Can servos loose power/torque over time?

[crawlinwithacat]

Howdy folks, I've got a ponderable about servos. First some background: I've got a pair of Savox 1230sg's on a sporty comp rig that seem to be pretty weak recently. Both are being run off a CCBEC (the original one) and a 3s batt. They are rated for 500oz/in @6.0v. I've got the BEC set around 6.6v to account for the ~0.1v output voltage discrepancy and the rest for a little extra juice just because. I've been running them for the better part of 3 years now. That whole time I was running the BEC at 6.2v. I was messing with it this morning and thought I would try bumping up the voltage a bit to see if it did anything and the result was not much. I did just upgrade to 2.2s so they are definitely struggling a bit more than with the 1.9s but even with the 1.9s I was beginning to notice them struggling more than usual.

So anyway, my two thoughts have been 'Do BECs loose output current or develop internal resistances over time?' and 'Do servos weaken over time?'. Though I realized that the BEC being the issue was a pretty unreasonable conclusion the more I thought about it. So I did some research and came across two threads with some plane guys talking about something similar and the two potential culprits they mentioned were the potentiometer and the motor. The potentiometer sounded like it was the cause of centering issues. They were saying that in the past, it was possible to take the pot apart and clean the contacts because the wiper would wear down the middle of the contact and decrease it's sensitivity. Not really my problem, though wouldn't hurt to spray some contact cleaner in there. The other thing was the motors wear out over time. The commutators get dirty and the brushes wear down over time, which creates more resistance and leads to a weaker motor. Makes sense, but it is interesting that my front servo seems weaker than the rear. The front servo has been in use for probably 6-8 months longer because 4ws was an afterthought. Seems like things are pointing to the motors. But I'm curious, has anyone else noticed a similar phenomenon? Or does anyone have any other insights into what might be causing this? Cheers!

 

[Panther6834]

The short answer is, "yes, and yes". Starting with the BECs, just as RC LiPos & cell phone batteries lose 'life' over a period of time, capacitors will also lose their ability to hold the amount of power they are designated for. By what percentage, that, I couldn't say.

As for the servos, the motors inside will also (sooner, or later) lose their 'efficiency' (ie. speed and/or torque). RC Review has done several videos, testing the actual vs claimed strengths of many servos. One of the primary things noticed with EVERY servo is that consecutive tests produce lower & lower torque results. This is primarily due to the servo's motor heating, causing loss of efficiency. Granted, once the servo motor cola down, it's efficiency returns to where is started...but, over time, as with all motors (including the engine in the vehicle you drive to/from work every day), it slowly loses its maximum power output. With a gas/diesel engine, it's original power output can be restored by thoroughly cleaning & rebuilding the engine. With the motors powering RC vehicles, the same can be done...which is also cheaper then buying a new motor. However, with the motors inside servos, it's probably not a very cost-effective way of going about things, as the cost of the parts, as well as the 'value' of your time, will probably be more than the cost of purchasing a new servo. Note, I am NOT referring to replacing a servo's gears... that IS worth doing (if/when required)...but the actual motor.


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[Voodoobrew]

I have found over heated traces on boards that caused reduced power. A deterioration of lubricatio. Can also reduce torque. As motors cycle hot and cold they could cause a reduction in power over time. I dont know how noticible any of this is but bottom line is,

If you arent happy with the servo, replace it.

The servo horn is a lever, so if you switched to a longer servo horn that would seem like less torque..

Adding Larger tires and mor weight also tax the servo more.

 

[Voodoobrew]

Also with our checkin i am sure the Savox 1230sg's are brushless. So no brush wear ro clean. Just bearings to lube.

 

[crawlinwithacat]

This all makes good sense you guys. Thanks for your input, it's given me some more things to think about. The next time I pick up a BEC for another build I will swap it and see if anything changes. Voodoobrew The servo horns have stayed the same. And thanks for letting me know that they are brushless; I will pull them apart and lube em up a bit. I will be replacing them soon I hope, Just tying to prioritize saving up for another build. I am still curious whether or not anyone else has noticed something similar with their servos...

 

[Voodoobrew]

If they ever got hot enough to cook the coating on the wire, that can cause powerloss or failure too.