Well - - Get with it Pat and go back and change it.

I can change the one in the quote if the poster doesn't want to do it?

Good Job. i changed the quote

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I took the cowl off again and tried tuning the engine. I ended up making it an eighth of a turn richer. Flying it today, it seemed like it did lose some power from richening it, but the throttle seemed perfect. The engine was smoother and got to full throttle as the stick was completely up.

Glad you got it sorted

I might have a mental block on this issue but I'm wondering why the need to adjust the linkages for a lot more servo throw.

I will grant that a long servo swing is less linear and could fall into the needed curve of the gas throttle, so on a radio without exponential such advice is good and historically wise, especially when considering that dealing with such issues was historically done mechanically including linearity or non linearity needs but I'm just not seeing raising it as a requirement for a computer radio.

As long as the throttle stick throw matches the barrel throw by whatever means (mechanical or end point adjustment), there will still be the non linear problem of the carb and the way to deal with it is to counter it with a non linear stick movement, aka exponential.

In the OP's original expression, he didn't use the full travel of his servo which leads to dead band and hysteresis exaggerations within his throttle control.

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Keep playing around with the linkage & expo untill you get what you want for good running.....then write it down......and pass it around! Capt,n

I have a simpler reason. Because it works, it works well, and it works every time.

I never run out of sub trim, never need exponential, require very little throttle to throttle mixing if any ends up required. And I have throttle stick movement that closely corresponds to a perceived rpm value. Makes things like a hover very easy to lock in with rpm control.

W8YE OK.... "Dead band and hysteresis exaggerations" as you say could/would be an issue, albeit as a sport pilot I've never sensed them. I've certainly however sensed disconcerting grossly non linear carbs on gas engines.

Tired Old Man... There are lots of ways to make things work and my only issue is presenting that increasing the throw of the servo is a requirement for solving the non linearity issue. In some ways, I'm not believing I'm even taking the devils advocate position here as basically I agree with your good advice not only for the issues that w8ye raised but reducing the servo throw and loading the arm effort on an outboard arm hole reduces the effective torque value of the servo and probably increases battery drain. So, for many esoteric reasons your advice was good but not because it is a requirement to deal with the non linear carb. As you, I also set up a throttle by doing middle stick and middle barrel at right angles on servo and throttle arm as the first step. Unlike you, I've had two gas powered planes that fit the complaint of the poster and required expo to counter the non linear carbs.

Last, I'm not sure this has been offered yet but throttle non linearity can be made much worse by over throwing the carb (moving the barrel past full open).

Dificult to over travel a gas carb unless the physical stop has been cut off. This is an issue dominated by glow engines.

Of note is the last 20 to 25% of butterfly travel on a gas carb does esstentially nothing for rpm. Peak rpm is achieved long before the butterfly is fully opened. How one uses their servo and carb lever travels sets the stage for any expo to balance out linearity. Once the function of a gas carb is understood it becomes easy to obtain linear performance between the throttle servo, throttle stick, and rpm output.

I've had the same issues as yourself and have found that every time they could be resolved with linkage lengths and arm positioning. I use a 9303 and a 10SG so I definately have programming options available should they be needed. On a personal basis, I use a throttle mix to balance out small issues in linearity, never large ones. If there are large issues, such as throttle travels that are below 70% either way for full travels, I look for mechanical means to correct most of it. Using lengths and positions in the beginning minimizes the need for a lot of programming later.

I don't care for sacrificing resolution and accuracy to make up for poor installation methods. I have never become 100% dependant on a computer to solve flight set up issues. I suppose many of the younger generation have due to what was available to them when they entered the hobby. Not a bad thing but I often get to fix throttle linkage problems for them when I get to a field.

Torque is a non-issue on a throttle servo/arm.

I was bench running a Zenoah G-23 a couple of weeks ago and the carb would over throttle on it considerably to the point of very noticeably reducing rpms. The motor doesn't have much running time but otherwise I don't know the history other than it was converted to an offset carb mounting block. A look into the throat revealed it was certainly over traveling so whether that is common or not, I can't say... it was certainly true on that engine.

Like you, I've been around a while and go back at least to the days when reversing servos was done with a soldering iron in the servo. Out of the hobby for seventeen years, radios certainly changed a great deal in that time.

As to the functions I found upon returning, I like em. No more soldering inside servos for one. Expo is another, I use it on almost every plane in the hanger to keep from having to fumble for rate switches. Another example, I've a World Models Cub that had a nasty tip stalling inclination that was all but eliminated by trimming up the ailerons at lower throttle settings to simulate wash out so I'm appreciative of what the transmitter function capabilities provide. While yes, wash out can be physically built into a wing, the plane was an arf and didn't have it and simulated works quite well as it is there only at lower throttle settings when needed.... otherwise it is not there affecting inverted flight. Last, the most fun and most taken to the field plane in my hanger is an Ultra Stick Lite with quad flaps and ailerons. Programming is so complex I'd personally never sort it out but Horizon provided the three pages of programming instructions for us.... took a couple of hours but the end result is a fantastically fun plane to fly.

Back to the subject at hand, in the end I do agree that using most of the servo travel on a throttle is the better course.

Ahhh yes, the days of reversing servos the hard way. We have indeed come a long way since then, and like you I very much enjoy the features and advantages of our modern radios. Dual rates, triple rates, reversing, flight modes, mixes, channel assignment, expo. Ya gotta love it.

Odd about that over travel you encountered. Normally there would need to be quite a bit of over travel for it to have any impact. Perhaps the throtle rod and plate had been reversed? I came up against that when reversing the plate and rod on a WB 25. No stops on the other side and had to add one of my own. The carb normally associated with a G-23 has a throttle stop tab on the cover plate.