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Lightest motor, gearbox, and 3 powerful servos…

Old 07-06-2011, 06:49 PM
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Location: Lodi, NJ
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Default Lightest motor, gearbox, and 3 powerful servos…

I’m currently building models of the USS Kearsarge, CSS Alabama, and will possibly soon be starting a model of the CSS Shenandoah (built on a CSS Alabama hull).

I’m hoping to fully RC these models, allowing me to not only control the rudder and propeller of each boat, but also rotate all three masts (adjusting the square sails without the need for actual rigging).

Due to the size of these hulls, weight is an overriding concern.

Once I finish getting these hulls sealed, I’m going to need to install the engines, stuffing boxes, and servos before proceeding with the installation of the decks and other detail parts.

Thus, I need to order the engines and servos now.

Since I’ve used it before, I’m thinking about going with the Ranger II remote;


I need a very light servo to control the rudder that is still powerful enough to turn the rudder and three servos that can be set to the same frequency to rotate all three masts simultaneously.

If anyone knows of a servos that would satisfy this need, I’d definitely be interested in hearing about them.

All three of these ships are also powered by a single propeller, and I was wondering if anyone could recommend a good, yet light, motor and gearbox to turn the prop.

Thank you in advance for any recommendations…
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Old 07-06-2011, 06:58 PM
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Default RE: Lightest motor, gearbox, and 3 powerful servos…

these work great and there little weight, only 9 gram's http://cgi.ebay.com/Mini-Micro-SG90-...item3369383436
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Old 07-07-2011, 04:10 AM
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Default RE: Lightest motor, gearbox, and 3 powerful servos…

I have been building model airplanes for years, just built my first boat. Enjoyed the build as for the first time I did not have to worry about weight! So your hulls must be very small. What size are they?

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Old 07-07-2011, 03:53 PM
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Default RE: Lightest motor, gearbox, and 3 powerful servos…

With the servos available today there is no concern over what frequency they operate at. Since that is determined by the Transmitter (Tx) you use, is not adjustable by you, and the servo won't care anyway. Basically any new servo you buy will work with any new Tx and Receiver (Rx) you buy. This frequency is different from the radio frequency of the TX. The Ranger you're looking at is a 75 Mhz radio, which will be fine for boats, (surface use). Make sure the TX and Rx are on the same channel.

The radio specs don't say how many channels are proportional, since they don't say, I will assume only 2, since this is a no frills entry level Transmitter (Tx). This will give you Two proportional channels and one switched channel.

A proportional channel has a stick or knob that you move on your Tx and the corresponding servo will move in a similar manner. For example you move the rudder stick fully to one direction, say left. The servo output shaft will rotate to one end of its travel. Now slowly moving the rudder stick on the Tx slowly all the way to the right will cause the servo shaft to slowly rotate to the opposite end of its travel. You wiggle the rudder stick the servo rotates to follow it, as fast or slow as you move the stick and a proportional amount of the travel.

The throttle channel operates in similar fashion through an Electronic Speed Control (ESC). To controll the speed of the motor.

A switched channel will send the servo to one end of its travel and keep it there till the switch is thrown to is opposite position. At which point the servo output shaft will rotate to the opposite position of its travel as fast as it can go.

To control three servos from one channel you buy a couple of servo "Y" leads. Plug the first Y lead into the receiver channel of interest plug the second y lead into one of the remaining free ends of the first Y lead. Next plug your mast servos into one of free ends of either Y lead. They will all rotate in synchronization, and at the command of the Tx.

If you want to save weight just use one mast servo and use linkage to connect all three masts to it.

If you want to be able to adjust the masts rotational angle to what ever angle you want while in motion then you will want a radio that has at least three proportional channels. The Ranger looks like it only has a switch for channel three. So when you use that switch all three masts will snap around from one extreme end of travel to the other.

I would recommend a different Tx that has at least three proportional channels, a matching Rx, a small ESC (for the motor), and two servos. One for the rudder and one for the masts, with some push rods and so forth. That will save you some weight.
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Old 07-08-2011, 01:06 AM
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Default RE: Lightest motor, gearbox, and 3 powerful servos…

Looking at the illustration in the ranger link, the 3rd channel looks like a rotary knob rather than a switch, so the 3rd channel might well be proportional.  If a new radio outfit is being bought for the project, a fairly basic 2.4GHz set would probably be better.  A 4-and-a-bit channel set should be comparable in price, offer more versatility, and avoid any further crystal hassles.  The aerials are easier to hide in a plastic boat, as well.
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