Scale Soaring UK

Hi John,
You say it burned out while it was at full aileron deflection. Was it also Stalled I wonder? Any servo will not last very long if it is operated in a stalled position, or coupled to stiff linkages.This is more likely to be the demise of a good servo then the need for extra heat dissipation. I don't think that the cooling holes will help here as the electronics heat up very quickly under these stressed conditions. Also you would need to make arrangements for through air flow to the servo as well.

If the servo was not stalled and the linkages were free, you either had a faulty item or you were using an incorrect servo with possibly too little torque for the job. Sorry John but I've been there ,done that. Regards Terry,

Hi John, HS82MG is a L.V. servo. What was the input voltages over the 15months? Ter.

[quote="JohnW"]Hi Terry. The voltage supply is 3S LiFe dropped to 6v – checked. I just find it somewhat alarming to see the damage. It must have got fairly hot.

Had a thought. I think I heard/read somewhere for mains electricity you should not use a long extension cable rolled up, due to producing a magnetic field which increases resistance thereby reducing voltage?! Think I burnt out a hedge cutter motor due to this. So to the analogy. If you curl up surplus wire in the small servo housing, could a similar thing happen?[/quote]


Extension coils are rated 240v at 13 to 30a. This is why they warn against coiliing generally if you connect up 5 electric heaters and put them on full pulling 13a etc.
What you have with a servo is negligible regarding voltage\current. What is likely to of caused the over heating is a dead short electrical fault caused by either running the servo at HV is direct to the life or just a breakdown of the servo\poor manufacture.
Don't worry about it to much, toss it in the bin and fit another (ensure you are running the servos at 6v or less), and you surface is free running and does not bind.
Cheers,
Jimbo.

Hi John, I agree with Jimbo. The fact that you have had several months use out of the servo without problems seems to point to the installation being O.K. After our discussion I now believe there was a breakdown of an electronic component within the servo which then created a dead short, turning the servo into an electric heater. Although the Hitec 82 MG can be considered a budget servo, there are a great many in use all over the world today so I would just put this one down to bad luck and as Jimbo advises throw it in the bin and buy a new one. Good luck with that and for 2017.

Regards Terry.

As Terry says, a component failure and dead short is the most likely.

BC

Just a thought: you haven't by any chance got your radio set up for 100Hz (10ms frame rate) operation? The HS-85 is an analogue servo and isn't designed to cope with the faster frame rate. I ask because I have used many of th se servos over the years without problem and certainly never noticed any heat build up issues.

Sorry, I have no experience of JR transmitters so can't help there. As for the symptoms of high frame rate on analogue servos, all I can say is that when I fell foul of this three of the four identical Hitec servos in my plane showed no problem at all, but one aileron servo was jittering wildly. I replaced it, and the replacement did the same so I spent a fruitless day ripping the wiring out of the model before the penny dropped - a firmware update to the transmitter had caused it to default to 10ms frame rate.