Determining Motor size

[Trout58]

Are there any tried and true rules/methods in determining what power/size motors will be required for a given model based on its dimensions, that is, how do you work out what you will need to propel and manoeuvre your model at scale speeds. I am building a 1/48 scale Iowa class battleship where i intend to have all four shafts powered by their own motors (4 motors) but have no idea how to work out what will do the job. I am assuming that in this world of advanced technology, and the wealth of experience held by the model ship fraternity, that there will be ways and means of best determining this......well i hope so? Any advice and guidance would be appreciated.

A second question in respect to scale: do you/are you supposed to use the correct scale propellers on all models. The reason i ask this is having looked at some of the models on this site it would appear that the propellers are not to scale i.e. they appear to be smaller. The scale propellers on my model would be:
2 at 4.25"
2 at 4.575"

Again all advice warmly welcomed

Cheers
Brett

[Laurent]

Hi Brett,

the best option to me, with your propellers, is to take 12 Volts low speed running motors, directly coupled to the propeller shafts. I'd go the automotive scrapyards path, getting some coolant electric fan motors used in some cars, like in VW "Rabbits", they are cheap & reliable.

If you want to go the model shop route, the best choice would be the Robbe "Power 1000", quite heavy but strong stuff:


have a look at this blog here under, scroll down the page, you'll find the specs of this motor:
http://www.imarablog.org/?paged=3

Regards,

Laurent

[ingura]

...

[Trout58]

Thanks very much guys for your assistance i have also sent an email to the guy with USS Enterprise model

[FrancisMcN]

Brett,

My HMS GLOUCESTER uses two old water pump motors that I rewound to run on 24V at about 150W each and that gives about 8 feet per second on about 300lbs displacement on a narrower hull than your battleship. I did toy with the idea of using ex 240V AC washing machine motors powered from a petrol driven generator to get some real power delivered and get the model up to near max speed but that wasn't acceptable for the Guinness world record rules so I settled for the DC battery version instead. For your model it might be worth looking into as the motors should be very cheap if sourced from a scrapyard and generators are fairly cheap compared to the serious number of batteries you would need if you were going towards the 2.8kW that Peter's calculations indicate. There would be plenty of room in the hull for that sort of set up but I don't pretend to know how that sort of set-up could be made controllable!