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Bilge Pumps
A hand operated Bilge Pumps converted to be motor driven is described on page 36 of the book "Dynamic Aquaria" vol2 Adey and Loveland
From my correspondence with Dr Adey, this appears to be his preferred type of pump and from what I can gather his the least impact on micro organisms within
the tank. When experimenting with this pump I came across two problems, firstly you have to build it yourself which meant finding an appropriate pump and
motor and secondly they are not compact. In operation though this was a wonderful pump and has a number of advantages over the centrifugal pump.
The pump I built had a flow rate of around 45lpm (10gpm) this would turn my tank over at around 12 times an hour, which was delivered to the main tank in surges
Main Components
Hand Operated Single Diaphragm Bilge Pump
These can be sourced from boating supply shops an come in different sizes and designs. I soon discovered the difference between a cheaper and more expensive model,
I originally went for a cheaper model (AUD$50) which failed after 3 and a half weeks of continuous operation. When I examined the pump I found a hole in the diaphragm
which was odd since the material was quite thick. Further investigation pointed to a design flaw in the plastic diaphragm housing which had protrusions which rubbed against
the diaphragm which slowly formed a hole. I have since settled on a pump made by Jabsco called the Amazon Bulkhead
Electric Motor
The only piece of information I had about this motor was it needed to run at about 30rpm and have enough torque to drive the bilge pump, it also had to be able to be rated to run continuously.
Dr Adey told me he used
vending machine motors, I soon found out there were hundreds of different vending machine motors. I finally stumbled across 2 companies (Oriental and SPG) that manufactured electric
motors from about 8w up they also made gear boxes that could be attached to the motors that slowed the drive speed, it was just a matter of choosing the appropriate
gear box to get 30rpm. Slowing the motor down through the gear box also improved the torque. I was also able to gain enough technical information about these motors
so that would be able to pick the correct motor and gearbox combination to give me the speed an torque I required. I had to first determine the torque required to move the
Bilge Pump I had chosen. Knowing the torque required I was able to determine the size of motor (wattage) that would do the job, to be safe I chose the next size up.
I finally settled on a SPG 25w Motor with a 30rpm gear box.
Crank Shaft
I was very fortunate in that I was able to find someone who was able to make the crank for me. All I had to do was give him the motor and the pump he did the rest. That
task required a greater skill than I had.
Pump side view
Pump Front View
Pump Top View
Completed Unit
The completed unit is shown above, I tried to photograph the pump from different angles so the reader can get an understanding of the construction, my main problem was
the only picture I had to work with was a photo out of "Dynamic Aquaria".
Placement
When the pump was put into operation the biggest problem I had was mounting and housing the unit.
The finished unit was quite large. There was one advantage the pump had in terms of placement, I could either place the pump above the tank and get it to suck the water from the sump to the main tank,
or place it below the tank an get it to pump the water up to the main tank from the sump, either way did not effect the pump performance. I eventually settled on placing the pump above the tank.
The periodic surge it created in the tank caused any expanded corals to gently wave with the water motion.
Noise
The main noise coming from the pump was the sound of the diaphragm moving, I did not find it annoying though some people might. The noise could be reduced by housing the pump somehow, though I would
recommend ventilating the housing since the standard operating temperature of the motor is quite high. I was asured by the distributer that the temperature was normal.
Deployment
The first time the I installed it on the tank it ran for three and a half weeks before, the diaphragm split and started to leak. After modifying the housing and replacing the diaphragm I ran the ppump for another
four weeks, after which time I examined the diaphragm again only to discover it was wearing in the same place the previous one di and would soon split. I decided at that time to go for a more expensive
bilge pump, but that also required modifications to the crank and motor mounting. Currently my budget for this pump has run out so I am waiting a while before revisiting the idea.
Update
I have now changed bilge pumps to a Jabsco model of a similar performance. When we tried to install
the new pump with the existing motor, it was discovered that part of the grear housing had worn due to the load on the
drive shaft. My only option was to go to a more expensive brand of gearbox "Oriental". When I was about to purchase the new gearbox
I had second thoughts regarding the torque of the existing motor and whether it was capable of driving the Jabsco bilge pump
seemed to be alot stiffer for want of a better word. I decided to go to the next model up (40w) only to discover there were no gear boxes
available in the ration I required, in the end I went up to a 60w motor, mainly because that was what was available
at the time. The new pump is now ready thankfully not too much bigger than than the first model. I am currently building a new tank and will
be deploying the pump with the new tank.
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