Two Elevator Servos
 

Hi guys,

I'm setting up a plane that has two elevator servos mounted to the sides of the fuselage. I have a Futaba 7 CAP and I understand that this paticular radio does not have a dual elevator feature. Also, as you guys know, if I mix two elevator servos together then when I use the trim, only one elevator servo moves. Can I use a regular y-harness or will I need a reversing y-harness? Just to clarify, one servo is mounted on one side of the fuse and another on the other side. Both servo arms point down.

Thanks

RE: Two Elevator Servos
 

Hi,
You can use a 'Y' reverser where one channel is reversed only, or run a standard Y with a reverser after. These are OK, but you will find that the reversed servo, will after some time not return to its central position, as the reversers tend to 'drift'. I have used these in the past, and have got frustrated with their operation.

The best way to do this (exept for buying new radio gear), is to use a JR matchbox. I swapped to these after having problems with the inline reversers.

The match box allows you to control upto 4 servos from a single input channel, then reverse any of them by programming it, which is very very easy.

Hope that helps.

Regards

W

RE: Two Elevator Servos
 

You can use a simple Y and no reverseing gadget is ever needed.

When you have split and independant elevators and the two protruding elevator servos out the right and left sides of the fuselage simply attach the push rods at the servos on opposite sides. One pushrod clips to the servo output arm on the Top side and the pushrod on the opposite side clips to the servo output arm on the bottom side.

Simple, no need for expensive gadgets, no reversed servos, trim functions as advertized and no disadvantages. Simple geometry.

John

RE: Two Elevator Servos
 

... Or you could use a Futaba servo on one side and a JR servo on the other. JR servos turn backwards from Futaba / Hitec / Hobbico / Cirrus ...

RE: Two Elevator Servos
 

be carefull mixing servos mate, if one turns faster than the other then both the elevators wont be at the same position and that can cause some problems in flight

RE: Two Elevator Servos
 

I've found Airtronics and Futaba servos to be reverse of each other as well... but as mentioned above, you probably don't want to mix servos in this application.

RE: Two Elevator Servos
 

Well yes and no, be careful at what you say While its true some manufacturers servos by factory default are reversed from some others. That statement above is not correct. I cannot speak for JR or hobbico or cirrus But I can say by actual experiance of deliberately using mis matched brands for the purpose of reversed function on dedicated and separate flaps that Hitc and Futaba servos are reversed from each other by factory default.

In that function the mis matched brands offers no problems however for Elevators which the question is about I would not suggest mis matching servos for reversing purposes. As noted by wild foamy.

Agine for the configuration of the OP's airplane its silly and pointless to throw money and complexity at a none existant problem.

Use the proper geometry.

John

RE: Two Elevator Servos
 

You can always buy a regular servo and a reverse version of the same servo. I know JR offers at least one model like this. It's called for in the PTS P-51. Maybe the F-22 also.

JSP20050 and JSP20050R These should match in all respects.

RE: Two Elevator Servos
 

Thanks guys.

How about this servo mixer from servocity.

http://servocity.com/html/servo_mixer.html

Will I still have the same problem? I pretty much already emptied my pocket so I don't know about the matchbox. I cannot get any other servos as I have already bought all the servos.

RE: Two Elevator Servos
 

Yes you will still have the same problem that unit will not fix your problem it does not reverse just one of the servo's.


If you have an ordinary 'Y' chord------You Do Not Have to Spend Money------

Reread Post #3

Use the ordinary Y chord on both elevator servos that stick outside the fuselage. Install one servo horn sticking straight up. Install the servo horn on the opposite side of the fuselage sticking straight down now just hook the pushrods up, one side goes just above the servo and the one on the other side side of the fuselages goes just below the servo.

Both pushrods will go to horns below the elevator halves .

You are done. Everything is fine, trims work properly and your Tx reversing switch will work normally.

John

RE: Two Elevator Servos
 

The problem is that the horn hits the elevator and does not clear it so that's not a option. I cannot get a smaller size horn as I am already at the minimum for 3D.

RE: Two Elevator Servos
 

Then that leaves the three options already talked about all involves money. If you want to use your Tx.

Use a reversing Y chord. This device reverses just one of the servos plugged into it. A mixing Y chord will not do this it is for an entirely differently purpose. An even more expensive matchbox may do this as well I don't know and never had a need for them.

Use a similar hitec servo one side (this is not a desirable choice)

Special order a matching servo reversed from factory default.

If it were me I would simply reposition the servos when they should be but I realize you may not want to do this.

John

RE: Two Elevator Servos
 

I think I'll probably go with the reversed y-harness.

RE: Two Elevator Servos
 

F.F. listen to JohnBuckner unless you have money to spend thats just burning in your pockets,Sheldons will take your $ if you want to spend it.
it's simple stuff mount one servo in its location hook the pushrod to the control arm.
mount other servo to other side of fuse oposite the other and hook up the other pushrod jsut make sure the servos are moving in the same direction if there not then flip one of the servos its simple really.
if your pushrod is too short then 1.25 will buy a new one you can rebend to fit.
buying a reversing Y connector,or a match box, not needed for this application .

RE: Two Elevator Servos
 

8 bucks is not kill me. Turning the horn pointing upwards will not work because of clearance.

RE: Two Elevator Servos
 

no, turn the servo around so you can switch the horn so it points down.
I have a servo syncroniser its 60.00 http://www2.towerhobbies.com/cgi-bin...9&I=LXCTS1&P=K
I also have 15 Y harnesses there 10$ http://www2.towerhobbies.com/cgi-bin...9&I=LXL307&P=K
neither of which is 8.00 so if you have a line on a 8$ reversing Y harness then leave a link because I will buy some

RE: Two Elevator Servos
 

Here you go!

http://www.chiefaircraft.com/rcmsec/...xtensions.html

http://www.horizonhobby.com/Products...ProdID=EXRA320

Heavy Duty:

Also on Chief.

http://www.horizonhobby.com/Products...ProdID=EXRA325

It's not a big deal, we'll see how it goes.

RE: Two Elevator Servos
 

thats pretty cheap,chief wants a 20$ min order.
and horizon is going to get you in shipping,you might check sheldons hobby's they will save you some $ in shipping I would bet.

RE: Two Elevator Servos
 

Frankie,
Hope i didnt confuse you too much, bad mouthing the inline reversers. They work, but just keep an eye on the centering of the servo, it will move. Make sure you have easy access to the reverser, so you can adjust the centering of the servo when you have to (they have a potentiometer which can be adjusted by a small screwdriver, which moves the center position of the reversed servo).

As an aside, do not mix makes of servo on the same reverser, most of them do not work.

If you have digital hitec servo's you can have one of them reversed $FOC by Hitec USA.

A matchbox is the ideal solution but if $$$'s are not available, use an inline reverser.

Cheers

W

PS: Be very very careful, swapping arms on elevator servo's to reverse them with horns on opposite sides. This almost never works as subtle differences in the setup will never give you correct matching of elevator halves.

RE: Two Elevator Servos
 

I can't remember, is the 7th channell on that radio proportional or not? If it is there should be some way to slave it to the elevator. The only Y you would need then might be for the batt(If the rec only has 7 slots). It may be that you would need a PCM reciever for this. Have never needed all of my 9C's channels so I can't recall. Regardless, even if you had the room I would not reccomend putting the servo arms one up and one down. This may work well on a sport model with moderate throws, but on a plane setup for 3-D you could see quite a difference in throws between elevator halves, especially at the end of the travel.

RE: Two Elevator Servos
 

LOL ... :D:D


If the professor on Gilligan's Island could make a radio out of 2 coconuts, why could't he fix a hole in a boat?

RE: Two Elevator Servos
 

Here's a reversing Y-harness that worked well for me in a surface vehicle, never used one in an aircraft...

http://www2.towerhobbies.com/cgi-bin...&I=LXAFN1&P=ML

RE: Two Elevator Servos
 

Yup exactly.

You may find that you have to adjust the reverse each time you go out to the field.

The occillator crystals used vary with temperature, causing the centering to be off constantly as conditions change.

RE: Two Elevator Servos
 

This is probably a really stupid question, but don't the servos already actuate in different directions with a regular y harness? I'm looking for a way to have my elevator servos teamed up so when I use the elevator trim, both halves of the elevator move.

RE: Two Elevator Servos
 

No. With a plain Y they receive the identical digital signal unless acted upon by an external device (reverser). Depending on the capabilities of your TX your 2 elevators will trim together if mixed by the TX. If you use a "plain Y" or "Y with reverser" they SHOULD trim together. Of course in your situation the plain Y would result in opposite movements of the elevators.

RE: Two Elevator Servos
 

Thanks Bruce, the y harness reverser is the way go and I'm using a 7CAP just for the record.

RE: Two Elevator Servos
 

I just broke out the soldering iron and screwdriver and reversed the servo internally. Works great. There's a thread on how to do that to just about any brand servo on here somewhere

RE: Two Elevator Servos
 

I was reading over the "answers" and there's too many![sm=confused.gif] The 7CAP has 3 free mixes. Pick one. U can just slave any free channel to channel 2, and if it's backwards, there's a reversing menu for all the channels... the only problem is that the 7CAP can only trim channel 2. If u use the trim, the slaved servo won't move and ur gonna have to go to the "subtrim" menu to make both elevator halves the same.

No need for a reversing y harness.

RE: Two Elevator Servos
 

The "Y" reversers are not as bad as some people say. I used them in two different planes for 5 years. They are a royal pain to set up as the reversed servo travel is not always symetrical with the non-reversed servo. Having a fully adjustable horn is a necessity.

With that said, I have only had to adjust the reverser during temp extremes. ie..summer/winter. I have finally switched to the Futaba 9C that does have twin-elevator servo capability. I'm sure that sells a lot of 9Cs that would have otherwise been 7C sales.

While the Y reverser is not ideal, it will work. Kinda like a nylon MA prop. :D