[PSUBS-MAILIST] Thruster Test

[hank pronk via Personal_Submersibles]

 Alan,How is the heat managing?Hank
    On Friday, December 7, 2018, 3:12:00 AM MST, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  
 
 Hi all,tested another 2 props today. Both 2 hp yamaha 3 bladed. One was aplastic 7&1/4 x 4, the other aluminium & similar but with rounded ends to the blades.They both worked much better than the Vetus prop I tried yesterday,the plastic prop being the better.By comparison the plastic yamaha prop had 60.62 lb. thrust from 1624 W while the Vetus had 45 lb. from 1694 W. Quite a difference; 26.79 Watts perpound of thrust as apposed to 37.66 for the Vetus. David, again it showed to be a lot more economical on power to run themotor slowly. At 11 lb of thrust it used 12.9 Watts per pound of thrust androse up to 26.79 Watts per pound of thrust at full power.So if the batteries are low, go slow. Cheers Alan

On 6/12/2018, at 7:34 AM, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:



Hi David,the extension ladder worked but was a bit of an effort pushing it outwith weight on it. I will grease it before the next prop test.As for thrust to watt ratio; I measured this at intervals from 18V to 44V.18.2V, 13.2W per lb. of thrust.26.8V, 19.5W per lb.33.6V, 24.4W per lb.38.4V, 29.9W per lb.44.6V, 37.6W per lb.So definitely a loss of economy as you open the throttle. The Vetus propis designed to work in a tunnel & I didn't have one on it. It will be interesting to see how the other props fare in this respect, & if these figures differ muchwhen I put a kort nozzle / prop guard on them.Alan

On 6/12/2018, at 3:58 AM, David Colombo via Personal_Submersibles <personal_submersibles at psubs.org> wrote:


Hi Alan, l never thought of using a ladder as a test rig. Was the thrust to watt ratio the same base at different speeds?David
On Wed, Dec 5, 2018, 2:03 AM Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Just did the first test on my latest brushless thruster version.
I started with a Vetus bow thruster which is normally housed in a tunnel, but
to simplify things I am testing several different propellors without nozzles first.
I have a 10mm prop shaft & the various off the shelf props need either drilling
out or sleeves made to fit them.
   I was getting 38.5 lb. thrust from 1,152 Watts & 45 lb. off 1,694 Watts, which
is comparable with some commercial thrusters but not with others. Some 
manufacturers are quoting thrust per Watt figures I find hard to believe.
Will see how the other props work.
   Testing came to an end when the automatic pool cleaner (which I had just
moved to the end of the pool) came down & knocked my prop off while I was 
jotting down notes. First swim of the summer finding the shaft pin. The prop
was held in place more or less by the force of the prop thrust & a tight fit.
Picture below is from left to right; load cell mounted on the vertical stationary
side of black test jig, motor controller, 48V rectifier with oil compensator on
top, grey load cel display, servo tester to control speed & laptop with Vesc Tool
program displaying data. 
The oil compensator is just for the testing, a much smaller & different system
will be on the sub.
Alan



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