Elevator Mis-match

[Flatlandman]

	Quote: Originally Posted by castlebravo
	Subscribed........Good luck Jeff.....I have a similar issue with the same servos but different radio. I still dont understand the part about the servo arm geometry needing to be positioned forward instead of 90 degrees to the linkage. I think your going to have to dumb it down for me Seth. CB

Im not seth but ill add a little bit. You dont really need to understand why just pay attention to your travel adjustment if you get more end points on the push than in the pull for equal throw then you just shorten your push rod then readjust the sub trim vise versa if more in the pull lengthen your push rod until you have your equal throw. The arm offset will be what ever it needs to be. Then just start the opposite side near the same place the original side ended up at.

[JoeAirPort]

Right on Flatlandman...right on....

[jon595]

	Quote: Originally Posted by JoeAirPort
	Right on Flatlandman...right on....

Ditto...

BTW, this is how it was done before computer radios and programmers. Once you see someone do it this way you will not use anything else. Get yourself a throw gage to make it easier to see.

[The_Wreck]

	Quote: Originally Posted by 3D-Seth
	No. You will end up with un-equal elevator travel this way. See attached picture that I drew. Because the servo is below the stab, when the servo turns towards the elevator, the linkage goes straight much quicker. When the servo turns away from the elevator, it has the reverse effect; pulls the linkage away much quicker. This is why it needs to be mounted with the servo arm towards the front of the airplane. **Note: this is only for fuse mounted elevator servos, not stab mounted elevator servos. Seth

Your drawing actually shows why the servo horn should be close to 90 degrees from the hinge line. If you draw a line from the hinge to the servo horn connection it is 90 degrees with the servo horn. Your illustration is the best I've seen yet that shows this. The servo horn relationship to the case never matters only its relationship to the hinge, whether it is in plane or out of plane like on a surface mounted aileron. There is a lot of different geometry issues that can cause the best position to be something other than 90 but it is a good place to start.

There is an excellent thread on setting up linear geometry.
http://www.flyinggiants.com/forums/f...-geometry.html

I have attachaed a couple of different servo protractors I have created. Depending on the installation they either go over the top of the case or over the whole servo.

[blackbeer]

After reading this thread through a couple of times I think I will go over my set up in my Yak. One thing I found buried deep in the manual for my 8U super is that there is a difference in the resalution between channels 1-4 and 5-8. I have one elevator servo plugged into channel 2 and one plugged into channel 8, or is it 7, I'll have to check, same with ailerons, one in channel 1 and one in channel 8, or 7 can't remember. I can center them and I can match max throws but in between is a different story. Any ideas on that situation. I'll be moving into the 2.4 relm this winter but for now it is my trusted 8U that gets the nod..............

Tom

[sweetpea]

matchboxes and Smart-fly equalizers can be had for very little money. (I have at least 5 matchboxes I'd sell as I have moved to the EQ PE's ).

This keeps them on the same channel and you can adjust endpoints and neutral as well as reverse them. In the realm of IMAC precision is the key. Or you can spend the money on a new radio.

[Flatlandman]

I prefer the matchbox set up rather than programing a servo.

[yakpilot]

Using a matchbox is usually quicker and easier, but if you want the servos to be in sync through their entire travel you have to program them. I've used matchboxs many times and they work well to set end points and centering, but often times you can't get the servos to match in the in-between points where they spend most of their time while in flight. Of course there are variables. If you've optimized the linkages and start off with servos that happen to match well then you are golden. But I've had servos the that were not matched very well from the factory, and once you start changing subtrims and endpoints by very much, you will get one servo that moves farther than the other for a given stick deflection. Anyways thats been my experience.

[blackbeer]

Well I used an EQ2 once on a 7C to get both elevator servos in sync but it put out so much noise I could barely get a ground check with that radio so I'm not ready to go that route again. Maybe I will need to break down and get a programmer but I wonder if that will overcome the difference in resalution between the channels in my radio.....................

Tom

[yakpilot]

Tom yes it would since you can then just use a Y harness and run them off of one channel.

[3D-Seth]

	Quote: Originally Posted by scott m lyons
	Seth with your setup wouldn't that mean if the servo was in the stab you would have to tilt the arm back?You could just flip the servo to the top meaning in the stab and the end of the servo arm were the linkage connects would be the same distance from the stab.I'm trying to make sence of it because I always setup my stuff like extra260 does and my stuff is always the same length and square.My end points are the same also meaning up is the same as down.I don't program the servos i do it in the radio and match-em.

No, Unless you mean parallel to the hinge line. Because the servo is rotated 90º

With the fuse mounted elevator servos, in the bottom portion of the drawing (incorrect way, mounting the servo arm 90º to the case), the arm and linkage straightens out very quickly, ending your travel, which differs from when it is pulled away from the horn, which pulls more throw much faster. Basically, you have 30º of up elevator, with 70º of down elevator (just random numbers), but yet in the same amount of time.

Basically, the same reasoning as to why your linkage isn't 90º to your servo arm on your wing mounted aileron servos, or stab mounted elevator servos. More travel.

Basically, its just offset to equal your travel in the same amount of time between your up/down throw.

Hope this makes sense.

Seth

[scott m lyons]

No y harness in giant planes.Or any plane for that matter if you can help it.

[blackbeer]

Ya, I'm not into Y harnesses at all. Been there, done that. I just went over to Servo City's site and there seem to be 3 different programmers with a huge difference in price. Could some one clue me in on which one to get. The one that is over 150 bucks is out for now but if one of the others would program my 5945s and 7955s I might be able to swing it.

Tom

[scott m lyons]

I Think we're miss understanding each other maybe? I mean like this.

[yakpilot]

	Quote: Originally Posted by scott m lyons
	No y harness in giant planes.Or any plane for that matter if you can help it.

If they are heavy gauge, why not? BTW we are not talking about 43% Carden here. For a 50cc it's just fine.