what motor for this prop - RC Groups
Shop our Airplanes Products Drone Products Sales
Thread Tools
Apr 29, 2011, 03:35 PM
Registered User

what motor for this prop

Helo everybody,

I and my friend,would like to make some underwater ROV. We already have housing wich has 0 graviti in the water, as shovn in the video:


The housing is made from aloy. His weight is 9 kg, and it is made for 100m deep water, where we alreadi tested it.

Now my question:

Wich motor can We use from hobby king to make truster for it, if I use this prop:


I will use three from them to control ROV. The motor must be inruner.

Can you help me.
Sign up now
to remove ads between posts
Apr 29, 2011, 09:01 PM
NeverAgainVolunteerYourse lf
nick_75au's Avatar
What voltage? this will affect what motor,

but In-runners are not ideally suited due to their generally high RPM, you only want about 5000 rpm. 99% of in-runners will require gearing to be suitable.

Apr 30, 2011, 02:41 AM
Registered User
I will use 3s lipo
yes i know that they have high rpm, but it is easier to make waterproof housing for them (torpedo shape).
Iam thinking to make inside diameter of housing the same size as motor, so I can glue motor with termal compound in the housing and so solve the cooling thing.

Some other Idea?
Apr 30, 2011, 04:09 AM
NeverAgainVolunteerYourse lf
nick_75au's Avatar
A properly sized motor will not need any additional cooling, an out-runner mounted directly to an aluminium plate will have enough cooling.

The motor you need would be about 500-750 or so Kv. I have seen Leopard in-runners with this Kv but they are so ridiculously oversized for what you need

I can't see how it would be easier to make a housing for an in-runner compared to an out-runner, you still need an opening to slip the motor in, a cable gland and a shaft seal

Apr 30, 2011, 04:35 AM
Registered User
Thanks for informations abaut cooling.

Can you sugest me some outruner motor from hobby king:

I will use 55 or 40 mm prop, 3s lipo, the weight of the motor doesent metter, i think that 100 W power per motor will be enought.

I was looking this motors:

Apr 30, 2011, 06:30 AM
NeverAgainVolunteerYourse lf
nick_75au's Avatar
The first motor has the right specifications however personal experience has not been so good, I brought 2 of them for my axe bow ship and found they vibrate too much, I even wrote a review

The second motor is better, I also have a 1250 Kv version of this in a fast skiboat model, but I think is still too high RPM for your purpose


I used to replace the first motor, but the diameter is probably too big for a nice streamlined housing


has the same specs as the first motor better quality?


Go through the brush-less motors by size 0.40+, lots of different motors, you will want a 35-36 mm diameter motor for the 55mm,

Now that you mention 40 mm prop, one of the low KV towerpro bell motors would drive that


If you were willing to go to 2 cell Lipo, you could increase the KV to around 1000 Kv, and drive the 40 mm prop with a 22mm diameter motor like this


Ive used this motor with my Springer tug on 6 volts with a 40mm prop to pull a full sized boat

Apr 30, 2011, 08:32 AM
Registered User
Thank you for fast respons,

I rudder use 55 mm prop, but if isnt other way, than I will use smoller one.

I think I will order for test second or third motor you post. Don you think, that thirt is to much powerful (800 W)?

or maybe this one:


Can you tell me something:do you use forvard/reverse ESC od just forvard for left and right truster
Apr 30, 2011, 07:45 PM
NeverAgainVolunteerYourse lf
nick_75au's Avatar
The motor while rated at 800 watts will only draw what the prop is asking for, the motor you linked to is still capable of 600W and is the same dimentions, I would if you choose it go to 7.4 volts still gives you almost 6000 RPM.

Fwd only or both would depend on your positions of motors.

May 01, 2011, 05:25 AM
Registered User
ok, I order both props 40mm and 55mm, I will also buy 800w motor for test, wich you propose. Firs I wil try with 3s konfiguratinon, if it is not good, I will try 2S configurations, in the end i can steel change motor setings to lover kv. For rov housing i will use this underwater light wich is made and tested to 100 m deep water:

I will only remove center led and put camera in that place.

Now Iam in dilema, should i put motors in each balast comora, or is better to make extra housing-torpedo shape and put them under balast tanks.

What do you think.
Last edited by capo; May 01, 2011 at 05:44 AM.
May 01, 2011, 06:23 AM
NeverAgainVolunteerYourse lf
nick_75au's Avatar
I really dont know, but i think maybe bottom is better to keep center of gravity correct.

I think that 3 motors would be required at minimum, 2 for forward thrust and turning (could use Fwd only ESC for this) and one for decending /acending, then make housing very slightly positively bouyant and use a reversing speed control to dive the ROV, but for this side of designing there are much better people on the board to answer, Ive had almost no experience with building, a small bit of experience with full size minehunting ROV, but understand power systems well


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Help! Right prop size for a motor and what microcontroller to use? Milo_Mindbender Multirotor Drone Talk 8 Apr 15, 2011 10:52 AM
Discussion what size prop is correct for this motor Rhondas Power Systems 11 Nov 20, 2010 08:43 AM
Discussion What prop for this motor? KMKAZE Power Systems 6 Sep 01, 2009 09:53 PM
Help with what prop for this motor and GB Mike Parsons Power Systems 8 May 21, 2003 08:52 AM
What will be the best motor/prop for this new plane??? Magna Power Systems 0 Oct 05, 2001 10:34 AM