I have mentioned about my ideas and thoughts about motorising the Moorhen's crane mechanism several times, but up till now, have kept most of the details quiet. Please appreciate tis was purely as it was still " under construction AND devopment". I have had at least 3 attempts to get the system to do all that I want and at minimal costs too.
YES I know you can buy proper r/c kits for cranes, but at a price!
This system I have now tested out works fine and only uses 1 x motor and 1 x servo to operate.
yes this only gives 2 functions, but thats sufficient to get some movement and action on/off deck so to speak.
Firstly, to "rotate" the crane I am using an MFA geared motor [500:1] with a chain drive from motor to central swivel shaft [which is hollow brass tube]. the gear wheels used also double drop the gearing down again, to lower rotation speed as much as possible. This motor is then controlled via an ordinary esc to a joystick control on the transmitter, so you get "left rotate/right rotate on the crane.
Secondly, I decided to simply "elevate" the crane boom, with a fixed length of winch cable attached to the gemini craft. this being the first item to put out in to the water when on duty, so rather than fix the boom in a set position and motorise the winch drum, I fix the drum and lift/lower the boom, it gives similar effect anyway.
The boom lift is controlled via a servo mounted underfloor, close to the central hollow drive shaft, as the servo operates a solid push rod through the centre of the swivel shaft, this then pushes up against the underside [inside] of the lifting boom, so as the servo is switched [via the landing gear switch on your transmitter], plus via a "servo morph" to slow things down, you get a nice gentle "raise/lower" of the crane boom.
It takes longer to explain in words than it does to actually get to work. you will have to take some time to get things correctly aligned fully, to ensure nothing is off centre or misaligned otherwise things get crossed up when the crane is rotated.
One thing I did learn, was that when you attach the upper hydraulic cylinders to the boom, DONT use a piece of rod which passes right through from one cylinder, to the other, as this "traps" against the lifting rod and siezes the drive up. use seperate pieces of rod, so the inside of the boom area where the lifting pushrod goes through is clear of obstruction.
now for the pictures:



These show the geared motor position, chain drive and central swivel shaft in place.


the latter 2 pics show the servo in "lift/ lower mode for the crane boom.