Model Boat Mayhem

Technical, Techniques, Hints, and Tips => BRUSHLESS Motors and Speed Controllers => Topic started by: davidm1945 on December 04, 2014, 06:05:27 pm

Title: Brushless bafflement.
Post by: davidm1945 on December 04, 2014, 06:05:27 pm
 Hi All,
     I have been lucky enough to be able to buy a 35” Frog Fast Patrol Boat. This was built in the 1960's to a very high standard by a gentleman from Worcester. It was fitted with a 3.49cc Frog water cooled diesel engine which I have removed. I am going to convert  it to electric power and would like to try a brushless / NIMH 7.2v combo.
     Right – I have spent the last couple of evenings trying to research brushless motors and ESC's and am baffled. OK so I am 70 years old but I thought I was reasonably intelligent but there is so much conflicting info (mainly to do with planes or cars) that I thought that the best thing was to throw myself on your mercy.....
       So, I am not interested in shooting it into orbit but would like scale speed or a bit more. I have a 35” Vosper RTTL running on two 480 brushed motors geared 3:1 which gives a nice scale speed.

 
        Recommendations please ….... Inrunner or outrunner? – KV ? - Amps ? - Geared or Direct?

 
         All advice (besides figure it out for yourself, you old f*rt) gratefully received.

 
  Dave.
 
Title: Re: Brushless bafflement.
Post by: Colin Bishop on December 04, 2014, 06:16:30 pm
Dave,

You may find this article on the Model Boats website helpful.

http://www.modelboats.co.uk/news/article/going-brushless/8029/

Colin
Title: Re: Brushless bafflement.
Post by: derekwarner on December 04, 2014, 08:39:27 pm
David........  %) our boxing kangaroo Nick_75au....  posted this link earlier this week.....I too am not confident in the black arts  >:-o ....however careful reading helped me  :-))

Simple explanations...it demystified the subject for me...... Derek

http://www.rcgroups.com/forums/showatt.php?attachmentid=4261513
Title: Re: Brushless bafflement.
Post by: davidm1945 on December 04, 2014, 08:55:52 pm
Quote from: derekwarner_decoy on December 04, 2014, 08:39:27 pm
David........  %) our boxing kangaroo Nick_75au....  posted this link earlier this week.....I too am not confident in the black arts  >:-o ....however careful reading helped me  :-))

Simple explanations...it demystified the subject for me...... Derek

http://www.rcgroups.com/forums/showatt.php?attachmentid=4261513 (http://www.rcgroups.com/forums/showatt.php?attachmentid=4261513)

Sorry, Derek it comes up as server not found - will try Googling rcgroups and look on forums.

Dave
Title: Re: Brushless bafflement.
Post by: Netleyned on December 04, 2014, 09:02:49 pm
Works for me.

Ned
Title: Re: Brushless bafflement.
Post by: davidm1945 on December 04, 2014, 09:06:09 pm
Quote from: Netleyned on December 04, 2014, 09:02:49 pm
Works for me.

Ned

Yep, and me now I've rebooted my router!

Dave.
Title: Re: Brushless bafflement.
Post by: derekwarner on December 04, 2014, 09:16:36 pm
Yes David....here is the same Adobe link waiting to open... Derek
Title: Re: Brushless bafflement.
Post by: Subculture on December 04, 2014, 10:16:06 pm
A 28-35mm outrunner in the range of about 1000-1500kv range (depending on prop diameter and pitch) would give you a good turn of speed.
Title: Re: Brushless bafflement.
Post by: davidm1945 on December 04, 2014, 11:26:12 pm
Quote from: Subculture on December 04, 2014, 10:16:06 pm
A 28-35mm outrunner in the range of about 1000-1500kv range (depending on prop diameter and pitch) would give you a good turn of speed.

Many thanks - that's what I was looking for, some idea of a starting point.
    I think a chart strictly applying to boats would be useful. Say :- Length of boat ... Weight ... Type of hull ... Scale speed ( Planing or non-planing) and then a recommendation for each type.
    I haven't had time to read the articles kindly suggested on here but I will asap.

Thanks again..
Dave
Title: Re: Brushless bafflement.
Post by: Calimero on December 05, 2014, 12:12:28 am
What props do you have ? Brand ? Type ? Diameter ? Pitch ?


Keep in mind that you'll need one ESC for each motor (while brushed motors can run from the same ESC, as long as the current rating is sufficient).
Title: Re: Brushless bafflement.
Post by: davidm1945 on December 05, 2014, 10:43:41 am
Hi Calimaro,
    The prop that came with the boat is a 34mm 3 blade with a deep pitch, obviously made to suit a 3.5 cc diesel. I am not too worried about the prop as they are cheap enough to experiment with to find the right one - motors and ESC's are not, so I need to get them right.
    Only a single motor in this boat so don't need to worry about 2 ESC's.

Dave
Title: Re: Brushless bafflement.
Post by: sparkey on December 05, 2014, 11:20:40 am
I have a sea commander which is the same size powered by a NTM prop drive 650kv 1295w out runner and 120amp tornigy water cooled ESC ,the batteries are 2x7.2v in series giving 14.4v  the performance is very good and run time about 29mins,the reason for such a large ESC is I always double the size due to chinese amps then you cant go wrong, this boat has been going for 2 years no problems ,I found the best prop has been a  50mm 4 blade brass giving a good turn of speed,hope this of some help,all my boats are brushless now,  Ray.   
Title: Re: Brushless bafflement.
Post by: davidm1945 on December 05, 2014, 03:12:14 pm
Thanks for that, Ray.

Dave.
Title: Re: Brushless bafflement.
Post by: Stavros on December 05, 2014, 04:00:44 pm
What a Handy download for brushless motors Thanks for that
 
 
Dave
Title: Re: Brushless bafflement.
Post by: Steven.T on December 05, 2014, 11:22:29 pm
I'm using a 1250kv outrunner and 2 blade plastic prop in my 34" fireboat, normally run it on 12v, this was on a 3s Lipo which is pretty close;
https://www.youtube.com/watch?v=g4C9rKfPKLo


The motor is a Turnigy and the ESC is a hobbyking car esc with a fan, cost about £30 in all if I remember rightly...
Title: Re: Brushless bafflement.
Post by: bj on December 06, 2014, 07:19:19 am
Quote from: davidm1945 on December 04, 2014, 09:06:09 pm
Yep, and me now I've rebooted my router!

Dave.
Strangely enough I got the following message
RCGroups Message[/size][/font][/color][/size]


Invalid Attachment specified. If you followed a valid link, please notify the [/color]administrator (http://www.rcgroups.com/forums/contacts.php?s=496ec86565b796d3fae38745a82ef268)
Title: Re: Brushless bafflement.
Post by: davidm1945 on December 06, 2014, 02:56:25 pm
Quote from: Steven.T on December 05, 2014, 11:22:29 pm
I'm using a 1250kv outrunner and 2 blade plastic prop in my 34" fireboat, normally run it on 12v, this was on a 3s Lipo which is pretty close;
https://www.youtube.com/watch?v=g4C9rKfPKLo (https://www.youtube.com/watch?v=g4C9rKfPKLo)


The motor is a Turnigy and the ESC is a hobbyking car esc with a fan, cost about £30 in all if I remember rightly...


Great video, Steven, I reckon that tells me all I need. I dont need too much speed so I reckon to run on 7.2v using your set up should be about right.
Many thanks to you and everybody that responded.


Dave
Title: Re: Brushless bafflement.
Post by: Leaky Bottom on December 06, 2014, 05:16:52 pm
Quote from: davidm1945 on December 05, 2014, 10:43:41 am
Hi Calimaro,
    The prop that came with the boat is a 34mm 3 blade with a deep pitch, obviously made to suit a 3.5 cc diesel. I am not too worried about the prop as they are cheap enough to experiment with to find the right one - motors and ESC's are not, so I need to get them right.
    Only a single motor in this boat so don't need to worry about 2 ESC's.

Dave

If the boat was built in the 1960s then it will more than likely have a BA thread on the prop and these are no longer available unless made to order by the likes of propshop and are anythink but cheap
Title: Re: Brushless bafflement.
Post by: davidm1945 on December 06, 2014, 06:22:47 pm
Good point, Leaky, I had pondered whether to attempt to replace the propshaft as I do prefer a ballrace shaft. If its possible then that's what I'll do, if not then I'll have to make or buy an adapter.
 Thanks for that, I hadn't thought of it I must admit!


Dave.