1/20th scale Model Torpedo - USN MK13 - more info
The ESC (speed controller board) may be one of a number of types.
The two, speed control, magnetic reed switches are US made and good quality "Littlefuse" versions and they are reliable and (magnetically) sensitive.
The finished 20th scale torpedo, complete with balancing weights and dual on/off switches. There are a couple of weights in the back section also. The weights are only on one side of the board to prevent body roll as the torpedo travels. The whole finished 20th Mk13 torpedo weighs 98 Grams and when it finishes it's run, it floats with the nose only out of the water. The two batteries are rated at 270mAH.
Production torpedo's are only available un-painted, the picture above just shows a possible colour scheme of silver at the rear and mid bodies and copper colored nose.
1/20th scale Torpedo Operation - all 20th scale models
The torpedo has a battery charging socket behind the batteries, this is connected directly to the two 270mAH Lipo, single cell batteries and should be charged, as soon as received, with a good quality Lipo charger at no more than 300mA charge current and set for 2 cells. a bare ended 3 wire charging cable is supplied with each torpedo, the red wire is positive (+) , the yellow wire is negative (-) with a central black wire for the central battery connection for use with a balance charger, these bare ends will need to be soldered to an appropriate connector to suit your charger. The torpedo should be charged with the on/off switch in the off position.
There is an on/off switch mounted in front of the motor and a further on/off micro switch mounted behind the motor which is activated when the front body is installed, which is shown in the picture above in the "off" position. When switched on and the forward body is installed the speed controller will make a beeping sound through the motor windings, however as neither of the reed switches are not close to a magnet the receiver emulator circuit, built on to the main board, will be set at high speed so the ESC will prevent the motor from starting, for safety reasons.
A small smear of vaseline, a layer of PTFE plumbing tape or similar should be applied around the joint between the front and rear bodies to keep water out (after final painting of course).
Waving a magnet near either of the reed switches (located between the motor and the gearbox) will cause the receiver emulator to go to the "motor off" or "zero speed" position and the ESC will make some more noises through the motor. The torpedo should now be "armed" and when the torpedo is moved away from the magnet, the motor (and propellers) will start. Be careful of the propellers, they are metal and they are sharp.
The 20th scale torpedo's are fitted with a speed control potentiometer located between the motor and gearbox which adjusts the motor and therefore the running speed
The torpedo can be launched from a roll off rack, over the side of the boat, or can be propelled out of a torpedo tube by air pressure or water pressure, the arming magnet(s) need to be mounted on the roll off rack or on the outside of the (non magnetic) torpedo tube and aligned with the internal reed switches inside the torpedo.
The torpedo has a counter rotating gearbox and twin counter rotating propellers, so that it runs straight and true. Once launched it will travel in a fairly straight line, just below the water until the battery reaches it's cutoff voltage, at which point it will slow down and stop. It will hang, props down, in the water with the nose slightly above the waterline and will need to be retrieved.
If you intend using these torpedo's in a large lake, or where you can't easily retrieve them from all around, you may need some sort of paddle boat at the ready, for the retrieval operation.
1/20th scale USN Mk13 Torpedo Specification
Overall Length - 204.5mm - 8.05"
Overall Diameter - 28.48mm - 1.121"
Overall Weight - 98 Grams - 3.45 ounces
Run Time - TBD
Maximum Running Speed - TBD - (adjustable) bear in mind that these may hurt and may cause injury if they hit you. Do not use near swimmers or animals.
I send all packages with tracking so that they don't get lost. Often packages are held at the customer's local Post Office as they can be too large for the customers mailbox, so if it has been a week or more since I notified you about shipment, please check with your Post Office. If I receive an attempted delivery message I will email you. If you don't pick it up after a couple of attempted deliveries it will likely get returned to us.
All packages are marked with the international Harmonised code for Reduced Scale Model Kits - HS950320.
The total price includes tracked parcel postage to most places in Australia, New Zealand, Canada, the US, UK or Europe.
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