Hey all,
Seeking some experienced advice on reasonably priced digital servos to fit to a 120CCPM Swash plate mechanism.
The helicopter is a 550 class nitro power train.
Looking for something reliable and robust to set and forget without too much trouble.
I have done some looking around but figured I would save a lot of time (and crashed helicopters) by making the right choice the first time based on an experienced opinion.
Cheers,
Harry.
Harry,
I’m assuming this is a flybarless heli. What size are the current servos? I am most familiar with 600 size heli’s and mine use standard servo size. I stick with Futaba servos but I know they can cost more. I tried going with a cheaper servo but found out that not all servos are shielded as well from the radio waves of the telemetry radios. These cheaper servos would jitter due to the telemetry radios. So I ended up buying what I knew works. And almost all of the Futaba servos I have purchased have been set and forget.
You’ll need to look at the website for your heli manufacturer and see what torque is recommended or look at combo kits being sold for your heli and see what the torque rating is for those servos. Then buy comparable servos.
Hey Bill,
Thanks for the reply. The helicopter actually has a flybar. Its a stock standard JR Venture 50.
The servo size is standard like you said. Specifically, the servos run on the swash plate are JR ES539’s rated to 4.8 kg/cm @4.8V so I assume something of similar rating but digital will do the trick here?
I noticed it is running a digital servo for the variable pitch tail, a JR DS820G rated to 2.4 kg/cm @ 4.8V but with a much faster response time.
Thanks for the suggestion re the Futaba servos, I will definitely give them a look. I did notice this jitter you mentioned too - hopefully modern servos will remove this issue as the current ones are likely quite old.
Thanks.
Harry,
You may want to check out this post I made on another recent thread where the user was putting a flight controller on a flybarred heli. It discusses how to set up some of the gains since it is a flybarred heli.
Regards,
Bill
Thanks Bill, very helpful as I was reading through the trad heli set up guide on the ardu website and saw they mentioned this specific parameter for flybar configuration - good to know.
I noticed in your post you mentioned the requirement for an RPM sensor? I didn’t realise this was a requirement. Could you explain this more?
Thanks.
Harry,
You can set up a throttle curve in ardupilot but if you want to use the built in governor, you need an RPM sensor so the governor can use it to hold the rotor RPM.
This makes sense - thanks. I’ve taken the throttle curve approach just to keep the first iteration of my build simple (trying to minimise the number of sensors required).
I’m using the standard values for the throttle curve (mentioned in the video series on the Traditional Helicopter guide). I assume these will be good to at least get me flying before fine tuning etc? They’re something like 30,35,50,75,100 for each point in the spline respectively if I remember correctly.
Hi Harry, a very good alternative to Futaba’s is the following:
https://www.savox-servo.com/Servos-c-1338/Coreless-Motor-c-1348/Savox-Servo-SC-1258TG-Digital-Coreless-Motor-Titanium-Gear/
I use them on all my FPV helis (570 and 700 class), “pull a lot” and never had issues. They don’t have problems with both telemetry radio modules and/or LR systems.
Hi Harry,
I agree with Ferruccio, the Savox servos work well. I started using them after Chris Olsen said that’s what he was using and recommended them. On my 800 and plus size gas and turbines I’m using there SV-1271SG, probably overkill for a 550 size. I was originally running BK servos and about a year ago I had a cyclic servo go intermittent in flight, it was a real hand full but we got it down with just some minimal damage to the landing gear.