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Trick (trik) -noun: a clever or ingenious device or expedient; adroit technique
R/C Tips and Tricks - Water-Resistance
Getting your R/C vehicle wet is never a good idea, but if there's a chance it will see moisture, be it rain, melting snow, splashes from puddles that appear out of nowhere, or a gentle dunking in the lake, it's a great idea to do what you can to protect it. And let's be honest, when the snow is covering everything in site this winter, will you be able to resist getting out there and seeing what your machine can do in the powder? I didn't think so.
With anything short of sinking to the bottom of a lake, the main things that can be adversely affected by the moisture you'll encounter are the tires, bearings, servos, and receiver. What to do? Keep reading...
Water-Resistant Tires?
Okay, there's no such thing as water-resistant tires in R/C, unless they're solid or completely glued to wheels without any air holes, both of which would make the vehicle rather bouncy.
Most R/C wheels have one or two holes in them to allow the tire to compress and rebound in reaction to pressure or vacuum. These holes are necessary for a properly-behaving vehicle, but they can also allow dirt and water to get inside the tire and become stuck, since there's no way for them to escape.
The solution is to punch or grind two small holes in the center of the tread of the tire between the tread blocks or pins. on opposite sides of the tire. The holes should be approximately 1/8" to 3/16" in diameter and will allow dirt and water to exit the tire as the tire rotates. Yes, having holes in the tread will allow dirt and water to enter more easily than without the holes, but at least now it can also escape.
Oh, and why punch or grind holes rather than drill or cut? Because you need to actually remove some of the tire material for this tip to work. Drilling removes a slight amount of rubber but not much, and it also leaves a hole with jagged edges that almost close it off so dirt has trouble getting out. Same with cutting with a hobby knife. It's easy to slit the tire, but not so easy to make a uniform hole in the tire which is what you need.
Water-Resistant Bearings?
There's no such things as waterproof bearings, although rubber-sealed units are definitely better than metal-shielded. Therefore, there's not a lot you can do with bearings other than fix what's broken after the fact. Good-quality rubber-sealed bearings are surprisingly resistant to driving in wet conditions, barring the aforementioned dunking in the lake, but it's a good idea to check them after damp bashing. Additionally, it's always best to try to dry the vehicle as much as possible with forced air after driving in wet conditions, and even consider a light spray of WD-40 (or similar) once it's mostly dry. This can help your bearings survive, as well as help prevent rust on hardware and thward other possible corrosion.Water-Resistant Servos
The exterior surface of and R/C servo usually consist of two plastic halves held together with four screws, with one hole from which the splined shaft protrudes. There are two ways to do make your servos water resistant.Method 1 - Black RTV - you'll need black RTV, a P6 o-ring, and some grease:
Step 1) remove the servo horn (if attached), then carefully remove the four screws holding the case halves together.
Step 2) gently separate the case halves slightly and run a very thin bead of black RTV along the gap
Step 3) press the case halves together, hold them snug between your index finger and thumb
Step 4) slide the case screws into the case and tighten them almost all the way, leaving about a 3mm gap under the screw heads
Step 5) dab a small amount of black RTV under the screw heads and tighten them, then remove excess RTV from screw heads and case
Step 6) apply a liberal coat of grease to the o-ring and slide it down the splined shaft until it meets the case, reapply grease if necessary
Step 7) dab black RTV around the servo wires where they enter the case making sure to seal the hole completely
Step 8) after the RTV cures, reinstall servo horn as normal and install servo into vehicle
Method 2 - Plasti-Dip - you'll need a can of Plasti-Dip, a P6 o-ring, and some grease:
Step 1) clean the exterior surface of the servo and hook a small wire through a hole on in the servo horn to serve as a handle
Step 2) while holding the handle wire and the servo wires in your hand, dip the servo into the Plasti-Dip so that the servo case parting line is immersed but the servo mounting ears are not, if possible; follow the instructions on the Plasti-Dip can for the length of time to keep it immersed and the rate at which you remove it
Step 3) let the servo hang to dry, but be wary of any liquid Plasti-Dip that may drip onto the surface below
Step 4) once dry, apply a liberal coat of grease to the o-ring and slide it down the splined shaft until it meets the case, reapply grease if necessary
Step 5) reinstall servo horn as normal and install servo into vehicle
Water-Resistant Receiver
You can't dip a receiver in Plasti-Dip to protect it, naturally, but you can still make it quite water resistant. How? Water balloons!Step 1) Make all the wiring connections to your receiver that you need and install the appropriate crystal
Step 2) Hold open the neck of a small water balloon while you have a friend slide the receiver inside, then work the receiver to the closed end of the balloon
Step 3) Tightly wrap the neck of the balloon (and the wires passing through it) with a small zip-tie, and consider adding another a half-inch away for extra insurance
Step 4) For the ultimate in water resistance, dab some RTV inside the neck of the balloon where the wires pass through the zip-tie in order to ensure no water can travel along the gaps between the individual wires
That's it! Installing the receiver in the vehicle is a little more difficult that normal because unless your balloon is rather snug around the receiver, servo tape won't securely keep the receiver where it belongs, and balloons usually don't stick to servo tape anyway. I usually use a couple zip-ties to secure the wrapped receiver to something else in the vehicle.
Receiver Box: If you have the space, consider throwing the entire assembly into an RPM receiver box intended for an RC10GT and screw that down to a flat surface. I did that on my HPI NMT as well as my RC10GT as shown below. The box itself isn't waterproof (there's a hole for the wiring), but it goes a LONG way towards keeping most of the moisture away from the electronics it contains.
Word of Warning: I'm not sure if it's a quality issue or chemicals or something else, but balloons don't last forever. I recently needed to use an ESC in a different vehicle so had to remove the balloon from it. It was all nasty and gooey and stuck to the speed control's case and cooling fins. The image below was taken after attempting to do some cleaning on it. Not fun! What I'm getting at is if you do balloon your servos, receiver, or speed control, keep an eye on them. Check them every couple months to see if the balloons are getting sticky or mushy and if so, replace them. Believe me, the time it takes to replace the balloons is much less than the time it takes to try to replace one that's practically glued on!
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Copyright © 2007 Bruce Johnson