Post by nemrod on Sept 29, 2005 10:22:11 GMT -8
During the Wazee dive we were eating dinner at a neaby casino. The discussion turned to scooters and home made scooters. I cannot recall who it was that said they wanted plans ofr a scooter. I mentioned that I had years back built such a scooter from plans I got out of Popular Mechanics. I have looked and looked and looked and cannot find the plans. They and the scooter--what is left of it----are probably in my hanger way back home which is a 12 hour drive. BUT, I found the website for them .
www.scubatow.com
Now the thing is that unless they have seriously upgraded the plans they are essentially useless. They have the thing made from plywood and aluminum and calk sealer using liquid acid motorcycle batteries. This was simply unaccdeptable and possibly dangerous. There was no provision for gas venting of hydrogen either---can we say bomb!!!!! Our house in Houston had a nice pool so I had the perfect test facility. I completely redesigned the thing using PVC type pipe of 10 inch diameter. I machined the ends using a drill press for O-rings of the X style. I used latches I bought from a supply company recommended by AquaVideo and through bulkhead gland controls from Ikelite to operate the power relay switch and light relay switch. The motor they recommended is a Shakspere trolling motor. It was 12 volt with a prop about 6 or so inches diameter. I recall it spinning at about 1500 RPM--not exactly sure. I used some gell cells from a electronics supply store of about 12 AH and wired them parallel providing 12 V and 24 AH. Mine, due to a miscalculation on my part, turned out to bouyant and I had to install lead weight. In any case it performed OK producing speeds of about 1.5 MPH which is about equal to what these new SeaDoo Scooters do. Problems are several. The motor seal is not intended for depth and mine leaked below about 60 feet, well, maybe it was 90 feet but I am not really sure when it leaked. The small high RPM prop is inefficient and trolling motors are designed with very low pitch weedless props that produce high thrust at low-low speeds. The motor had a speed control that was some sort of resistence that just burned up battery power but allowed RPM to be increased or decreased. The prop shroud was made from the PVC tube by cutting slots into it. In the end I became distractred by other things and set it aside.
In contrast the Tekna scooters I have aquired have an 800 RPM direct drive , constant RPM 24 V motor. The prop is variable pitch and is nearly 12 inch diameter and speed/thrust is varied by adjusting prop pitch. The motor RPM remaining mostly constant requires amp draw to increase or decrease inversely to prop pitch. The original amperage was 15 A I think. The prop and shroud design for these is still used on most every scooter made today and even the SeaDoo units prop and shroud are very similar though smaller. The SeaDoos by the way use a small geared hobby type motor to drive the prop. Most pro type units (expensive use direct drive motors. I think the motor is a GE. I just installed two new batteries in one, they are 12 V 18 AH and are wired in series for 24V and 18 AH. Initial bathtub tests are promising! I plan to run the machine in the Y pool this weekend. Hope they don't freak on me, I think they have gotten used to the weird SeaHunt guy in the deep end of their pool.
James
www.scubatow.com
Now the thing is that unless they have seriously upgraded the plans they are essentially useless. They have the thing made from plywood and aluminum and calk sealer using liquid acid motorcycle batteries. This was simply unaccdeptable and possibly dangerous. There was no provision for gas venting of hydrogen either---can we say bomb!!!!! Our house in Houston had a nice pool so I had the perfect test facility. I completely redesigned the thing using PVC type pipe of 10 inch diameter. I machined the ends using a drill press for O-rings of the X style. I used latches I bought from a supply company recommended by AquaVideo and through bulkhead gland controls from Ikelite to operate the power relay switch and light relay switch. The motor they recommended is a Shakspere trolling motor. It was 12 volt with a prop about 6 or so inches diameter. I recall it spinning at about 1500 RPM--not exactly sure. I used some gell cells from a electronics supply store of about 12 AH and wired them parallel providing 12 V and 24 AH. Mine, due to a miscalculation on my part, turned out to bouyant and I had to install lead weight. In any case it performed OK producing speeds of about 1.5 MPH which is about equal to what these new SeaDoo Scooters do. Problems are several. The motor seal is not intended for depth and mine leaked below about 60 feet, well, maybe it was 90 feet but I am not really sure when it leaked. The small high RPM prop is inefficient and trolling motors are designed with very low pitch weedless props that produce high thrust at low-low speeds. The motor had a speed control that was some sort of resistence that just burned up battery power but allowed RPM to be increased or decreased. The prop shroud was made from the PVC tube by cutting slots into it. In the end I became distractred by other things and set it aside.
In contrast the Tekna scooters I have aquired have an 800 RPM direct drive , constant RPM 24 V motor. The prop is variable pitch and is nearly 12 inch diameter and speed/thrust is varied by adjusting prop pitch. The motor RPM remaining mostly constant requires amp draw to increase or decrease inversely to prop pitch. The original amperage was 15 A I think. The prop and shroud design for these is still used on most every scooter made today and even the SeaDoo units prop and shroud are very similar though smaller. The SeaDoos by the way use a small geared hobby type motor to drive the prop. Most pro type units (expensive use direct drive motors. I think the motor is a GE. I just installed two new batteries in one, they are 12 V 18 AH and are wired in series for 24V and 18 AH. Initial bathtub tests are promising! I plan to run the machine in the Y pool this weekend. Hope they don't freak on me, I think they have gotten used to the weird SeaHunt guy in the deep end of their pool.
James
