[PSUBS-MAILIST] Brushless thruster test 2

Sat Feb 6 21:18:25 EST 2016

Great stuff Cliff! Do you know how the Kipawa compares to the standard MK
prop without the nozzle?

Best,

Alec

On Sat, Feb 6, 2016 at 5:29 PM, Cliff Redus via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Thanks Alan.  To reciprocate, attached are our initial test last week.
> The variable pitch prop is not out of the machine shop yet so main goal was
> to evaluate test rig with Minn Kota MKP-33 prop ( two blade, 4" pitch, 11"
> diameter)  that matches with the MK-101 lower unit. We are going to use the
> MK-101 and MKP-33 prop as the control for our new prop.  We also tested a
> Kipawa 80/01 (3 bladed prop, 5"pitch, 11" diameter).  The Kipawa prop will
> fit in my ducted nozzle so measured the bollard thrust with and without the
> nozzle.  We are still analyzing the data but some initial results.  Bollard
> thrust of the MKP-33 of 67 lbs is low relative to the 101 lb rated thrust.
> A quick look on web shows that manufacture thrust rating are 30-40% higher
> than a bollard thrust test.  Test rig is fully calibrated.  With the Kipawa
> prop, the bollard thrust is about 10% higher when using the nozzle than
> without.  BTW, this is an open water prop and is not designed to be used
> with this nozzle. A ducted nozzle prop needs to have more of a square tip
> to keep water from moving from the high pressure side of the blade to the
> low pressure side.   Like you my initial reaction is that we could be
> having the same boundary or end effect because of the proximity to the pool
> wall.  We did prove the system worked. Not sure why both rpm and current
> are dropping over time when the measured battery voltage is constant?
>  Next week, we are going to repeat the test with the thruster oriented
> along the long axis of the pool and see how the thrust compare.
>
> On your test, a couple of questions:
> 1) How long did run each test point?
> 2) On the first test sequence, 3800W and 81 lbs bollard thrust for input
> HP of over 5.  This seems like quite a bit of power to develop this amount
> of thrust. Do attribute most of this to this boundary effect or
> recirculation affect?
> 3) On each of these test points, your are stepping through higher and
> higher power to the thruster.  For any one of these points, how repeatable
> is thrust?
> 4) Thrust is proportional to density * n^2*Dia^4.  I think to be able to
> make sense of data from different props with different diameters and
> pitches, you need an angular velocity or speed measurement.  Can you
> measure the motor speed with this type of motor.  For our test we use a
> proximity switch and count pulses to measure speed.
> 5) Are you planning on testing any ducted props?
>
> Cliff
>
>
> On Sat, Feb 6, 2016 at 2:41 PM, Alan James via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>>
>>
>> ------------------------------
>> *From:* Alan James <alanlindsayjames at yahoo.com>
>> *To:* Personal Submersibles General Discussion <seaquestor at gmail.com>
>> *Sent:* Saturday, February 6, 2016 11:18 PM
>> *Subject:* Brushless thruster test 2
>>
>> This is mainly for Cliff's benefit, as he is going to be doing some
>> thrust testing.
>> Tested 2 different props out. One being the same as the first test, the
>> yamaha 7&1/4" x 4" pitch
>> & the second was a Vetus 6 blade 108 mm ( 4")  for 25kg bow thruster. No
>> stats on the pitch but it
>> looks about 180mm or 7".
>> My watts measurement is done off the battery whereas other people quote
>> their output at the motor.
>> I am comparing my motors performance to statistics from commercial
>> thruster brands but not sure
>> where they are measuring there power from.
>> Had some wacky results from the yamaha prop again. It was the more
>> powerful & I think I am getting what
>> is called a "short circuit" effect through having the motor about 28" out
>> from the pool edge & in about 3ft
>> of water. Short circuit is where an edi is formed & the water moves from
>> the output to the input in a semi
>> circle around the thruster. This is caused by water bouncing off a pool
>> wall, or in my case the inlet flow
>> bouncing off the wall or pool bottom.
>> I was running off a 40V 5 amp  Lipo battery & the voltage dropped a bit
>> during the tests.
>> Ist test was 10 kg (22 lb ) at 500 W
>> 2nd 11 kg at 1000 W & 39 V
>> 3rd 15 kg at a huge 3,400 W
>> 4th 37 kg at 3,800 W & 85 amps.
>> As you can see some inconsistent results there, and some missing figures
>> like amp draw, as I needed
>> an assistant to read the figures.
>> Next is the Vetus prop.
>> 1st 10kg  547 W  39 V
>> 2nd 11 kg  634 W  11 amps  37.81 V
>> 3rd  15 kg  998 W  27 amps
>> 4th  20 kg  1700 W  39 V
>> 5th  24 kg  2500 W
>> It's amazing what a difference a prop makes.
>> In conclusion, I need to ditch this rig & buy a longer plank of wood to
>> do tests in the middle of the deep end.
>> I have a more sophisticated volt / amp meter that stores results & plots
>> on a computer & I need to employ that.
>> I need to buy a similar motor but a sensored version, as there was too
>> much cogging at low speed.
>> Sensoreless motors read the back emf produced by the motor to ascertain
>> the position of the rotors & can stop /start
>> & rotate backwards on low speed where there isn't enough back emf
>> produced.
>> I need to replace my motor controller with a sensored controller,
>> probably Kelly & buy a bigger life po4 battery.
>>    I also want to wire the motor to a WYE configuration which will give
>> me .73 less rpm. So will gear it down a bit.
>> Some good news is I have found people on boating forums adapting these RC
>> brushless motors & an absolute
>> guru who uses these motors for traction vehicles & has posted pages of
>> information on them.
>> Cheers Alan
>>
>>
>>
>>
>>
>>
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>>
>
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