Throttle servo installation - RC Groups
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Feb 19, 2013, 07:05 AM
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Throttle servo installation

Good day all

Moved to gasoline engine. Got DLE 20cc, on EDGE 540T. Did my first flight couple days ago. Considerin that I'm a heli pilot, and was flying only trainer TT40 plane, it was riski transition. But hey, managed well..

one thing observed, is throttle response. I got flexible pushrod to engine. without tube, as carb has spring to close the throttle. However, does not perform good.

Also, I installed the servo about 30cm away from engine. As I used to read that on gas planes, need to install servo far away. How true is it? What about the helis then? Gas helis has all electronics right next to the engine.

I'm planning to move servo forward, and have METAL pushrod. Any concerns?
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Feb 19, 2013, 07:49 AM
Registered User
ace4rc's Avatar
Most of my planes the servo is within 6" of the throttle. As for the linkage, pushrods are good as long ao you use a plastic link, not metal to metal. On my carbs I use the ball links as in the pic, either 2-56 or 4-40 works well. With the 2.4 radios and equipment of today I don't worry about where I place any of my electronics. Like you stated all electronics are well within the 6" perimeter on a heli.
Feb 19, 2013, 08:02 AM
Registered User
Interesting fact...I thought the metal pushrod acts like a magnetic transponder, so high voltage can jump on wire and transfer to THR servo, which at the end can cause interference with radio.

I've posted here recently moving to 2.4 system. I still have old faithful Futaba 9cap, 72mhz pcm. Worked good for me in the past. Nowdays people are worried about 72's, and all are pushed to have 2.4. IMHO, I think this is just marketing. And only downside of 72 is 2 people flying on same channel, resulting in shootdown. I you check flyzone, for participants, it is not a problem.

So you also don't recommend to move closer than 6"?
Feb 19, 2013, 10:26 AM
Registered User
Metal on metal is thought to create "whte noise," a form of interference. Most throttle arms now days are plastic or non-metallic in nature. I don't think distance has anything to do with it except for maybe weight and balance purposes where you want to move the weight of the servo aft or near the center of gravity. Do not worry about high voltage jumping on anything. Your spark ignition should be sheilded and grouded and that is the source of high voltage. It is said that using 2.4 Gig systems negate the effects of ingnition noise, don't know about that.
Feb 20, 2013, 10:48 AM
Registered User
You are right, I checked the wire isolation, it is connected to negative. This proves my theory about the helicopters.

Other question, is about the spring on carburetor butterfly. I got DLE 20cc, which has a spring which keeps the butterfly closed. Some people suggest removing the spring, as the servo constantly has to fight the force. I put standart Futaba S3004 servo for that job, and it seems working ok, no buzzing. What is peoples opinion on the spring and the type of the servo to be used ?
Feb 20, 2013, 11:19 AM
KV4PL, FAA 107 Certified
FloridaFlyBob's Avatar
I unhooked the spring from the arm. I've been told to use metal gear servos in gassers because of the vibration. I'm sure it's strong enough, it's a matter of will it hold up.
Feb 20, 2013, 11:38 AM
team sleprock
whiskykid's Avatar
I remove the spring and idle screw from botth my 20cc and 50cc, and use standerd futaba servo, as I fig there really is no strain on the servo!

I am relitivaly new ta this, but they both seem to work fine! and I am running 2.4 on my 50cc plane and 72mhz on my 20cc plane!
Feb 20, 2013, 12:48 PM
Registered User
Removed idle screw? Can you describe more. Did you cap it with blind end screw? Or just left open to atmosphere?

Are there any electronic gurus here? I've built myself linear regulator, BEC. based on 3x LM7806.

they get hot without heatsink. So may add one. Question: is there anyone using BEC here? Which commercial BECs are they? Do they get hot? I guess most of them are linear. So wonder how hot they become after flight (if not are outside the plane, so get cooled)
Feb 20, 2013, 12:49 PM
Registered User
here it is
Feb 20, 2013, 01:19 PM
IDLE SCREW. What the gentleman was referring to was the idle speed screw, not the idle mixture screw.
Feb 20, 2013, 01:23 PM
team sleprock
whiskykid's Avatar
[QUOTE=jeka616;24194815]Removed idle screw? Can you describe more. Did you cap it with blind end screw? Or just left open to atmosphere?
not the "low speed mixture screw" "the idle screw" the screw on the outside of the carb, that sets the low speed idle! with a servo you set the idle with trim! that way you can shut the engine down with the trim on the radio!
Feb 20, 2013, 01:39 PM
Registered User
Ok got you now. mixed the idle screw with the idle mixture screw.

I tried to shut off the engine with butterfly fully closed, but it kept spinning at very low RPM, just like with choke closed. so ended up installing kill switch.
Feb 20, 2013, 01:40 PM
Registered User
any thoughts on BEC?
Feb 20, 2013, 01:57 PM
team sleprock
whiskykid's Avatar
hopefully someone else can help ya out with the BEC, as I just use a dedicated 4.8 ni-cad for my ign. that completely seperates the ign. from the radio! and I use a regular switch too turn ign. on and off!

so I can kill my engine with trim, or manualy with switch!
Feb 21, 2013, 09:38 AM
KV4PL, FAA 107 Certified
FloridaFlyBob's Avatar
Everything i've read says to use some sort of kill switch from the TX either an opto switch or a servo on the choke. I'm using 2 batteries in my hellcat with a dle20, a nimh 4.6 on the ignition and a life on the RX with a choke servo. My dle20 stops as soon as I close the choke. On my waco with a OS GT33 I'm using the power setup from troybuiltmodels with a regulator and a ibef to the ignition for power and also the killswitch on aux3 on the TX. The regulator has 2 seperate inputs and outputs and I have 2 2800mah lion batteries going to 2 channels on the RX. Here's the link for TBM

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