How do i go about setting up a throttle servo so that it gives me the ability to set trim for correct idle on my nitro engine? Today I was trying to increase the idle on the engine and noticed I had the trim on the transmitter at max. What is the proper proceedure to set throttle servos on a nitro/gas engine? thanks for your time and help.
-ABV

cgretired posted this, works great

http://www.rcuniverse.com/forum/m_83...tm.htm#8375449

Wow, rgm762 !! I'm glad you found that posting. I hated to re-write the whole thing again!!

CGr.

Geeze CG,you are retired, you have all the time in the world

Hi Irish.

Weeeeellll... not exactly.. sort of doing a little tripple dipping right now.

What's fer breakfast this AM? Doing any flying today? I did some in the big bird yesterday (Airbus AB320 from Tampa to Philadelphia)

CGr.

A really short answer that covers linkages for all functions is that it's always a good idea to adjust the airplane to remove TX trim found during the model's initial flights.

Adjust the linkage in the same manner it was adjusted while assembling the model.

what kind of servos does that Airbus take? No flying for the past week, either rain or wind. Doing a little building. GP Ultimate kit. I think it is a hard build. Not real happy with the quality of the wood. Some so hard you can't put a pin in it, others so soft you can squeeze it. Breakfast === one egg basted soft, 2 strips bacon not crisp, one slice of Oat Nut bread, crispy hash browns and chock full of nuts coffee.

ABV.... CGRetired offers a very good outline. I'll offer another method but it depends on the availability of the round blank servo disk (a substitute is the round wheels with holes) but if they are available , this method is the easiest way to adjust the throttle linkage to a servo on a basic radio. If using the white round wheels with holes, first paint the surface with a marks a lot pen.

1. Mount the servo, motor and throttle linkage and be sure that low throttle will kill the motor

2. Place a quick link on the throttle rod or cable

3. Place throttle in about the center position (doesn't have to be perfect)

4. Slide the quick link and tighten around the center point of the disk

5. Set throttle stick at low and run the trim all the way down

6. Pull or push the cable to fully low throttle and swipe the quick link pin across the surface of the disk to make and show an arc

7. Set the throttle stick on high and trim fully up

8. Pull or push the cable to wide open throttle and swipe an arc again on the disk

9. The two arcs will have a crossing point, at this point drill for the quick link connection

The servo now will just reach the endpoints of the linkage travel so will not bind and will allow the trim to kill the motor.

goirish ,I can relate to the wood in the GP Ultimate , it was the worst kit I have ever built as far as wood quality . I ended up cutting most the parts by hand . The rest of the GP kits have been really nice, must have been a bad run . Contact GP to see if they well replace the wood for you.

CGR's post is most informative, but...

Only SOME brands of servos have the servo arms that will angle slightly when rotated to the next arm (if you use JR, you're out of luck)

And you don't ALWAYS want the arm to be at 90 degrees.

When the arm starts at 90 degrees from the pushrod, you will get the most amount of travel, but sometimes, you're stuck between a rock and a hard place, IE, when one hole on the servo doesn't give enough throw and the next one out gives you too much.

A blank arm like AA5BY suggested is a possibility, but it is easier to use the arm you have and rotate it off the 90 degree mark - which will give you less throw.

Yeah, that makes sense, Minn. Now why didn't I think of that... Just kidding, of course.

At some point, we'll have all the methods and can make an application for each installation.

The hardest part of this, because all throttles and servo's are not created equal, is finding the right method that allows full throttle from min throttle/no trim, to full throttle/full trim AND do that without causing a binding servo. Now, that's the trick to this whole thing. You want the throttle to move from end stop to end stop without actually trying to move beyond the throttle stops. That causes binds and will drain a battery very quickly. In fact, in some situations, if the bind is severe enough, you can see the servo want to twist after the servo arms reaches throttle stops.

CGr.

Mike, you mention, but the drawings don't point out that the 90 degrees is to the push rod, not necessarly the servo case. I bought a used plane and the guy had the pushrod coming across the fuselage at a 45 degrees to the servo case. He set up the arm for 90 to the case and of course, things didn't work as you would have liked.

Ithink the imporant point of this thread is thay you really have to mechanicaly set things up correctly, Even with a computer radio. The throttle is the hardest servo to set up in the whole plane in my view.


Don

I realized that as I typed it, and I only typed it because if you've been in this hobby long enough, you've run across one of those cases where the throttle cable is NOT coming in at a 90 degree angle.

The illustrations assume that the pushrod IS coming at a 90 degree angle.

Ya call THAT a big bird? We have our B-777 flying now. It's been worldwide already. ANC, CAN, SIN and TPE for some stops.

 pull the floorboards up on an Airbus and all you see is 2 cable bundles about a foot across, running from the front to the back of the plane. Fly by wire , literally. Kind of spooky ,when you think about it.

I didn't say I flew it, I flew IN it. What can you do when the airline you fly on uses "fly-by-wire"? [X(]

Mike, Don, perhaps my emphasis was to point out the "square" position of the servo arm to the servo. This is, of course, assuming that the servo is square in the tray and square to the fuselage. That's the way I try to mount them.

Now, please consider that I've been in this hobby for considerably less time than the true experts have been, and what I tried to explain was what I experienced and tried to practice. The important point that I really wanted to spell out is that the servo movement must not conflict with the movement of the throttle arm, they must be consistent and equal. The servo must not push the throttle linkage any further than it can move or else binding and severe battery depletion is an absolute. It will just plain happen.

So, when I set up my throttle, it's probably the most time I spend on any of the linkage setup's because when the throttle stop stops.. well, that's it. If the servo keeps moving, well, it will not, or it will flex the linkage, or it will twist the servo, it will bind and cause problems.

Every one of the suggestions provided in this link will most likely work (mine did.. does) in your application, but a little brain function is necessary to make it work for the application at hand given the equipment in use.

Servo's provide movement in some arc of the circle, and I guess not all are the same. The trick here is to make your servo work, regardless of who makes it, for your application. The best advice is to work with it and spend some time with it. It's not just a "throw it together and hope it works" situation because that is an invitation to disaster.

CGr.

What was the last US fighter built that wasn't fly-by-wire? At least in part. If not completely fly-by-wire they are at least hydraulically controled, still no direct mechanical connections.