Powering a small model - Armidale

[sjbatche]

I have been asked several times over the last few weeks about the components that I use in my small model ships so I thought that I would post some info on a few of my small models.

Starting with my Armidale Class Patrol Boat – HMAS Wollongong lll:

Although this model is not the smallest in my fleet there was still a big challenge to overcome to make it a successful functional model. Because the real ships have a relatively small displacement, everything in the model had to be kept as light as possible so that it sat alright in the water.

Below are a couple of photos showing the internal components of my Armidale. One photo shows the motor and gearbox fitted in place and another photo with the motor and gearbox slid forward. The wooden block in the center of the hull now serves no purpose. It was originally going to be the mount for two smaller motors.

The motor is a small hobby motor that I picked up from Dick Smith Electronics ($4.95). I made a small gearbox so that the single motor drives both shafts. An idler gear is used to reverse the direction of one shaft. The gearbox and motor assembly slide onto the propeller tubes and it is held in place by the gears mounted on the prop shafts.

I have started using LiPo batteries as a power source for my small models as they are quite light and small for a given capacity. In this case a 4000mah 7.4V battery gives a reasonable running time. The speed controller is quite small, about 25mm square. I have purchase several of these from Hong Kong recently (bigdotunclestore.com). These are sold as model car speed controllers but they have performed well in my ship models so far.

The rudder servo is a small 16gm servo once again from a Hong Kong hobby shop.

I will post photos of the set up in some of my other small models in the next few days.

Steve.

[BsHvyCgn9]

Thanks for posting this info Steve (especially the site for those little ESC's!! Never could remember that name! LOL).
I saw a nice Airfix E-boat kit that I might have a go at if I find a spare moment!!

Cheers Bruce

[scott154]

Hi Steve,
Thanks for all your help with the small crafts, I have some batteries and speed controls on the way from Hong Kong.
just read your post on the Fremantle class and your paragraph on the speed control, are you running a different power supply for your motor and then one for your speed control or receiver. Cheers Scott

[sjbatche]

Scott

I only use one battery in each of the small model ships. I generally use a 2cell (7.4 volt) LiPo battery. The Electronic Speed Controllers that I use have a Battery Eliminator Circuit (BEC). As is suggested by its name, this eliminates the need for a second battery just to power the receiver and servos. In this case the one battery supplies 7.4Volts for powering the motor and 6Volts, via the BEC circuitry in the speed controller, to the receiver and the servo.

Be aware that not all speed controllers have a BEC function.


Steve

[BsHvyCgn9]

G'day Steve,
Do you use a low voltage detector inline with your Lipo batt's or do they not get flat enough 2 worry about over discharging the cells?? ( I know that Brushless ESC's detect low cell volts don't think the brushed type do.)

Cheers Bruce

[sjbatche]

Hi Bruce

I don't have low voltage cutouts. I have not run my models to the point of flattening the batteries to that extent. The small brushed motors don't draw huge current and you can usually tell when the battery voltage is starting to fall as top end speed starts to drop off. It is then time to take the model off the water or change the battery. I am sure that one day I will get caught out but for now this works for me.

Steve.

[BsHvyCgn9]

I suspected that was the case! I have a little brushless powered jet sprint boat that can suck a 2s 2200Mah dry in 15mins.
I will have 2 hunt around for something small 2 play around with!!

Cheers Bruce