Esc,motor and prop combo

[adambrum]

I have been looking at different thruster combos and have decided to go for brushless motors and think i have come up with a good combo but i just wanted a second or third opionion.

For power im going for 10 d-cell 10000mah to get me 12v

Motor http://hobbyking.com/hobbyking/store/__ ... 700kv.html

Esc http://hobbyking.com/hobbyking/store/__ ... ramm_.html

Prop will be a robbe 3 blade 50mm and as a bonus the prop and motor are both m4.

Anyone see any issiues with this set up ?

Thanks Adam

[bikerbones1968]

Looks good to me adam. I just replied to a similar post with these tips below. I see from your choices you considered all these aspects anyway but for anyone else reading this post it might be helpful.

"When you are selecting components here are a few tips to keep in mind.

1. Be aware of the operating voltage the motors are rated at, and what your power supply delivers.

2. Make sure you buy sensorless brushless. Unless you are running in dry enclosures and magnetic couplings etc you will destroy the sensored type as soon as it gets wet.

2. Get low KV rated motors. Typically somewhere around 750kv to 900kv are good. kv ratings are the RPM per volt so a 12 volt supply on a 5000kv rated motor will spin it at 60000 RPM at full voltage. This kind of speed will create what is called prop cavitaion and this is not what you want.

3. Prop adapters. They come in a variety of sizes and with various ways to be mounted. The key here is to know the shaft diameter of your motor and get a prop adapter according. Make sure your props are sized to fit the adapter also.

[jonnyhas]

Hi guys just a quick question as I am not very sure about outrunner or inrunner motors can these motors Adam has mentioned run straight from 11v without the speed controller? My Rov is not controlled by a arduino or the like and is straight forward fwd or rev and am looking for alternative motor options.

Cheers jonny

[KR2_Diving]

Hey Jonny!
In short... NO. When you run brushless motors, you mush have some form of speed controller. If you want to skip a fancy controller and wire direct to a motor via switches, you should look for brushed motors. Generally these are cheaper, but may require a bit more maintainance as they have pads which can wear out over time... Especially if not rinsed with clean water after a dive...

[ngkb]

I have a question, so does that mean all outrunner motors are water proofed?

[KR2_Diving]

I have a question, so does that mean all outrunner motors are water proofed?

Hello ngkb,
I think you have mixed a few no-related terms into your question.

Generally speaking, DC motors are "waterproof" by design. This has to do with the principles of electronics. Electricity takes the path of least resistance. At the relatively low voltages that most hobby ROVs run at, the water actually has more resistance then the copper windings of the motor, therefore the electricity "stays in the motor."

There are 2 key points to take out that that last paragraph. DC voltage, and Low Voltage.

If for example, you took a dip with an AC motor running of 120VAC, you are likely to get a bit of a shock, or worse...

A great example of this, many DC brushed hobby motors for RC cars actually recommend running the motors underwater to "break them in."

It is very important to note however, that the speed controllers (ESC) used to control brushless motors are NOT water proof!!

Now, in your question, you also use the term "Outrunner."

This is a term generally used to describe one of the physical properties of a brush-less motors.

Here is a exerpt from a website that I think describes it best.

Types of Brushless Motors

There are two types of brushless DC motors called the inrunner and outrunner. The inrunner motor has permanent magnets located on the inside of the stationary electromagnets. An outrunner motor has the permanent magnets located on the outside.

Inrunner Motors
Inrunner motors are good when high speeds are needed. They are more efficient than outrunner motors the faster they spin. However, due to the gearbox, it makes the motor more susceptible to parts failing.

The characteristics of inrunner motors are:
1. High RPM
2. Low torque
3. Requires gearbox
4. Noise

Outrunner Motors
Outrunner motors spin slower but output more torque. They are easier to use since a gearbox is not required and run very quiet.

The characteristics of outrunner motors are:
1. Low RPM
2. High torque
3. Quiet

So, in summary:
Brushed and Brushless DC motors are water proof!
Outrunner Brushless motors are best option for beginner ROV builders.

Hope this helps!

[dna1990]

Outrunners can be harder to mount in some cases.

Think of a typical hobby motor. Inrunners. It has a round cowling, sometimes with two flat sides. And a spinning shaft that come out of the center. Mount this cowling to something: ziptie, JB, or place inside a pipe of some sort...and a prop on the shaft. You got a thruster.

An outrunner doesn't really have that fixed cowling. Instead the whole outside rotates about the shaft (I suppose in physical terms acting as a flywheel sorta to gain more torque). The mount is usually a fixed point that has mounting holes for some sort of bracket. Getting this bracket fixed to a part of the ROV has proven a challenge for my students.

Still a good choice in terms of battery to thrust, just not as easy to snap on to an ROV.

[ssrc30]

Outrunners can be harder to mount in some cases.

Think of a typical hobby motor. Inrunners. It has a round cowling, sometimes with two flat sides. And a spinning shaft that come out of the center. Mount this cowling to something: ziptie, JB, or place inside a pipe of some sort...and a prop on the shaft. You got a thruster.

An outrunner doesn't really have that fixed cowling. Instead the whole outside rotates about the shaft (I suppose in physical terms acting as a flywheel sorta to gain more torque). The mount is usually a fixed point that has mounting holes for some sort of bracket. Getting this bracket fixed to a part of the ROV has proven a challenge for my students.

Still a good choice in terms of battery to thrust, just not as easy to snap on to an ROV.

Did you ever manage to get those outrunners mounted? I've decided to go with a outrunner setup using 3x 800kv marine motors with 50mm props and 45 amp esc's. Not sure if that's the ideal setup for this combination, but I am pretty sure it will be ok. My only major problem is figuring out how I will mount the motors to the frame of my rov.