Torpedo Launcher 2021
It's taken me a while but I have a finished the torpedo launch system for operational torpedoes launched from torpedo tubes, this system uses compressed air from an on board compressor.
I have tried various methods over the years to generate the necessary force to move the torpedo out of it's tube and I have some scars to prove it, I still have all my fingers and both eyes still work reasonably well so I have erred on the conservative side, ditching such things as high pressure CO2 cartridges as just too dangerous!
80-100 PSI compressed air does a great job of launching a 20th scale torpedo, as long as the torpedo fits the tube reasonably well.
Below is the circuit of the launch controller that I have produced. and below that is the layout diagram for the printed circuit boards that I just had made (May 2021).
The battery is connected to the XT60 plug connector at the right side, the compressor is plugged into the XT60 socket connector to the left. above the left connector is a couple of connectors in parallel which connect to the receiver, there are two connectors so that the receiver channel can also plug into something else if desired. The large round thing to the left is a pressure sensor switch that controls the compressor and maintains the 80 or 100 PSI pressure in the tank.
The CO2 cartridge to the right of the picture is empty and is used as a compressed air tank to give sufficient volume of air to fully launch a torpedo.
I have used commonly available solenoid coils but without the usual aluminium bases which have been replaced by a common air manifold that interconnects all five solenoids.
The circuit for the launcher uses discrete cmos logic and is a sequential controller that can fire four separate torpedoes and then also feed air and power to the smoke generator.
The circuit measures the input signal from the radio control receiver, if the PWM signal width is short (~1mS) both the counter and shift register are continuously reset by the input pulses, every ~22mS or so, this ensures that the circuit cannot misfire, when the input signal width gets above the set time (~1.5mS) the counter starts to count using the input pulses until Q6 goes through a complete cycle (around 1.5 seconds), this output then clocks a logic 1 through the shift register from the D input, when Q1 and Q2 are different (Q1 has gone high but Q2 hasn't yet) the XOR gate fires the first mosfet "Fire 1" then this cycles through "Fire 2", "Fire 3" and "Fire 4 at about 1.5 second intervals between. Once Q8 goes high the last mosfet "Smoke" is continuously turned on so that smoke can be "made" for as long as desired.
At any point if any of the receiver PWM signal pulses drop below the set minimum (~1.5ms) the whole circuit resets to the starting state!
So you can use a switch on the transmitter or you can use a linear control on the transmitter, whatever you have available, to operate the circuit. You can also stop at any stage, say just "fire 1" and then stop, then you can start again at any time, this will try to launch torpedo 1 again but there is no torpedo in the tube any more so just a puff of air and then proceed to "fire 2".
The launcher in operation.
This video also shows a fully operational 1/20th scale USN Mk8 torpedo being launched from an Elco 1/20th torpedo tube, these are made in a nylon type material for strength. The body for the torpedo and the torpedo tube and parts are on my shapeways shop - https://www.shapeways.com/shops/pt-boat
The compressor is just the compressor, the motor and the four LIPO batteries removed from an automated tyre pump unit, with XT60 connectors fitted to plug into the launcher board. The batteries power the compressor and the launcher board and the launcher board can power the receiver. The launcher has a 5 port air manifold, again from my shapeways shop, made in high resolution "fine detail" plastic to get a good air seal on the air solenoids, the nylon type material doesn't work for this application as the surface finish is quite rough so the air solenoids don't seal very well and the compressor runs almost continuously. There is also a 3 port manifold for the Schnellboot as it can only launch two torpedoes and make smoke.
(c) copyright 2021 John Drain