Split elevators

[Anthony Blair]

I am a new builder seeking advice on how to connect split servos. I have done google searches and even found and older thread within our group, but technology changes quickly as does the advice being given!

I have found the following;
1) connect halves with block or dowel
2) use a split pushrod, Dave brown most popular next to a wooden dowel
3) mk bell crank assembly
4) dual servos
5) dual pushrods with Sullivan dual ball joint connector

So, what opinions are out there? Thank you for your input and/ or suggestions.
Anthony

[Vic Koenig]

  Servos are hardest to do because no two servos have the same amount of throw. even with programmable inputs from the TX its hard to do well because high rate will not match low rate accurately. If I was doing it I'd use a dowel and join the elevator. Then put the servo at the back of the fuse, accurate, lightest solution, and simple to set up.   Vic K

Anthony

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[Bernie & Jude Olson]

I’ve tried every one of those methods and they all work.  This last time I joined the two halves with a piece of 3/8 sq basswood that extended 2 inches into each elevator half.

 

 

A short piece of 3/8 basswood is glued onto the joiner where the control horn attaches to get enough ‘meat’ for the joint.

 

 

Bernie Olson

[Tommy Scarmardo]

On my SPA airplane I have it joined just as Bernie does. On my 2 meter ship I use the DEPS system... (dual elevator pushrod system) with carbon pushrods and téflon tubes.
Either works well but I really like the DEPS..a little more work to install but not bad if installing it while building the fuselage.

[Duane Wilson]

I'm using an MK bellcrank for the first time on my Blue Angel as Bernie did. We'll see how it goes. Bernie, what do you think about them?

Sent from my iPhone

[Bernie & Jude Olson]

Three of my SPA planes have MK Bellcranks with mixed results. They do work,
but they cost as much as a good servo and they aren't without issues.

The MK provided a nice solution for the Ralph Brooke Crusader. That plane
started with an internal elevator control horn (per its 1965 plans) that
eventually slipped in flight. Fortunately, the plane was still controllable
and landed OK, albeit badly out of trim. Then I installed a split pushrod
(Dave Brown) that wasn't stiff enough and the elevator exhibited flutter.
The fault wasn't with the basic pushrod but rather with trying to retrofit
it into a model that was already built. It took a couple of bends in the
pushrod to get it to slip in and the pushrod wasn't supported. That made
the installation too soft. Finally, I installed an MK Bellcrank based on
success with them in the Blue Angels and it works great. The fuselage had
to be cut open to install the MK so it's better to do it when the plane is
being built.

Both Blue Angels have an MK Bellcrank. One of them was replaced last year
when it started developing a bit too much play. That replacement has now
started to squeak but still functions OK. As with any of our flight
controls, keep a close eye on them.



Bernie

-----Original Message-----
From: spame...@googlegroups.com [mailto:spame...@googlegroups.com] On
Behalf Of Duane Wilson
Sent: Monday, July 04, 2016 10:26 PM
To: SPAme...@googlegroups.com
Subject: Re: [SPA] Split elevators

[chue...@comcast.net]

Both Ed Hartley and I use(d) the MK bellcranks, and they work very well when installed properly -- which is not hard to to.  The only thing about the MK thing is that there are more parts to get aligned and keep working properly.  I have also used the old-timey wire/dowel connecting the elevators with one push rod and control horn (if you don't get it right the first time, you are in trouble -- no adjustment), as well as the split dual push rod system.  The dual push rods can be split at the elevator servo or in the rear of the fuselage.  In any system except the MK bellcrank, the elevator servo positioning and elevator system geometry are critical.  If not done properly, the push rods will not push evenly on each elevator and you will get more deflection in one elevator than the other, which leads to roll coupled with pitch.  If the servo arm describes an arc in the horizontal plane of the airframe, you will get differential elevator with every system except the dowel (which is actually no longer a split elevator) and the MK system.  Ed and Dennis Hunt taught me a lot about setting up an airplane so it performs as you need it to, and that included a couple of tricks for the elevator.  If there is interest, I can do diagrams showing these little things that make tings really work well.

Phil Spelt, KCRC Emeritus
AMA 1294, Scientific Leader Member
SPA L-18, Board Member
Oliver Springs, TN  (865) 435-1476v  (865) 604-0541c

---

[Tommy Scarmardo]

There's a couple advantages to the DEPS system...easy to install while building , very light and strong , easily adjustable and absolutely no slop. My 2 meter airplane is 6 years old and the system is still like new. Just a thought ! Available from Central Hobbies.

[chue...@comcast.net]

Yes, DEPS is what I meant by the elevator push rod split at the servo.  Don't know why anyone would want to spend $20.00 for something that is easily made in the shop with 2 pieces of wire and 3 clevis connectors.  I have also installed this after the fuse has been installed -- not hard at all...

Phil Spelt, KCRC Emeritus
AMA 1294, Scientific Leader Member
SPA L-18, Board Member
Oliver Springs, TN  (865) 435-1476v  (865) 604-0541c

---

There's a couple advantages to the DEPS system...easy to install while building , very light and strong , easily adjustable and absolutely no slop. My 2 meter airplane is 6 years old and the system is still like new. Just a thought ! Available from Central Hobbies.

[Tommy Scarmardo]

Phil the DEPS I"m refering to is two carbon push rods inside teflon sleeves with titanium connectors...very strong , slop free , and no friction.

[chue...@comcast.net]

OK, much more technical than what I make...

Phil Spelt, KCRC Emeritus
AMA 1294, Scientific Leader Member
SPA L-18, Board Member
Oliver Springs, TN  (865) 435-1476v  (865) 604-0541c

---

Phil the DEPS I"m refering to is two carbon push rods inside teflon sleeves with titanium connectors...very strong , slop free , and no friction.

[Duane Wilson]

Phil the DEPS I'm referring to is two carbon push rods inside Teflon sleeves with titanium connectors...very strong , slop free , and no friction.

Do you have a picture of this?

Duane

-----Original Message-----
From: spame...@googlegroups.com [mailto:spame...@googlegroups.com] On Behalf Of Tommy Scarmardo
Sent: Tuesday, July 5, 2016 10:30 AM
To: The Senior Pattern Association <SPAme...@googlegroups.com>
Subject: Re: [SPA] Split elevators

--

[Jim Johns]

Duane,

 

https://centralhobbies.com/singleprod.php?id=1710

 

Jim

 

From: spame...@googlegroups.com [mailto:spame...@googlegroups.com] On Behalf Of Duane Wilson
Sent: Tuesday, July 05, 2016 5:54 PM
To: SPAme...@googlegroups.com
Subject: RE: [SPA] Split elevators

 

Phil the DEPS I'm referring to is two carbon push rods inside Teflon sleeves with titanium connectors...very strong , slop free , and no friction.

Do you have a picture of this?

---

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[Duane Wilson]

Jim—All I can say is WOW…your command of catalogue databases is impressive.

 

Now go to Cullman and “win one for the guppy!!!”……or something like that, (saw it in a movie once).  I’m back from vacation and good as new!

 

Duane

 

From: spame...@googlegroups.com [mailto:spame...@googlegroups.com] On Behalf Of Jim Johns
Sent: Tuesday, July 5, 2016 7:01 PM
To: SPAme...@googlegroups.com
Subject: RE: [SPA] Split elevators

 

Duane,

 

https://centralhobbies.com/singleprod.php?id=1710

 

Jim

 

From: spame...@googlegroups.com [mailto:spame...@googlegroups.com] On Behalf Of Duane Wilson
Sent: Tuesday, July 05, 2016 5:54 PM
To: SPAme...@googlegroups.com
Subject: RE: [SPA] Split elevators

 

Phil the DEPS I'm referring to is two carbon push rods inside Teflon sleeves with titanium connectors...very strong , slop free , and no friction.

Do you have a picture of this?

 

---

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--

[Jim Johns]

Duane,

Google is your friend. 

Jim

Sent from my iPhone 6S

On Jul 5, 2016, at 6:35 PM, Duane Wilson <avlwi...@charter.net> wrote:

Jim—All I can say is WOW…your command of catalogue databases is impressive.

 

Now go to Cullman and “win one for the guppy!!!”……or something like that, (saw it in a movie once).  I’m back from vacation and good as new!

 

Duane

 

From: spame...@googlegroups.com [mailto:spame...@googlegroups.com] On Behalf Of Jim Johns
Sent: Tuesday, July 5, 2016 7:01 PM
To: SPAme...@googlegroups.com
Subject: RE: [SPA] Split elevators

 

Duane,

 

https://centralhobbies.com/singleprod.php?id=1710

 

Jim

 

From: spame...@googlegroups.com [mailto:spame...@googlegroups.com] On Behalf Of Duane Wilson
Sent: Tuesday, July 05, 2016 5:54 PM
To: SPAme...@googlegroups.com
Subject: RE: [SPA] Split elevators

 

Phil the DEPS I'm referring to is two carbon push rods inside Teflon sleeves with titanium connectors...very strong , slop free , and no friction.

Do you have a picture of this?

 

---

<~WRD000.jpg>

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[Tommy Scarmardo]

The only thing I did different was I didn't glue the two carbon rods together near the servo...I put titanium threaded ends on both rods and attached them to either side of the servo arm with Dubro ball joint ends with one screw and lock nut and loc tite.

[chue...@comcast.net]

He said it was at Central Hobbies.  I went there and found it right away.  Carbon fiber and Teflon and titanium are overkill for anything I fly, including SPA pattern planes.  As I said, I have made them using music wire and ply braces. With the elevator servo mounted with the arm vertical, there is no roll coupling.

Phil Spelt, KCRC Emeritus
AMA 1294, Scientific Leader Member
SPA L-18, Board Member
Oliver Springs, TN  (865) 435-1476v  (865) 604-0541c

---

[chue...@comcast.net]

Hah!  Nice touch, Tom -- that really eliminates any friction...

Phil Spelt, KCRC Emeritus
AMA 1294, Scientific Leader Member
SPA L-18, Board Member
Oliver Springs, TN  (865) 435-1476v  (865) 604-0541c

---

The only thing I did different was I didn't glue the two carbon rods together near the servo...I put titanium threaded ends on both rods and attached them to either side of the servo arm with Dubro ball joint ends with one screw and lock nut and loc tite.

[Tommy Scarmardo]

It's not a matter of overkill or not...It's very light and strong , friction free , and trouble free. The carbon rods never seem to change trim with temperature variances. This is definitely not the only way to do it but it's one I like very much.