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>> Home > Forum > Electrical Related > Motor size advice
Motor size advice
(1061 views)
Author Message
Morkullen
(Petty Officer)





Forum Posts: 5
19th May 2018 17:53  
>> Permalink
mdlbt.com/41905

I am building the Thornicroft MTB MM337 (again) I last built one many years ago and put a small diesel engine in it at that time.
However, I plan to go all electric R/C on this one and would appreciate advice as to what size, (Make /Model) type of motor could be used. Also which battery pack for the motor. Any and all suggestions would be greatly appreciated.

canabus
(Fleet Admiral!)





Forum Posts: 123
20th May 2018 07:59  
>> Permalink
mdlbt.com/41911

Hi Morkullen
I suggest a Hobbyking 3639-1100kv 35mm brushless motor with a 60 Amp ESC and a 2 blade 40mm prop.
Battery a 3S Lipo 5800mah 25C will give you more than 1/2 hour.
I had his setup in my 34" Sea commander with very good performance.
Canabus

Morkullen
(Petty Officer)





Forum Posts: 5
20th May 2018 09:14  
>> Permalink
mdlbt.com/41912

Thank you Canabus. I will check it all out.

Many thanks again.

Morkullen

Morkullen
(Petty Officer)





Forum Posts: 5
20th May 2018 10:52  
>> Permalink
mdlbt.com/41914

Hello Canabus. Just looked at the motor and battery info you supplied and neither of the specs are available or have been superceded. The problem for me is that I do not understand what all the figures mean. As an old electrical engineer, 1100kv means to me that it is 1100 kilo volts!! I dont think so! Other than being a part number, does 3639 mean anything? Similarly 3S? Lipo 5800mah OK, but 25C? Is there a site anywhere which will explain these number to me?

Best regards,

Maorkullen

RNinMunich
(Fleet Admiral!)





Forum Posts: 2218
20th May 2018 11:59  
>> Permalink
mdlbt.com/41915

Hi Maorkullen,
kv means rpm per volt applied.
Thus the 1100kv motor does 1100rpm / Volt OFF LOAD!
3639: These 4 digit numbers generally mean diameter and length; i.e. 36mm diameter, 39mm length.
xS means the number of cells, of nominal voltage 3.7V for LiPos.
Thus 3S is a 3 cell battery of nominal 11.1V.
25C is a theoretical measure of maximum short term current the battery can deliver in terms of a multiple of it's nominal capacity in Amp hours.
Thus in this case 5.8 x 25A = 137.5A. But not for long!! and afterwards the battery would most likely be wrecked and useless.🤔
So it's really only a marketing gimmick not to be taken very seriously.
Hope this unravels some of the mystery, cheers Doug 😎


Young at heart - slightly older in other places 😉 Cheers Doug
Grant me the Serenity to accept things I can't change,
the Courage to change things that I can, and
the Wisdom to know the difference!
Morkullen
(Petty Officer)





Forum Posts: 5
20th May 2018 12:36  
>> Permalink
mdlbt.com/41916

Thanks again, Canabus.

Well explained. Hopefully now I can find something that fits the bill.

Best wishes

Morkullen

RNinMunich
(Fleet Admiral!)





Forum Posts: 2218
20th May 2018 12:42  
>> Permalink
mdlbt.com/41917

Er, that was me 😉. Have fun and don't blow anything up! 😲
Cheers Doug 😎


Young at heart - slightly older in other places 😉 Cheers Doug
Grant me the Serenity to accept things I can't change,
the Courage to change things that I can, and
the Wisdom to know the difference!
Morkullen
(Petty Officer)





Forum Posts: 5
20th May 2018 17:48  
>> Permalink
mdlbt.com/41920

Sorry Doug. Nice post. Many thanks.
Morkullen

RNinMunich
(Fleet Admiral!)





Forum Posts: 2218
20th May 2018 22:21  
>> Permalink
mdlbt.com/41930

No sweat😉 Hope it all works out.
BTW: Canabus got me started on brushless last year. He answered my plea for help upgrading my old Sea Scout. Everything he recommended is now fitted and works a treat, with power in reserve. 😊
All the best, Doug 😎


Young at heart - slightly older in other places 😉 Cheers Doug
Grant me the Serenity to accept things I can't change,
the Courage to change things that I can, and
the Wisdom to know the difference!
jacko
(Lieutenant)





Forum Posts: 3
31st Aug 2018 19:44  
>> Permalink
mdlbt.com/45617

I to am looking for advice in motor and battery combo for this boat and anybody knows what this is 😊 its 34 inchs long


Attached Files - Click To View Large

Westquay
(Fleet Admiral!)





Forum Posts: 681
31st Aug 2018 19:56  
>> Permalink
mdlbt.com/45618

I do believe that's a Sea Commander, an Aerokits model.

Martin

RNinMunich
(Fleet Admiral!)





Forum Posts: 2218
31st Aug 2018 22:03  
>> Permalink
mdlbt.com/45625

That was also my first thought Martin👍
So Jacko, that means that all of the above applies also to your boat!😊
Happy shopping and boating. Cheers Doug😎


Young at heart - slightly older in other places 😉 Cheers Doug
Grant me the Serenity to accept things I can't change,
the Courage to change things that I can, and
the Wisdom to know the difference!
onetenor
(Fleet Admiral!)





Forum Posts: 380
1st Sep 2018 16:06  
>> Permalink
mdlbt.com/45662

Very nice too.👍