ROV Thruster 10,5 Lbs From DT700 Brushless Motor

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About: DIY for underwater.

If you are going to build an underwater robot (ROV) then the first question is the choice of the thruster. Having a good thrust you can lift heavy loads, work in current and install additional equipment. If your thruster has high efficiency you can use even a small battery and the running time will be great. But where to get such a thruster?

You can made high-efficient thruster with superior performance from an inexpensive but very popular DT700 brushless motor. It will be more efficient and powerfull than Blue Robotics T200!

Step 1: Items

1. DT700 hexTronik brushless motor from Amazon or eBay - $14.4

2. Kort nozzle set - $40 (and now on Amazon)

3. An epoxy resin - $4

Step 2:

Step 3: Preparing DT700 Wires for Underwater

You should prepare DT700 for it. Although most brushless motors can work in water, it is recommended to make some modifications. Over time (after 100-1000 hours) microscopic damage appears on the wire's protective coating. Leakage of current through these holes can lead to malfunctions in the ESC or RC controllers. Moreover electric current into these holes causes electrochemical corrosion, which leads to a rapid destruction of the wires (after 10-100 hours). To prevent this we should impregnate the wires with epoxy. The engine will operate underwater with increased power so it is necessary to ensure a good heat dissipation. To do this, choose an epoxy with a high thermal conductivity.

At first we used Thermally Conductive Potting Compounds only, like this one but this summer we tested few types of inexpensive epoxy, like this and find them perfect. Ideally, you should use a vacuum chamber to remove air, but even without it we get a fairly stable result. The basic requirement for an epoxy is that it must be sufficiently liquid to have time to fill the space between the wires. If there is air left it can lead the motor to overheat at maximum load.

Step 4: Additional Preparations

If you will use thruster at high power you should prepare DT700 for it too. Our test show this two small screws can not keep the motor from turning at maximum load. Even if you screw them hard they will not be able to hold the shuft securely and leave only shallow scratches. This can lead to a break in the wires and damage to the motor. I recommend you to drill a sink as on the photo. This completes the preparation.

Step 5: Assembling the Thruster

1. Put the ring on the motor shaft so that the mounting holes match each other.

2. Insert the ring into the Kort nozzle and tighten with three screws.

3. Insert the motor wires into the nozzle holes

4. Insert the motor into the nozzle until it stops.

5. Secure the motor with the supplied hex wrench.

6. Install the left or right propeller and fix it with the supplied nut.

The thruster is ready!

Step 6: Our Test Result

Within a year we use these thrusters on our ROV and there have never been any failures. The propellers have never broken, despite the large number of algae in our lakes. Thrusters consume little energy but give a lot of thrust so we use batteries on board and it lasts for 5-8 hours of continuous operation. Our last test showed a record thrust of 10.5 pounds (4,78 kg) at 12 volts 25 amps and it's more than Blue Robotics! We also measured the efficiency of the thruster. At a current of 1 amp it is an incredible 52 grams per watt (1.83 ounces per watt) and it's also more than Blue Robotics!

It's one of the best DIY thruster for ROV MATE. With such efficiency and thrust you can make a powerful underwater robot, suitable for professional work.

Make an instructable with our thruster and permanent link to this article and get 2 (two) Kort nozzles for free!


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23 Discussions

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AlwiNoeN

2 months ago on Step 6

Nice design. do you intend to share nozzle and impeller measurements (mm)?
more detailed volt / amp information?
Do you have any suggestions on how we can survive the ESC heat? Should we use a product called Marin ESC?

4 replies
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DIYunderwaterAlwiNoeN

Reply 2 months ago

There is current/thrust chart at 12v in our instructable.

Dimensions: 96x118x120mm.

Marin ESC is ip67 but for a ROV you need ip69 (maybe ip68 for an arm jet thruster). We recommend you to pot it with epoxy.

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AlwiNoeNDIYunderwater

Reply 7 weeks ago

This nozzle can be used in many designs. can be used as a lifeguard even in the seas. but of course after the necessary tests are done.
Below is a comment about the torpedo boat, yes, it can be applied for design. Tests seem to be very successful as you see and say, but it is best to test with different designs and get results.
Therefore, we would like to see your results in different designs.
However, since the ESC temperature will increase in radio control systems, I would like to say that marin esc is required.
Your tests are results in wired systems, but radio-controlled systems must be cooled to ESC. Fan cooling will not be sufficient since the system will be completely closed.

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DIYunderwaterAlwiNoeN

Reply 7 weeks ago

We use epoxy potted ESC for all of our thrusters. No heat even at maximum load.

20180924_012849[1].jpg20180924_012819.jpg
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AlwiNoeNDIYunderwater

Reply 7 weeks ago

Yeah, now it's clear. Since the ESC plate is completely in contact with water, heating does not occur. In fact, cooling with water becomes a kind of marin esc :) Congratulations, a very successful project.

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Mipy

Question 4 months ago

Amazing instructable, I would just like to know how deep these can operate as I am trying to build an ROV myself.

2 more answers
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DIYunderwaterMipy

Answer 4 months ago

We tested it in our hyperbaric chamber up to 30 Bar without any problem.

F0GH3S3JA36RTE4.LARGE.jpg
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NIW

Question 4 months ago

Could you go into more detail about the potting process? I was wondering how you got the epoxy to not get in other parts of the motor and how to get the epoxy to drain throuh the whole coil.

1 more answer
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apenn1

Question 5 months ago

Hi, is there any chance to get the 3D-Model files, for those of us who have a 3D printer ?

1 more answer
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DIYunderwaterapenn1

Answer 5 months ago

We spend a year to make the design and now patenting it via Amazon so cannot share anything.

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mustbeyakkin

Question 8 months ago on Introduction

Hello. I am new to Instructables. I purchased 2 of your thrusters and the DT700 motors. I will be using them to propel my kayak (hopefully). I will not need remote control since I will always be sitting in the kayak when I use the thrusters. Can you recommend a speed controller that can be purchased in the U.S?

Also, since I will not be using any remote option on the speed controller, how can I control the amps sent to the motors? I would like to control this with a knob or something similar.

Many Thanks

I now have all of the components available for assembly. (Hobbypower 60A-SL ESC) Can I use a 12v battery or do I need 11.1 volts as recommended for the DT700 motors.

1 more answer
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DIYunderwatermustbeyakkin

Answer 8 months ago

Hello. As I can see this one suitable:

https://www.amazon.com/dp/B071777MG2/ref=psdc_2234...

You can connect two motors to this one ESC.

It has forward/reverse function but some of them cannot 100% reverse and usually the most of functions closed and you have to buy a program card to open. So you should ask seller about.

All of ESC can be operated with an ESC tester any one suitable:

https://www.amazon.com/GoolRC-Tester-Consistency-H...

https://www.amazon.com/RCmall-Digital-Consistency-...

https://www.amazon.com/Hobbymate-HBS100-Voltage-di...

Besr regards.

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wbraun1

10 months ago

Will this work to power a diy fishing torpedo? Can I use a lipo jumper battery rather than the SLA battery? Do you have any other information that may help me with a fishing torpedo project?

1 reply
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DIYunderwaterwbraun1

Reply 10 months ago

Yes, it will be perfect for a fishing torpedo and of course you can use a lipo battery.

We can help you with design and calculation. What thrust you need?

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kksjunior

1 year ago

Loved the design! Voted!

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mantfish

1 year ago

Really cool instructable! I love the design!

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TheThinker

1 year ago

Nice! Do you plan to share your 3D thruster model designs too?

1 reply
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DIYunderwaterTheThinker

Reply 1 year ago

We worked on the Kort nozzle design for a year and built about 50
different variants before we made it better level efficiency than the
Blue Robotics T200. Perhaps we can do something new and then publish the file of the first model, but for now we would like to get at least a
small return from it. I hope that price seems reasonable for the amount
of times it take to 3D print one and given that
this is our design and our work. At the same time we can send this Kort
nozzle for free to someone who made an instructable with our motor.