Servo buzz
 

I have a Hangar 9 carbon cub nearly complete but I notice at the very end of the elevator and rudder I get a servo buzz if I hold the joystick at the end of travel.
I didn't use the CA hinges for that very reason. To try to avoid any unnecessary resistance to the servos. The servos are high torque and the pushrods and nylon hinges felt very loose before I hooked them up to the servos. Is a little buzz at the end of travel a problem? The servos are running off the flight battery pack of my ESC so I know the battery isn't low. Besides, it does it if I use a standard battery or the flight pack battery. I know the surface throws aren't excessive either. Do I need to eliminate the buzz somehow or is it not a huge problem?
thanks everyone!

The buzzing in this situation indicates that the servo is under load and may in fact be completely stalled. This results in high current draw and much reduced flight times.

You would most likely get away with ignoring it as you are not likely to use full stick movements for any length of time. However to ignore it is bad practice and you should either ease off the hinges or reduce the servo travel on the TX if you have a computer radio.Moving the link one hole out of the control horn or in on the servo arm works as well.

Wearing my club safety officers hat if I saw this on an inspection I would require it to be fixed before the model could be flown.

Are they digital or analog servos? List the make and model number of the servos.

Otherwise you say they feel "loose" but are the control surfaces turning smooth each way when you move them by hand without the linkage attached?

If the surfaces aren't hinge-bound then you may simply be pushing the servo too far.

The best way to set-up the servos is with the use of an amp meter. You connect the meter between the servo and the receiver and note the current draw as the servo moves the control surface. It should remain fairly constant through the motion but if the amperage increases at the end of the stick movement then you are overdriving the servo and could risk burning it out.
At that point you go into the travel adjustment section of the radio and lower the travel amount for that control surface. Then test it again in the other direction and make travel adjustments if necessary.

If you don't have an amp/current meter then you can lower the travel until you hear the loud buzzing soften or stop.

That would be my recommendation. Your radio trim may get "re-adjusted" but moving the pushrod will stay where you put it.

Thank you! I used nylon hinges instead of CA because with CA hinges they really buzzed. I don't care for CA hinges at all. The nylon hinges were done very carefully and are loose. I suspect it may be friction because Hangar 9 uses metal push rods in a nylon sleeve. They naturally have a slight bend and I bet they are a little tight. I'll try to find the friction area and see if I can form the pushrod some.

The HS-485HB updates the very popular HS-475HB by adding more torque and greater speed. With its top ball bearing, heavy duty, high impact Karbonite™ gears and high performance circuitry, the HS-485HB offers lots of torque and features excellent centering and resolution.

• Applications: Heli's and Aircraft up to 72” or up to 12lbs when using just one servo per control surface.
• Note: Be aware that high vibration gas (not glow) engines combined with large contol surfaces and large thows (3D models) can put undue strain on the gears. Metal geared servos are recommended for these applications even if under 12lbs.
• Warning: Do not use thread lockers on Karbonite geared servo as it will cause the output shaft to fail.

[h=3]Features[/h]

• Top Selling Heavy Duty Standard Servo
• High Impact Karbonite Gears
• Top Ball Bearings
• Ehitecxcellent Centering and Resolution

[h=3]Specifications[/h][TABLE="width: 647"]
[TR="bgcolor: #666666"]
[TD]Motor Type:[/TD]
[TD]3 Pole[/TD]
[/TR]
[TR="bgcolor: #858585"]
[TD]Bearing Type:[/TD]
[TD]Top Ball Bearing[/TD]
[/TR]
[TR="bgcolor: #666666"]
[TD]Speed (4.8V/6.0V):[/TD]
[TD]0.22 / 0.18 sec @ 60 deg.[/TD]
[/TR]
[TR="bgcolor: #858585"]
[TD]Torque oz./in. (4.8V/6.0V):[/TD]
[TD]67 / 83[/TD]
[/TR]
[TR="bgcolor: #666666"]
[TD]Torque kg./cm. (4.8V/6.0V):[/TD]
[TD]4.8 / 6.0[/TD]
[/TR]
[TR="bgcolor: #858585"]
[TD]Size in Inches:[/TD]
[TD]1.57 x 0.78 x 1.49[/TD]
[/TR]
[TR="bgcolor: #666666"]
[TD]Size in Millimeters:[/TD]
[TD]39.88 x 19.81 x 37.85[/TD]
[/TR]
[TR="bgcolor: #858585"]
[TD]Weight ounces:[/TD]
[TD]1.59[/TD]
[/TR]
[TR="bgcolor: #666666"]
[TD]Weight grams:[/TD]
[TD]45.08[/TD]
[/TR]
[/TABLE]

[h=3]Spare Parts[/h]They are Hitec HS-485hb standard ball bearing analog servos.



These servos came in a plane I bought from a friend. He told me they were high torque servos, but when I looked them up they are just standard servos...hmm...now it's starting to make sense. They are recommended for a "smaller" model. Maybe I'll have to go with a better servo. It's in a hangar 9 carbon cub. Do you think I should replace at least the elevator servo to a higher torque servo?

I'll try that..thanks!

First disconnect the pushrods from the elevator and rudder control horns. Give full throw on the elevator and then rudder, if you still have buzzing the problem is not the hinges or overdriving the surface.

Thanks, I tried that. It's resistance in the pushrod. But only at the very end or travel, and, if I back the gimble off a micro hair, it stops...weird..

Do you think I need a better servo than what I'm using? It's a hangar 9 carbon cub ,so not overly big but not 40 size either..

I personally would use some stronger servos with torque around 100oz/in on the rudder and elevator. However, as long as you use a 6 volt battery pack and only fly it scale then your servos will be OK.
If the linkage is not binding then you are overdriving the servo. Lower the travel setting in both directions.