its arc in cases where the firewall is very close to the arm. Have used this method with lots of success.

A thought on pushrods for the throttle. Except in the case of ignition engines (due to ignition RF noise) for all glow engines I usually will avoid nyrod or stiff stranded cable types. Instead I will use .031 or therabouts music wire avaliable at most hobby shops. At the servos use an EZ Just for infinite adjustment and at the throttle end use a Dubro or GP brass soldered on thread to which a plastic clevis (no metal pin types) is screwed on. This wire will provide just as much flexability than nyrod or cable types but with much less friction for a totally free running throttle linkage. For some airplanes with a relative straight pushrod run housing is not even required but just a short piece of nyrod inner tube for a guide not to far from the servo as well as in the firewall or a setback using this type you can also use the nyrod inner rod as quide if you like or if it is flexed quite a bit. This is much smoother running than nyrod or cable .

John

RE: Throttle control question
 

I enlarged the hole in the fire wall and installed the flex-cable. It works without flaw. I appreciate all the input to resolve my issue.