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[Brian60]

Right guys in my quest for operating two sets of towing pins and a working sharks jaw (detailed in another topic) I have gone with an operating unit from Action which drives an electric motor, no problem.

In the other topic it was suggested I use servo's, which when I have sat and mulled it over is rather better and simpler than the idea I had in mind which was mechanical with rack and pinion gears.

So to this little problem. I have 4/5 sanwa servo's model 102 that I have lined up for the job. I have included a couple of photo's if someone could offer solutions please. Should I removed the entire electronic components from the shell and just leave the motor connected? I would normally just take the motor out, but giving up the case means giving up the easy mounting points for the motor. Also the motor has a pressed fit gear that I can't get off, so keeping the case makes things easier all round.

Right up inside the case I assume is the potentiometer for detecting end of travel, this has to go because I was continuous rotation. Its beginning to look like I should junk all the electronics and just run two wires from the motor to the Action unit. Does anyone have  further ideas or input for me?

[inertia]

Brian
Unless I've missed the point somewhere I think the suggestion was to use a servo to raise and lower the towing pins instead of a switch unit and motor/gearbox, rather than try to modify a servo so that it can be driven by a switch. The point is that a servo will already accept a signal from the receiver and can be moved from one end of its travel to the other simply by moving the transmitter stick (or 2-way switch if you're using an auxiliary channel like "retracts"). That's what servos are designed to do. You just plug the servo into the receiver and off you go - no need for anything further than maybe making a cam to operate the towing pin as per the diagrams on the previous thread.
If for some reason you do need continuous rotation then special servos are available to do just that e.g. http://www.ebay.co.uk/itm/like/121330229349?limghlpsr=true&hlpv=2&ops=true&viphx=1&hlpht=true&lpid=108&chn=ps&device=c&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108  or you can modify a servo - just google "continuous rotation servo" and you'll find several tutorials.
MFA make a wide selection of small geared motors http://mfacomodrills.com/gearboxes/gearboxes.html
Dave M

[Brian60]

Yep I understood the idea of the servo instead of the switch Dave. But I have to operate 3 servos for the action I want and don't want to give up the channels on the transmitter just for this small operation. So I am exploring all possibilities of operation.  Difficult to explain what's going round in my head, I'm even having trouble drawing the schematics!

So far I have two sets of towing pins (4 pins) to raise and lower,  1 set of shark jaws. internal and external lighting, possibly anchors (not sure yet) rudders, two drive motors, bow thruster and stern thruster, maybe a working waterfall winch. Quite a lot to be operated from a 5 channel Tx, so some functions will have to be double up on the tx sticks. Thats why I can't just plug the servo's into the receiver.

Brian.

[malcolmfrary]

The easy answer is to mechanically disconnect the pot shaft from the output gear.  Some gears have a little insert which can be removed.  The output gear (assuming it has a full set of teeth going all round) usually has a moulded lump which catches corresponding webs inside the lid to prevent it rotating the pot beyond its limits.  This can be removed in seconds with a fine saw.  If plugged into a channel, with the stick central, adjust the pot until the motor stops. 
You now have a winch which will turn not just 360, but any number of degrees until you get bored or the string gets to one end or the other.  As long as the stick is off center, the electronics will drive the gears and output shaft.  The downside is the lack of any noticeable deadband, so re-finding the off position can be tricky.  For that, remove the servo electronics and replace them with either an ACTion Pico, or one of those cheap Chinese 10A ESCs.