This is the LEGO "slow" motor:
Fortunately, the slow motor is realtively simple to make water-resistant, and the process is completely reversible, so there is no risk of losing or destroying the motor. Still, you should look over the whole procedure before beginning and make sure you have all the equipment you need.
Materials
- Hot glue gun and glue sticks
- O-ring with a 3/16" inner diameter:
- Vaseline or any other type of petroleum jelly:
- LEGO axle extender:
Procedure
- Seal Holes with Hot Glue.
The slow motor has a bunch of holes and grooves where water can enter. First, let's look at the top.
As you can see, we need to fill in the four holes inside the connecting cylinders of the brick as well as one hole in the middle groove. (Water can also enter at the sides of the black square as well as through its pegs, but we'll take care of those later.) Carefully use the hot glue to do this, and note that you don't need that much.
Next, let's take care of the back of the motor, where there are two holes and a groove that goes all the way around. Again, make sure you get the glue into all the openings, but try not to overdo it.
Finally, on the underside, there are five different spots we need to take care of.
- Seal the Electrical Connector Brick
As mentioned before, the black square on the top of the motor, which connects to a power supply cord, is also vulnerable. However, we can't just put hot glue over this area, or else we won't be able connect the power to it. The solution is simple, if a bit crude. We're simply going to connect a power cord to the brick and then apply the hot glue all over it, completely sealing it onto the motor. (Don't panic - you can always pull off the hot glue to get the cord back if you need to.)
To start off, connect a power cord to the motor, put some hot glue under the cord, push it down into the glue, and then add a bit more glue on top.
Once the hot glue dries, add more all over the brick part of the cord. You want it completely covered by the hot glue, as well as the grooves on the side where it makes contact with the motor.
- Create a Water Barrier at the Axle
At this point, there is one remaining place where water can enter - where the axle meets to the motor's body. While we can't perfectly seal this location, we can make a barrier that will resist water entry. To begin, take some petroleum jelly and spread it around the base of the axle.
Now get the o-ring, and put it onto the axle.
Put the LEGO axle extender onto the axle and push it down as far as you can. This will lodge the o-ring against the motor's body, and some of the petroleum jelly will squeeze out. Use a napkin, paper towel, etc. to wipe it up the excess.
- Test the Motor
Now that you've sealed off all of the places on the motor where water can enter, test it by putting it under water, shaking it to remove any air bubbles, and then turning it on.
If air bubbles keep coming up, then you probably have a leak somewhere. Try to see where the bubbles are coming from and use a little extra hot glue to seal the hole. If bubbles are coming from the axle, you made need to redo step 3.
Done!
You now have a water-resistant slow motor. Please note that you may still get occasional leaks, but that's not too bad. When you take the motor out of the water, gently shake it to remove water that might have seeped in.
