Do servo motors loose torque over time?
07-23-2013, 05:14 AM
#1
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Do servo motors loose torque over time?
I was given a 1/4 scale cub never flown with a zenoah g38. The servo's are the standard JR's 527's and I think they are too wimpy so I installed some S134 1/4 scale Futaba servos that I had in my old parts lot.
These have supposedly 112 oz of torque although I can stall them very easily by holding the arm, they don't seem any stronger than the standard ones, I never heard of an electric motor getting weak (ac anyhow) not sure about DC thats my question, anyone have input, I can't really afford a couple hundred bucks for good ones right now and it is just a docile cub, maybe the standard jr 527 ones would be ok afterall? There is 1 servo for elv. 1 for rud. 1 for each aileron. The plane ready to fly weighs 19.5 lbs with no fuel.
Also this cub came with the instruction booklet and it says Balsa USA 1/4 scale piper cub j-3 but the plane spec. says something like 14-16lbs and 108" wing. this one weight 19lbs and the wing is closer to 112" tip to tip, the booklet says also says 90-1.08 two stroke but this has a zenoah g38.
These have supposedly 112 oz of torque although I can stall them very easily by holding the arm, they don't seem any stronger than the standard ones, I never heard of an electric motor getting weak (ac anyhow) not sure about DC thats my question, anyone have input, I can't really afford a couple hundred bucks for good ones right now and it is just a docile cub, maybe the standard jr 527 ones would be ok afterall? There is 1 servo for elv. 1 for rud. 1 for each aileron. The plane ready to fly weighs 19.5 lbs with no fuel.
Also this cub came with the instruction booklet and it says Balsa USA 1/4 scale piper cub j-3 but the plane spec. says something like 14-16lbs and 108" wing. this one weight 19lbs and the wing is closer to 112" tip to tip, the booklet says also says 90-1.08 two stroke but this has a zenoah g38.
07-23-2013, 05:39 AM
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RE: Do servo motors loose torque over time?
I'm not really sure, but If it was me getting a new giant scale ready to fly I don't think I'd be willing to risk it with old questionable servos. I'd rather wait until I could afford newer servos.
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07-23-2013, 08:16 AM
#4
RE: Do servo motors loose torque over time?
My theory is that the pots get corroded and the response becomes poor due to the increased resistance. I wouldn't settle on less than a decent set of metal gear servos with a G38 up front.
07-23-2013, 08:29 AM
#5
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RE: Do servo motors loose torque over time?
Ok what a decent set of metal gear servos cost? The airframe sure does resonate with vibration with engine running, the tail shakes like crazy and the wings tip with torque of a rev.
07-23-2013, 10:13 AM
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RE: Do servo motors loose torque over time?
I have Hitec 645´s on all surfaces of my BUSA 1:3 scale Super Cub. Weighs in at 46lb and is powered by a Zenoah GT-80. I use this servo almost exclusively. Reliable, cheap and plenty of power for the models I fly.
07-23-2013, 11:39 AM
#9
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RE: Do servo motors loose torque over time?
Simple answer ....... Yes. Especially with cheap servos that use cheap motors. The commutator in the motor can get dirty over time which means higher resistance and less power from the motor which means slower speeds and less power from the servo. Some cheap servos also use carbon composition brushes that gunk up (that is a highly technical term) the commutator. Oil residue from the motor bushings can contribute to the problem. Higher quality servo motors (cored or coreless) suffer less from the above problems as they usually use all metal brushes that offer better performance over the life of the servo motor. Add to the above the fact that higher quality servo motors also have better magnets which help maintain performance over the life of the servo. More than anything else in a servo, the motor adds most to the cost, reliability and overall performance of the servo. Cheap servos are cheap for a reason.
07-23-2013, 12:25 PM
#10
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RE: Do servo motors loose torque over time?
I was surprised at these Futaba quarter scale servos being so weak, I'm going to perform a test to see how much weight thay can lift before stalling under both 6 and 4.8 v power, maybe i'm just underestimating the power in my index finger stall lol.
07-23-2013, 05:02 PM
#11
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RE: Do servo motors loose torque over time?
The freakin battery was low and thats it! i put a 2000ml 6v lipo in line and boy o boy what a strong servo they are, the Futaba s134 1/4 scale.
07-23-2013, 05:58 PM
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RE: Do servo motors loose torque over time?
ORIGINAL: a70eliminator
I was given a 1/4 scale cub never flown with a zenoah g38. The servo's are the standard JR's 527's and I think they are too wimpy so I installed some S134 1/4 scale Futaba servos that I had in my old parts lot.
These have supposedly 112 oz of torque although I can stall them very easily by holding the arm, they don't seem any stronger than the standard ones, I never heard of an electric motor getting weak (ac anyhow) not sure about DC thats my question, anyone have input, I can't really afford a couple hundred bucks for good ones right now and it is just a docile cub, maybe the standard jr 527 ones would be ok afterall? There is 1 servo for elv. 1 for rud. 1 for each aileron. The plane ready to fly weighs 19.5 lbs with no fuel.
Also this cub came with the instruction booklet and it says Balsa USA 1/4 scale piper cub j-3 but the plane spec. says something like 14-16lbs and 108" wing. this one weight 19lbs and the wing is closer to 112" tip to tip, the booklet says also says 90-1.08 two stroke but this has a zenoah g38.
I was given a 1/4 scale cub never flown with a zenoah g38. The servo's are the standard JR's 527's and I think they are too wimpy so I installed some S134 1/4 scale Futaba servos that I had in my old parts lot.
These have supposedly 112 oz of torque although I can stall them very easily by holding the arm, they don't seem any stronger than the standard ones, I never heard of an electric motor getting weak (ac anyhow) not sure about DC thats my question, anyone have input, I can't really afford a couple hundred bucks for good ones right now and it is just a docile cub, maybe the standard jr 527 ones would be ok afterall? There is 1 servo for elv. 1 for rud. 1 for each aileron. The plane ready to fly weighs 19.5 lbs with no fuel.
Also this cub came with the instruction booklet and it says Balsa USA 1/4 scale piper cub j-3 but the plane spec. says something like 14-16lbs and 108" wing. this one weight 19lbs and the wing is closer to 112" tip to tip, the booklet says also says 90-1.08 two stroke but this has a zenoah g38.
As for the motors losing torque, I have operated model trains for 40 years and have some that are almost that old, they run just like the dayI bought them,
In the last week I took my old Kraft radio out of storage and tested it. These servos are 33 years old, and have had more than 20 years of regular use in 4 different aircraft and 3000 flights, then unused for about 10 years..
3 of them were perfect.. the 4th needed one drop of oil on the bottom of the motor shaft and now they are as good as new..
Vid here..
http://www.youtube.com/watch?v=CMFvPE_yhmo
Edit - just saw your last post.. guess all is good to go then.
07-23-2013, 06:14 PM
#13
My Feedback: (19)
RE: Do servo motors loose torque over time?
ORIGINAL: a70eliminator
The freakin battery was low and thats it! i put a 2000ml 6v lipo in line and boy o boy what a strong servo they are, the Futaba s134 1/4 scale.
The freakin battery was low and thats it! i put a 2000ml 6v lipo in line and boy o boy what a strong servo they are, the Futaba s134 1/4 scale.
07-23-2013, 06:22 PM
#14
My Feedback: (19)
RE: Do servo motors loose torque over time?
ORIGINAL: Rob2160
I guess there are many reasons a servo could lose power over time. Many of them listed by others above..
As for the motors losing torque, I have operated model trains for 40 years and have some that are almost that old, they run just like the day I bought them,
In the last week I took my old Kraft radio out of storage and tested it. These servos are 33 years old, and have had more than 20 years of regular use in 4 different aircraft and 3000 flights, then unused for about 10 years..
3 of them were perfect.. the 4th needed one drop of oil on the bottom of the motor shaft and now they are as good as new..
Vid here..
http://www.youtube.com/watch?v=CMFvPE_yhmo
Edit - just saw your last post.. guess all is good to go then. [img][/img]
ORIGINAL: a70eliminator
I was given a 1/4 scale cub never flown with a zenoah g38. The servo's are the standard JR's 527's and I think they are too wimpy so I installed some S134 1/4 scale Futaba servos that I had in my old parts lot.
These have supposedly 112 oz of torque although I can stall them very easily by holding the arm, they don't seem any stronger than the standard ones, I never heard of an electric motor getting weak (ac anyhow) not sure about DC thats my question, anyone have input, I can't really afford a couple hundred bucks for good ones right now and it is just a docile cub, maybe the standard jr 527 ones would be ok afterall? There is 1 servo for elv. 1 for rud. 1 for each aileron. The plane ready to fly weighs 19.5 lbs with no fuel.
Also this cub came with the instruction booklet and it says Balsa USA 1/4 scale piper cub j-3 but the plane spec. says something like 14-16lbs and 108'' wing. this one weight 19lbs and the wing is closer to 112'' tip to tip, the booklet says also says 90-1.08 two stroke but this has a zenoah g38.
I was given a 1/4 scale cub never flown with a zenoah g38. The servo's are the standard JR's 527's and I think they are too wimpy so I installed some S134 1/4 scale Futaba servos that I had in my old parts lot.
These have supposedly 112 oz of torque although I can stall them very easily by holding the arm, they don't seem any stronger than the standard ones, I never heard of an electric motor getting weak (ac anyhow) not sure about DC thats my question, anyone have input, I can't really afford a couple hundred bucks for good ones right now and it is just a docile cub, maybe the standard jr 527 ones would be ok afterall? There is 1 servo for elv. 1 for rud. 1 for each aileron. The plane ready to fly weighs 19.5 lbs with no fuel.
Also this cub came with the instruction booklet and it says Balsa USA 1/4 scale piper cub j-3 but the plane spec. says something like 14-16lbs and 108'' wing. this one weight 19lbs and the wing is closer to 112'' tip to tip, the booklet says also says 90-1.08 two stroke but this has a zenoah g38.
As for the motors losing torque, I have operated model trains for 40 years and have some that are almost that old, they run just like the day I bought them,
In the last week I took my old Kraft radio out of storage and tested it. These servos are 33 years old, and have had more than 20 years of regular use in 4 different aircraft and 3000 flights, then unused for about 10 years..
3 of them were perfect.. the 4th needed one drop of oil on the bottom of the motor shaft and now they are as good as new..
Vid here..
http://www.youtube.com/watch?v=CMFvPE_yhmo
Edit - just saw your last post.. guess all is good to go then. [img][/img]
As for Kraft, I have lots of experience with that equipment both from a service standpoint and as a user for over 2 decades. They had their share of servo motor problems also and the quality of the motors varied over the years. Not a Kraft problem .... but a vendor problem and everybody in the industry experienced it from time to time. While after a long period of no use, the servos may still wiggle when powered up, I wouldn't trust a valued airplane to them. I have boxes full of those old servos and they can stay right there.
07-23-2013, 06:28 PM
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RE: Do servo motors loose torque over time?
ORIGINAL: drube
How is the centering on those 645's?
How is the centering on those 645's?
07-23-2013, 10:05 PM
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RE: Do servo motors loose torque over time?
Looks like you found the problem - weak battery - but it wouldn't hurt to send the servos in to have get some maintenance done and testing by professionals. It's been years since I sent in any radio equipment but when I did I sent my stuff to Radio South. The prices were good, everything came back working properly and it was about a two week turn-around.
07-24-2013, 02:22 AM
#17
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RE: Do servo motors loose torque over time?
Ok made a mistake on the battery, not a lipo but rather a 6v nimh, Also just wnted to mention that the battery I had for testing was a 4.8 flat pack that was bad, I did not hold a charge even though I had charged it the day before.
And to all who replied, thanks I understand about dirty scratchy pots and cheepie servos but it was the motor torque that was in question and I'm pretty sure my answer is within the above replies, thanks.
And to all who replied, thanks I understand about dirty scratchy pots and cheepie servos but it was the motor torque that was in question and I'm pretty sure my answer is within the above replies, thanks.
07-24-2013, 05:43 AM
#18
RE: Do servo motors loose torque over time?
Make sure you also have heavy gage wiring and good connections for your servos. The voltage at a servo (under load) will indicate whether or not the battery, switches, wiring, and connectors are adequate for high torque servos.
07-24-2013, 06:00 AM
#19
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RE: Do servo motors loose torque over time?
Got ya, the servos in the wing do have extensions that are quite long, 6 volts output should give me a better buffer than a 4.8 pack, it should be easy enough to measure the outpul voltage at the servo connection itself.
It could become especially an issue being I'm using a Y patch for the wing servos.
It could become especially an issue being I'm using a Y patch for the wing servos.
07-24-2013, 08:03 AM
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RE: Do servo motors loose torque over time?
Servos don't have to be old to go bad. New ones can fail from not having the correct torque servo on the surface that it is moving. You wouldn't put a standard 43oz servo on the elevator of a 50cc Edge, however two standard 43oz servos would do fine on all surfaces of a 1/4 scale cub. The G38 is a good match for a 1/4 scale cub with the full wing. I don't know where the 112" ws came from since both the Sig and Balsa USA have 105-108 WS. I fly both the Balsa Usa cub and the Sig 1/4 scale clipped wing cub with a Fugi24 engine They both fly great on 1/2 throttle, easy take offs and landings are smooth,but the clipped wing at full throttle gives nice aerobatic loops and stall turns. Your g38 should be fine, and this larger engine is probable the reason for the 19lbs weight.
07-24-2013, 09:54 AM
#21
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RE: Do servo motors loose torque over time?
I was looking at the plans last night and it states 108" wing 12lbs, I don't get it, maybe 12lbs with no motor or hardware installed, I'll post some photos if I can for you to analyze, it was a Senior gentleman that gave it to me, said he built it but never learned to fly. All i can say are the wingd bolts are a pain to eccess
07-24-2013, 01:52 PM
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RE: Do servo motors loose torque over time?
Most servos use sealed-can motors and sealed-can motors are supposed to gain torque and speed throughout their lifespan....
This is due to the brushes wearing,andcausing less internal resistance. If the brushes or thecomm are pitted, then more resistance is created.
However; a servo has more variables, such as potentiometers and a drivetrain. Coreless motors are another exception: the motor brushes wear more quickly.
The "all metal" brushes, previously mentioned, actually wear more quickly because there is no lubricant in the brush - longevity is sacrificed for more RPM's.
So, a servo motor can lose torque over time, if it becomes damaged or dirty, but can also gain torque over time if there are no other negative variables present.
Happy flying....
07-24-2013, 05:16 PM
#24
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RE: Do servo motors loose torque over time?
i have been flying a busa cub thesame as you have with an old gas engine for years and 4 extensive repairs that have added a few pounds to it. every servo is a standard futaba but the elevator is rigged with two servos. there must be hundreds of flights with not a single problem except for some hard contacts with moter earth,,,hehe these servos are over 15 years old now. im building a sig 1/4 cub now with a 20ccgas and it will have stardard servos with two in tandem for the elevator. i may use two for the rudder only because i fly off grass and i found that the ground steering dosent work to well unless you keep up the taxi speed. im building fowler type flaps for the sig and will use two standsrd servos rigged up to a torgue rod so if one servo dies i wont end up with one flap and a big crash.
07-24-2013, 06:57 PM
#25
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RE: Do servo motors loose torque over time?
ORIGINAL: ssautter
Most servos use sealed-can motors and sealed-can motors are supposed to gain torque and speed throughout their lifespan....
This is due to the brushes wearing, and causing less internal resistance. If the brushes or the comm are pitted, then more resistance is created.
However; a servo has more variables, such as potentiometers and a drivetrain. Coreless motors are another exception: the motor brushes wear more quickly.
The ''all metal'' brushes, previously mentioned, actually wear more quickly because there is no lubricant in the brush - longevity is sacrificed for more RPM's.
So, a servo motor can lose torque over time, if it becomes damaged or dirty, but can also gain torque over time if there are no other negative variables present.
Happy flying....
Most servos use sealed-can motors and sealed-can motors are supposed to gain torque and speed throughout their lifespan....
This is due to the brushes wearing, and causing less internal resistance. If the brushes or the comm are pitted, then more resistance is created.
However; a servo has more variables, such as potentiometers and a drivetrain. Coreless motors are another exception: the motor brushes wear more quickly.
The ''all metal'' brushes, previously mentioned, actually wear more quickly because there is no lubricant in the brush - longevity is sacrificed for more RPM's.
So, a servo motor can lose torque over time, if it becomes damaged or dirty, but can also gain torque over time if there are no other negative variables present.
Happy flying....
As for the pot, it can only affect positional accuracy of the servo. I can't think of any condition where it could affect the torque or speed of a servo. Gears, shafts and bearings can certainly affect both servo speed and torque all of which can change over time.
The OP's original question was about servo motors and I can't think of any condition that can happen over time (age) that could possibly increase servo speed or torque given a fixed input voltage.
