Waterproof Servo

[greenman407]

No big deal. I wanted to put a servo up front in various submarines to control bow planes without having to put it in the Subdriver and then try to figure out a way to actuate the planes. It can be done, as many have done it ,but it just seemed to me to be a lot of trouble. So I purchased waterproff servos from Traxxas only to find out that they are not waterproff, by no stretch of the imagination. Fine then! I will just make my own. In my mind I am totally satisfied that if you use "Goop" to seal up all the seams and screw heads and wires ,no water will get in. However the output shaft is a whole different situation. I was told to put o-rings around it but that didnt work either. Thats because the shaft is splined outside of the servo case and no o-ring that I know of will seal a splined shaft. So , time to open up the servo and see whats under the splined area. As I suspected on the Futaba s-148 and newer s-3003 there is no bearing and you find a nice smooth shaft that we can work with.

[greenman407]

Into my o-ring kits I went and chose a Quad ring that measured .208 x .070. This quad ring has a good interference fit to the shaft. While we are at it lets put two on there as we have the room and it will make me feel better. Now the case.

To properly seal using these o-rings you have to drill out the case to 11/32". Here of course much care is needed to get the hole centered and in good shape because it is your sealing surface.

However when you do that you must first apply some epoxy to the inside of the case in order to have a solid foundation to seal against after you drill such a large hole.

[greenman407]

Sorry, Im not to good yet with posting pictures and text on this site. Then apply silicone grease to the shaft and seals. Install first the seals into the case and then push the shaft through and push it all together and install the screws. Then check the operation of the servo to make sure we havent put the output shaft gear in oriented improperly. On the bottom of the gear you will find a tab that limits the extent of travel of the servo. If you get it put back wrong you will lose a great deal of servo travel. Just be observant of that when you pull it apart. When you are done it will look like this and you can then go out and defy the water once again! Oh yeah, dont forget to seal up the seams and screw heads and wires well or it will be a short trip. I use "goop" because it is thinner than silicone and spreads out and seals on its own without having to go back and try to smooth it out. Cheers

[Slats]

Greenman I have mucked around with this myself and the Traxxas "waterproof servo".

I have to say that IMO and IME the advantages of a waterproof servo are not that great.
First you have to ensure that the servo is indeed "waterproof", but the bigger issue I found was then ensuring that the electrical connection back to the WTC was waterproof too. OK some will say that's easy. What I find is a pain is getting an effective long term removable waterproof electrical connection . It can be done - but its something I'd rather not pursue. Reliability in this hobby is king for me. Push rod hookups I find can suffice in even tight situations.

In the end we have a WTC for a reason, I'd rather have a a reliable WT push rod seal and push rod to a hookup than go the wet servo route.
That said - I like what you are trying here. I hope it works out for you.

Best
J

[greenman407]

I guess time will tell. So far so good. I use corrosion x on the connection. If it does work out in the long term it will save a lot of aggrevation.

[He Who Shall Not Be Named]

Mark,

At the risk of coming off as an opportunistic piler on, I'm agreeing with John's observations. Specifically, the troubles presented by the 'wet' servo out weight the advantages of locating the servo in the most advantageous position for the job it has to do. You got a dry cylinder in that boat .... USE IT!

Kevin Rimrodt and I worked a boat of his years ago in which we were running servo wires in the wet (the 'external' servos were each in their own watertight cylinder within the boat), external of the WTC. We were experiencing glitching of the external servos. Turned out that the servo wires were not as waterproof as we assumed. They worked fine in air, but the moment the boat was in the water and the wires got wet, the servos started their dance-of-death. Out of the water, they were fine again.

Better to keep all the electronics together in one big, dry, happy family.

David,

[Albion]

Thinks its been discussed on a number of forums, this servo is not meant for immersion, it is something that can be used in an area where water could spray in.

[RonP-UK]

Years ago (1970s) futaba did a waterproof servo that really was waterproof, dont know what happened to them but this was in the days of "M" series radios so I guess I am showig my age.
More recently (1994) I met a guy at the Groton meet who ran a small company, who's name escapes me now, but he marketed a spray liquid called "The Stuff", you sprayed it onto your electrics and hey presto the whole lot resisted water. He had a naked reciever, servo and battery pack in the bottom of a fish tank working away quite happily for the two days of the event.
I have never seen it in the UK and don't know if it is still around but it was bloody good stuff and I still have a bit left after 16 years.
(Don't sail in lumpy water)

[AQUASUB]

I agree Mark you will find that it is better to keep the most sensitive components as safe as possible, years ago I ran with water proof servos and they worked for a long time but eventually failed at the wrong time.
That is why I came up with the mini hydraulics, water does nothing to it and a lot stronger and smoother with loads of travel or a few mms, easily customized by the builder!

Dave

[greenman407]

Dave. Will your hydraulics return to the same nuetral point, exactly, again and again?A electric servo will , thats why its critical so that your adjustments on your ballast tank be dead on every time otherwise you will have problems. As far as the waterproffing of servos goes its still an atractive idea for me and I have had a measure of success. The next step in the evolution of this is to do as has been suggested before and that is to fill the lower section of the servo where all the electronics are with silicone seal. To do this I will drill multiple holes in the lower case and using the included nozzle squirt in the silicone until I am satisfied that its all filled up. Then after installing my Quad ring as was discussed earlier drill one hole in the top and pour in mineral oil and seal up the hole. Obviously you have to take one apart first to know where you can drill these holes so that you dont damage anything. Then dip the whole thing( my idea ) in liquid electrical tape or a similar product. Dont let any get on the splined shaft. Oh yeah. Youll have to take the bottom plate off too and smear on the silicone manually there to make sure it gets good and covered.