Torpedo Model

thingiverse

This is a model of a generic torpedo designed for use with a 500 size electric motor, although smaller ones can be easily adapted. I have created all parts, except the propeller, using Sketchup and exported them to STL. The propeller was designed with jSDN and also exported to STL. BOM ------- 4 x Fins (plastic, printable) 2 x Body tubes large (plastic, printable) 1 x Body tube small (plastic, printable) 1 x Nose (plastic, printable) 1 x Engine mount (plastic, printable) 1 x Tail (plastic, printable) 4 x Coupling rings (plastic, printable) 4 x M3 40 mm screws 4 x M3 nuts 2 x M3 8 mm screws 1 x 3 mm diameter shaft 1 x 3 mm inner diameter brass tube 1 x Electric motor 500 size 1 x 7.2 V NiCad battery 1 x 25 A electric speed controller (ESC) 1 x Arduino-style programmable board Printing ---------- I used a XYZPrinting Da Vinci Jr 1.0 printer with XYZPrinting natural PLA. The general printing parameters were: * No support material or build plate adhesion needed * Standard speed * 210-215 deg extrusor temperature Specific parameters for the fins: * Solid printing (100% infill) * 0.1 mm layer height Specific parameters for the engine mount: * Support material used * Honeycomb, low density Building --------- Glue the two large tubes and the small one together, inserting the coupling rings between each pair. I use Araldite style epoxy adhesive. Make sure the tubes remain straight while the glue is curing. Glue the remaining coupler to the nose, then fit it into the body tube without gluing and let it cure while placing it straight. Trim and drill the aft cone and the motor mount so that the screws fit easily. Glue the four fins into the recesses of the aft cone. Glue the brass tube to the aft cone. I use Poxipol style Epoxy mastic, which you can form clay-like and then fit into the cone to wrap the brass tube. Fit in place the motor, the full shaft, and the motor mount with the aft cone in order to properly align the brass tube and the shaft. Once everything has cured, glue the nuts to the inner part of the motor mount. I use Poxipol style mastic. Prepare all electronics and wires, allowing an access of length for easy manipulation. Once everything is ready and thoroughly checked, it's time to provide watertightness. Fill the four screw holes with vaseline, and cut a rubber ring between the aft cone and the engine mount. Then glue the engine mount to the body tube. Then fit the nose dome to the body tube without actually gluing it. I use duck tape to snap fit it firmly. Operating ------------- You may find the schematics and the program for an Arduino board in GitHub: https://github.com/humbertomb/torpedo_mk1 Program the Arduino board to power the motor for a short amount of time (2-10 s depending on the size of the pool you will be testing it). Use a Reed switch for magnetic activation of the program. Trim the torpedo a little nose up, and put enough ballast so that you get close to neutral buoyancy, but stay in the positive side.