The Remote Operated Vehicle (ROV) Project Begins
Happy Days arrive in these cold dark nights. The anticipated parcel from china is placed into my hands from what looks a bitter cold postman. A quick check on the packaging brings a smile to my face. There in large letters are two words ‘Hobby King’.Ignoring all around it is a quick sprint through to the draw for the scissors. Is it just me or is it the same for all? When you want to open a parcel that you have eagerly been waiting to turn up it takes an eternity to get open. Once the blunt scissors has demolished an extremely large box there are seven little parcels laid out on the table that confirms the thruster motors have eventually arrived.For me the most important item of this build has to be motor propulsion but with so many motor options out there which do you choose? After a month of scanning the web researching different RC motors looking at thrust figures, required voltage, amperage use, batteries and dimensional sizes I could still not decide. There are thrusters out there for sale with the cheapest options being offered by a company called Blue Robotics who are based on the west coast of America. Their cheapest thruster costs £90 each and when you multilpy this by six then add the delivery charge and import duty suddenly it has become rather expensive.I decided to take an easier and cheaper route and use a combination that has already been intensively researched by many. The full design, test results and STL files of all the thruster components are all available on the net athttp://www.svseeker.com/wp/sv-seeker-2/underwater-rovs/open-source-towed-sonar.The motors they choose to use are the NTM Propdrive 28-36 750KV Outrunner that during testing achieved 3.3Kg of thrust in forward and 2.9Kg of thrust in reverse. We are liking those figures so its time switch the printer on and enjoy some late nights printing.We first tried a couple of prints in PETG basically because that was set up on the printer but also to see how it would look printed in a bronze filament. We had just used most of a reel for the latest printer we were building and it looked class against the aluminum. The parts printed fine but the colour was just not right so the PETG made way for a new reel of black ABS.To help the ABS stick to the bed we used a 25 perimeter brim with plenty of ‘Pritt stick’ on the glass. We also applied a thick layer over the edges of the brim to ensure there would be no separation in the latter stages of the print. Apart from the propeller we printed all parts with a 50% infill with support from bed only. Nozzle temperature was 235 and the bed set to 95 degrees.The propeller design is very 3D printer friendly and is made up of four parts. All four parts are secured together by the propeller adapter but we shall be also be applying some ABS cement to all at a latter date. There are two options of propeller available ‘Printprop22’ and ‘PrintPropBLUEROBOTICS’ with the latter having the better thrust results. There are also two mirrored files so both clockwise and anti clockwise propellers are available for printing.The propeller was printed a little differently as we wanted to make sure the blades were as strong as possible. To do this we used two different process levels. The lower process level which started at the bed to just below the start of the propeller blades were completed with a 50% infill. The upper process level which was basically only the blades were completed with a 100% infill. We will be smoothing all the printed parts with acetone later in the build.
Well one set complete just another five more to go.