Author Topic: WHAT MOTOR  (Read 1927 times)

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BIKERBOB

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WHAT MOTOR
« on: August 29, 2011, 09:48:00 »
HI ALL
I AM NEW TO TUGS
I AM ABOUT TO START THE BUILD ON A 38 INCH TUG (SCALE 1 TO 25)
SCALE PROP WOULD BE ABOUT 3" IN DIA WITH KORT NOZZLE.
APPROX WHAT RPM SHOULD THE PROP TURN FOR REALISTIC LOOKING SPEED? REAL TUG RAN 10 KNOTS
I WILL BE USING 12 VOLTS FOR POWER; WHAT MOTORS WOULD YOU RECOMMEND AND SHOULD THEY BE GEARED?
THANK YOU FOR YOUR HELP

zeevaart1

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Re: WHAT MOTOR
« Reply #1 on: August 29, 2011, 10:14:39 »
Hello BIKERBOB, welcome to this beautiful forum.
I would say somewhere between 2000 and 3000 RPM.
If it runs slower,then you have no speed,and no power.
If it runs to fast,than you get cavitation.
And your tugboat changes in a Speedboad.
It's better with a gearbox.
I use usually for big models 12 volt wheelchair engines.
For smaller ships in scale 1:25 I use 12 volt decaperm/hectoperm.
« Last Edit: August 29, 2011, 10:33:18 by zeevaart1 »
with best regards Cor
www.bergingshaai.nl

Model Tug Man

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Re: WHAT MOTOR
« Reply #2 on: August 29, 2011, 10:47:32 »
Welcome to the Forum Bikerbob. Good to have you with us. Before attempting to answer your question a few questions about your model and it's intended use:

Will your model be used for towing or just cruising around?
Since it has a kort nozzle I am assuming that it is modeled after something fairly recent but this may not be the case...???
Assuming a 4 blade prop since it is in a nozzle.

This will help us understand what you want out of your model and may save you some time and rework later. Hope you decide to post a build thread so we can watch your progress. If you do then don't forget--lots of pictures. Best of luck with your project.

TM
VGJQ

mike_victoriabc

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Re: WHAT MOTOR
« Reply #3 on: August 29, 2011, 11:10:03 »
Welcome Bikerbob - what is your location - help send you in the right direction.

A few of us are happy using the Robbe gear drive & motors - 3:1 and 5:1 both work well. 5:1 units might be best for that nozzle. See what others suggest.

BIKERBOB

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Re: WHAT MOTOR
« Reply #4 on: August 30, 2011, 03:54:21 »
You are right MODEL TUG MAN; here are the particulars of the full size tug
A spanish tug "puerto de bilbao" free plans on the internet for those that are interested; search tug name
Built in 1979; 1420 hp and 20 ton bollard pull
hope this helps

BIKERBOB

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Re: WHAT MOTOR
« Reply #5 on: August 30, 2011, 03:59:02 »
Mike

appears we are countrymen; I am from a small town "Stirling" Ontario

Volker

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Re: WHAT MOTOR
« Reply #6 on: August 31, 2011, 06:27:00 »
With a length of 38 inch, a weight of between 33 and 44 lbs, a prototype speed of 10 kts, and a prop-diameter of 3 inch you'll need a load speed of the motor of approx. 2000 rpm without a gear. That gives an idle speed of the motor of between 2900 and 3300 rpm. The motor should have about 50W.
Robbe gives for their motors mostly the load speed, Graupner mostly the idle speed. But check please.
I calculated the motor requirement with the Excel-sheet I introduced in the following thread: http://modeltugforum.com/index.php?topic=3120.0
Volker