Servo experts required!

[GarydNB]

Right, I'm building a very small model yacht and need to know if anyone knows a way of converting a mini servo into a proportional winch which means 720⁰ from end to end (2 turns). Needs to be proportional, some builds on yt etc. are bang bang and don't stop at any point in between.
Gary

[Martin]

Only way I know is to:

1. Remove the feedback pot from the servo.
2. Remove the mechanical stop on the final output gear, so the servo can rotate 360 degrees.
3. Now you replace the feedback pot, external to servo, using either A) a multi-turn pot, or B) some external gearing that reduces the servo rotation sufficiently to drive a normal (less than one full turn) pot.
4. Wire the original feedback pot wires to the new external pot. If the new, multi-turn servo, is uncontrollable, it's likely because you got the feedback pot wiring the wrong way round, so just swap the outer two wires over.

A fairly easy way to do 3 B, if there's sufficient room in the model, is to use a second servo with its motor, amplifier, and first few gear stages removed - so it becomes just a reduction gearbox driving a feedback pot.

It's simpler to have a multi-turn servo that drives forwards or backwards, but isn't proportional - it's either going forwards, backwards or stopped - a bit like the throttle or elevator trim servos on reed models. That just requires removing the feedback pot and mechanical stop from the servo, and doing a slight hack to the servo amplifier, so it has big dead band near centre signal, where it doesn't drive either way. With that, you can sail your yacht and set the sail wherever you like, and it will stay there - but you have to be careful not to drive the servo too far either way, so that the winch cable runs out of travel, and stalls the servo - that will quickly flatten your battery, and possibly burn out the servo motor or amplifier.

[Shaun]

Hi mate, have a look at the component-shop on eBay, they sell winch servos but maybe too large.

[Rafael]

Hi mate, have a look at the component-shop on eBay, they sell winch servos but maybe too large.

Agree with Shaun. If your winch servo is one that uses "normal " PPM input then buy any new powerful "cheapish" one. It will be far reliable. If it a non PPM ( eg 5 wire ) you will have to source one from the same brand and period )

Winch servos have a limited niche , but is far safer if you can swap it with another RC "skipper?" for a 90° degree one

If you like to reinvent the wheel ( like me ) be prepared for some challenges

[MaxZ]

Hi Rafael,

Small yachts often use a standard servo with an elongated arm, if necessary with double haul. Have you considered that?

Max.

[MaxZ]

Small yachts often use a standard servo with an elongated arm, if necessary with double haul.

"Double haul" could be the wrong wording, as it seems to be associated with Fly Fishing. What I meant is that the end of the mainsheet is fixed to the deck, and from there it runs through a hole in the elongated servo arm, and from there to the boom. Like so:

[GarydNB]

That's the system that I currently use in my 'footy' yacht but I wondered if it would be viable to convert a small (sub 15g) servo just out of interest. I use the winch servos from the Component Shop for bigger boats but weight is at a premium in a 12" long boat.

Thanks all.

Gary