NOTE: This article is for the older design Swampworks pump with an impeller made from a bent brass sheet, not the new cast epoxy impeller type!

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    The Swampworks pump is an easy to build and fairly powerful pump. It has a problem in its' stock form, however. The problem is that if the pump is running and water starts to come in the pump does not prime until more than an inch of water has entered the hull. This is also true if the pump is pumping and suction is lost (for instance as the ship rocks in a turn), the pump will not start pumping again until the water level has risen. Even if the pump is off and is turned on after water starts to come in, there must be between 3/8 to 7/16 inches of water before it primes. The above problems are caused by the large amount of space between the top of the impeller and the top of the pump housing. This is caused by the fact that the collar is attached to the top of the impeller (see Figures 3), rather than between the blades (see Figure 4). The collar placement is due to "mass production" constraints, not through any fault in the general pump design. Figures 1, 2, 3, and 4 illustrate the differences in the pump in its' stock and modified forms. Figures 1 and 2 are shown in the same scale . As can be seen the housing for the modified pump is much shorter than the stock housing. The impeller in the stock housing sits higher and has more empty space around it. This means that the water has to be higher for the stock pump to prime, and the empty space is filled by uselessly churning water after the pump does prime.

                Figure 1                                                                 Figure 2

            Figure 3                                                                                 Figure 4

   I will explain how to rebuild the pump to solve these problems and to increase the output of the pump at the same time. The first thing to note is that I use either a Dumas 4.8V or one of the 380 type motors, instead of the Swampworks motor. Either of these motors are also good for drive (prop) motors in Cruiser and smaller ships. The 380 type motor can be purchased from H&R Company, Inc., Sales: 800-848-8001, Fax: 609-802-0465, 16 Roland Ave., Mt. Laurel, NJ 08054-1012, Web Page: http://www.herbach .com, E-mail address: sales@herbach.com. They cost only $0.75 each for 10 or more. They also sell a 550 type motor the Johnson HC600 motor: TM93MTR2354 (also $0.75 each for 10 or more), these are good for drive motor in both larger Cruisers, Battlecruisers and Battleships. The minimum order is $25.00 so you may wish to go in with a friend, or stock up on both sizes. All the statistics referenced in this article (before and after) are with the Dumas 4.8v and 380 type motors. The reason I use these motors instead of the Swampworks is that I run 6 volts in my ship, and the Swampworks motor is designed to run best at 7.2 volts or more. The pump improvements will help those of you using the Swampworks motor but I have no data on how much.

    Below is a table comparing the before and after data using a Dumas motor as an example (each test was run several times):

Test (note 1)                                              Stock Swampworks    Improved                 Improved
                                                                    with Dumas 4.8V    with Dumas 4.8V     with 380 type motor

Pump 1 gallon to end (note 2)                    1 min 40 sec              1 min 25 sec            45 seconds
Pump 1 gallon to mark (note 3)                 1 min 30 sec              1 min 20 sec
Pump 1/2 gallon to end (note 4)                 55 sec                         45 sec
Current Draw                                             3.2 amps                    3.2 amps                 6 amps
Starts at ? if Running (note 5)                   1 - 1/8 inch                3/8 inch
Starts at ? if water added first (note 6)    3/8 - 7/16 in                1/8 inch
Empties to:                                                  1/8 - 3/16 in               1/16 inch

Note 1: All measurements with 6 inch rise from bottom of tub to outlet and 1/8 inch outlet.
Note 2: Put water in tub, let the pump pump until water flow stops, add 1 gallon, and pump
                until the flow stops again.
Note 3: Fill tub to a mark higher than in Note 2, Add 1 gal and time until water again reaches
                that mark.
Note 4: Same as #2, but 1/2 gal. Typical amount a Cruiser holds.
Note 5: Turn on pump and add water until pump starts pumping.
Note 6: Add some water, turn on pump, see if it primes, repeat until pump starts pumping.

    The impeller modification involves unsoldering the collar from the top and resoldering it between the blades (see Figures 3 and 4). You may wish to use an old drill bit placed through the hole in the impeller and the collar to keep them in the correct register during this process. The next step is to solder the collar to the impeller. Clean the impeller with some sort of parts cleaner to remove any gunk left on it from manufacturing. Sand both the impeller and collar. Solder the collar on the inside of the impeller (between the blades). Another modification you may wish to make to the impeller involves the ridge at the top of the housing. You can either leave things as they are and install the impeller so as to miss this, or file the corners unit the impeller clears it. The later course allows you to eliminate more of the dead space.

    If you are going to use a Dumas 4.8 or 380 motor you have to use different screws than those supplied. The motor is held onto the pump housing with screws. The Swampworks motor has taped holes to accept the screws. The Dumas motor has holes for the screws, but they are not tapped. The 390 motor has tapped holes but with a different thread. Use stainless steel sheetmetal screws to attach the Dumas motor. The Dumas motor may have an 1/8^th inch brass sleeve on the motor shaft, you have to remove this sleeve, as the Swampworks collar fits the 3/32^nd" shaft without the sleeve. First take a file, and file one side of the brass sleeve on the shaft. File until you have cut through the sleeve, but before you have cut into the shaft. You can now easily remove the sleeve.

    The H&R 380 type motors come with an attached gear assembly that has to be removed. The attaching screws have a TORX head that a standard screwdriver will not fit. I used one of the small pin-vise type flat blade screw drivers that was just wide enough to fit in the socket (see Figure 5). I first ground down the very fine point to a thicker cross-section to strengthen the end. I put the point in the screw socket and using pliers on the screw driver shaft broke the screw free, then removed it using finger pressure. The shaft end has a pot metal gear attached. The easiest way to remove this is with a Nut Breaker. These are used to crack stuck nuts so that pieces can be unbolted without damaging the bolt or stud. A typical nut breaker is shown in Figure 6. You place the ring over the gear and place the point between two teeth and tighten. The gear will break in two with little effort.

  Figure 5    Figure 6

    If you modified the impeller to clear the housing ridge you need to countersink the motor mounting holes so that the heads will sit below the surface. Figure 9 shows the mounting holes with one countersunk. The easiest way to do this is with a Pilot-Point drill. This drill has a small pointed pilot section and a square shouldered main body. Figure 8 is a picture of one of these drills. Mine are Black and Decker drills, but other manufactures may make them. A ¼" drill is the size you need for this job. It is best to use a drill press for this operation so that you have better control, but if you are careful you may be able to do this freehand. You can skip this step and just leave a little more room between the impeller and the housing, if you wish.

Figure 7         Figure 8

                      Figure 9

   Screw the motor to the housing and put the impeller onto the shaft. The impeller should sit just above the screws (and the ridge at the top of the pump housing if the impeller was not modified to clear it). Now hook power to the motor and make sure the impeller runs freely.

    The next step is to determine the placement of the outlet and how much to cut down the housing. With the impeller installed measure the height of each blade at the top and bottom at the location you wish to drill the new outlet hole. Drill the hole so that it will end up at the center of the smallest and largest measurement. Drill a starter hole. Then drill the next hole a little smaller than the outlet tubing. Drill the above holes vertically into the side of the housing. After you have drilled the last hole, with the drill running, tilt the bit over until the hole comes out at about 45 degrees to the housing. Look at the original hole to see how the new one should end up being positioned. Be sure the outlet hole is pointed in the same direction of rotation as the old hole! Test fit the outlet and wiggle the bit in the hole until you can insert the outlet. You can either reuse the original outlet, or if you need the end of the outlet to be vertical, use a piece of 3/8 inch tubing bent into a 90 degree elbow. If you use a new outlet piece contour the end inserted into the housing to fit flush and not stick into the impeller area. You may also want to chamfer the inside of the outlet where it is attached to housing the to form a slight funnel shape. This will help a little to reduce turbulence,

    Now take a piece of square balsa just a little bigger than the old outlet hole and force it into the old hole until it sticks fully into the inside of the case. Soak the wood on both sides with thin superglue and let set. Be careful to not get any more than necessary on the inside of the housing. After the glue is set, trim both sides flush and soak the wood again. If you want, glue a thin piece of plastic over the outside to reinforce the patch.

    Reinstall the motor and impeller. Install the outlet. Test (power) that the impeller still does not hit. Place (do not glue now) the plastic ring in the bottom as close to the impeller as possible without hitting. Measure the distance between the ring and the bottom of the housing. Remove the motor and impeller and trim the bottom of the housing, leaving about 1/8 to 3/16 of an inch extra for "feet". The stock housing "feet" are 1/4" high. Cut out scallops (similar to original housing) between the new bottom and the ring position. I formed slots as shown in figure 11 to allow more area for water flow.

    Each time you take an assembled pump apart you will need to fabricate new bottom ring. Fabricating them is simple if you have a set of dividers. Dividers resemble a compass, but have sharp points on both legs rather than a point and pencil lead (see Figure 7). You may be able to get a set at a stationary or arts supply store. Get a good sturdy set with the built in adjusting screw. A cheap set may not retain the adjustment while scribing. Start with a sheet of plastic of the right thickness and lay out a number of rings using the outside dimension of the original ring. For each ring run the dividers several times over the circle to scribe the plastic fairly deep. Now using the same center mark scribe the hole for the center opening. You can scribe enough rings from one 12" X 6" sheet for a lifetime, in 15 minutes! Using scissors cut each ring from the sheet, leaving a ring of scrap around the piece. Then carefully bend the plastic at the scribe marks to break the ring free. To remove the center, use a SHARP knife to cut an "X" from the center to the inner ring mark and bend the resulting tabs to break them off.

    Reinstall the motor and impeller (use blue Lock-Tite on the screws and set screw). Check again that it does not hit. Install the ring, check for hits, and glue it in with thick superglue. Glue on the screen. Glue a strip of plastic over the set screw hole, leaving a slight gap at the top to allow the air to escape so that the pump can prime.

    You now have an improved pump. The above modifications can be done in an evening. Figures 10 and 11 show the original and modified housings. Figures 12 and 13 show a cutaway of the housings with the impellers installed. Note that the positions of the outlet and setscrew holes have been moved for clarity.

        Figure 10                         Figure 11

Figure 12                     Figure 13

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