Model Boat Mayhem

Technical, Techniques, Hints, and Tips => DC Motors (Brushed) and Speed Controllers => Topic started by: Chris G on May 10, 2015, 01:48:12 pm

Title: Which motor?
Post by: Chris G on May 10, 2015, 01:48:12 pm

I am building a Robbe fishing boat length 830mm, beam 340mm displacement 9.5 kgs. The motor recommended by Robbe is a Starmax 48 which I would guess has been unavailable for quite some time O0
I have in my spares box a couple of Johnson 600's would one of those be suitable or do I need a geared motor to achieve scale speed?
I have a long way to go before I fit the motor and finish off but one of the frames that I am due to cut out any time soon requires holes to take the motor to be fitted.
I would be really grateful for some help :-))
Many thanks Chris G

Title: Re: Which motor?
Post by: malcolmfrary on May 11, 2015, 09:25:31 am

The Starmax 48 was a 48mm diameter motor.  The correct 600 would certainly do the job, whether yours have the right internals is altogether another question.  Johnson are a big company and fit a wide range of internals into the same size can to give a very wide range of performance.  Since the boat appears to be a heavy displacement type, it will probably have a large, relatively slow turning prop, so a fast motor would need gearing one way or another.

Title: Re: Which motor?
Post by: Chris G on May 11, 2015, 01:38:22 pm

Thank you so much for the reply,
Your comments seem to line with the replies to another question on here put on shortly after mine and titled 'Tug setup' and I think that all seems to make sense.
I will talk to component stores and given the spec of the boat and a 50mm prop I am sure they will have a recommendation.

Malcolm thanks again and your comments regarding the Johnson motors I was not aware of, will bear it in mind, perhaps that is why they were so cheap.
Regards Chris G
   

Title: Re: Which motor?
Post by: Time Bandit on May 11, 2015, 09:10:13 pm

This one here should do the job pretty well

http://www.componentshop.co.uk/800-dc-motor.html

600 is definetly too small for a 10kg boat.
You´ll need around 3W per kg weight to bring it to hull speed and the slow reving 600´s are all at around 10W.

The ROBBE starmax was a 12 pole Bühler motor with 39W, pretty equivalent to this one here http://www.hobby-lobby-modellbau.com/onlineshop/product_info.php/info/p3804_B-hler-499-BB-HQ--Langsaml-ufer-12-Volt----2170.html

Title: Re: Which motor?
Post by: Chris G on May 11, 2015, 09:24:22 pm

Many thanks Tobias I well talk to the Component Shop. You are right it will be quite a lump when finished and that is another story.
Thanks again and best regards Chris G