Thruster Testing Stand


#1

Last build day I hacked together a thruster testing stand out of paint sticks and a packaging scale to measure bollard pull. I decided to make a more robust and better version of it out of laser cut acrylic which would also have mounts for attaching different types of nozzles. The goal is to build up a testing stand that would enable the simultaneous capture of bollard pull, motor rpm, and ESC voltage and current (for power). With this setup, we would be able to characterize motor, propeller, and nozzle efficiency curves, and quantify our propulsion analyses to help drive better design.

The CAD files for the testing stand are here:CAD and laser files



I'm using a kitchen scale to measure the bollard pull; both lever arm lengths are 500mm.

The L-arm is held together with 4x M5x25 bolts

The base is held together with 3x M5 threaded rod, with one of them acting as the pivot point.


#2

Hey Colin:

This looks really excellent!

I'm still puzzling over how to do a tachometer pickoff (Hall, optical, whatever) that won't change the dynamics of the prop in the water. Maybe I should take another look at measuring rpm via picking off one of the motor phases.

So does one of the scales around OpenROV HQ have a digital port on it?

-Walt


#3

Hey Walt,

Yeah, we were puzzling over that as well. I think optical detection might be the most straight forward. We got this laser tachometer on Amazon which came with some retro-reflective tape, and we were thinking of using a sort of para scope/mirror thing to measure through the water without the instrument getting wet.

Ultimately we'd like all telemetry from a test (pull force, RPM, current, voltage, servo value, etc) to be displayed in one data set on a computer, so we may make our own optical RPM sensor (perhaps using an IR emitter and detector potted in clear urethane potting compound or something like that.). The kitchen scale has a strain gauge (configured as a wheatstone bridge) in it that we think we'll be able to pull values off through the ADC on an Arduio which could also be measuring the other things.

Eric


#4

Do you have any numbers yet from the test stand?

i'm very interested to see some numbers between the V-15 propeller, and the cornwall boat props(eric mentioned a time ago that he would order some of those)


#5

The CAD files don't seem to be opening on the google docs. Is there another way to look at these .ipt's?


#6

Try this link

I'll convert the ipts into STEP files! They'll be in the drive folder in a few minutes


#7

Hi Colin,

could you please measure the current over a single motor wire during tests?

If the current in one of the tree motor wires isn´t more than 12A i try some changes.

stefan


#8

It appears this test is conducted without the ducts. Is that right?

I wonder if the large efficiency increase seen using the graupners would be as extreme if the duct was included. The deltas look like they are designed to run in a duct.

This is just baseless observation, from looking at the posted photos. Please let me know if I am talking out the wrong end =]


#9

Hi Colin:

Nice stand ¡

May I know how the testing basin looks like ?

Regards


#10

Did you ever post any of the test results you got from this stand? I don't see anything.


#11

http://openrov.com/profiles/blogs/preliminary-propeller-efficiency-testing


#12

Ah, thanks. Didn't see that info anywhere.