installing remote control water pump

Discussion in 'Radio Control' started by Fatal-Noogie, May 26, 2013.

  1. Fatal-Noogie

    Fatal-Noogie New Member

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    I'm considering building a remote control fire engine with a working water pump. Has anyone here rigged a water pump or hydraulic pump or air compressor for remote control? Where should I search for affordable, small water pumps that are easy to integrate into fixtures? I thought about using a fountain pump, since they're easy to find, but I don't know if fountain pumps get damaged as the water supply runs out and they start pumping air, since they're designed for continuous water use. Another consideration is wiring/power. I could hook the fountain pump's 'ON/OFF' switch to a linkage for a servo motor, but that's not very sophisticated. I'd rather control the voltage to the pump the same way an electric RC car controls the voltage to the drive motor. A potentiometer might be overkill, but controlling the amount of power going to the pump motor would affect the water trajectory and allow for more options for the operator to play with. I'd probably put the water thru a compressing valve for extra speed. I want the water to shoot at least 4 meters. Given that this project could take months to complete, I'm on the fence about whether to begin, but I appreciate any advice/comments nonetheless.

    I've never built an RC vehicle from scratch, but I did lots of hardware/electrical/electronics work for the Robotics Club at my engineering college, so I know how to plan circuit diagrams, crimp/solder wires, read performance curves to choose gear ratios for motors: all that jazz, and I know a decent amount of fluid mechanics. Radio control is something I never learned about in theory or practice. If you guys could recommend a good hobbyists' book for that, that would be awesome.
  2. silveroxide

    silveroxide Well-Known Member

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    If you do build a sump pump for RC boat I would like to see how you accomplish that. I have the large Limbergh PT109 which I converted to RC, When I bring it in, I have to drain some seepage. I used to turn it upside down but I came up with drainage holes at the aft and use screws to open and close the drain holes. I thought about the same thing and was thinking of using a battery operated air pump, but never got around to it.
  3. Fatal-Noogie

    Fatal-Noogie New Member

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    Have you tried using rubber washers with the screws? That might keep some water in, but I don't know what the seam looks like under the hull, so I don't how you could waterproof that. Maybe try weatherstripping, like the kind that's typically used to seal the tops & bottoms of doors.

    Out of curiosity, do you use your RC boat on freshwater lakes/pools or in saltwater bays/inlets? That might affect what type of pump or waterproofing you use. I think some types of pump blades are more susceptible to corrosion if there's extra salinity. (Although maritime chemistry is not my specialty. You might know more than me.)

    How far is it vertically from the bottom of your boat to the float-line. You'll probably need a pump that can sustain water pressure at least that far, or else it will back up in the tube (so none of these tiny pumps that just splash the surface). Most hardware stores have pipe fittings/adapters for just about any diameter, so you can match one end to the outlet of a fountain pump, and the other end of the adapter to flexible nylon tubing, which you can buy by the foot. Then you can string that to the outside.

    All this is brainstorming. I won't have time to attempt my own project for a few months. Let me know how your project turns out if you add more modifications to the boat.
  4. zathros

    zathros -----SENIOR---- Administrator Moderator

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    You can use a "grease box", which is a box that the shaft runs through. It is "frenched" into the exist of the output shaft on the inside of the hull, and you pack it full of grease. You make the holes for the shaft to an extremely tight tolerance. When you pack the grease box full of grease, it keeps the water out. if you had a lathe, and where able to machine very light screws in the opposite direction of the water entering (opposite direction that the shaft is spinning), the the shaft spinning would keep the water out. You cannot have the threads enter the grease box or it will pump out the grease. The rear seal of the M.G. 1275 c.c. engines have a reverse helix groove that keeps the oil inside. If the caver is overfilled with oil, it will leak out of the back seal when parked. The picture below shows one method. In the old days, a wooden box was tacked into the back of a boars transom, and it was packed with grease. Usually the sealing was done with oakum stuffed into a groove, which would swell up and seal the shaft. Tight at first, but settles in as a great seal. :)

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  5. Fatal-Noogie

    Fatal-Noogie New Member

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    When I read silveroxide's post I think I misunderstood the problem, or at least the source of seepage. I didn't realize it was coming in through the axle for the propeller. (I assumed the propeller was driven from above the float-line by chain or beveled gears, much like a motor boat.)

    I don't know if silveroxide has a lathe, but I'm curious: do you know any suppliers who sell the specialized parts you describe, like the M.G. 1275 c.c. rubber seals? I thought McMasterCarr had watertight grease bearings, but I can't find them now. However, if their list of hydraulic pump-to-motor adapters are watertight, then those might be applicable. Otherwise, their hydraulic pumps might be used place of a fountain pump for a less elegant solution than zathros's.
  6. zathros

    zathros -----SENIOR---- Administrator Moderator

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    I would make a housing out of two part epoxy, the water proof kind, that looks like "white clay". You can mount the seal in the epoxy, using a series of well greased o-rings, mounted in epoxy. You can use a small sheet of aluminum to form the cage, make it slightly smaller that the diameter of the o-rings outside diameter. The aluminum can easily be removed (grease the outside with Vaseline) from the epoxy, with the shape remainig in the epoxy. You now have a housing you can file and epoxy in place. You can either epoxy in the o-rings or use a small clamp on the shaft with a rubber washer to hold the o-rings in place. I have a machine shop, so I can only say that this is how I would do it if I did not have sealed bearing, which also could be mounted in epoxy. You have to be careful to not thrust the shaft into the motor or you will wear out the bearings. It could be coupled to the final output shaft.

    I think a grease box, using a rubber hose is the easiest way. :)
  7. silveroxide

    silveroxide Well-Known Member

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    I should mentioned that I resolve my seepage problems with a simple solution. I removed the shaft and replaced the tube with stainless steel one so that the brass shaft would not wear out too fast with brass on brass. I packed the tube with regular petroleum jelly and the seepage has stopped, at least for now. I will replace the petroleum jelly later on with automotive axle grease when I do my maintenance on my car.