I had often considered making a radio controlled version to see how the real ones would behave in the presence of it.
So a visit to a hunting shop soon had me in the possession of a very realistic male mallard duck decoy.
Now to find out how easy it is to cut into the decoy and remove a top section for access without damaging the outside finish too much. Fortunately the plastic was not particularly thick (about 1mm), and a sharp bladed knife was used to do so. I followed a feature line around the duck’s back and up to its neck. The head was then carefully detached as well, since I wanted to make the head turn to help with the realism.
The back removed, and the finished model.
The drive unit under construction.
Next I needed to decide how to propel it through the water. A water jet system seemed a novel way and could make it very manoeuvrable, just like the real things. As quite often is the case, a search of the workshop found suitable bits and pieces to be able to give this idea a go. Zinc plated mild steel was formed into tube sections of a diameter to just clear the propeller. A 90 degree, lobster back bend, was fabricated out of three such pieces soft soldered together. The propeller shaft tube was fastened in place in what was to be the vertical portion of the drive unit.
The front end of the ballast compartment (full of sand so I soon found out) was removed to make way for the drive unit. A suitably sized vertical tube is supported by a cross frame and glued into the ducks body. This had to line up with the centre of the neck hole. The propeller shaft is driven via a small pulley, attached to its top end, and a suitably sized O ring belt connecting to the electric motor.
Some construction details.
The motor is mounted on a metal bracket supported by the cross frame. There is a U shaped bracket (which supports the duck’s head) and another pulley fastened to the top end of the propeller shaft tube. Steering is achieved by rotating these, and hence the drive unit. Because a standard servo only gives 90 degrees of rotation and I chose to have the head and drive unit turn about 200 degrees, a method of amplification was needed. Hence a large pulley mounted on the servo output turns the smaller pulley below the head. A length of string is used to connect these together. See photos for the details of this. The servo is located in a hole cut in the metal bracket, between the motor and the cross frame,
The top end of the propeller shaft.
The motor control is built around an eight pin Picaxe chip. A five volt regulator supplies power to the chip and also the receiver. There are four progressively faster forward speeds and the reverse function on the trigger-grip control actually starts the digital sound device. This is the same as I used for the air horn in my Fiat railcar. (I did purchase two at the time.) The quack sounds were downloaded from the internet.
I have not added any extra ballast to the model. The hanging drive unit provides ample stability.
Mallard ducks are not fooled; however I have had a paradise duck respond to my quack, quack with its own🙂.
Yes, it does go............
That wind again.
26.02 | 08:23
this is a beautiful model. I first saw a ststic DM model at Napiers Lillip...
29.04 | 04:09
Fantastic video Dean!
20.08 | 11:21
Thats great Dean love to see the video.