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Archive for the ‘jet pump’ Category

Jan
05

Better 30mm Jet Pump

30mm pump, 4 Blade Impeller, jet pump, scratch build Comments Off on Better 30mm Jet Pump

Did a trial run in the surf at Purau bay, no video but ran pretty well primes much better on the waves then the NQD unit.

The pump can dissipate way more power than I currently have in it, in fact my old 4500kv Cyclone motor with water cooling died a flaming death on 3C having ran well on a 2C for a while:) Should have known better I measured 68A on a 53A motor in the bath, I tried to keep out of the top of the throttle but obviously not enough.

I have 2 options a 600W 2900kv on a 2 or 3C, and a 910W 1100kv which can run a on 6C

I also have a gaggle of alternate props I will be turning down to fit the pump, the current pitch is 31mm I have a 22mm which should be interesting.

The tip clearance is around 0.8 mm there is a wear ring not shown here which fills in 0.5mm of the 0.8mm.

Looks like the 2 blade polycarbonate prop is the winner thrust wise finaly its ready for her second time, the first time (her maiden) is never that special :)

Please see Original Design The 4 blade impeller shown is not as efficient as the 2 blade modified prop alternate, until I curved the blades more and got 38 Amps draw with the 2900kv 600 Watt heli motor. The 2 blade was drawing 59 Amps on the 600 Watt heli.

The stator is somewhat similar to a Graupner units shown below making jet boat impeller

Left: Very pitchy 2 blabe Graupner Impeller

Right: One of my other models with a home made 4 blade impeller, works well

Cutaway of Graupner pump

My impeller very simple will be intersting to see how it performs, I have a 2 blade impeller also

Steering mechinism

Cooling system

Dec
27

Yellow Boat 2 Upgrades

coroflute, coroplast, Corriboard, jet pump, scratch build, servos, water cooling, water jet, yellow boat Comments Off on Yellow Boat 2 Upgrades

New Yellow Boat 3 Jet pump

Yellow Boat Maiden

First Yellow Boat failures ESC's died in both boats

very high ambient today over 31°C

, at the lake, burned out FET's after all the surfing at Sumner I'm surprised after all the reliable running, still we live and learn air cooled in a closed space like the hull was a bit too good to be true.

Fitted 50 Amp water cooled ESC, which is a marinized aero ESC to Henry's boat, as the HK 50A boat ESC's don't seem that great, lots of motor noise and heating, regardless of settings it seems.

Changes:

Replaced faulty servo with metal gear type

New improvedWater cooled ESC

Water cooling for motor

Water cooling pump

Thrust vectoring modification

Thrust vectoring in action

Thrust vectoring trim tab

Archimedes s crew type pump and cooling system for motor.

Flexible coupling for thrust vectoring servo push rod.

ESC installed aft as the boat trims very bows down note the water cooling, water is pumped and scooped (when moving) from under the boat, and flows through the motor then the ESC and out of the transom so you can see that it is working.

Cooling pump switch, always turn on before launch, it takes a while to prime usually after a bit of forward motion you should see a flow from the outlet. Forward motion will also generate flow but the pump will stop over heating when you stop so you can stop and start as much as you like.

Radio is mounted to avoid water. Both servos are Turnigy 180 degree metal gear type

New Parts

H-KING 50A Fixed Wing Brushless Speed Controller

Turnigy TGY-R5180MG 180 Degree Metal Gear Analog Servo

ESC

Amp rating: 50A
Burst Rate (15sec): 55ABEC Current: 2A, 5V (Linear)

Voltage: (2-4 cell Lipo)

I added two Aluminium cooling tubes boned to its heat sink

Weight: 12g

Size: 23.2mmx12.0mmx21.6mm
Torque: 2.0kg.cm (6.0v)
Speed: 0.12sec/60deg (4.8v) - 0.10 sec/60deg (6.0v)
Voltage: 4.8-6.0vType: Analog MicroGear Train: Metal
Ball Bearing: NoLead Length: 180mm
Plug: JR/Futaba

The water pump showing the motor out on an old servo left, and the intake scoop, you can see the end of the screw

The pump used an ancient Greek idea the Archimedes' screw

This is the screw I used its for GIB board

Principal of operation

Dec
22

Yellow Boat 3 Power Test Scratch Built hull, water jet and cooling pump made from Coroplast and junk

100A ESC, 500 watt motor, heli motor, jet pump, scratch build, scratch built jet, yellow boat Comments Off on Yellow Boat 3 Power Test Scratch Built hull, water jet and cooling pump made from Coroplast and junk

Yellow Boat 3 Power Tests with Turnigy 500W H450 2100kv

Scratch Built hull, water jet and cooling pump made from Coroplast and junk Yellow Boat 3 Power Test

Boat build log here

Jet pump build here

Cooling pump testing here

Test results
Dynamic losees
29.5 Watts
2.3 Amps

Peak power
532 Watts
47.5 Amps on a 3C

Impeller
30 X 30 two blade

Quite pleased with test results pretty good match motor to impeller it seems. Tried a 30 X 35R impeller which drew too much current the 30 X 30 seems just about optimal.

Home brew cooling small centrifugal pump made from junk, with a scoop on the hull. The pump is mounted directly above the scoop and primes its self with the standard trim at rest.

I also found that if I re-introduce the out let from the cooling circuit into the jet ramp, there is a tendency for the water to be sucked through by the main drive when the throttle is up thus improving cooling flow at high loads, a win win. I wanted a pump because taking a tap from the pressure side of the jet outlet uses some thrust and is only available at speed, with low throttle or stopped there is no flow and this I thought would cause over heating when stopping after a long high power burst, which I do when surfing at Sumner.

The tiny pump on test

The cooling circuit. I found that if I re-introduce the out let from the cooling circuit into the jet ramp it helps with coolant flow.

Turnigy 450 H2218 Brushless outrunner 2100KV with water cooling added, big bore pipes just because that the brass I had in stock.

Spec.

Model: 2218

Turns: 6

Cells: 2~4S

Kv: 2100rpm/V

No load Current: 1.9A/10V

Max power: 500W

Weight: 67g

Shaft diameter: 3.17mm

Dimensions: 27.2 x 36.5mm

Recomended ESC: 2~4S/50A

Hobbyking SS Series 90-100A ESC with a water cooling plate added its an overrated ESC so should do the job easy. Will need a BEC I have a 5A in stock also.

Spec.

Weight: 85g

Size: 70x50x13mm

Cells: 2-7S Li Po

Max Current: 90A [over 70A use 6S only]

Burst : 100A

No BEC

Generally the larger jet is much more effective at lower throttle in the bath, this will be better for trolling in the swamp. On the lake speed remains to be seen, but I can't believe it will be disappointing given the flow and power levels I'm getting on test. I suppose its possible the nozzel velocity is lower than the NQD jet, that said I have read that if the ratio of nozzel velocity is greater then 6:1 then all will be well with the world.

Given the area increase from 3.14159 cm² to 4.818 cm² which is an area increase of 1.533 at the same nozzel velocity the mass flow would increase by 1.533 times.

So every second the following would seem to add up

So as we know the NQD 20 mm jet pushed around 950 grams on Yellow Boat 1, the nozzel velocity must be around 3.023 Meters / Second with no losses? This is where I get into the realm of I don't understand :O fluid dynamic being so complex, although non compressible fluids like water are less complex mathematically than the calculations for air for example

Just for fun with an exhaust velocity of 22.5 Meters per Second that's around 80 kph

Every second a bar of water from the 20 mm jet has a volume of 7069 cm³ So the mass flow would be 7.069 Liters per second so 7.069 Kgs sec

Every second a bar of water from the 30 mm jet has a volume of 10841 cm³ So the mass flow would be 10.841 Liters per second so 10.841 Kgs sec

Definition from Wikipedia

One watt is the rate at which work is done when an object's velocity is held constant at one meter per second against constant opposing force of one newton.

So transpose the above to make kg the subject

With no losses I recon 500 Watts could move 22.22 Kgs to 22.5 Meters a second in one second. Sounds like a lot of water 22.2 Liters Umm???

However the impeller is probably only 60% efficient this is true in air a turbine can only be 59.8 % efficient its called the Betts limit I think.

So 22.2 X 0.6 = 13.33 umm 13 Liters a second sounds like a lot ?

One way to test this is to measure the amount of water the pump moves over a fixed period of time, simple then to workout all the things we want to know.

Nov
29

Scratch built 30 mm Jet Pump Area Ratio 2.8:1

jet pump, NQD 20mm Jet Drives, scratch built jet, water jet Comments Off on Scratch built 30 mm Jet Pump Area Ratio 2.8:1

Jet Pump Detail

Development continues on the bigger jet for Yellow Boat 3 short tank test shows peak 27 amps didn't measure the thrust but it was lots, nearly emptied one end of the bath. Should be interesting to run it on the water will be building yellow boat 3 soon

Turnigy 450 H2218 Brushless outrunner 2100KV

This motor is specifically designed for the 450 helicopter range and a perfect fit for any of our HK450 helicopters.

Model: 2218
Turns: 6
Cells: 2~4S
Kv: 2100rpm/V
No load Current: 1.9A/10V
Max power: 500W
Weight: 67g
Shaft diameter: 3.17mm
Dimensions: 27.2 x 36.5mm
Recomended ESC: 2~4S/50A

Moulded my own Jet 30 mm Reduction ratio 2.8:1 maintained the same are reduction ratio as the NQD jet and turned down a 35 mm prop for an impeller.

Its metal loaded car filler and one layer of woven roving glass fiber. have a bearing mounted in a brass stator which I will locate with. the wear ring will be part of the nozzel housing, so it will be a duct and pump design like some jet skis

KMB Products / Shop jet drives 28-mm-SWEEPER Jet

The 28-mm-JET is currently the smallest of the SWEEPER JET SERIES. He achieved at a speed of 13,000 - kp 4-20000 rev / min has a thrust of 2.5. Measurements of power and road tests of the Johnson-700-neodymium motor was at 12 - 14 cells thanks to its power output a favorite of light boats with jet propulsion. For boats with double / triple-jet propulsion is usually the 12-volt version or the Johnson-800 with 14 - 20 cells cheaper. As a rough guide to determine the size and the number of jets should correspond to the weight of the thrust of the boat.

As an example: 6 kg boat = 2 x 28-mm-JET or 1 x 33-mm-JET. The operating speeds should be between 15,000 - below 20,000 U / min.

The power consumption is approximately equal to that of a 42 to 45 mm propeller pitch 1.5.

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