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Author Topic: Replace 700BBs  (Read 2966 times)

Ryanb

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Replace 700BBs
« on: July 12, 2016, 10:19:00 AM »

Please could someone give me a straight forward simple answer as to what brush-less motors and ESC that can replace 700BB motors.


Thank you in advance.
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IKB

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Re: Replace 700BBs
« Reply #1 on: July 12, 2016, 10:48:41 AM »

Hi Ryanb,

What is your application / setup? For example, a scale lifeboat or an all out drag boat?

Alex
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Ryanb

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Re: Replace 700BBs
« Reply #2 on: July 12, 2016, 10:50:18 AM »

Sorry, should have been more specific.


It is 1/16 Severn class life boat. Currently running 2 x 700bb on 4 blade 40mm props.
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IKB

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Re: Replace 700BBs
« Reply #3 on: July 12, 2016, 10:57:28 AM »

Hi Ryanb,

Have a read of my 1/16 Trent thread which should answer your questions

http://www.modelboatmayhem.co.uk/forum/index.php/topic,54771.msg567557.html#msg567557

Alex
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IKB

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Re: Replace 700BBs
« Reply #5 on: July 12, 2016, 11:07:01 PM »

Hi Ryanb,


You have the correct programming card for that ESC, the motor selection depends on several factors:


  • Battery voltage
  • Prop selection
  • Performance expectations
Apologies if you know the net bit, but I thought it may be useful.


The, "Kv" rating of the motor tells you how fast it will theoretically rotate per 1v of applied power, so if you ran your boat on 12v and used the 1100Kv motors you listed, then in theory the props would have a max RPM of, 12 x 1100 =  13200 RPM, unlike brushed motors, brushless motors don't really slow down under load, they just drain more current until a limit is reached, so it is important to select cautiously.
One point to note about the motor you have chosen, is that it is quite short, this tends to suggest a lower power motor, what I am referring to is wattage, which is stated as 315W, which will be the maximum that can be squeezed out of this motor using the highest voltage it will take, which in this case is 14.8v.
So with P = I x V, we can calculate that for this motor the maximum wattage is, 22 (maximum stated current) x 14.8 = 325.6w, remembering that manufacturers prefer to air on the conservative side when publishing figures, but if you are running 12v, then the wattage falls to, 22 x 12 = 264w (ish).
Considering you are probably running the same props as me, I would suggest a motor with more wattage, as my video on YouTube shows, there is no lack of poke  :-))


I can highly recommend Overlander's motors, I use them in several of my fleet and am very satisfied with all of them:


http://www.overlander.co.uk/tornado-thumper-v3-3548-05-900kv-brushless-outrunner-rc-motor-latest-model.html


As you can see from the link, my motors are 710w a piece, but I am running on 3s, (11.1v) so that reduces the rating to 532.8w assuming a max current draw of 48A, they are also slower motors being 900Kv, giving, 900 x 11.1 = 9990RPM, but the thing to remember is, this is almost identical to the output speed of my old 850's and as a general rule of thumb, the lower the Kv rating, the higher the torque, which also tend to be lower drain so more time on the lake!


Hope this helps,


Alex
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mudway

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Re: Replace 700BBs
« Reply #6 on: July 13, 2016, 03:07:19 AM »

The Tornados look nice but their website gives no information on the size of the motor only that the shaft is 4mm and it weighs 157gms. Are any other details available?
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IKB

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Re: Replace 700BBs
« Reply #7 on: July 13, 2016, 10:41:11 AM »

Hi Mudway,

The name of the motor tells us a lot about it, 3548/05 900Kv, this tells us that the motor is 35mm in diameter, 48mm long, it has five coil windings in the stator and it will give 900RPM per volt of applied juice, the link below gives quite a nice explanation:

http://www.dronetrest.com/t/brushless-motors-how-they-work-and-what-the-numbers-mean/564


Alex
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mudway

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Re: Replace 700BBs
« Reply #8 on: July 13, 2016, 01:49:20 PM »

Thanks, that solves that problem. I thought the number was just a manufacturer's code.
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Ryanb

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Re: Replace 700BBs
« Reply #9 on: July 13, 2016, 04:38:50 PM »

Thank you for the advice, that makes much more sense.


Not disregarding your info, I have been looking at Mtroniks, whom I like, I know a little more expensive but they make things simple, what are the thoughts on this?


http://www.mtroniks.net/prod/Boat-Speed-Controls/G2-Hydra30-System.htm#description
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IKB

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Re: Replace 700BBs
« Reply #10 on: July 13, 2016, 11:29:48 PM »

Hi Ryanb,


I can't fault you for wanting to buy the Mtroniks offering, I am a big fan of their brushed controllers and use them in just about all my models, the only point I would make, is that their setup on 12v will give about 300-350w, which is half what I have, don't get me wrong, I am by no means an expert on this subject, I can only recount my experience, I would suggest a swift email to them explaining what it is you want to do, as they give no guidelines as to the type of prop besides 45-50mm, but which type and how blades is that?


Alex
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Ryanb

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Re: Replace 700BBs
« Reply #11 on: July 14, 2016, 08:54:22 AM »

Them and action are all I know. I will give them a call today.

In terms of power, I appreciate the are 1/2 what you have but I assume they will still give plenty? It's a life boat around the late at scale, not drag racing?
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mudway

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Re: Replace 700BBs
« Reply #12 on: July 14, 2016, 11:04:57 AM »

The only time I saw lifeboats running was at Beale Park and I wouldn't describe them as slow.  Very impressive though.
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rnli12

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Re: Replace 700BBs
« Reply #13 on: February 04, 2017, 02:16:32 PM »

Hi,


Just picking up on this thread, I have a severn lifeboat with 58 mms props much bigger than the normal 35 - 40mm I use on turnigy   d3536/6 1250 kv I'm starting to think I my need lower kv to increase torque?


Regards ,


Rich
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Regards,

Rich

IKB

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Re: Replace 700BBs
« Reply #14 on: February 04, 2017, 03:10:41 PM »

Hi Rich,


General rule of thumb, bigger can = lower kv = more torque, the bigger the can size, the more mechanical advantage you have, hence why outrunner motors are slower & torquier than inrunners.


Alex
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canabus

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Re: Replace 700BBs
« Reply #15 on: May 25, 2017, 08:01:15 AM »

Hi All
The Hobbyking L5055 Series have a good KV range with all the specs you require.
Also the G60 series.
One of our club member is using two L5055-400kv motors via 70mm korl drives in his tug boat on 3S Lipo batteries.
Very powerful beast!!
The speed is a bit over scale speed at full throttle so he backs it off a bit, but, in push mode he has a bit in reverse.
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