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Old Jan 16, 2011, 03:04 PM
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Huntsville
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Jim -

Most of the molded wings we use have an extra layer of Carbon on the inner top skin in the area we mount servos. This is to help stiffen the skin and prevent oil canning. We can generally get away with epoxying the servo directly to the skin, I've used this technique for many planes in the past.

This is falling out of favor lately. Most folks now use a servo frame bonded to the skin so that the servo is easily removeable. There is still a bit of technique to get it right. The servo frame doesn't do much if anything to prevent flex in the skin under high servo loads.

Some folks like to tie the servo to the bottom skin as well to reduce any flex. I've seen threads that document this, I'll try to dig one up and steer you that way.

Found one - http://www.rcgroups.com/forums/showt...nting&page=188
A discussion of wing servo mounting starts at post 2816 and continues for a while. I'm sure that there are others out there, but this one covers the gist of it.
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Old Jan 16, 2011, 03:29 PM
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Jyvaskyla, Finland
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Originally Posted by Robglover View Post
Jim -

Most of the molded wings we use have an extra layer of Carbon on the inner top skin in the area we mount servos. This is to help stiffen the skin and prevent oil canning.
With todays F3J planed getting lighter, with the large size, I have started a new practice of laminating extra layer of carbon under servos. Weights next to nothing but seems to improve stiffnes, and no more servo pictures on top skin.

I recommend servo mounts. They are practical and improve mounting by spreading loads to larger area. However, with MKS servos it is easy to use self made wooden mounting slugs.

It is also important to fix servo to uderside of wing. This can be done with plywood strip epoxied to servo and skin. You pull out the plywood strip if you need to service the servo.
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Old Jan 16, 2011, 03:44 PM
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United States, AL, Madison
Joined May 2002
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Jim,

This excellent Shadow build threads shows lots of photos of installing servos with glue-in mounts. Hope it's helpful

http://www.rcgroups.com/forums/showthread.php?t=841007
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Old Jan 16, 2011, 05:13 PM
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Harbor City, CA
Joined Oct 2003
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I also have pics on my blog of several different planes with may different ways of mounting wing servos.
Some guys even just (gasp) glue the servo directly to the wing skin, without a mount at all. To remove, you use a twisting motion and some hope.
It is always a good idea to mount a rib outboard of the servo tying the top and bottom skin together.
Lots of the molded planes are coming that way already. My original carbon NaN Xplorer didn't have the rib in the wing, I added them. But just recently, I ordered some "spread tow" lighter carbon wing tips for the plane, and they were in there, factory installed! I was pleased.

R,
Target
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Old Jan 16, 2011, 06:53 PM
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Thank you all. That Shadow build was very informative. Just what I was looking for. What is the source of those threaded flap horns? I like the idea of having something replaceable.

Jim
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Old Jan 17, 2011, 12:55 PM
RIP MC
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United States, CA, Midway City
Joined Dec 2003
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Originally Posted by JOddino View Post
Thanks for the report. I picked up a pair of these servos at the AMA Show on a whim and am very happy I did. I confirmed your values of about .08 deg per microsec and deadband less than .001.

My Futaba 14MZ has a range of 1200 microseconds (900 to 2100) and is a 2048 so its resolution is 1200/2048=.5859 microseconds. I set up my trim to give me .6 microseconds per click (steps=1, rate=24%) and I get about .048 degrees per click of trim (.6*.08 ). And the servo moves on every click. You can't be much more precise than that. That corresponds to .024 degrees of elevator travel on my pattern plane. I'm not sure the plane can respond to a .024 degree change in trim. How do you guys set your trim sensitivity? My theory is to have it as fine as possible but something must move on every click.

The servo is a real work of art. Can't wait to fly them.

Jim O
Wow I had no idea you are thee Jim Oddino , a living legendary r/c radio pioneer in this thread. Nice!

If I were to run the H version of this servo on ele, I would change the trim steps to the minimum value that will allow me to sense a change in the plane when 1 click is achieved. It probably would end up at trim steps of 2 or 3 but it will depend on the servo and ele control horn length relationship ...well and of course the cg.

For flaps, I set the flaps to trim with T5 and T6 on the 14 at the minimum steps to fine tune for a perfect TE.

Because of the lack of gear slop, at least for me, I don't have to guess at how much the flaps will blowback at various speeds when in the various flight modes. And, I don't have to turn the plane upside down and avg out the camber or reflex amounts either .

On a nitty picky note, the Futaba 2.4g radios with all the 2.4g RX's the amount of travel in microsecs is a very consistent 880us to 2160us = 1280us. I never thought to divide by the resolution of 2048 to get the us steps . Thanks Mr. Oddino!

Most TX/RX pairs I had a chance to play with, the max pw range were in the 1160-1180us range. This includes the 14MZ in either PCM or FM mode. 100us short of Futaba's 2.4g 1280us, which is about 10 degrees of servo throw in most cases.

Lastly, regarding the wing installs with frames, it is definitely a good idea to brace the frames or tie them into both the top and bottom skins to prevent them from flexing. That Shadow build was one of my first builds and I didn't have as much a clue as I do today in regards to getting a solid, almost flex free install with good geometry of the linkages.
Tuan
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Old Jan 17, 2011, 01:00 PM
Detail Freak
target's Avatar
Harbor City, CA
Joined Oct 2003
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www.soaringusa.com
should be able to hook you up with all your sailplane hardware needs...
They have frames for these servos.

Also, I like
www.aircraft-world.com
Very reasonable and fast shipping from Japan, really.

Hobby-Lobby has some usable parts as well.

And if you want to get Graupner parts (they have some nice 4mm diameter aluminum threaded horns)
http://v-eastonline.com/

Hope that helps you.
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Old Jan 17, 2011, 02:21 PM
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Originally Posted by fnnwizard View Post
On a nitty picky note, the Futaba 2.4g radios with all the 2.4g RX's the amount of travel in microsecs is a very consistent 880us to 2160us = 1280us. I never thought to divide by the resolution of 2048 to get the us steps . Thanks Mr. Oddino!


Tuan
You are correct. I hadn't measured it since I converted to 2.4. I measured 1272 so the resolution is closer to your .625 μsec. Thanks for the info on sailplane hardware too.

Jim
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Old Jan 17, 2011, 04:07 PM
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Originally Posted by fnnwizard View Post
Wow I had no idea who you were , a living legendary r/c radio pioneer in this thread. Nice!
Tuan - he still IS a living legend

And of course he flies the right radio too!!!

Jim- are you getting into soaring now?? You'll love it. Nothing subjective here, you make your time or not, and you hit the spot, or not. And the 14MZ is an awesome glider radio.
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Old Jan 17, 2011, 06:04 PM
RIP MC
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United States, CA, Midway City
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Originally Posted by Silent-AV8R View Post
Tuan - he still IS a living legend

And of course he flies the right radio too!!!
Fixed! If the 14mz is good enough for Mr Oddino. It most definitely is good enough for us
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Old Jan 17, 2011, 08:40 PM
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United States, CA, Los Angeles
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Originally Posted by Silent-AV8R View Post
Tuan - he still IS a living legend

And of course he flies the right radio too!!!

Jim- are you getting into soaring now?? You'll love it. Nothing subjective here, you make your time or not, and you hit the spot, or not. And the 14MZ is an awesome glider radio.
No, I'm not getting into sailplanes and I hate to admit it, I find the top sailplane and helicopter guys are a lot more interested in the technical aspects of R/C and therefore a lot more interesting to me than most of the top Patten guys. Most of them are sponsored and aren't looking for better equipment. I mentioned the 6125 on the pattern forum on RCU and got one response that showed no technical appreciation. I even included Tuan's data.

Yes, pattern flying is very subjective and therefore very frustrating. I try to tell myself that I know when I'm flying well and it doesn't matter what the judges think but there is something about human nature that makes you want to win whatever the "rules" of the game are.

Tuan- The difference between a legend and a veteran is the veteran is still doing it. I'm not sure I'm doing it but I'm trying to be a veteran.

Just a hint at how long - I flew in the first TOC in 1974.

Jim
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Old Jan 18, 2011, 12:29 AM
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i was thinking about that last reply. In the old days one could gain an advantage with superior equipment. Now days all the equipment is so good that one can only gain an advantage by tweaking and practicing and figuring out how to do everything perfectly every time. So the good guys are always out at the field and don't have time to have any fun experimenting with new stuff.

Jim
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Old Jan 25, 2011, 10:43 AM
Detail Freak
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Harbor City, CA
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Can someone please confirm for me that the holes in the 6125 will take a 3mm machine screw nicely? Or, will it need to be a 2.5mm??
Heck, I might even be inclined to use a 4-40 screw if it will fit.
Basically, if someone can measure the hole ID's, that would be great. Thanks!

R,
Target,
away from home and his servos.
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Old Jan 25, 2011, 11:50 AM
Eggcellent...
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United States, CA, Orange
Joined Oct 2006
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Originally Posted by Silent-AV8R View Post
And of course he flies the right radio too!!!
So he flies JR?

Tom
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Old Jan 25, 2011, 12:16 PM
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Tampere, Finland
Joined Oct 2009
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The mounting hole inside diameter is about 2,93 - 2,95 mm. I was not able to measure it more accurately.

3mm threaded rod (actual outside diameter 2.90 mm) went nicely through, a nice fit. Hope this helps.

Got the servos yesterday from SoaringUsa, I had very good and fast service from them! The servos will eventually go to a 4m v-tail Xplorer, mini-version for ailerons, standard 6125 for flaps and the h-version for v-tail. I will probably get the Xplorer in May, so there was (and is) no hurry.

Tommy

Quote:
Originally Posted by target View Post
Can someone please confirm for me that the holes in the 6125 will take a 3mm machine screw nicely? Or, will it need to be a 2.5mm??
Heck, I might even be inclined to use a 4-40 screw if it will fit.
Basically, if someone can measure the hole ID's, that would be great. Thanks!

R,
Target,
away from home and his servos.
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