Model Boat Mayhem

Technical, Techniques, Hints, and Tips => Other Technical Questions... => Topic started by: tugger on October 20, 2009, 10:08:08 pm

Title: Servo winch
Post by: tugger on October 20, 2009, 10:08:08 pm

Could anyone out there tell me if it is possible to convert a servo into a fully rotating winch by removing the potentiometer.
Thanks

Title: Re: Servo winch
Post by: Umi_Ryuzuki on October 21, 2009, 01:20:51 am

Yes,...

You can actually leave the potentiometer in the servo. Sometimes you
have to leave the pot in servo, as the gears sometimes use the pot as
a hub pin.  In this case, you turn on your transmitter, and center the control
that you are planning to use for the winch/servo.  Then turn on the reciever and servo.
Turn the potentiometer back and forth till the servo stops. Then cement the
potentiometer so that it will no longer turn. If there is a gear that rides on the pot, then
take a small drill bit, and bore out the flat spot in the hub so that it can turn freely over the pot.
Reassemble the servo, and you should be good to go.

Another method, would be to center the pot as perviously described, then use a multi meter to
measure the resistance to each side. Typically the pots are 5k, so it should measure 2.5k...
Purchase some resistors to match, and place these between the three wires that the pot is
normally soldered to.  In this fashion the motor will turn either way non stop when your transmitter
control is moved away from center.

 :-)

Title: Re: Servo winch
Post by: Martin (Admin) on October 21, 2009, 01:30:54 am

Thanks Umi.

Also see:
http://www.modelboatmayhem.co.uk/forum/index.php?topic=5704.0
http://www.modelboatmayhem.co.uk/forum/index.php?topic=11554.0
http://www.modelboatmayhem.co.uk/forum/index.php?topic=8595.0

Title: Re: Servo winch
Post by: malcolmfrary on October 21, 2009, 10:18:28 am

A few extra points -
Some output gears connect to the pot shaft using a shaped insert.  If this is the case, life becomes easier.
It is obviously vital that the output gear has teeth all the way round.  I discovered this on a large servo, part was left blank.
All the output gears I have seen have a moulded cheek that acts as a mechanical stop against webs in the case moulding.  Easily removed with a junior hacksaw blade.
The deadband is a bit narrow (correction, very narrow) but this is not a problem with good batteries and wiring.  If creeping happens, the line will go to one end of its travel or the other.  As very low power is being used at this time, it it not a problem in practical terms.