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Old Oct 20, 2011, 11:16 AM
chak is offline
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Joined Sep 2011
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Typical thrust and current for BLDCs

Hey guys,

I am starting off with my ROV design and I am a newbie here so may be you guys can help me. I hope to start making the ROV soon and will keep posting here much like Robe did a few years ago. Few questions first :

I am thinking about using BLDC motors thrusters so
1. Do I need to water proof them for use in fresh water ? I will be testing my ROV in the lake nearby (hopefully before it freezes)

2. I am inclined towards using a 900 kv motor with a 50 mm prop as it seems to be a popular choice here. Although I could not find much data on how that choice is made, so can anyone throw some figures for:
1. typical max thrust (in lbs) for this combo
2. max current sucked from the batteries at this combo

3. What other considerations do you all keep in mind while choosing the motor and prop ? Any drag estimates ?
what are the typical speeds that you get with the above combo?

I guess thats mostly it for now.
Will keep you all posted for progress

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Old Oct 21, 2011, 12:43 AM
robe_uk is offline
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Londonderry UK
Joined Nov 2004
420 Posts
Brushless motors can be ran in the water without any waterproofing, I assume the controllers are to be in your housing.
I think the main reason for the choice of motor is to have one which will not spin the prop to fast and have good power just like the 900 kv, plus they are cheap
I still have no figures for actual power usage yet but I hope to soon, there was a thread started here in which someone was going to test different motor/props for comparison but it seems to have stalled before it started.

Anyway good luck with your build and please keep posting even if it is at the slow rate I update at

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