Electric 300sx build!

[SUPERJET-113]

I'm sure you have the engine(well "motor" now in electrical terms lol) compartment sealed up very well. Do you get any water in there, and is that motor water resistant? Just curious!

Such a cool project with your Son, have fun figuring this all out with him!

 

[Quinc]

I'm sure you have the engine(well "motor" now in electrical terms lol) compartment sealed up very well. Do you get any water in there, and is that motor water resistant? Just curious!

Such a cool project with your Son, have fun figuring this all out with him!

I believe so! we stripped the ski and fiberglassed all the openings and I used a seal on the hull and on the hood. Only water at the end of the day was from me taking off the hood and splashing water on the chain. The motor is rated for ip67, and the controller is potted. I am more worried about ruining the battery and bms.

My personal goal is to get up on plane even if that means holding onto a rope behind a boat and then completing the worlds longest submarine trick. lol

 

[te4250]

Usually with an electric motor it is constant torque from 0 rpm until base speed, which is where max power occurs since power is just the product of torque and rotational speed. After that you can weaken the magnetic field in the motor to achieve higher rpm, torque drops at this point but power remains constant. I would assume to a point spinning the pump slower would be more efficient, so propping so that you hit the max speed you can hit for the given max power at the base speed is probably what you want. However it would seem erring on the side of too shallow of a prop wouldn’t give up much since you can always over speed with field weakening to get to your top speed somewhere in the constant power region, with the only downside being some extra losses due to spinning the pump faster but that’s just a guess. Going with too steep of a prop you will hit max speed before you hit max power, resulting in both lower top speed since you never operate at peak power output and slower acceleration since you’re pulling a steeper prop with the same amount of torque

 

[Quinc]

Possibly the cause of the chain heat. Going to try changing from a 10T to a 12T driveline sprocket. *Huge pain in the arse to drill/grind through a hardened sprocket..

2.2.1 Chordal Action

The Complete Guide to Chain: Chordal Action

chain-guide.com

2.2.1 Chordal Action​

You will find that the position in which the chain and the sprockets engage fluctuates, and the chain vibrates along with this fluctuation. Even with the same chain, if you increase the number of teeth in the sprockets (change to larger diameter), vibration will be reduced. Decrease the number of teeth in the sprockets and vibration will increase.


This is because there is a pitch length in chains, and they can only bend at the pitch point. In Figure 2.13, the height of engagement (the radius from the center of the sprocket) differs when the chain engages in a tangent position and when it engages in a chord.

Figure 2.13 The Height of Engagement


Therefore, even when the sprockets rotate at the same speed, the chain speed is not steady according to a ratio of the sprocket radius (with chordal action). Chordal action is based on the number of teeth in the sprockets:


Ratio of speed change = (Vmax − Vmin) / Vmax = 1 − cos (180°/N)


Figure 2.14 shows the result. In addition to the number of teeth, if the shaft center distance is a common multiple of the chain pitch, chordal action is small. On the other hand, if shaft center distance is a multiple of chain pitch + 0.5 pitch, chordal action increases. Manufacturing and alignment errors can also impact chordal action.


In a flat-belt power transmission machine, if the thickness and bending elasticity of the belt are regular, there is no chordal action. But in toothed-belt systems, chordal action occurs by circle and chord, the same as chains. Generally this effect is less than 0.6 percent, but when combined with the deflection of the pulley center and errors of belt pitch or pulley pitch, it can amount to 2 to 3 percent.

 

[Quinc]

Worked with the ElectroBrapp guys yesterday and got the controller settings dialed in. 6500 rpms, instant power, (in the video it had soft start) and will hit the motors full power at 33ft lb/s of torque. So far the motor sounds a hell of a lot better/quieter too.

Any guesses on top speed with a 75lb kid riding it? And will it get it my fat 230lb arse up out of the water?! =)

 

[Storbeck]

Something doesn't add up.

36 ft lbs at 6500 rpms would be 44hp, or about 33K Watts, which is way higher than the "14kW Burst" that they are advertising.

44hp should get you on plane easily, and haul ass with a small kid, that would be approaching stock 650 power levels.

 

[Quinc]

My bad its 33ish ft lbs.

If the motor has enough power to get up to the full 6500rpms and with the overdrive sprocket setup that would make for 9100 rpms at the impeller. Which should make for one hell of a speed run.

Motor Specs:

Brand: QS Motor, QSMOTOR

Motor Design: Single Axle


Magnet Height: 70mm, 40pcs, 5 pole pairs

Diameter of stator: 120mm

Rated Power: 2000W

Rated Voltage: 72V (as default)

Speed: 60KPH

No-load rpm: 2800rpm without flux weakening, 4400RPM with flux weakening.

Max Torque: approx 45.4N.m without Reduction ratio, approx 216.7N.m with 1:4.77 Reduction ratio

Reduction ratio: 1:4.77 (as default)

Max Efficiency: 88%

Continuous Battery Current: Pending (72V)

Peak Battery Current: 60A (72V)

Suggest Peak Phase Current: 250A

https://www.electroandcompany.com/product-page/qsmotor-qs120-428-sprocket-drive-type-1

 

[Quinc]

Top speed run! And I was able to stand up on her! For a second.. lol

Next video/ride will be without chains and sprockets and direct with coupler.

 

[fx1mark]

Here's the cooling setup on a rc boat. I wonder if there is a way you could use the water outlet on the pump to cool the driveline off.

 

[Quinc]

Making progress!
Thing is very quiet now. Just barely a slight hum if you are close enough to hear it. And still no issues with motor over heating. Also got closer to getting my fat arse up on plan. Going to try swapping the skat 16 to a 15 next and see how she does.

 

[plaidward]

How much time are you getting out of that single battery?

 

[Quinc]

How much time are you getting out of that single battery?

Haven't tried with the new setup, but in the last video with the speed runs and me trying to ride it, the kiddo got around 20-25 minutes. I also have another battery so I can swap them out pretty fast and put one on the charger (45-60min).

 

[orangefinger]

Absolutely great job !! This is where the future jet skis will be going . Amazing work !! And special props to your son.

Save yourself the Tesla angle, I worked in the factory for a year and you are better off doing your invention and R&D yourself....

Now next project and food for thoughts, need more torque ( freestyle ) simultaneous charging battery with little paddle wheel when you are
you are riding ....

Keep up the good work, this is a great thread. ! And thank you for sharing

 

[Quinc]

Absolutely great job !! This is where the future jet skis will be going . Amazing work !! And special props to your son.

Save yourself the Tesla angle, I worked in the factory for a year and you are better off doing your invention and R&D yourself....

Now next project and food for thoughts, need more torque ( freestyle ) simultaneous charging battery with little paddle wheel when you are
you are riding ....

Keep up the good work, this is a great thread. ! And thank you for sharing

I thought about adding a solar panel as a joke.

For freestyle the cost is just too damn high for batteries. This jetski I probably have 1100-1300$ into not counting the second battery. And my plan is to swap out the guts into a dirt bike for the kids in the winter. I am also learning that these 300/440 pumps are crap for bottom end.

Do you all think that a steeper pitch impeller would cativate less? It has a skat 16 in her now and I have a new pjs 17 on the shelf. Also any other tips that might help the pump?

 

[smokeysevin]

For cavitation, I think you have to reduce the suction pressure on the intake side by making it larger or flow better. At low speed you are probably creating too much vacuum due to the tq curve of the motor vs the stock motor. You could probably also go with a larger diameter pump and prop so it loads up more evenly rather than getting the snot spun off it right out of the hole.

Sean

 

[Quinc]

For cavitation, I think you have to reduce the suction pressure on the intake side by making it larger or flow better. At low speed you are probably creating too much vacuum due to the tq curve of the motor vs the stock motor. You could probably also go with a larger diameter pump and prop so it loads up more evenly rather than getting the snot spun off it right out of the hole.

Sean

Thinking more about this im contemplating stripping down my carbon bob and throwing the e-motor in it.. hmmm

 

[kevbo]

The pressure on the front side of the blades need to be as high as possible in order to make the most thrust. The only way to do this at low hull speed is with large inlets and low pitched impellers. Low pitch is necessary to create a boundary layer over the front of the blades. Getting water to stick to the blade makes a big improvement at low pressures. Freestyle boats need thrust at low speeds so using a larger pump is a much more efficient way to get there.

 

[bird]

I thought about adding a solar panel as a joke.

For freestyle the cost is just too damn high for batteries. This jetski I probably have 1100-1300$ into not counting the second battery. And my plan is to swap out the guts into a dirt bike for the kids in the winter. I am also learning that these 300/440 pumps are crap for bottom end.

Do you all think that a steeper pitch impeller would cativate less? It has a skat 16 in her now and I have a new pjs 17 on the shelf. Also any other tips that might help the pump?

Swap it into a 650sx hull

 

[Quinc]

Took her out for a ride on fully charged battery and put the motor/controller in full power setting. Only hit 18mph. Not sure if I should go up to a 17 or down to a 15 degree impeller to get rpms/speed up?

 

[Crab]

I was looking at this