Scott_S.

Is there a rule of thumb for this?
I struggle more than necessary and just read in a manual on Horizon's web site where you should have the throttle valve at mid position and the servo in dead center for best results.
Thanks in advance for any thoughts!

BarracudaHockey

My Feedback: (11)

It shouldn't be all that hard.

You want a servo arm length that allows you to have at or close to 100/100 for your end points.

Center the servo, center the throttle barrel.

Make sure that full throttle is full open.
Full down and full low trim is fully closed.
Full down and mid to high trim is a reliable idle.

If your throws are way off like 120/70 then your pushrod length is wrong.

BuschBarber

My Feedback: (2)

With computer radios, if the Low End Point, for Throttle, is too low (below 50%), the Throttle Trim will not be very effective. I have used various JR and Futaba radios and it seems that the sensitivity of the Throttle Trim is proportional to the Low End End Point. If the Throttle Low End Point is closer to 100%, small movements of the Throttle Trim have greater effect. As the End Point number goes down to 30%, the Throttle Trim has little effect.

I usually set the Throttle End Points to 100/100 and move the Throttle Barrel to fully closed, mechanically. I move the Throttle Stick and Throttle Trim to fully closed. I set the Throttle Arm at 45deg from Neutral and hook up the pushrod to the Throttle arm. I turn on the Tx and Rx and move the Throttle Stick to Full Throttle.If it Binds, I dial back the End Points until it stops Binding. If the High End Point goes below 50%, I move the Pushrod Clevis in one hole on the servo arm.

Once the Travel is set, I set up Throttle Cut, if the Tx has that. Next, I run the engine an set the Throttle Trim to be below half for a low idle. You may have to tweak the numbers a little to do that. Closing the Throttle Trim all the way should shut off the engine. If you have Throttle Cut, you can leave the Throttle Trim at Idle and just press the Throttle Cut button when you want to shut off the engine.

I usually install a Fiber Optic Kill Switch, for Gas Ignition engines, operated by a switch on the Tx.

BarracudaHockey

My Feedback: (11)

Good point about throttle trim.

Higher end points give better resolution in any case.

BuschBarber

My Feedback: (2)

Thanks!!

I saw Ray Stacey on Sat at the LHS Christmas Party. I mentioned that you were going to be in the area again.

Scott_S.

Exactly!.....but I did not know what the hell was going on at the time. Great explanation, thanks.

I'm going with these little fellows from Sullivan on my winter build this year:

http://www3.towerhobbies.com/cgi-bin...?&I=LXYCH3&P=7

These things look like high quality and very forgiving on the alignment part, and half throttle with centered servo arm.

Scott_S.

This sounds complicated to me. I'll start 100/100 but will surely have to trim it back to keep from stressing the servo.
I'm gonna print this out and use it to set it up. I had way too much gimbal stick movement at half throttle and less and it
was too sensitive above half throttle and then BAM it would be wide open. Oh well.....my first nitro build.

Could I start at 100/100 with butterfly valve at 50% and then try to do it all on both ends with mechanical adjustments....
then that might let me use minimal trim/subtrim?

I think the Sullivan ball joints would just about eliminate any binding as far as linkage goes.

You are starting the valve closed and the Hangar 9 manual says start at half valve position but whatever works for you.

BuschBarber

My Feedback: (2)

I would like to see you use 4-40 rod and connectors rather than 2-56.

Scott_S.

On a OS55 or Saito 82 ? Plane is H9 Saratoga and Showtime 50.

BuschBarber

My Feedback: (2)

Starting with mechanical adjustments is fine. Your Throttle Arm usually has two holes in it, an Inner and an Outer. The Inner will give you More throw and the Outer will give you Less throw. The Servo Arm is just the opposite and you can use a larger or smaller Servo Arm to suit your needs. You can hook the Throttle Pushrod up to either the Throttle Arm or the Servo Arm, temporarily, and move the servo to see if you will need More or Less throw. Once you determine which holes to connect the Pushrod to, you can start playing with End Points. The important thing is to keep the Low End Points as high as possible to give the Throttle Trim more resolution. The same is true for the High End Points, to give the Throttle more resolution.

Many times I use EZ connectors at both the Servo Arm and Throttle Arm so I can fine tune the Throttle Pushrod length. Just make sure the screw is a Socket Head so you can tighten it snugly.

BuschBarber

My Feedback: (2)

As long as the Pushrod does not Bend or Flex, use whatever you want. I like all my Pushrods to be Rock Solid under load.

Scott_S.

That's where I had problems. It was the Z bend and EZ Links and did all adjustment with radio end points. Like you say, its kills the resolution. I won't make that mistake again.

Scott_S.

Most guys I fly with are using weed eater string on throttle cables, seems to work well in an EZ Connector. Monofilament is tough stuff and would absorb tons of vibration. Same principle as Sullivans Golden Rods I guess.

BuschBarber

My Feedback: (2)

In order for Throttle Cut to work, the Carb Barrel or Butterfly needs to be fully closed, with the Throttle Trim at Zero. I use that as a starting point, with the Throttle Stick and Trim all the way down. I turn on the Tx and Rx and place the Throttle Servo Arm at 45deg from Neutral. As you move the Throttle Stick towards the Center, the Servo Arm moves toward Neutral. As you move the Throttle Stick to Full Throttle, the Throttle Arm should be close to 45deg the other side of Neutral.

When you go to set up Throttle Cut, when you press the Button or Switch, the Barrel or Butterfly will be fully closed.

It seems easier to me to start with the Low End setup and then move to the High End.

BuschBarber

My Feedback: (2)

Weed Eater String or Nyrod has an advantage in that you can curve it around obstacles in your path to the Throttle. Since it is more flexible, is important to Secure it at intervals, so it does not Flex.

I have a friend who constantly has problems with his Throttle Pushrods because it comes loose all the time and flexes. He either uses not enough glue or weak cable. Braided Wire or Nyrod, that slides inside an outer tube, shouldn't extend more than two inches beyond the outer tube or it can flex, especially as it gets worn.

N429EM

Is "End Points" the same as "Travel Adjustment"?

The DX7 manual uses the term "Travel Adjustment". So, am I doing the same thing, just as a different name?

Thanks,
EJ

BuschBarber

My Feedback: (2)

Yes!! Some radios refer to the term End Point Adjustments and others to Travel Volume/Travel Adjustment. In the case of the Throttle, you will see the term Throttle Curves, as well. In many instances, the Throttle does not move Linearly. A Throttle Curve allows you to adjust the Throttle movement so that it behaves more Linearly. After you adjust Travel Volume, you can adjust the Throttle Curve. With the engine running, the engine RPM should increase proportionally to the movement of the Throttle Stick.