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Old Jan 11, 2011, 01:42 AM
VHO
glider misguider
Armidale NSW Australia
Joined Feb 2007
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Welcome back JoJo

Happy New Year.
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Old Jan 13, 2011, 11:48 AM
RIP MC
fnnwizard's Avatar
United States, CA, Midway City
Joined Dec 2003
3,215 Posts
Numbers for the DS6125H:
Throw is 110 degrees over 776us-2172us, center is 1474us

Current consumption on 6.6v is:
Idle = 12mA
First sustainable buzzing = 42mA
Note: Again, the servo itself does not buzz unless there is force on the arm.
Peak current, moving servo gently back and forth = 368mA
Peak current, springing of TX stick = 1080mA
Peak current, stall = 1290mA

Speed unloaded to 60 degrees at 6.6v: avg is .116seconds with low being .111 and high .124

The motor for the H series is larger but seems to be lower Kv. The gears look to be the same as the mini.

Again, I am impress with the lack of gear slop and precision of this servo.
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Old Jan 13, 2011, 01:07 PM
I just wanna fly
slozuke's Avatar
USA, CA, San Luis Obispo
Joined Jul 2005
593 Posts
So, it looks like the 6125 mini could work fine as a flap servo.
I usually use a 368BB in my Supra which has torque rated at 53 oz-in @4.8V, 60 oz-in @6v. The 6125 mini is rated at 66.66 oz-in @ 4.8V, 80.54 oz-in @ 6.0V.
Also the 368 only has a single bearing whereas the mini is a dual bearing.
Speed is faster and the only downside is a .05 oz weight increase.
You could even go with the 6125 std if you wanted absolute strength with a bit more weight gain.
Still, the unknown factor is the durability factor.
Hmm, this may be my next servo of choice.

Brian
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Old Jan 13, 2011, 02:10 PM
RIP MC
fnnwizard's Avatar
United States, CA, Midway City
Joined Dec 2003
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Just from my quick test of torque, it should be more than enough for any F3J flaps.

Not sure if Bob will be carrying any of the heli line MKS DS95, but those would be the ultimate Vtail servos. Not sure if they enough torque for flying stab during launch dive pull out.
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Last edited by fnnwizard; Jan 13, 2011 at 02:22 PM.
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Old Jan 13, 2011, 02:57 PM
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United States, AL, Madison
Joined May 2002
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Quote:
Originally Posted by fnnwizard View Post
JNot sure if they enough torque for flying stab during launch dive pull out.
Exactly how much torque is required for the launch pull-out? Has anyone measured?
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Old Jan 13, 2011, 03:11 PM
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Norway
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Quote:
Originally Posted by nuevo View Post
Exactly how much torque is required for the launch pull-out? Has anyone measured?
It deppends on the tailplane size / airfoil / setup / etc.
So a lot of parameters. (lets talk about all moving tailplane only)

BUT I have found that lets say a 368 is not enough but a 761 is enough on a Pike Perfect/xloprer. Same on a Skymax / crossfire F3B model. Volz XP is excellent but almost not available anymore. So in my mind I have Airt.761, grp.3288, JR.181/378, MKS 6125 or Volz XP unless I go for bigger sizes (I have a standard size Futaba in one of my Pike's and that is performing
The 368 (some sold as JR361) servos can do it but the speed of the ping suffers (speed goes down on servo because of power needed). This means constant trajectories in the zoom is not achieved.
Problem is that these things are difficult to meassure. One servo might say they have this and that torque but in reallity the speed goes down even though it managed the task in time.
But I would presume that any servo with more than lets say 4,5kg force is enough for most or all F3J/B models out there.
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Old Jan 13, 2011, 03:53 PM
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United States, CA, Midway City
Joined Dec 2003
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Quote:
Originally Posted by nuevo View Post
Exactly how much torque is required for the launch pull-out? Has anyone measured?
In addition to what Jojo wrote, here's another look at a different aspect of it. I just copied it from a post I made a while ago.

The stabs on the Xplorers look to be aero balanced so the torque requirements to move the stab are small.

Dr. Drela once wrote the G force of the pull out from dip into zoom is where the servo would experience the most needed torque if the stab is not mass balanced on the pivot point. He assumed 100G's.

On the big stabs (3800-4000X's): The stabs are about 2.2oz and balance about .75" behind the pivot point. I try to get no more than 15 degrees of stab deflection with 45-50 degrees of servo movement.

This servo movement depends on how short the horn is and the amount of lateral shift the pushrod can move and not bind anywhere.

The load on the servo then would be:

100G x 2.2oz x .75 (mass behind pivot) x .33 ( servo throw/stab throw relationship) = the loads would be about 54.45 oz-in.

At 50 degrees of servo throw to get 15 on the stab, the torque then is 49.5 oz-in.

The above figures do not depend on how much deflection is at the moment of the pull up.

Also, is important to get that ele pushrod stiff and it's housing glued down correctly.
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Old Jan 13, 2011, 04:05 PM
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United States, AL, Madison
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Thanks Tuan & Jojo for sharing your wisdom & experiences. One more clarification if I may.

I was thinking about Dr. Drela's comments when I asked the question. I thought the pivot point in relation to the 25% MAC was important, not pivot in relation to the mass.
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Old Jan 13, 2011, 04:37 PM
RIP MC
fnnwizard's Avatar
United States, CA, Midway City
Joined Dec 2003
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Quote:
Originally Posted by nuevo View Post
Thanks Tuan & Jojo for sharing your wisdom & experiences. One more clarification if I may.

I was thinking about Dr. Drela's comments when I asked the question. I thought the pivot point in relation to the 25% MAC was important, not pivot in relation to the mass.
In normal flying the 25% mac is all that matters. And if the pivot point is at that magical 25%, the aero loads on the flying stab are balanced.

It's only during the "whipping action" of the pull-out from the dip on launch will the servo see this stab mass load. Ideally, stab mass should balance right on the stab joiner (pivot point) so that the joiner would take up all the load from the whipping tail, but I'm not sure it's possible to build like that.
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Old Jan 13, 2011, 08:15 PM
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Norway
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Quote:
Originally Posted by fnnwizard View Post
In normal flying the 25% mac is all that matters. And if the pivot point is at that magical 25%, the aero loads on the flying stab are balanced.

It's only during the "whipping action" of the pull-out from the dip on launch will the servo see this stab mass load. Ideally, stab mass should balance right on the stab joiner (pivot point) so that the joiner would take up all the load from the whipping tail, but I'm not sure it's possible to build like that.
One needs it to be slighter forward.. Otherwise it will not be stable in high speeds. And elevator airfoils are different on different models. Some manufacturers just copy and meassure another plane without taking it all into account. So for one plane the servo can be weaker than on another plane.
In other words you are right that pivot point is very important to minimize loads.

Jojo - www.jojoen.no
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Old Jan 14, 2011, 01:04 AM
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prondel's Avatar
France
Joined Aug 2003
990 Posts
MKS DS-6125 Mini and H servormances test results

I have published MKS DS-6125 Mini and H servormances test results on www.planet-soaring.com.

Pierre
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Old Jan 14, 2011, 02:01 AM
registered user
Australia, QLD, Gold Coast
Joined Sep 2008
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Where is the cheapest place to buy these servo's ?
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Old Jan 14, 2011, 03:11 AM
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Tuomo's Avatar
Jyvaskyla, Finland
Joined Aug 2003
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Quote:
Originally Posted by AlpineDSacro View Post
Where is the cheapest place to buy these servo's ?
A more approriate question is: where are they available?
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Old Jan 14, 2011, 04:52 AM
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France
Joined Aug 2003
990 Posts
The ones I know:

In US: soaringusa.com

For European people:

in stock (except the H) at http://www.flashrc.com/589-mks.html
In Germany: http://www.mttec.de/
In UK: T9 hobbysport
And probably some others ...
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Old Jan 14, 2011, 07:17 AM
Registered User
King Of Prussia, Pennsylvania, United States
Joined Sep 2001
223 Posts
Service?

Bob - How are you going to handle service/repairs for these servos? With Airtronics and Hitec I can send them back to them directly for repair. JR goes to Horizon. What will the process be with MKS?

Thanks!
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