So....my pro rig went for a swim

[mrG]

After the comp last sunday I was running some practice courses. I told myself one last run and it was time to pack up. So I'm at gate 6, which was a steep down hill side hill kinda gate, and my rigs rear starts to come over so I give it half throttle to pull out of it. That's when it went bad (though I'm still not sure how it happened). My crawler doesn't tip but just ahead is a 6" shelf running diagonal that it drops off of and bounces up and a little to the side. Then bounces off another rock backwards and cartwheels 2 1/2 times into the water. It was only in the water for a few seconds and everything seems to be good. But I thought I should open the servo to make sure all the moisture is out. The only other time I've opened a servo was to replace the o-ring on the case of a 7950. I planned on spraying it out with alcohol then lubing the gears with a dab of luberex dielectric grease. Any thoughts or suggestions would be appreciated. It's a Futaba bls172. Thanks.

 

[JohnRobHolmes]

You are on the right path already. Open it up and let it breathe, and knock off water with compressed air or alcohol.

 

[gman350]

After you get it dried out real good, coat the circuit board with CorrosionX and let it dry real good.

Put some grease where the servo gear sticks out of the case. Some servos have an o-ring there already.

Then use silicone gasket maker to seal the cases, make sure you get around where the wires go into the case too.

 

[Postclanker]

I'd certainly worry about all the electronics....
A nice uncooked rice dip for a few days will help dry it out also....

 

[mrG]

I'll pass on the corrosion x and gasket maker, don't want the extra weight on my pro rig. Besides shouldn't be in the water, ha.

Opened the servo and there were a few drops of water in it. Who knows what would have happened over time. Still need to open the axles and motors and check all the bearing. I'll lathe the comm while I've got the motors open. Does anyone know the minimum length for checkpoint brushes?

 

[Trubble]

Youch!

I feel your pain, my Poison Dart wound up belly up, and under the waves in the Wisconsin River a few years back.

I hit the ESC and Receiver with a couple seconds of heat gun blast, but nothing more, fired up and runs fine to this day.

The servo I had on it at the time lasted two years before a catastrophic comm failure. I didn't see any evidence of water inside the servo, but with an expensive one like you've got, wouldn't hurt to check, and do some freshening up while you're in there.

 

[JohnRobHolmes]

IIRC 6mm for checkpoint is a good stopping point on brush length. The spring pressure just gets lower and lower since there isn't anything to hang up besides the brush shunt, so you might be able to push it a little further without harm. I think the shunt is embedded into the brush about 4.5mm, and you don't want to get that far.

 

[mrG]

"thumbsup"

 

[mrG]

I got everything back together just before the comp yesterday and my servo is running noticeably warmer. This is odd because when I was resembling my rig I noticed that the servo horn had been rubbing on the servo case, so I shimmed out the horn so it no longer touches. But the grease I ended up using was permatex tune up silicone dielectric grease, which is thicker than the luberex grease. I found out the luberex is petroleum based. Could just the grease make that much of a difference? The steering is bind free.

 

[666]

I've had Hitec refuse warranty on a servo saying I used wrong grease. Just saying.

 

[mrG]

So I finally got a chance to open my servo. I wiped the excess grease off and reassembled and made sure not to over tighten the case screws or the servo ear screws. It seems to be running cooler now.

 

[mrG]

Well I ran my crawler for a bit yesterday and the heat a this weird squeal are back, way frustrating!
Here's a video of the sound it's making.
https://youtu.be/83FskCtE0Eo
The last movement is when you can hear the squeal best. When I looked at the gears they were all fine. The only other thing I can think of is that the motor or motor bearings are bad. Guess I'll send it to futaba.

 

[fyrstormer]

Sounds like a dry bushing in the gear assembly. Did you thoroughly re-oil all the gear hubs?

By the way, dielectric grease is not intended for lubrication, it's intended for water displacement. It feels slippery on your fingers, but under heavy load it won't do much. Metal gears need petroleum grease to work well; silicone is not optimal for metal-on-metal lubrication.

Get some wheel-bearing grease from the auto parts store, thoroughly degrease all the gears, and regrease them with the wheel bearing grease. Use a tiny drop of oil to lube each gear hub, unless it goes into plastic, in which case use a tiny drop of silicone shock oil. Use a toothpick to apply the oils in small-enough amounts so it doesn't contaminate the grease on the gear teeth.

For the record, I run a Hitec HS-7955TG servo in my Wraith (and all my other 1:10 vehicles that don't require low-profile steering servos), and the only service I've ever had to perform was opening the backplate and letting it dry-out overnight when it started spazzing after a bath in the local creek. I dabbed the circuit board dry, let it dry out in front of a space-heater overnight, and coated the circuit board with clear nail polish to waterproof it. It's worked fine ever since.

 

[mrG]

Trying a different grease is worth a shot.