DA-100 and throttle servo / arm

[pepatrick]

Ok...time for me to admit that I am an idiot when it comes to setting up throttle servos in an airplane. I have alwasy been able to do it and it works, but is there a recommended servo arm for a DA-100. The throttle servo is a 8611a (it was dirt cheap) and I am using a SWB 1.25" arm. What hole should it be in...what should the endpoints be....any other advice would be helpful to. Radio is a JR 12x...for what its worth. The particular plane is a QQ Python using the stock servo location.

[The Dirt Doctor]

	Quote: Originally Posted by pepatrick
	Ok...time for me to admit that I am an idiot when it comes to setting up throttle servos in an airplane. I have alwasy been able to do it and it works, but is there a recommended servo arm for a DA-100. The throttle servo is a 8611a (it was dirt cheap) and I am using a SWB 1.25" arm. What hole should it be in...what should the endpoints be....any other advice would be helpful to. Radio is a JR 12x...for what its worth. The particular plane is a QQ Python using the stock servo location.

Pepatrick, I got this from Dean Nistetter: following is how I set up my carb servo linkage. I first set my transmitter ATV's to 130% for both ends of the throw. Then with the transmitter on I place the throttle stick in the center throw position. With this done and still on I set the throttle linkage such that the carb butterfly valve is roughly half way to full open (it will look like its at a 45 degree angle). This sets a good starting point to get everything mechanically linear. Next you'll need to adjust each end point of the servo throw through your transmitter so that at full throttle stick up the butterfly valve just reaches full open and at full throttle stick down the butterfly valve is just slightly open (showing a tiny bit of gap/air in the carb throat). If you have the mechanical idle stop backed off far enough you'll still be able to adjust your trim from this position to completely shut the butterfly valve and kill the motor. Once you start the motor for the fist time after setting this up you'll likely need to make some small transmitter adjustments for the end points to get the idle where you want it. I also program a transmitter switch to stop the motor by closing the carb without messing with the trim tabs. You can also accomplish stopping the motor by activating a choke servo if you use one. I actually set up both ways to kill the motor but deactivate them through a condition switch when I'm in the IMAC mode.

One other thing that I did in addition to what Dean describes is to measure the length of the carb arm from the center pivot point of the shaft to the center point of the servo hole. I try find a servo arm the same length (i.e. from servo center to hole center). Also, put a piece of masing tape on the carb insulating block and put a mark at full and idle points. This gives you a set reference points.

Good luck,

Bobby

[Flyfalcons]

Start with the innermost hole on the servo arm and see if you can get full range of travel on the throttle arm. If that doesn't work, go to the next arm out. This will maximize your throttle resolution by allowing you to use as much ATV as possible.

[JoeAirPort]

I copied this post from your duplicate thread and will delete mine from the other one.

What I try to do is max out the end points and use the closest hole on that SWB arm and furthest hole on the DA throttle arm to get full throw of the butterfly. I always have my servo arm at a right angle to the servo case with the throttle butterfly at 50% of its full rotation...at half throttle stick. This usually gets me a very good feeling thottle using all the of the transmitters resolution (full ATVs). It makes the throttle feel smoother. With that SWB arm you may not be able to get close enough in. You may need to drill another hole or use a smaller servo arm....I'd have to see it to be sure.

I just went to grab my DL-50 that was setup on my 30% Edge (going into my new 30% EF yak). This setup used Hitec 1 inch arms with the 4 holes in them on both sides. The push rod was on the 2nd hole closest to the servo, 3rd hole closest to the throttle shaft. I think my end points were not far enough out though. Only about 100/100 out of 140/140 max. I really should have drilled a new hole in the middle of two on one of the arms but was too lazy.

PS: Also ignore that 1st hole closest you see on my servo arm, I drilled that one myself. The pushrod is really on the 2nd hole. not the 3rd (and someone always catches the stuff that doesn't make sense in my posts).

[The_Wreck]

Simple....The objective is to get your ATV values to be the same when fully open and fully closed. And to get them as big as possible. +- 140 on Futaba would be perfect. In reality they are something less. I am usually happy with +-90 or better.

Make them larger by moving the linkage towards the servo on the servo arm. Make them the same by adjusting the length of the linkage.

[The_Wreck]

Probably the .75" or 1" hole on the servo is where you need to be.

[pepatrick]

Guys..I appreciate the help...This is all great stuff...

[JoeAirPort]

	Quote: Originally Posted by The_Wreck
	Probably the .75" or 1" hole on the servo is where you need to be.

Yeah I agree. It all depends on the DA throttle arm. If the DA arm is a fixed distance of say 1" then it'll probably be .75" on the SWB arm. If the DA arm is 1.25" then 1" on the SWB arm etc etc. The 1/4" or maybe less difference between the attachment points on both push rod ends is enough to get that servo to swing to the max end points while getting the throttle plate to swing to its max as well. This is all because all servos at max ATV's rotate at a bigger angle than the throttle butterflies rotate on the Walbros.