Another Jet Propulsion Try


#43

Hey Max,
my old torqeedo build (not a foil) was a side project in the company I worked before, so I do not have access to it any more.

The actual built is running now.
The past two days I did some testing on the Wörthersee, unfortunately without the proper battery pack… (old,worn out RC battery Packs with 12S1P 5000mah)
It really has plenty of power and the jet works pretty well, but due to the battery not for a long time…
I did not manage to get on the foil yet but for me it looks pretty good at the moment.

you can see a small preview on my Instagram page:

Cheers!


#44

What prevented you getting up on the foil?


#45

one reason i did not try to get up on the foil was that i did not mounted a thrust pad at the time of the test ride, so the surface of the board was to slippery to get up on it, the second reason was that the cooling pump was not working properly at the moment so i decided to use full throttle just for a few seconds…

but it was just the first test, i will continue testing when i have a new battery…


#46

Hi Boris,
This is a very nice build. I just re-read the complete thread, I had missed part of it. I really like your plug system. The simplicity of direct jet drives is so nice. Once I give up on the belt experiments I am thinking about reusing that SSS 360kv for jet experiments. What motor are you using? Did you measure your currents? Are you planning to share your CAD? Hope you get your batteries soon and will share more tests with us.
Grüße aus LA an den wunderschönen Wörthersee,
Merten


#47

Don’t give up. It looks promising.


#49

Hi, can you share your STL files for the printed pieces?


#50

Hello Boris,
at the same place I tested my jetdrive yesterday :grin::grin:


#51

That’s looking good! Can’t wait to see it in the boat!


#52

Hey Thorsten, your jet drive looks great!
What components do you use for it (ESC, Motor, Impeller)


#53

I will not… but the progress is very slow at the moment because i ran out of money and time for this project.


#54

Hello Boris,

I used a Leopard 5692 motor with 600KV and a flydragon 150A esc from flycolor. Running on 12s


#55

Hi Merten, i always try to focus on a simple design… so the jet drive is the best option for me, first i used the SSS 56114/500KV, i had about 150-160A when I hit full throttle. To much for a durable setup.Take care, the lower the KV of the motor the lower the max current… Currently I am trying to use a outrunner with a lot more tourque, and power…
I would share my CAD designs but they are not in a good shape because i already changed many things and I did not updated all the models


#56

150A is not bad no ? For what speed ?


#57

I did not measure it but I would say without coming out of the water, it was about 35-40kmh


#58

Been doing a lot of riding and testing and what I found is peak amps can be super high and kill your wiring/esc/connectors if not managed properly with quality parts or current limiting. 150A is a ton of juice and things wont last long with most ESC’s at that level.

Here are my findings:
There i a point where you get maximum thrust to current from your motor. Once you motor torque has maxed out and you continue to pull the trigger for more throttle the thrust stays the same or drops while the amps go from 150A to 191A. I have tested a ton of jet propulsion setups now and see this in EVERY test we do.

191A in our example gives less thrust as motor is flooded with to much current, heat, magnetic field and thrust fades, and at the same time you drain the life out of your battery SUPER fast.

How to reduce or better yet eliminate this? if your ESC has throttle settings you can set mad throttle to 75% and it just may happen to be near perfect. We did this with a few setups. Meaning a full throttle we would only draw 150A and get max thrust without the huge excess current for longer periods of time.

The best solution we found now if you ESC can do this we use our own custom VESC, and you can limit your current. Now we have completely eliminated excess current permanently so we have less heat, less strain on electrical system, and a dramatically longer batter life.

Our system peaks around 150A for me to get up riding 115kg (255 lbs), and then im cruising at 45A, or fast riding at 20+mph at 80A.

Hope this helps with tuning?


#59

Have you thought about a mean to focus the spray cone, sign of a better efficiency ?


#60

That is about the bottom line what we found last year too, With impeller drive we could not get below 1,8KW with 100kg at optimum cruising speed. Then moved on with prop and the 1KW we need now is pretty harmless for batteries&electronics without fragile water cooling:wink:


#61

But yet there are some that seem to think that a jet is more efficient than a prop and gear (obviously not aimed at you) :joy::rofl::joy::rofl:


#62

Well it has advantages though, but at the moment the eficiency is a big argument;-)


#63

he was referring to the commonly spread statement, that any gearbox setup would be the most inefficient solution (compared to DD or jet)…
e.g. here and at many other places…