Hi all,

I am having some real trouble here, I have Split elevators on my WM Extra 300s, I am using 2 x Hitec HS654MG, with a EMS SR-2Y servo reversing Y lead:
Now, the problem is: I turn on the TX and RX and the elevator half (with the reversing part of the lead) slowly goes down, get to the max servo movement and buzz's (like its trying to go further) then after a while comes up and works fine, then after a minute or so..... repeats the process, and then continues to keep doing this.

Odd huh??? can anyone help, I am wanting to maiden it very soon, but clearly its not getting airborne while this is happening!!!

Thanks

RJ

Did you ever think the unit might be bad

Exactly why I reverse servos internally.

This is a very common problem with servo reverser's and exactly why I do not use them. I have seen first hand one that locked an elevator half full down in flight.

The other thing is the servos you have are not programmable. If you have the ability, put both elevator servos on separate channels and depending on the radio, you can either set dual elevator servos or mix the two channels, then reverse whatever one needs it in the radio.

If you let us know what TX/RX you are using and depending what it is, we may be able to help you attempt this

I have the Futaba 7CAP with the elevator trim bug, so I had to use a Y connector also. I got the MPI Miracle Y connector, and am pleased with it.

i use jr matchboxes now and will never, ever use any kind of y-harness again. the matchboxes are great. lots of adjustments and you can get your elevators perfect.

Ok,

Thank you all for the help, I am using a Futaba 7UAPS (PCM 1024).
Well, I am guessing that the reversing Y lead is the problem, so whats my next step - I have used all the channels in my RX, so by the sound of it my best option is to use a standard Y lead and reverse one of the servos internally - how hard is this to do? And how is it done?

RJ

kainisrj,

I hate to have to many mixes going on so what I do is when I order my servos if they are not digital it's about $8.00 to have one reversed internally and if they are digital they can be reversed by a servo programmer. When I ordered my HS-5645MG Digitals I forgot to have this done so I'm sending it to ServoCity and as long as you pay the shipping both ways they will reverse it with a programmer for free.

http://www.maxxprod.com/mpi/mpi-5.html

Look at this first, they are half way down the page. They work great.

Thanks again all,

Hows this though........ I just pulled the reversing y lead out of its foam padding, and turned the system on, still same problem........ then i thought i would just have a play around with the little trim pot (or what ever its called), so i tweaked it back and forth with a screw driver, this obviously sets the elevator trim, then i set it so the elevator looks right, and now - its work 100%. I have turned the TX and RX on and off, in different orders etc, and the trim stays perfect, everything is workin - what do i do now - do i risk it?
I am still a little way off a maiden flight - ie. the engine still needs to be tweaked, so i will keep an eye on the Y lead, if anything happens between now and flight day..... I will send my servo away and get it reversed properly!

What do you guys reckon? Shall i risk it - even if all goes 100% form now till the maiden flight?

RJ

Clearly I Have spoken to soon!!!

Nope - Same Problem!!!!!
Ok I have to options now...................
1. Send my servo away to get reversed
2. Try to figure out how to use 2 channels on my radio to run both elevator servos? (i cant seem to find anything in the manual) - can anyone help me with this?
its a Futaba 7UAPS

RJ

Im not a futaba guy...but they do have a support forum here, and im sure they will help you.

Well..............
It just gets more interesting - After taking the Reverse Y lead out of the system, I tried a few things, and it turns out the servo it dodgey!!!
A brand new Servo!! Its still doing the exact same thing, buzzing its way right to the end of its travel, then holding - then centering itself again??
I tried it in 2 other channel ports on the RX and .... same thing!!! must be the servo?

RJ

If you have a standard Y harness , can't you just put the servo arms in opposite directions?

"Problems that go away by themselves usually come fack with all their friends".

Reversing a servo is easy if you can handle a small soldering iron and tiny wires.

Yes, but with most arfs the servos are positioned to have the servos going opposit directions.

Can you explain how to reverse a servo?

Well I'm in the camp that says you just don't use reversing Y harnesses but some folks do it so if that's what your committed to rather than using a matchbox, so be it. But either a Y with modified servo travel direction, a reversing Y, or a matchbox will have to be the solution as the Futaba 7 channel systems do not natively support dual elevator servos.

As to whether or not you could accomplish it with a mix I can't say as I'm not familiar with that radio, just the 9C Super and 9ZAP that I use...

You have a bad servo, replace it and I think you will solve your problem. I have flown a giant scale P-47 all summer with a Y-reverser and have had no problems. Like anything else they represent a weak spot in a system that can be disabled with even the slightest glitch. As trustworthy as our systems are, they are still pretty fragile when you think about it. Good luck fixing your problem.
Tommy

You can use a mix, but the elevator trim adjustments don't get passed to the slave channel.

To reverse a servo you must open it up and reverse the motor leads and the outside leads to the pot. The pot has three leads leave the center one alone. Four leads total.
John

Isn't true that you cannot reverse a Futaba servo because of it's surface mount technology?

Open it up and look. Just because it's a SMB board doesn't necessarily mean you can't modify it. If there are wire leads and you are good with a soldering iron you are home free. If the pad lengths are long enough to be cut and wires added to reverse the motor and the potentiometer leads you are also good to go. It should be rather obvious and you are the best judge of your abilities. If you've never had a servo apart or put a gear train back together and you are all thumbs it's better left alone. In my opinion its better to buy a Match Box or a digital Hitec servo and have it reversed if you have doubts.
John

I purchased a couple of reversers and found that due to the small SMD pots that are used, the set values "drift" with temperature and humidity.

IMHO these things are NOT worth the grief. I ended chucking mine, as it always required fine tuning at the field.

As others have indicated, more channels on a TX mix, a reversed servo, or a more stable matchbox are better.

another way if you just use a y lead is to make sure that the sevo's horns are 1 up and 1 down what i mean is on 1 servo the horn is facing up and the other servo the horn is facing down