What size motors do I need?

[wartsilaone]

I am building a ferry from scratch so I don't have any recommendations for motor size. The model is 144cm long by 20cm wide and will displace about 12Kgs.The hull has a flat bottom and is very boxy. It has two 50mm props on 30cm shafts. I hope to run the ship at scale speeds so the motors do not need to be fast running, just have plenty of torque. Can anyone help me?    

[Jon Godsell]

Hi,

Suggest that you go here: http://www.modelboatmayhem.co.uk/forum/index.php and sign up.

Nice piece of work BTW

Cheers,

Scouse.

[wartsilaone]

 just registered with the web site, many thanks.

[Gulfspan]

http://www.rcgroups.com/scale-boats-55/

Thats a good site too ..

Many factors play into the motor selection ..which may also require gear reduction .

1  what type of prop
2 what type of ferry, High speed,transit ferry,or larger ferries
3 If you have the props ,,what are its rpm limitations hence gear reductions

generally a 550 can motor with gear reduction for most larger ferries with low transit speeds, 15-30 knots, work well in most applications

[wartsilaone]

The ship has 4 blade props and the service speed is 18.5 knots which gives a scale speed of 7.5cm per second.

[Gulfspan]

So ..you can use a very cheap Johnson 550 can motor and couple it to a 3-1 gear reduction ..

Typically most users use 12v DC in these motors ..

Try these pages

http://www.mackproductsrc.com/Power%20p2.htm

You will also require ESC..Electronic Speed Control's..1 or 2 thats up to you ..
Depending on your transmitter you can mix port and starboard to get full independant control of the motors with two ESC's
With one you get both forward ,both astern


My personal choice for ESC's are the Mtroniks

http://www.mtroniks.net/products.asp/subcatID/2/brushed-marine-speed-controllers.htm

20 amp min each ..or a single 40 amp to drive both..

You did get left and right hand rotation prop's ...I hope...

[Pilot3]

Hello,

I would go for a triple 555 from model motor direct best run on 12 volts.

Regards

Glen