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Servo setup: EPA, current, and linkages

F

flylow3d

50cc
YellowJacketsRC said:
Gyro,
I was asking for clarification, not suggesting you were wrong :)

Joe I do understand. What I was thinking was on the CC I could set voltage where I wanted it and did not need to check. Obviously I was missing the point. I understand clearly now that the amps are going to go up as the servo begins to bind.

So now I have three questions. The first is how do I check current on the servos?

Second, I often find that as I break a new plane in, the control surfaces will loosen up after a bit of use. If, as in Wedoitall's case, I am getting high amps in the last little bit of throw, Should I back down, and then try again after 10 or fifteen flights?

I understand that I get better resolution with EPA at max. I also understand that I should use as short a servo arm as I can and still get proper max throw so that I can max out the EPA AND get maximum mechanical advantage. My question is, what happens if I have EPA at max and I use the dual rate to cut back the throw? Do I still get maximum resolution?
Click to expand...

#1- There are multiple devices available that can be used to check the current draw of servos. If you are looking for a plug and play type device then I would recommend either of these. I have used both and they work great.

http://www.horizonhobby.com/products/digital-servo-and-receiver-current-meter-HAN172 (For one servo)
http://www.fromeco.org/Products/05FRCQCM/ (For multiple servos--40% wing with 3 servos for example. )

If you want a cheaper option, the you could use a simple multimeter and just make an adaptor.

#2- I do exactly what you suggested. I simply set the plane up with max epa and the throw I want. If there is some binding, then I will use the Dual rates to lower the throw until the binding goes away. I will then fly the plane for 10-20 flights and then go back and set the dual rate back to 100 and check the current draw again.

#3 Changing the dual rate in this case is identical to reducing the EPA. So even if your EPA is maxed out, and you reduce the dual rate to fix binding for example, it would be identical to reducing the EPA. A plane should be setup with the dual rate set to 100 and then only adjust the EPA.
 
YellowJacketsRC

YellowJacketsRC

70cc twin V2
Thanks Gary and Joe.

Joe, I am a bit confused... under point #2 you say that you use maxed EPA and adjust dual rate. But in point #3 you say that A plane should be setup with the dual rate set to 100 and then only adjust the EPA. These seem to be contradictory statements. Can you clarify for me?

Thank You for the Lessons!
 
F

flylow3d

50cc
Yep. Happy to clarify. In both cases I am using the epa to get the desired throw. After this part of the setup is finished, I then use the dual rate to lower the travel to take away any binding that might be occurring because the surfaces are stiff. Now the reason I adjust the dual rates here is simply to make it easier to increase the throw back to what I had originally setup. For example, if you knock your dual rate down to 90 % for the first 20 flights, then to return to your desired throw you would simply change that back to 100%. There are no numbers to remember here. If I had used epa to temporarily reduce the throw, then I would have to remember the original epa value or re-setup the plane..
 
Last edited by a moderator:
YellowJacketsRC

YellowJacketsRC

70cc twin V2
Makes sense! One last question to be sure I understand the whole process. When setting it up in the beginning, if I have 100% dual rate, then I may not be able to get EPA to the max available right? I usually set up by deflecting control surface and running EPA all the up. Then I back the EPA back down one click at a time until I see the control surface start to move. Then I click it back up one click so as to leave it set at the Max throw physically available. If the EPA value is really low, I will re-do my servo arm length in order to bring EPA back up and repeat process. But in the end I will have dual rate at 100% and the EPA as close to max available as I can get without pushing the servo past the physical limit.

Is this correct?

If it is, I now understand that I should test the current at this point and back down throw using dual rates at this point to keep from over amping the servo motor. Then I can come back after 20 flights and retest current and adjust.

Do I have it?
 
cwojcik

cwojcik

70cc twin V2
YellowJacketsRC said:
Makes sense! One last question to be sure I understand the whole process. When setting it up in the beginning, if I have 100% dual rate, then I may not be able to get EPA to the max available right? I usually set up by deflecting control surface and running EPA all the up. Then I back the EPA back down one click at a time until I see the control surface start to move. Then I click it back up one click so as to leave it set at the Max throw physically available. If the EPA value is really low, I will re-do my servo arm length in order to bring EPA back up and repeat process. But in the end I will have dual rate at 100% and the EPA as close to max available as I can get without pushing the servo past the physical limit.

Is this correct?

If it is, I now understand that I should test the current at this point and back down throw using dual rates at this point to keep from over amping the servo motor. Then I can come back after 20 flights and retest current and adjust.

Do I have it?
Click to expand...

That's perfect!

The only change I like to make is that you should set your ailerons to the lowest common denominator...for example, don't max them all out in every direction. If your left aileron is getting 40 degrees up and 41 down, and your right aileron is getting 39 degrees up and 42 down, then you should adjust your EPA's to get 39 degrees on both ailerons in both directions. Failing to do this will result in weird rolling behaviors.

Regarding the RJX servos, I was plain scared of them after running them on my Extra for a few flights while with a separate pack. They were so fast and violent I was afraid of breaking something. So on the Laser, I used a Castle BEC Pro set to just 6.5V. So far (maybe 30 or 40 flights) they are still performing very well. They are still insanely fast, center great, and have plenty of power.
 
YellowJacketsRC

YellowJacketsRC

70cc twin V2
Thanks Cody and Joe.

Yes I learned how to set ailerons to lowest common denominator from Mr. Jewett. I simply use a ruler and measure throw from the trailing edge of the wing next to the fuse.
 
zmonster97

zmonster97

Member
cwojcik said:
That's perfect!

The only change I like to make is that you should set your ailerons to the lowest common denominator...for example, don't max them all out in every direction. If your left aileron is getting 40 degrees up and 41 down, and your right aileron is getting 39 degrees up and 42 down, then you should adjust your EPA's to get 39 degrees on both ailerons in both directions. Failing to do this will result in weird rolling behaviors.

Regarding the RJX servos, I was plain scared of them after running them on my Extra for a few flights while with a separate pack. They were so fast and violent I was afraid of breaking something. So on the Laser, I used a Castle BEC Pro set to just 6.5V. So far (maybe 30 or 40 flights) they are still performing very well. They are still insanely fast, center great, and have plenty of power.
Click to expand...

What are these RJX servos you speak of?:popcorn:
 
3dbandit

3dbandit

100cc
zmonster97 said:
What are these RJX servos you speak of?:popcorn:
Click to expand...

The RJX servos are heli cyclic servos commonly used on 500 size heli's.

They are available from heli direct under the brands RJX and BK servos.

The BK servos are whats included in the goblin helicopter combo kits.

They are 147 oz torque and 0.03 sec transit time.

Here is a link to the RJX Servos: https://www.helidirect.com/rjx-fs0391-mini-cyclic-servo-p-31360.hdx

BK Servos: http://www.helidirect.com/bk-mini-c...otor-speed-003s-torque-106kg-blue-p-32266.hdx
 
YellowJacketsRC

YellowJacketsRC

70cc twin V2
Anybody here know much about servo current draw? For example, what should the expected amp draw for one of my HS 7245 servos running at 8 volts in my 64" MXS?

Ballpark is all I am concerned with
 
wedoitall

wedoitall

Member
on mine approx. .18-.20 was what i was getting at max delfection on my elevator and rudder. Ailerons was alil less.
 
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