hi~

A pacifist!

The belt couldn’t withstand high RPM.

Small chain also could not withstand high RPM and high torque.

I think it’s better to think about it in a gear way.

# Timing Belt Reduction

**sungmok_jung**#69

**borntosurf222**#70

Hi Chris

Did you make the impeller and housing and if yes would you consider selling them if enough of us pitch in to make it more cost effective?

thanjks

Peter

**borntosurf222**#71

Hi Max

I found an ALine motor at 50kv with an 80mm diameter and 7000 watts power. He has one that can be water cooled but the Kv is higher.

**borntosurf222**#73

Hi Max

Here is a summary of the email I sent Alien…

links have both motors I was interested in.

I asked if he is giving max power or sustained constant power and I have to email him again…anything under 100mm seems to peak out at about 6kw

I need a 6 kilowatt motor with 50Kv for about 40-48 volts for a motorized surfboard with 105 litres boyancy like the water wolf one

This was my first choice for the motor: https://alienpowersystem.com/shop/brushless-motors/c80100-outrunner-brushless-motor-50kv-6000w/

but is that 6000 watts peak or continuous and lastly do you have an ESC you recommend for either motor as well as a charger based on a 16000 amp hour LiPo battery?

And do any of the ESC come with water cooling?

Below is a motor that was water cooled and I was curious if it was very similar to the one above but could it be made as a 50Kv or 80 Kv wound motor?

**borntosurf222**#74

Hi again Max

To be honest I joined the forum to motorize my oold windsurfer after an old work injury turned into frozen shoulder…grrrrrrrrrrrrrr lol

I strongly agree with Pacificmeister that a gear reduction based on the number of failures will be an issue but the 100 mm BLDC motors will need to out of the water and in the board.

I figured out the waterwolf I am so keen on is suffering from an extra forty pounds of drag just from the frontal area of the motor.

This is about 2/3 of the 30 Kg everyone seems to agree is needed to get up on plane…

IE: 30 x 2.2=66 pounds minus ~40 pounds

Listed below is the source…(FYI I am not this smart :P) so dont be fooled

Lastly for my case I feel I need to decide on my desired top speed then pick a propeller with the right pitch and then redue the total area in a way proportional the differential in loads (a 1000 pound boat to a two hundred pound human) so about a factor of ??? where is our propeller expert when we need him…

Here is the most relevant:

**Problem:** Calculate the drag force due to air resistance on a 3" diameter rough sphere moving through the air at 90 miles per hour, with an air temperature of 50oF and air pressure of 14.7 psi.

**Solution:** The density of air at the specified conditions can be calculated using the ideal gas law: ρ = (MW)(P/RT) = (29)(14.7/([345.23(50 + 459.67)] = 0.002423 slugs/ft3. (See the article: Use the ideal gas law to find the Density of Air at Different Pressures and Temperatures for more details.)

The velocity needs to be converted to ft/sec: V = (90 mi/hr)(5280 ft/mi)/(3600 sec/hr) = 132 ft/sec.

The frontal area of the sphere is: A = ΠD2/4 = Π(3/12)2/4 = 0.04906 ft2.

The value of the drag coefficient, CD, from the table above is 0.4

Finally, substitute values into the drag force equation: FD = CD(1/2)ρV2A = (0.4)(1/2)(0.002423)(1322)(0.04906) = **0.414 lb**

**millesth**#75

I’ve contacted Bruno from APS before about the Power rating of his motors.

Motor rating is for Peak Current only. For exemple, he said that, for the 4000W Powerglider version, the constant power is “only” 2500W".

**PowerGlider**#77

for the 4000W Powerglider version, the constant power is “only” 2500W".

These values are for air cooling. I stressed this motor with 80A in D-current mode with low RPM for several minutes, fully submerged, with “optimized” throughput of water. No reason to fear that its overheating.

Do not make the coating too thick.