Servo Humm....Any ideas?
#1
Junior Member
Thread Starter
Join Date: Aug 2007
Location: Suffolk,
VA
Posts: 16
Likes: 0
Received 0 Likes
on
0 Posts
Servo Humm....Any ideas?
Need some advise gents. My rudder/ nose gear servo hums about 70% of the time, when in the null/neutral position. I've tried to adjust the clevises by a few turns to release any strain/load with negative results. I can remove the push rods from the control horn and the servo acts normally (indicates a loading problem I believe). I've swapped servos, same results. I'm using the following gear:
Thank you in advance.
Futaba 9001 analog servos
4.8v 1500ma battery
2.4GHZ 7 channel receiver
Sullivan fibergalss pushrods / 2-56 rod
GB Skylark 70
Thank you in advance.
Futaba 9001 analog servos
4.8v 1500ma battery
2.4GHZ 7 channel receiver
Sullivan fibergalss pushrods / 2-56 rod
GB Skylark 70
#3
Senior Member
Join Date: Oct 2004
Location: Sundom, FINLAND
Posts: 365
Likes: 0
Received 0 Likes
on
0 Posts
RE: Servo Humm....Any ideas?
Many servos tend to hum even with the slightest amount of binding present. Of course you should try to make the pushrods move as smoothly as possible, but sometimes it's really tricky to remove the humming altogether. Make sure there isn't excessive binding, because that might drain your rx battery quicker than you want. Don't lose any sleep over the occasional humming, though. If you think about it, most of your servos will be under load all the time in flight anyway. For instance, if you have to trim your ailerons a few clicks during your maiden flight, then your aileron servo(s) will be under constant load in flight from then on (think about it, and you'll see what I mean). They'll be humming up there, but you won't hear it. I'll probably be flamed for this, but...
#5
My Feedback: (24)
Join Date: Jan 2004
Location: Peachtree City,
GA
Posts: 1,351
Likes: 0
Received 0 Likes
on
0 Posts
RE: Servo Humm....Any ideas?
I have some Futaba 9202 in a Cap and they will hum without any linkages connected. It used to worry me but I've not noticed the battery draining quicker so I stop worrying about it.
#6
Senior Member
My Feedback: (1)
Join Date: Feb 2004
Location: Nevada City ,
CA
Posts: 602
Likes: 0
Received 0 Likes
on
0 Posts
RE: Servo Humm....Any ideas?
Heres my theory on humming servos. I try my best to get the best and smoothest pushrod connections I can, but sometimes I get those humming servos also.
My test is: if a small twitch of the stick, or a small tap on the rod makes it fall into place and stop humming, then I dont worry about it. I figure that, in flight, the vibrations from the engine and the motion of the plane will always be jostling the pushrods around a bit, so they will naturally fall to the neutral position..
If I cant get it to stop humming by twitching the sticks, then I disconnect the pushrod from the servo and push it with my fingers, trying to find whats making it bind any, till I get a smooth connection.
The point about flight loads is great also
My test is: if a small twitch of the stick, or a small tap on the rod makes it fall into place and stop humming, then I dont worry about it. I figure that, in flight, the vibrations from the engine and the motion of the plane will always be jostling the pushrods around a bit, so they will naturally fall to the neutral position..
If I cant get it to stop humming by twitching the sticks, then I disconnect the pushrod from the servo and push it with my fingers, trying to find whats making it bind any, till I get a smooth connection.
The point about flight loads is great also
#9
Senior Member
Join Date: Sep 2002
Location: Oslo, NORWAY
Posts: 1,579
Likes: 0
Received 0 Likes
on
0 Posts
RE: Servo Humm....Any ideas?
I like to address these type of problems using highly advanced technical equation. [sm=bananahead.gif]: F'iT!
Let 'em hum. Once the engine is on... you don't hear it anyway.
In the air, your servos are humming continually anyway. As soon as you input even the slightest command, the air pressure is forcing the surface in the opposite direct.
Your servos have to fight against this.
Let 'em hum. Once the engine is on... you don't hear it anyway.
In the air, your servos are humming continually anyway. As soon as you input even the slightest command, the air pressure is forcing the surface in the opposite direct.
Your servos have to fight against this.
#11
Senior Member
RE: Servo Humm....Any ideas?
Servos that hum are usually drawing more current than necessary.
If you really want to analyze the problem put an ammeter in the servo line and observe the current draw. Observing the current draw is a positive method to test and correct servo binding. Listening for the hum is a very crude method of testing. I am always surprised at the difficulty to achieve linkage that does not have some binding. Servos will sometimes bind and draw too much current and no hum will be observed.
Bill
If you really want to analyze the problem put an ammeter in the servo line and observe the current draw. Observing the current draw is a positive method to test and correct servo binding. Listening for the hum is a very crude method of testing. I am always surprised at the difficulty to achieve linkage that does not have some binding. Servos will sometimes bind and draw too much current and no hum will be observed.
Bill
#12
My Feedback: (7)
Join Date: Feb 2002
Location: Keller, TX
Posts: 2,051
Likes: 0
Received 0 Likes
on
0 Posts
RE: Servo Humm....Any ideas?
When you are checking for smooth linkage, also check for any excessive "up or down" force (perpendicular to the normal servo arm motion). A pushrod pressing down on the arm can cause the humming.
#13
RE: Servo Humm....Any ideas?
Do you have a FM set-up with Nicad batteries? If you have a PCM set-up and NIMH batteries,,will alleviate a lot of the humming,,,this is just a minor aggrevation using NICADs. Iswapped all of my stuff to PCM and NIMHs. I noticed a huge difference.
TAZZZZ
TAZZZZ
#14
Member
My Feedback: (1)
Join Date: Feb 2008
Location: North Bend,
OR
Posts: 58
Likes: 0
Received 0 Likes
on
0 Posts
RE: Servo Humm....Any ideas?
ORIGINAL: tazzzz
Do you have a FM set-up with Nicad batteries? If you have a PCM set-up and NIMH batteries,,will alleviate a lot of the humming,,,this is just a minor aggrevation using NICADs. Iswapped all of my stuff to PCM and NIMHs. I noticed a huge difference.
TAZZZZ
Do you have a FM set-up with Nicad batteries? If you have a PCM set-up and NIMH batteries,,will alleviate a lot of the humming,,,this is just a minor aggrevation using NICADs. Iswapped all of my stuff to PCM and NIMHs. I noticed a huge difference.
TAZZZZ
To the OP:
Digital servo's will hum all the time. Analog servos should not hum. A humming analog servo indicates binding somewhere. The binding can be anywhere in the circut, control rod hooked the the servo arm at an odd angle, control rod binding at some point in the fuselage, even the binding can be caused by the hinges being too stiff ( I've never cared for ca hinges for this reason).
Vance
#15
My Feedback: (9)
Join Date: Sep 2004
Location: Long Beach,
CA
Posts: 689
Likes: 0
Received 0 Likes
on
0 Posts
RE: Servo Humm....Any ideas?
ORIGINAL: bla bla
I like to address these type of problems using highly advanced technical equation. [sm=bananahead.gif]: F'iT!
I like to address these type of problems using highly advanced technical equation. [sm=bananahead.gif]: F'iT!
Once the plane is 3 feet away and the engine, do the servos still hum? WHO KNOWS!??? As long as there isn't any excessive binding in the linkages, you are good to go.
#17
Member
My Feedback: (1)
Join Date: Feb 2008
Location: North Bend,
OR
Posts: 58
Likes: 0
Received 0 Likes
on
0 Posts
RE: Servo Humm....Any ideas?
ORIGINAL: tazzzz
OK,,,in my experience,,it cleaned up my act right off the bat. TAZZZZ
OK,,,in my experience,,it cleaned up my act right off the bat. TAZZZZ