Thrusters

3D Printed Prop and Kort Nozzle

The best thing that came from all of our testing is a 3D Printer version odone by Ole Hermann Godø.  Download the files: Ole_Herman_God0_Thruster.7z

Drawing: 3D_Print_Prop_V1.pdf

Performance numbers in forward are:
12v
1A = 0,5kg - 1,1lb - 17,6oz
5A = 1,5kg - 3,3lb - 53oz
10A = 2,3kg - 5lb - 81oz
13A = 2,65kg - 5,8lb - 93,5oz
19A = 3,3kg - 7,3lb - 116oz (Max)
 

Reverse:
1A = 0,45kg - 1lb - 16oz
5A = 1,3kg - 2,8lb - 45,8oz
19A = 2,9kg - 6,4lb - 102oz (Max)

 ROV THRUSTER

3D printed thruster for hobby ROV. 3D printed parts. NTM Prop Drive 2836 750KV brushless motor.

The design Ole Hermann Godø created was inspired by the Blue Robotics Kickstarter which now has there products for sale at  www.bluerobotics.com.   Starting at $100, they are relatively expensive thrusters as compared to Ole Hermann Godø's creation, but they are very good quality.  The only possible flaw is the windings on the out runner motor have not been potted which leaves the windings exposed to abrasion from the sea-water.

Thruster Prop Testing

Our starting point for testing will be to duplicated the OpenROV groups test done on the Rotor, 5-Blade: Delta-V 15
Part # EFLDF151 blade as a baseline.  Then test additional blade to try and imporve on the amp-hour/thrust ratio achieved by OpenROV and HomeBuiltROV's

Motors Used in Test Below:
HomeBuiltROVs:  750 gph bilge pump
OpenROV:  2213N 800Kv Brushless Motor

HomeBuiltROV's Testing:
http://www.homebuiltrovs.com/mayfair750test.html

OpenROV Testing:
Test Stand http://openrov.com/forum/topics/thruster-testing-stand
Test Results http://openrov.com/profiles/blogs/preliminary-propeller-efficiency-testing

Rotor, 5-Blade: Delta-V 15 Part # EFLDF151  $7.99

Graupner 2308.65 is 200% more efficient than the 5-Blade: Delta-V 15 at 66w and when the V15 is not in a shourd.

OpenROV Parts 2213N 800Kv Brushless Motor 3mm shaft, Outrunner  Max 9.5A  11V

OpenROV Parts EZRUN 18A Brushless ESC $24 Output: Continuous 18A, 2-3S LiPo

OpenROV Parts

2213N 800Kv Brushless Motor 3mm shaft, Outrunner  Max 9.5A  11V http://www.hobbyking.com/hobbyking/store/__8622__2213N_800Kv_Brushless_Motor.html

EZRUN 18A Brushless ESC Output: Continuous 18A, 2-3S LiPo
http://www.hobbypartz.com/ezrun-18a-v2-esc-for-rc-car.html

Propeller Selection

We made an attempt to CNC mill our own propellers from Delrin plastic.  The approach was simple, take what we know about 27" diameter 400 rpm boat propellers and apply it to 2.5" diameter, 6000 rpm propellers. 

68 mm diameter, 24 mm pitch, ROV propeller

In actually testing this blade preformed very poorly, only generating 16 oz, 454 grams of thrust with 120 watts. The motor was generating 4,500 to 5,500 rpm as expected so we believe the a good deal of the problem lies in the thickness of the blades, which are 2.25mm thick compared to .7mm of the very efficient Graupner 2308/65 prop or the .9mm blade of the Delta-V 15 fan blade.

Graupner 2308.65 Prop Suppliers:
www.wheelspinmodels.co.uk
www.cornwallmodelboats.co.uk
 

After taking our various motors apart we found that all but the HobbyKing Donkey use little bearing on both ends of the coils.   The HobbyKing Donkey has a single brass bearing.  We like that design because it provides no air pocket that will compress and allow seawater to pass through the bearing.  So oil in the bearing will stay in place longer and collect less debris.

Thermal epoxy for potting the coils.

https://www.youtube.com/watch?v=RIOuPMg99GA

Other Motor Options
    Gear head motors: http://www.pololu.com/category/51/pololu-metal-gearmotors 
    Gimbal Drive Motors: http://hobbyking.com.au/hobbyking/store/__976__973__FPV_Telemetry-Gimbal_Motors.html 
    Servo Motors:  http://www.servocity.com/html/planetary_gearbox.html
    Ceramic bearings: http://www.bocabearings.com

Prop Chart: http://www.funrcboats.com/prop_chart1.htm
Prop Calculator: http://www.radiocontrolinfo.com/RCcalculator/BoatCalculator.php
Servo Gears: www.servocity.com