Can you help me choose a linear actuator?

[angryemu]

Hi, I just burnt out my aliexpress linear actuator on my 30' ~4000kg yacht. It was a 12V 800N 20mm/s actuator. It was working nicely for a while (~15 mins) but the conditions were a bit rough and the boat was experiencing a bit of weather helm. I think it is a duty cycle problem. My actuator is rated to 25% duty cycle and in these conditions with the actuator being quite slow it was constantly making corrections

I'm looking to replace it and have found one that is 12V, 400N and 52mm/s with the thought that if the corrections are faster then less time the motor is moving between them and 400N still seems quite a reasonable amount of force? https://www.aliexpress.com/item/1005006225654918.html Interested on any opinions on whether or not that may solve my problem.

I also wondered whether people have experimented with the parameter "servo.period" as I guess that would effectively help manage duty cycle, but not sure at what cost to efficiency of steering corrections?

[Onno]

The biggest problem is that the technical data of actuators are incomparable, I have tested many with, for example, 2x better specs compared to our current actuator, but they appear to not even meet the specs even a quarter!

The first thing I see on your drives is plastic gears....

[angryemu]

Good point. Yes my drive has plastic gears. I expect that would be a problem of durability but shouldn't affect performance such as a burnt out motor after pretty minimal use.

[Onno]

it could mean that it is not the weakest point so something else will fail earlier, you might have found out what...
I see with our drives no duty cycle problems I think they are specified as 20% but in heavy seas on full load on heavy rudder ships we have never seen them fail.

[angryemu]

What drive are you using? Sorry if I missed that earlier in the thread. Thanks

[Onno]

https://pcnautic.com/en/product/raymarin...eplacement

[angryemu]

Thanks. I sailed my previous 34' yacht up the east coast of Australia with a Raymarine ST4000 and it was reliable. The Pcnautic would be a great actuator if a decent replacement for that!

[Onno]

it is even better!

[seandepagnier]

You burnt it out? Wow!! What failed exactly? Normally the overcurrent protection should trigger before the drive actually burns out or fails. You might consider installing an NTC temperature sensor on the motor if it actually overheated.

Yes, faster speed is usually better up to a point. The one I am using is 170mm/s with 50N force:
https://www.aliexpress.us/item/2255800497051447.html

but it is probably not suitable for most boats. I would suggest one slower with more force for most boats. I am often sailing at 10-12 knots of speed, and I have a balanced rudder I made out of carbon fiber which you can generally steer with 1 finger.

Faster reaction time can actually end up using less power because there are less overall corrections.

[angryemu]

It appears so. I don't know exactly what failed, I just noticed the actuator stop working and then pypilot telling me no controller connected, then it would reconnect again but actuator still not work before disconnecting itself again? Turns out the motor on actuator is shorted and kaput. I guess motor controller was in a reset loop coz it was connected to shorted motor?

Conditions were by no means crazy, 10-15kts and probably 1.5 - 2m seas. #1 Genoa fully unfurled and full mainsail. I was using wind function on pypilot at the time. My tiller is pretty heavy in these conditions. My guess is duty cycle but it's just a guess.

Prior to this occurring (like a day before) I did open config settings on pypilot plugin and was scrolling around until I noticed that my mouse scroll wheel movements changed whatever settings I was hovering over, I.e. unintentionally. I tried to change them back to whatever looked like default or normal but may not have succeeded. I'll be more careful next time

I've ordered PCNautic on Onno's advice. Hope it's good ?