Need help adjusting thottle servo
 

Ok so some may remember me some may not but a couple weeks ago I was in here looking for some help on my engine, well the engine is fixed and I put it back on the front of my plane. When I removed the engine to repair it I took the control horn (I believe thats the name) off of the engine throttle thing. Now after just putting it on with the control rod connected with the throttle all the way shut I realized that now if I cut the throttle all the way down on my radio to get a nice idle the plane stalls. I've spend days on this and thought I had it but then realized that the servo is just chattering because its under too much load I suppose? Its hard for me to explain it but maybe someone understands what I'm saying... How do I install the throttle control arm so that its partly open while the stick is fully down and also prevent it from binding when fully open or closed? Its like the servo travels too far for the engine. Sorry for any rambling and hope someone can chime in. Thanks guys, Bob

RE: Need help adjusting thottle servo
 

Go into the servo endpoint menu in your radio and adjust the throttle servo until you get it where you want it.
Jordan

RE: Need help adjusting thottle servo
 

I looked through the manual for my radio and couldnt find anything about that. Not to mention the original radio had no menus to go through so somehow it was able to align properly but I cant figure it out for the life of me

RE: Need help adjusting thottle servo
 

What radio are you using?
Jordan

RE: Need help adjusting thottle servo
 

Futaba T6XAs

RE: Need help adjusting thottle servo
 

This is what I could find on Futabas site
<u><font size="3">

Setting ATV values on your system: </p></font><font size="3" face="Times New Roman,Times New Roman"><font size="3" face="Times New Roman,Times New Roman"><p align="left">1. Enter the programming mode, and get to the </p><p align="left">2. To set the RIGHT aileron motion, move the aileron stick all the way to the right and hold it. The letters "</p><p align="left">3. To set the LEFT aileron motion, move the aileron stick all the way to the left and hold it. The letters "</p><p align="left">4. To set travel volumes for other channels, press the </p>

5. You may set each channel separately, anywhere in between 10% and 120%, and if you wish to rapidly return to the default 100% setting, press both the (+) and (–) keys simultaneously. </p></font></font><font size="2" face="Arial,Arial"><font size="2" face="Arial,Arial">ATV </font></font><font size="3" face="Times New Roman,Times New Roman"><font size="3" face="Times New Roman,Times New Roman">screen with the up or down arrow keys. The channel indicator is below numeral 1 for ailerons, the percent symbol will be flashing, and you’ll notice that you can change the </font></font><font size="2" face="Arial,Arial"><font size="2" face="Arial,Arial">L/D </font></font><font size="3" face="Times New Roman,Times New Roman"><font size="3" face="Times New Roman,Times New Roman">indicator to </font></font><font size="2" face="Arial,Arial"><font size="2" face="Arial,Arial">R/U </font></font><font size="3" face="Times New Roman,Times New Roman"><font size="3" face="Times New Roman,Times New Roman">(or vice versa) by moving the aileron (right) stick. In Steps 2 &amp; 3 you will see how you set the travel directions independently for each stick (or knob or gear switch) motion. </font></font><font size="2" face="Arial,Arial"><font size="2" face="Arial,Arial">R/U</font></font><font size="3" face="Times New Roman,Times New Roman"><font size="3" face="Times New Roman,Times New Roman">" should appear next to the flashing percent sign, meaning you are setting either Right or Up travel (with ailerons it’s right or left only, but the display is set up to use the same indicators for elevator and throttle, thus the dual meanings for the letters). Now if your servo is stalled or binding, you’ll hear a buzzing sound. Hit the minus </font></font><font size="2" face="Arial,Arial"><font size="2" face="Arial,Arial">DATA INPUT </font></font><font size="3" face="Times New Roman,Times New Roman"><font size="3" face="Times New Roman,Times New Roman">key until the buzzing stops. If the servo is not buzzing, leave the setting at 100%. Later, after flying the model, you may wish to increase or decrease this number depending on how rapidly the model rolls to the right (you may also use dual rates to reduce your model’s responses). </font></font><font size="2" face="Arial,Arial"><font size="2" face="Arial,Arial">L/D</font></font><font size="3" face="Times New Roman,Times New Roman"><font size="3" face="Times New Roman,Times New Roman">" should appear next to the flashing percent sign. Again listen and hit the minus </font></font><font size="2" face="Arial,Arial"><font size="2" face="Arial,Arial">DATA INPUT </font></font><font size="3" face="Times New Roman,Times New Roman"><font size="3" face="Times New Roman,Times New Roman">key until the buzzing stops. If the servo is not buzzing, leave the setting at 100%. You may wish to increase or decrease this number depending on how rapidly the model rolls to the left (or use dual rates as mentioned before). </font></font><font size="2" face="Arial,Arial"><font size="2" face="Arial,Arial">CURSOR </font></font><font size="3" face="Times New Roman,Times New Roman"><font size="3" face="Times New Roman,Times New Roman">key to select the channel you wish to change. The little triangle moves and indicates the active channel. Repeat steps 1-3 with each channel in sequence, taking care to set the travel for both directions. </font></font></u>

RE: Need help adjusting thottle servo
 

I did mess with the ATV adjustments and I noticed when above half throttle or below half throttle it would adjust the distance traveled but also the amout it would move between lets say, half throttle and full throttle, was very minimal which caused me to have no noticable change in RPMs until I reached half throttle and lower.

RE: Need help adjusting thottle servo
 

You could try moving the control rod in on the control horn may work as well. Its also possible to try adjusting the ATV and them messing with D/R and expo.
Jordan

RE: Need help adjusting thottle servo
 

I just looked and when I have it properly adjusted on the low end, the carb opens up fully when the radio stick is just about half way, I just cant understand how it worked before and now its so far out of whack.

RE: Need help adjusting thottle servo
 

So when the throttle stick is down the carb is closed? and at half stick its fully open? If that is the case then just adjust the D/R until you get full travel. This should give the carb full travel with full travel of the throttle stick. If that doesn't work then I'm out of suggestions.
Jordan

RE: Need help adjusting thottle servo
 

Yeah stick down, carb closed, half stick carb fully open. I'll give that a shot and hopefully it gets the job done. Thanks for your help.

RE: Need help adjusting thottle servo
 

Another thing that may help is move the control horn outward on the servo horn it will give more throw then. When you put the control rod back in the control horn on the carb did you use the same exact hole? also when you put it back in you may not have gotten the engine back exactly and that may be why its off but its hard to say.
Jordan

RE: Need help adjusting thottle servo
 

Bob,

Here's what it sounds like to me – when you put the control arm back on the carb you didn't get it in the same position it was in previously (I've done the same thing). Here's the easiest way I to reset everything:

- Disconnect the pushrod from both the servo and the carb.

- Reset the throttle settings on your radio back to stock with every electronically centered.

- Move your throttle to the mid-point (½ throttle) position and make sure the arm you put the control rod into on the servo is sitting at the 0 or 90 deg. point.

- Move the throttle barrel to its half-open position, and loosen the barrel control arm.

- Hook up the clevis on the barrel control arm and depending on how you hook the pushrod at the servo end:

- If you have a Z-bend at the servo end, then tighten the throttle barrel control arm making sure the barrel is half-way open. Try to get it in the best position for good movement either direction – you may have to screw the clevis in or out to do this.
- If you us EZ-connectors, position the throttle barrel control arm to what appears to be the best position for your particular setup, tighten the arm down on the barrel, then tighten the EZ-connector on the servo.

- Go into the programming on your radio and start programming the endpoint, ATV, etc.

Hopefully this will work for you – this is the procedure I use for all my engine installations, regardless if it's new to that airframe or I've had the engine off the plane for repair/maintenance work.

Hogflyer

RE: Need help adjusting thottle servo
 

G'day

When I started flying RC models back about 1989, the radios did not have the adjustments that modern ones do so I hated adjusting the throttle throw. I eventually worked out the following method.

1. On the servo and on the motor are levers with holes in them. Pick holes so that the push rods are about the same distance from the centre of the pivot point. This way the servo and the throttle lever will both move through about the same arc angle.

2. Use a Dubro EZ connector on one end (usually the servo though I often use them both ends). This makes for very quick and easy adjustments.

3. Open the throttle fully. Turn the radio on and set the servo to the full throttle position. Tighten the EZ connector at the servo end (assuming the other end is fixed).

4. Try things out. The full throttle should be OK because you set it that way. What you are looking for is to see that the throttle is slightly open (about 1mm or 1/32 inch).

5. If it is way out - say the throttle is way too far closed. Then you need to reduce the overall travel. You can do this by moving the connection at the engine end out to a hole further from the pivot point or moving the connection at the servo end in closer to its pivot point. If it is not moving far enough, then do the reverse.

Once you have it pretty close, then you can use the power of your computer radio to make fine adjustments if you need to. It is better to get it mechanically close than set it up mechanically way out and rely on the computer radio to fix it.

Also, I use Hitec servos. An HS-422 or even the cheaper HS-311 make good throttle servos. They come with an adjustable servo arm which is great for servos as you can adjust the length of the servo are really easily.

Hope this helps a bit.

Mike in Oz

RE: Need help adjusting thottle servo
 

Hogflyer, Thanks for your input, If I leave the throttle barrel half way open and try to tighten the screw down it pushes the throttle closed.

RE: Need help adjusting thottle servo
 

About every other month we go through this very problem and there are numerous posts as well as compete threads on making throttle adjusements without using the TX End Points. You can search on Transmitter Linkage or Transmitter End Points and find the applicable threads.

Transmitter end point adjustments are the LAST thing you should be playing with. The first thing to do is to adjust the mechanical linkage to get the best linearity and travel out of both the servo as well as the throttle arm without going to the mechanical end stops. That way you will get the best resolution and prevent binding of the servo. Once that is done, you can make fine adjustments to the throttle... that's FINE ADJUSTMENTS, to the throttle channel.

None of the initial adjustments and settings should be done with the electronic end point settings on the transmitter.

CGr.

RE: Need help adjusting thottle servo
 

SOme new info, the control rod is on the outside hole on both control horns. The manual says to connect the rod when the throttle and trim are both down/closed. I did that but the horn on the carb can be moved 360 degrees so I'm not positive where its supposed to be when the throttle is closed. When connected that way it still travels too far when fully opened, the ATV fixes this but like I said earlier from what I can see it doesnt just control how far it goes in either direction it also makes the movement between half stick and full stick open very little preventing any speed changes between those two stick positions. Is this normal? If so I dont think I like that method becuase I dont want to be full throttle when I'm at half stick.

RE: Need help adjusting thottle servo
 

Bob,

The first thing you need to do is make sure that the throttle control horn is at 90 degrees to the control rod when the throttle barrel is at mid travel. The same applies to the servo end as well, but since you say things were fine before let's assume for now that the servo end is correct. As stated by others, there are some very good explanations already in the forum with some very good drawings to illustrate.

RE: Need help adjusting thottle servo
 

Bob, the closest a servo can get to linear movement is when the servo is centered, and the arm is perpendicular to the push line of the linkage. Not the Center line of the plane but the actuall linkage push line. The carb movement needs to match that movement so the carb arm needs to be perpendicular to the throttle linkage at the center point also. As pointed out by a couple of the otherpostershere, the mechanical linkage has to be right before any sub trim, end point or expo is introduced with the computer. Also, make sure the idlestop onthe carb is backed of so the carbcan fully close.. This mechanical setup is a must. If your carb is opening full at half throttle, the mechanical is way off, and it is highly unlikely that you can correct that with the computer.

Don

RE: Need help adjusting thottle servo
 

Here is what I wrote way back when. Although the general idea is for non-computer radios, the throttle linkage should be handled the same way as a non computer radio because the first setup should be mechanical, with minor trims done with end point.. MINOR trims. Using end points does a real number on you resolution, so leave it alone until you are thoroughly satisfied with the mechanical setup and only need to dial in some minor amounts of trim.

So, with that, here we go.....



I've seen some questions about binds in throttle linkage and proper set up of the throttle linkage especially with non-computer radios, (those without end point adjustments) So I thought I take a few moments and write this setup description and post it here in the beginners forum.

This setup may also be found in other locations, such as in RCKen and Minnflyer's "Getting Started" web site and possibly in the AMA Sport Aviator magazine. My intent is not to re-invent the wheel, but just to offer this as a point of interest to those that may be interested.

I hope this helps.

************************************************** **********

Because non-computer radios do not have end points you have make all the adjustments, including centering, mechanically. The stick movement relates to 100% servo movement. So, you have to work with the mechanical settings of the "levers and bell-crank" action of the servo arm and the throttle arm.

First, select the servo you intend to use for your throttle, most likely a standard servo.

Your setup will depend on what position your throttle servo will be in the servo tray on your particular model. The servo can be mounted so the throttle arm points to the front of the servo (short edge) or it can be setup to that the throttle arm is pointing to the side of the servo (long edge). Make sure you do your centering on the side if the servo as mounted in the servo tray slot for the model that you will be using. See the below diagram.

Once you have selected the correct side of the servo you are using, it’s time to zero the servo. You can do this either with the servo in the servo tray or outside of the servo tray. Obviously, if you do it in the aircraft, in the servo tray, you will be all set. If done outside, then you have to make sure the servo is mounted squarely in the servo tray once you are ready.

It’s time to center the servo arm. You can only do this using one of the other channels with trim set to the mid point or at zero (no plus or no minus trim, just set it to the mid point on the TX). Connect the servo to that channel (rudder, elevator, aileron... whatever, but NOT the throttle). Center the transmitter stick and the trim tab of the channel you are going to use for the centering operation. Plug your battery pack into the receiver. The servo will move to the center. If the servo arm is not 90 degrees to the side of the servo, then remove the servo arm and rotate it 90 degrees as shown in the diagram. Each arm is offset somewhat to enable you to find the ONE of the four arms that is correctly centered for that servo. If you do not have a four arm servo, get one. Once you have done this, secure the servo arm into the servo using the servo arm screw and tighten it down. I would also either cut the other arms off or mark the one you intend to use with a permanent marker so that if you remove it, you will remember what one you centered on.

Once you have done that, your servo will be centered with the centerline of the servo arm perpendicular to the side or top of the servo (again, see the diagram). Again, you have set the centering for that servo so use that particular servo for your throttle.

If you have not done so, go ahead and install the servo in the servo tray slot and connect the servo to the throttle slot in your RX.

Now, center the throttle and the throttle trim on the TX. (If using a computer radio, then use the screen for the trim and center the trim so that it is neither + or – trim.) Set the TX aside, yeah, leave it on.

Fully open the engine throttle by rotating the engine throttle arm so the throttle is visibly fully open (goes to the end stop and you can see that the throttle is fully open in the carburetor throat. Set the TX throttle AND trim to fully open (all the way up). Now, connect the linkage using the hole on the servo arm that is the furthest away from the center and the same on the engine throttle arm.

One point here. If you are using a clevis on the engine side of the linkage with metal rods and if your engine throttle arm is metal, do not use a metal clevis. Use a plastic one such as the Dubro Safety Lock Kwik Link (2-56) Dubro part number DUBQ1510 or something like it. You do not want metal-to-metal connections on the throttle. This could create electronic noise with metal to metal connections in a high vibration area such as the throttle linkage. And, I would stay away from using the cheap plastic clevis’ that come with many ARFs and kits.

Adjust your linkage so that they match up (rotate the clevis or ball socket so that the linkage matches up with the hole in the throttle arm without moving the throttle arm). Lengthen or shorten as necessary but be precise and make sure the throttle arm does not move once you put the thing together (plug in the ball socket or attach the clevis).

Now, move the trim to fully closed and slowly move the TX throttle until you go to full closed while carefully watching to see if the servo arms ‘wants’ to go further when fully closed. If it fully closes with no binding, then go to full closed with the trim. Again, if no bind, then you are ok.

If it binds, or the servo ‘wants’ to go further than the throttle will allow it, then choose a next hole on the servo that is closer to the center. And try it again. Leave the linkage on the engine alone for now.

Re-check for binds and that the throttle opens and closes fully with no binds with the TX fully open and closed with both settings for the trim. If no binds then you are ok. If it binds, then more adjustment is necessary. Continue to adjust as necessary until you are happy that it opens fully and closes fully with no binds. Now, you should have correct adjustment and trim settings so that you can close the throttle with the trim to shutdown the engine when finished. The goal here is to have your TX throttle at full open with the trim at full open and the servo arm moving just to the end point, and fully closed with trim at full closed just to the end point. No more, no less. AND using as much of the throttle rotation as you can. This gives you the most throttle resolution with no binds.

One additional point here. There is a device called TXservo that allows you to center the servo and test the full range of any servo with a PC and without your transmitter. But, I won’t go beyond saying that this can be done and that this device does exist. If you want to see what I mean, then do a search on the internet for TXServo.

RE: Need help adjusting thottle servo
 

A slightly finer point of throttle adjustments that some might want to consider as well. I've seen several references to having the servo arm perpendicular (90 degrees) with the throttle stick at the midpoint. This setup, while functional, guarantees a non-linear throttle response in flight, with nearly all the change in engine RPM in the first half of the throttle movement. Unfortunately, our carbs do not respond linearly. This can be adjusted by setting your throttle throws and adjustments such that when the throttle is closed, the throttle servo arm is about 10-15 degrees from being parallel with the control rod, and at 90 degrees with the throttle at full open. This geometry reduces the amount of actual throttle movement during the first part of the stick, while increasing movement near full throttle, and you'll see a much more linear response.

Brad

RE: Need help adjusting thottle servo
 

CG's info works great, i refer to everytime i set up the throttle on a plane, works everytime regardless of which radio or servo i use. here's the originaly post

http://www.rcuniverse.com/forum/m_83...tm.htm#8375656

anyway to make this a "sticky" ?

RE: Need help adjusting thottle servo
 

OK.. great!! Glad to help. As BKDavy suggests, though, my process can be improved by using his method rather than perpendicular centering the servos. Good stuff, here.

Regarding a sticky, well, we've discussed that among the Mods and, well, we'll just keep posting it as necessary rather than fill up the first page of the forum with sticky's.

CGr.

RE: Need help adjusting thottle servo
 

CGR, great detailed How To.

With out a doubt, the throttle is the most difficult of all controls to get setup right for all the reasons pointed out above. As you point out, there is no "Easy Button" from the commercials when it comes to setting up the throttle. I fell into the trap of doing the mechanics with the " That looks about right, the computer will fix the rest" train of though. Iwas always Tweaking the computer trying to get it to idle, shut off and get full throttle around full stick. Even with a good mechanical setup, the throttle can be a bit troublesome. However with a good mechanical setup, the computer can work it's magic with end points and expo to give a near linear engine to stick response.

You have to do what CGR said first though or you are just chasing your tail.

Don


Edit Added

I though I should point out that the linkage must not impart any side to side motion on the barrel of the Carb. The barrels are spring loaded with a not very stiff spring. You can push on the throttle arm end of the barrel and get some side to side movement due to the spring and the slop in the spiral grove in the barrel. On some carbs, this end play can be the equivalent of almost a full turn on the Idle mix. This can cause you some interesting problems on the idle and transition. Make sure your linkage is not introducing side play in the barrel. IEthe push rod is is pushing parallel to the crank CL.

Don

RE: Need help adjusting thottle servo
 

Thanks, Don.

CGr.