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Waterproofed servos

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Postby RPM » Tue Aug 12, 2003 1:59 am

Well after alot of testing and failures I have determined that there is really no reliable way to "waterproof" servos for submerged use. They all seem to get wet {just enough} inside somehow or another. O-rings,tool dip,glue,tape,liquid electrical tape,vaseline etc has proven to be "water resistant" at most. I never really liked the idea but tried to make it work....

There is a big difference beteween putting a servo in a cup of water and actually using it in a sub for hours on end. Even meticulous preperation of the servo failed after a few hours of operation, and NEVER on the bench. So I will use small water tight boxes for each servo; the little containers with the clear lids so I can see WHEN {not IF} the water gets in :D

Just thought I'd share my findings with the group, I know that there is nothing more frustrating than checking everything at home, everythings great, then putting it in the water and 10 minutes later its all the way back home and into the shop. :angry:
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Postby TMSmalley » Tue Aug 12, 2003 9:30 am

Maybe Jeff Jones will tell us how he does it. He's used waterproofed servos for years with nary a failure, and he runs his boats a lot. Maybe certain brands of servos are more easily waterproofed?

Comon' Jeff - fess up! What's the secret?

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Postby raalst » Tue Aug 12, 2003 4:53 pm

For that one moment you feel like testing it just
one more time,
I think you should consider the O-ring with an
mineral oil filled servo. The mineral oil doesn not conduct
If there is no air in the servo, the water pressure and oil
pressure cancel each other out.

However, pools may not want to risk your servo
breaking down....(and ditto for mother nature).

I have seen this method being used in "real" motor pods
on ROV's. not (yet) tried it myself though.

Thanks for sharing your testing with us !


Ronald van Aalst

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Postby Scott T » Tue Aug 12, 2003 5:44 pm

??? How could one of these servo holders on the Small World
Models WTC be modified for a singular installation of a remote servo?
The seals must hold up. How was this accomplished??
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Postby 74-1047665942 » Tue Aug 12, 2003 5:45 pm

Don't know what I did diff from you. I did this, sanded all the edge's of the servo, went over them with c/a, went over that with silicone. Put an "0" ring between the top rotating gear exit and the control arm that was coated with vasoline... This worked for over 6 years in my fleet boat controlling the fwd dive planes. good luck, you may want to add a fresh coat of vasoline each time... worked for me..... Jeff Jones

Postby rcade » Tue Aug 12, 2003 6:03 pm

I like the mineral oil idea. How would you keep the oil in servo from leaking out (since water leaks in). One time on the rug or firniture and the wife would go ballistic (just kidding honey). Granted the oil is more viscous but will have a tendancy to leak out of screw threads, mating sufaces, etc. Once full the servo could be dipped in epoxy up to the lip on the output shaft - not over or the shaft would get glued. That would be a real shaft, wouldn't it? :p
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Postby RPM » Tue Aug 12, 2003 6:04 pm

Hi Jeff, I did just like you, but I dident ca the case together, I guess you could caus the standard servos are pretty cheap.
The thing is I got 3 servos in the water, and it seemed to go back and fourth beteween wich one got a drop in it.
That problem should be over as I'm working on the little containers for them that I can see into also.

Seemed like the water kept coming from the O-ringed side, but really dont know for sure. I get these servos watertight and she will be pretty reliable.

Just on the topic of problems, you should have seen me with my main induction valve it mostly worked out now though.
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Postby RPM » Tue Aug 12, 2003 6:13 pm

Oh, speaking of mineral oil guys, last night I decided to try submerging a disassembled servo in mineral oil to see its performance. The results were not encouraging as the speed was way down{obviously} as was the torque to a lesser extent,and it seemed to have centering problems....I think the pot dident like it too much, nor did the motor brushes.
I wonder if a coreless servo would work better, I think it might solve the motor brush prob, but the pot is still there...

A oil filled servo the dident LEAK oil would be perfect. We really dont care so much for servo speed in the subs, so it might be workable. I am leaving the servo in oil for a long time to see if anything degrades over time.
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Postby SSN22 » Tue Aug 12, 2003 9:26 pm

As opposed to trying and waterproofing the whole servo, why not just waterproof the circuit board, because that is what shorts out and causes poor performance of the servo. Use a good water proof epoxy, on the circuit board, because CA is conductive. Or if you really want to go overboard, you could then use the CA on the joints, and then the tool-dip on it.

Haven't tried this out yet, bet am planning to soon.

I think that Steve Reichmuth uses waterproof servos in his Trenchant. Any tips, Steve?

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Postby RPM » Tue Aug 12, 2003 11:02 pm

hi John, What about the pot? if the wiper in there gets wet its game over,That is the prob. The little plastic box is working out great so far. I will post picts of it later
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Postby smwarships » Tue Aug 19, 2003 7:32 pm

Hello All ,
I took each servo and wiped down the outside case with
rubbing alcohol including the wiring .
After that dried I applied tool dip , I use the black dip , this
color seems to be thicker . I apply 3 to 4 coats letting each
coat dry for 30 minutes , the final coat dries for one day .
Then I apply automotive bulb grease to the gear for the
servo arm . Then I put an "O" ring over the gear , I use an
"O" ring that fits snug . Then put the servo arm in place an
tighten the screw ......
When I apply the tool dip on the case , I also coat the wiring
harness that sticks out of the case , about 1.0" .

This seems to work fine so far .
There is a SubCommittee member on the westcoast that uses
this procedure and has used it for years without loosing any
servos to water leaks .......

Darle :D
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Postby RPM » Wed Aug 20, 2003 12:29 am

I finally drilled a hole in the servo and installed a nipple and piece of silicone tubing, I now can blow in the tube and see if the servo holds pressure { dunk it and look for bubbles}. I am now confident that the servo is really waterproof. The good nipple to use are from R/C glo engines, the muffler pressure tap.
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Postby smwarships » Wed Aug 20, 2003 12:34 am

Hi RPM ,

If your trying to make the servo water proof ?
Why are you drilling holes in the case ?
Seems to me that defeats the ideal ????

Darle ???
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Postby Dolphin » Wed Aug 20, 2003 12:36 am

Reading all these responses carefully. The mineral oil idea sounds interesting, and yes this is what is used in deep diving oceanographic submarines and ROV's/UUV's. The amazing 'Deep Flight' one man submarine uses oil in their electronics and motor housings just for the reasons you stated Ronald. BTW, the propellers used on the 'Deep Flight' vehicle after much experimenting was found that ordinary plastic R/C airplane props (made into a six bladed prop) worked the best. Was privileged to be invited along on a detailed tour of the Deep Flight shop once in the late 1990's in Richmond, California.

Back to servos, Jack Kocher taught me how to water proof ordinary futaba servos. I was so impressed with their resistance to water (tossed in a 6 ft. depth swimming pool for a 7 days and afterward operated as well as before) I took the technical risk of having all my servos outside the WTC (rudder, stern planes, bow planes)! . Jack Kocher uses his in his 1/32 fleet boat. It gives you greater flexibility in internal arrangements. Also the servo's torque and leverage can be used to it's most since the servo control rods do not need to pass through a water tight seal.

You take the servo apart, you gouge out carefully with a large drill bit (one or two turns by hand only) scooping out the plastic around the pinion wheel to allow clearance for the small rubber 'O' ring. Fill the servo and the 'O' ring facing with silicone grease, reassemble the servo so the 'O' ring does not bind or is too loose. Before tightening the servo casing closed, it should float about a 1/32 " open, and needs compressing to tighten due to the 'O' ring.

Rewire and connect 'Daniel Wood head' 3 pronged underwater connectors to the servo leads, seal with shrink tubing, injecting the tubing with silicone adhesive. Then dip the servo into the red rubber tool 'stuff'. Important to make sure all openings around the wires entering the servo case is coated thoroughly.

I remember someone (was it Jeff Jones?) that lost his boat in a deep pond once. If I remember the story, the boat was recovered from deep pond water 6 months later, everything was soaked and ruined....except the water proofed servos which continued to operate perfectly as the story goes. In building future R/C/ subs, all my designs will use one water proof servo in some form, so far Trenchant has been water tested and works fine so far any ways. I trust Jack Kocher's ingenuity, he is amazing! I am a static modeler being slowly shown the ways of the R/C side of things. I will leave this to the experts, but this above is what Jack taught me. Thanks Jack! Perhaps Jack will read these messages and fill in the rest.

Steve Reichmuth

Postby RPM » Wed Aug 20, 2003 12:54 am

Darle, You cant test it otherwise but just use it and see, besides if the nipple leaks you will see that too and fix it. I thought about the oil filled thing, one way to look at it is if you seal the servo to hold the oil, it will then be waterproof without the oil, so it is kinda a moot point...

By the way I run my sub in back of the Deep Flight shop in Richmond, they got a kick out of my "toy" and invited me in to their shop, talk about cool stuff and megabucks spent! :O

I also noticed immediately the cut down APC props, works for me.

Edited By RPM on 1061355650
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