Electric 300sx build!

Quinc

Buy a Superjet
Location
California
can of graphite. Hopefully reduce friction with the chain and reduce some heat and noise.

81vdlNSmZ8L._SL1500_.jpg
 

SUPERJET-113

GASKETS FOR CHAMP BRAP!
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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

Buy a Superjet
Location
California
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
 
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

Buy a Superjet
Location
California
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​


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

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.


Figure 2.14 Speed Variation Versus the Number of Sprocket Teeth
 

Quinc

Buy a Superjet
Location
California
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?! =)
 
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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

Buy a Superjet
Location
California
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. :eek:
rpms.PNG
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

 
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