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DS8411 shudder

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Old 03-30-2004, 03:26 AM
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AUS50518
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Default DS8411 shudder

Danny,

I have a couple of 8411 servos which hunt around centre. They were fine when new but after about 50 flights (F3A on rudder) they hunt. (Off centre, rock solid.)

The first servo is the standard metal gear version which has already had the pot replaced by O'Relly here in Australia.

The second servo is an 8411SA mail ordered from Central Hobbies (O'Reilly doesn't import the SA), it also lasted about 50 flights before the hunting warranted replacement.

The linkage setup is a short carbon rod with helicopter ball links - virtually zero slop. The rudder is very free on the hinging and doesn't provide a static load to the servo. The tail wheel is not connected to the rudder. Any suggestions to make the servo last longer??

Secondly, I intend to send the 8411SA to Horizon for service, can I expect the repair under warranty?
I will send the 8411 as well for service, can you estimate the cost for repair if it is just pot replacement?
(I figure if I am going to send one freight for both would be almost the same.)

Thanks in advance,
John B
AUSTRALIA
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Old 03-30-2004, 09:47 AM
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Default RE: DS8411 shudder

Can you lightly touch the control surface when they are jittering and have them stop? If so, the problem is likely not the pot. If they do not stop, it is likely the pot. Is there excessive play in the gear train? Other things that you can check are to make sure the servos are not mounted too rigidly (servo screws too tight, eyelets in the grommets the wrong direction, servo mounting rails too tight against the servo, etc) or a bad extension, battery, etc. The 8411SA purchased through the US from a Horizon dealer has a 3 year warranty. I can not guarantee that it would be warranty without seeing it, as long as the warranty conditions are met, it would be.
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Old 03-31-2004, 03:08 AM
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Default RE: DS8411 shudder

A light touch stops the vibration, at least temporarily. My initial thoughts were that in flight the airflow would be enough to stabilise the rudder. However as the servo ages you can see the rudder vibrating in flight (shiny surface and the sun in the correct aspect).

There is definitely gear slop, is it excessive? Not sure.

Mounting checks out OK. Extension lead has minimal resistance and the plug pins look clean. (Cycled the plug 20 times with no change.)

Whether it is the pot or something else I will send them in and hope for the best.

Thanks,

John B
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