How to get a good impeller (for jet propulsion)


#1

Hello,
I have been doing research and development for increasing the efficiency of impellers (and propellers) for many years. Today I know very much about the hydrodynamics of the impellers. That’s why I can design a impeller for every jet propulsion.

For e-foil, however, it is not possible to obtain a highly efficient impeller because it is not produced anywhere.

The quality impeller must be made of metal. Good aluminum is sufficient. The plastic filament used for 3D printers is therefore totally inappropriate. The water pressure would bend the blades very easily, which reduces efficiency.

The impeller can be designed in several performance types

  • for beginners (material is enough carbon)
  • for speed
  • for pull (acceleration - when the rider has a big weight)
  • for races

For e-foil is the best jet propulsion

  • it does not need an expensive gearbox (it’s better to spend money on a good impeller)
  • uses the battery with the highest possible efficiency
  • e-foil reaches the highest possible speed
  • impeller can be produced on a CNC milling cutter very easily and economically (not large machining waste)

This topic is to make it easy for a company to start producing impellers in several performance types and at a reasonable price. One company is able to cover the need for all e-foils around the world.


#2

I agree with you as well and why I have focused on nailing down a super durable and affordable design.

I posted on another thread a new 3D printed impeller out of aluminum which is cool WNT: Jet Propulsion?


#3

Hello WNT, we need your help in impeller design. Can you send us your email?


#4

Hi,

Wondering if there is a viable impeller for Efoil yet? I want to go direct drive.
thanks!


#5

Has anyone seen this one?


#6

A brief UP for this two and half month post that looks/looked very promising.
@WNT: what has been the impact of this post for you ? Is it MHZ who answered you first, 4 weeks after your call ? Have you been in touch with one or a few individuals ?

I just wanted to come back on @Kyle’s (amazing ?) link.
the MHZ watercraft Hydrofoil Set | Impeller | Nozzle | Stator | Bearing for €415.00 shipped to Europe, 346€ shipped outside Europe.

The MHZ-watercraft equation is:
SSS 56104/1000 recommended In-runner motor + 25V battery + 200-300A ESC = 4KW with 20-24Kg (200-240N) expected thrust
The equation is unseen so far for a 64mm (2.52") diam. impeller with rather high KV

  • 1000KV motor @25V = 25.000 rpm direct drive since impeller
  • Battery: 25V means less electrical risk, less cells therefore more capacity in Ah for a given volume (18650 cell footprint), 3.6V per cell (Li-Pol or Li-Io)
    MHZ%2064mm%20Hfoil%20impeller
    What do you think about that ? The long awaited solution ?

The SSS 56104 exists in the following KV’s 360, 420, 500, 650, 790, 1000, 1400, …
Technical data for SSS 56104 1000KV Inrunner motor:
Upm: 1000KV (upm/Volt) Max. 50000 upm
Poles: 6 Rotor armiert
Max A: 280A
No load current: 3,3A
Volt: 50V
Watt: 14000W
Torque: 2,75Nm
Max Lipo: 8-12S

I am missing a few points.
1 - I was thinking that the impeller solution was rather efficient… Low rpm, low power. big thrust.
Here, they use nearly the most powerfull KV motor of its range at half of its possibilities (25.000 rpm versus 50.000 max rpm) and a direct drive. Any explanation ?
@Vefoil : what KV, voltage and rpm are you using for your jet solution ?
2 - In the MHZ solution, a 69mm stator (outside diameter) assembled to a 59mm Outer Ø of the aluminium pipe. I don’t think that’s a flush assembly …a 64 mm Outer Ø motor + alu pipe with 2mm wall thickness would have been better.


#7

the way i see things (and i might be wrong ):

1- 25k rpm is high rpm, higher will get caviation issue and it is already pretty high for an impeller
lower power, well 4000w is not low for me
big thrust: no 24kg for me is just the beginning for fun

with a 56014 1000kv @280, at half rpm you will probably get 280A if needed, that 's a lot !

a 56014 550kv with 12s make more sense to me, 150A can be handle with a good 300A esc

if you want to use 18650 , it’s better to increase voltage , you will be limited with amp, 0.15mm nickel can take only 5A, for 150A peak setup, you will need 30 // 0.15 nickel strip , you can double them , so that’s already a nice pack 15*12 cells and we are above most 3C cells

start and fly up take some power and motor can Amp peaks above the max rating (tp motor for sure, scorpion what i have read, SSS ?)


#8

http://transistor-man.com/submersible_thruster_testing.html
He is getting ~60kg @3,5kW…so yours is ~6kg/kW this one is ~16kg/kW
So I guess your efficiency is pretty bad…

Also you will have a lot of heat problems at cabels, connectors, Fets and motor if you use anything close to 200A continuous.

If your thruster needs 25kRPM i would rather go for SSS500KV and drive it with 50V. (like @Alexandre said)


#9

i think that why diy impeller surfboard keep blowing good esc…

@Giga : any gain for the fets to active “free wheeling” on the esc


#10

Seems that VeFoil has 2 favourite motors Home Made Flume
especially (2017-12-17 a "long " time ago :wink:)

VeFoil 250Kv, 100A, 3.1Nm Torque (63% more torque than SSS 500kv, 55% more than SSS 360kv)

The following post is worth reading too imho http://www.efoil.builders/t/how-i-will-make-it-true-some-points-to-think-about/858
It sets up the principles found when using a Jet propulsion with a Sup Board. 23 posts in a day then … nothing
@SUP-MIKE data for his jet sup board:

79mm impeller, 394kv, tp5670, 10s, 80a, 25kg is static thrust, 15km/h
impeller pitch is 58mm and gap to nozzle is 0,5mm - pitch ratio = low = 58/79 = 0.73

This being said, the way to go is surely the one opened by @Winging_it and his post:


He improved a spreadshhet called “Hydrofoil Medium AR.xls” …Very informative (imperial units only) metric version in progress since… early March


#11

thank you for the link, but i am working on this project for the past 2 years now, i think i have read over and over everything i could found on the net, i have done my impeller bodyboard already, right now i am learning to foil and i happy but using my propeller setup , i realise that i made the right decision not to choose impeller design because of my weight

supmike made something very nice but 15km/h 3300W with 79mm impeller?

what i am trying to say, think it’s harder to design a good impeller and at some point for “heavy poeple” it may be not the way to go

Virus did a very nice job with his impeller setup, but i don’t know how fast it can go (?)

i used this “setup” for my foil (but smaller size motor), i saw the video in 2016, i ask him what gearbox is used, for the propeller the uk company burned in 2017… that’s one of the fastest diy board i have seen so far


#12

You are correct. This setup on a foil would make the fastest efoil! It’s a pity the prop factory had the fire last year! There must be others making small cleaver props though. You may be able to get a design from them and print one…


#13

We tested that setup and didnt find it provided the thrust or speed we needed, but our motor was too low of KV at only 310kv. We will be testing it again shortly with with 550kv motor and 12S power.

We found our own impeller design worked much better than MHZ at this time. We have higher pitch, 3 blades, and different nozzle and 69mm OD is getting a little big/drag for the nozzle.

Keep in mind you need to use higher KV than you think. When batteries are run the volts drop so you may think your pulling 49-50V at full power but in reality with Multi-Star batteries at least you really only pulling like 44-46 which means your impeller is much slower than you think/want.


#14

I do not follow this idea because of different points:
A “all in one pod” with motor,esc and batteries inside gets to heavy and can not be controlled by 2.4ghz or bluetooth.
I’m convinced that a jet will not work as efficient as a prop but a gear also waste power and low kv inrunner motor is also not usable - at long last prop with gear to have a multipurpose device to use it as esurf and efoil - the esurf doesn’t run with lower power when lifted - instead full power all the time to have fun.


#15

Something interesting for jet drive systems:


#16

A bit of “archeology”.
The search for a small and powerful jetdrive started some 25 years ago with the RC boats.
Here is Peter Hawkins 2002 Mini Jetsprint project (Jet boat racing). Seems he lives in New Zealand. The 2nd half of this page is sooo interesting :

  • rotor design, stator design,
  • 4 axis CNC insight
  • 2.2 to 3 kw motor (Zenoa 23cc 3-4HP) so our power range
  • practical test method for @VeFoil: fixed angle (40° say), the more focused and longer water jet the better.

Enjoy : http://www.modeljetboat.com/jetboat/jetboat.htm
Hey Peter, we just need one of your rotor and stator/Nozzle for testing. Would you have a pair to send us ?:grin:


Pocket NC 5 axis mill
#17

Yes that is a great builder and great read, saw that last year as well but always interesting to review again having more knowledge, thank you!