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New giant scale rudder servo

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Old 11-26-2011, 08:34 PM
  #1
euroLenny
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Default New giant scale rudder servo

I've been developing a linear servo for rudder actuation.

-Real 576 ozf moving (holding power will break airframes) at 4.5A stall on 2 cell LiPo (20mA at idle, 300mA at minimal load(swinging the rudder at the wind))
-0.08 sec/60 deg.
-No less than 12 ball bearings.
-Composite frames for rigidity.
-Active gear wear compensation.
-Non contact absolute position feedback, NO POTS.
-The position information is updated more than 1000 times a second, resolution of 0.001 inches.
-Return to center is measured to 10 thou (that's the thickness of two sheets of notebook paper).

I'm seeing if there is any real interest. I have a short video of the creature moving under it's own steam

http://youtu.be/wTSMG8PjwMw



Thanks in advance.

Regards,
Leonard
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Old 11-26-2011, 09:13 PM
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Default RE: New giant scale rudder servo

Could that be rigged to travel 6", it looks like it would work on my fowler flaps on the 1:5 SCALE Howard 500! I designed a 5:1 multiplier from Servo City gears. I also could use the on the flaps for my 1:10 scale P-3 it's travel is much less.
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Old 11-27-2011, 05:04 AM
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Default RE: New giant scale rudder servo

Hi,

Anything is possible. I am concentrating on the current development for now. Variations will be considered in the future.

Regards,
L
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Old 11-27-2011, 05:22 AM
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Default RE: New giant scale rudder servo



why try to re invent the wheel ? what do you gain over just buying a servo ?
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Old 11-27-2011, 05:37 AM
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Default RE: New giant scale rudder servo

With this design one could replace two high torque servos with a single. You are not purchasing an extra servo and it's connection hardware, you also use less energy during flight get more speed and more torque for your trouble. You wont have pots to go bad, plastic cases that distort under load, micro gears that wear and develop slop, the list really does go on.

The servos design as we have today hasn't changed in 50 years. It is time.

Regards,
L
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Old 11-27-2011, 05:43 AM
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Default RE: New giant scale rudder servo

Will be watching with much interest!!!
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Old 11-27-2011, 05:58 AM
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Default RE: New giant scale rudder servo

really ??/ um 8911's um 7980 um sellco alot of single gaint scale servos come to mind ..... that one would use a single servo on a gaint scale airframe...



TH gear's don't whare nearly like metal gear's i'm just tryign to make a point all the the things you'v said the normal servo's already do and probly do it better and cheaper then this design

so my quesiton is where is the design come in to play on the market place ???


"The servos design as we have today hasn't changed in 50 years. It is time. " that's a bold statment are you sure about that ?


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Old 11-27-2011, 09:50 AM
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Default RE: New giant scale rudder servo

I would encourage you to continue with your project. Ganging servos in series to get enough power is really a lash up anyway you look at it. If you can keep the cost down the market will decide if it has merit.

Dennis
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Old 11-27-2011, 09:59 AM
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Default RE: New giant scale rudder servo

Anyway, a linear motion servo in a rudder setup with crossed cables, would help us to get rid of most of the expo function, so that we can have full advantage of its torque throughout its complete travel.
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Old 11-30-2011, 06:57 PM
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Default RE: New giant scale rudder servo

Installed in 50cc Extreme flight Yak fuselage.

12oz hanging at 9.25" from rudder hinge line. Sorry about the video quality and the shop mess.

This is after 1 hour continuous on a half charged 2 cell lipo. If the video were of better quality you could see the rudder out-accelerate gravity on the down stroke

This test replicates deflecting the rudder 45 degree from 0 when going 75 mph (for an hour).

Regards,
L



http://youtu.be/sqWndmM_zXI
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Old 12-01-2011, 12:04 AM
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Default RE: New giant scale rudder servo

Thanks fot the video.
But I think that a 50cc rudder is not really a significant test for a servo.
Try to do a test with the loads and travels required by a giant scale rudder.

Just run on a test bench with leverages and weights. No need to be a real model rudder.
I suggest you to keep the lead firmly attached to the lever to avoid secondary loads.
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Old 12-01-2011, 06:22 AM
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Default RE: New giant scale rudder servo

All correct Roberto

I had to convince my mech eng that my control system could handle the spring-mass characteristics of a pull-pull cable arrangement. He is convinced, it's his fuselage. I was also using the rig to burn in the servo, so far 20 hours of run time, in 2-3 hour batches.

I think the take away is with 12oz at 9.25 inches = 111 oz-in torque at the hinge then with a 1.9 inch control horn gives 210 ozf at the servo output, nominal, for hours on end.

Regards,
L
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Old 12-01-2011, 04:52 PM
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Default RE: New giant scale rudder servo

Here is a proposed configuration for rotary output.


1000 in-oz torque

0.096 sec/60 degree

5" arm shown.

Regards,
L
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Old 12-01-2011, 08:47 PM
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Default RE: New giant scale rudder servo

I think the liniar setup is the way to go. It would greatly simplify rudder installations on 40% size airplanes. Would it be possible to get 600 oz out of it? It looks really fast so maybe re gear to get the increase in power at the sacrafice of some speed?
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Old 12-01-2011, 10:05 PM
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Default RE: New giant scale rudder servo

Nice!
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Old 12-02-2011, 12:36 AM
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Default RE: New giant scale rudder servo


Quote:
ORIGINAL: speedracerntrixie

I think the liniar setup is the way to go. It would greatly simplify rudder installations on 40% size airplanes. Would it be possible to get 600 oz out of it? It looks really fast so maybe re gear to get the increase in power at the sacrafice of some speed?
I agree.
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Old 12-02-2011, 04:39 AM
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Default RE: New giant scale rudder servo

We are all on the same page.

Linear output is being worked in parallel (no pun intended) with rotary.

Speed,
Yes that is the plan. At this point, quite frankly, the speeds that this thing can attain is starting to break airframes. With the force and acceleration, I am not able to keep a set of pull pull wires tight. I have already jarred the hinges loose in the test fuselage.

I am shooting for 1000 in-oz at 0.10 sec/60 deg.

More details as they become available.

Regards,
L
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Old 12-02-2011, 02:50 PM
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Default RE: New giant scale rudder servo

personally I would rather have multiple servos in a rudder set up using an SWB tray or something similar, that way if one servo fails regardless of torque you can still have some sort of rudder control, whereas a one servo setup puts rudder control at risk due to failure or lockup and as we all know chances are it will lock up in the hard over position as compared to inline with the Vstab...Just my humble opinion is all!
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Old 12-02-2011, 04:52 PM
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Default RE: New giant scale rudder servo


Quote:
ORIGINAL: Hooked-On-RC

personally I would rather have multiple servos in a rudder set up using an SWB tray or something similar, that way if one servo fails regardless of torque you can still have some sort of rudder control, whereas a one servo setup puts rudder control at risk due to failure or lockup and as we all know chances are it will lock up in the hard over position as compared to inline with the Vstab...Just my humble opinion is all!

When was the last time you had a legitamate servo failure? For me it's been about 27 years not to mention that most guys on their giant scale stuff tend to use top of the line of whatever manufacturer they select. I have seen issues introduced by not correctly seting up multiple servo setups but never a locked servo. The only way to avoid that is to use the SWB floating tray. What are those nowadays, like 150.00? I would put my money on a single high quality servo being more reliable then 3 servos tied into a matchbox or equalizer any day. But then again like I said, in 13 years and about 50 IMAC contests I have not seen a single servo lock up.

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