My first try, a pair ofYoungsters jets, 4084 620 kv on 6s 4p 5000 nah
Did another test today, after moving the esc 20 inches away from motor, used 10 gauge for the phase wire extension that stayed nice and cool but the stock motor wires thin 12 14 gauge were 150deg in 10 minutes. To hot for me, might move the motor up shorten board another foot
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More not so good video,
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In way to run cooling tube next the motor wires to cool them ? Like you twist them around cooling water of the motor ?
Hi Alexadre, it was only the first 4 inches from the motor, small wire the 10 ga was next to aluminum water tube
Decided to move esc’s back to the motor jet box and add a foot or so more 8ga battery wire and test again. It’s a big board I’m trying to decide how far forward to put the batteries
Well anyway, thanks jetboy for the heads up on the bearings I will be watching them close. The rear bearing is exposed to the water
And thank you Jezza for the silicon nitride idea.
6x15 mm full ceramic 128.77 each and rated at 11,000 rpm.
Boca has some hybrid stainless steel races nitride balls for about 20 bucks I might try. Rated for high rpm
Sorry I haven’t responded sooner. Been busy doing covid 19 remodel work on my house. I get so busy normally that I never finish anything on my own place so I’ve been knocking out lots of projects for the last few weeks.
I have bad news for,you those 4084 motors won’t work I used one successfully on a board using the very small jet 4 that MHZ sells for model boats, it worked great and still does actually as I had a feather weight friend put with me last week and he rode a 10’ board with that motor and jet on 6s and it worked fine but slow.
However when I tried them on the youngster set up both myself and Mark fried the windings on those motors, so on 8 and 10 s the torque that those jets were producing pulled big amps and the first time just popped the 100 amp breakers I was using then when I swapped the 100amp ones out for 200amp breakers the breakers did not pop but the motors ran like they were clogging after stripping them down the insulation on the three phase wires was melted and they were shorting against the case and each other I insulated them with much thicker insulation but when I ran them the kept cogging and I figured the coating on the windings had failed and they were not usable any more .
I told mark about this and he admitted that he had had the same problem. I was a bit ticked off because he never told me that until I told him about my experience. .
I was kinda screwed at that point because the jets were in a pelican box and it would not accept the SSS 50104 motors cause they were too long so I had to buy 2 “Leopard 5692 motors I think they were they fit and are 520 kv so plenty of torque but after I got then I saw that they were rated for continuous amp draw of 88 amps and I think that is not a realistic number for a jet board my tests have shown peaks in the 180 amp range on take off and steady amp draws of 136 but it’s been difficult to test more than a few times static tests need two people and they don’t give up you the real peak number since there is no rider adding their weight to the load. And so far I have not found a power meter that goes over 150 amps that is also,small enough to fit into the battery box. The last one I tried was a 150 amp power meter and I melted a wire off last time I tried it so all that told me was that my peak was well over 150 amps right lol
Anyway what appears to be a bullet proof motor is any of the 56 series SSS ones they go as low as 420 kv in the 56104 size and if you have the room the 56114 is 360 kv so you can run 12s flat out with that motor and the rpm will still be in the acceptable range that the jets like to,run at .The higher KV Leopard motors don’t have a j
Higher amp rating but also will spin a lot faster if you use 10 or 12 s so not sure I’d use Leopard again .
I have not even tried to run the youngster set up since the last fail. Mark has not responded to my questions about the plastic melting so I haven’t wasted any more time or money on that set up.I think with my weight on the board it’s doomed to fail particularly if as I suspect the plastic around the bearing race has already melted on one drive . I was hoping that he would give me a new drive that way I could take the one that keeps failing out replace it with a new unit and then cut the old one in half to see what is going on inside that would have helped both of us I think but no response from him so I’m done with youngster jet pumps I’ll stick with MHZ
Hope this helps you a bit. Math should be sharing all this date with his customers particularly when he knows a particular motor doesn’t work
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I’m going to wait until my next test to respond , but thank you
I did just purchase two more jets from mark
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Ok, another static test today tied to the dock, all was good until I got close to 100 amp +draw that was full throttle the motor wires, first few inches became to hot to hold again test fail. Reading the specs on the motor says max amps 105.
So thanks jetboy, I wonder if I used a 10 cell the amps would drop enough?. Ordered a pair of SSS 56104’s 500 kv I want to make this work
Plan on finishing my 10s 10p battery trying it on this setup and then the new motors
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An inflatable Chinese answer to Mark’s design. Brand name: Kedean. Allows for standing / lying down riding with two joysticks with a wrist dead man switch.
For simplicity and extra room to store the electronics components, I had this U-shaped inflatable board design in mind to insert a bigger waterproof case receiving a hydrofoil. Wondering how much they would sell the inflatable board only.
just buying the board would be interesting. Unfortunately, I have not found one yet.
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With a Jet board the bottom shape and rails become really important in how it handles and turns. While these inflatable ones are be great for a little ride-about, they handle terribly when you actually want to start turning properly.
I can imagine that. Fortunately, our hydrofoils turn airborne and such a board with a flat bottom would really interest many people looking for compactness but reluctant to buy the slot-typed inflatable board:
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My dad and I just finished building an electric surfboard with the jets from the Brit (Mark).
We still needs to fine tuning the ESC’s
- Jets used (2) are from Mark. See YOUNGSTERS JETS on YT.
- Board is a cut down Vision Softlite – 8’0 softtop surfboard
- Motors used are Surpass hobby 56102 600KV Brushless Motor
- ESC’s are from Flier. Model: ESC 240 16S
- Remote is a Maytech V2 (Fully Waterproof Remote Control).
- Two waterproof 12 / 24 volt 200 amp circuit breakers.
- LiPo’s are 6S Zippy 4500 mAh (40C). I’m using 2 banks of 3 lipos in parallel.
The jets / motors are (should be) doing about 13440 RPM at WOT (600*22.4)
(That is when running free…)
The most difficult part of the build by far was getting the battery and motor cover watertight.
We were using two really nice marine hatches, but they were leaking so much, and it was impossible to stop this )-:
Now we are using a cut down pelican case as motor cover (nice to keep the towels in too), and a PVC drainage lid as battery cover. The pelican case will be changed to the PVC drainage lid system later this summer.
I know… The PVC lid looks horrible, but is working great and has about a 250mm diameter!
PVC lid looks like this: https://media.wildkamp.nl/productimages/default/870px/15078172.jpg
We have cut the pipe part away to just below the screw threads, and glued it on top of a plexiglass 8mm plate. This plate is glued directly onto the foam, and put the skin of the board above it. It’s absolutely 100% water tight.
My dad and I already started on building a new version of the board with integrated hatches.
This new board will be made from wood. The weight of the new wooden board itself will be around 7 KG, and have a partly removable deck for access to the two jets and battery’s.
Video of my 2nd run on the board. https://www.youtube.com/watch?v=81WGsLw6IYQ
Top speed is 30 km/h (@ 22.4 volt (6S)), but will be a little bit more when the ESC’s are tuned.
LiPo’s feel a little bit warm after running the board till end of session.
ESC’s and motors are nice and cool. The wires (LiPos > ESC’s) do feel warm too, but nothing alarming.
There is about 1 meter of 2 negative and 2 positive wires (AWG8) between the Lipo’s and ESC’s
The next time out we are going to test some cap banks just before the ESC’s. This should cool things down a bit.
a picture from before changing the hatches. (I have more pictures, but can only post 1 as new subscriber to this forum)
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Hello Kian, very well done, I can relate to the hatch problem. The board looks like a great choice. How thick is it? What do you think your run time will be? Any details, pictures would be great, even V2.
I think that the hatch works perfect when dry starting, but as soon as you need to do a water start, it will start leaking. We have tried about everything to get it to stop leaking. We even cut 2 hatches in half and glued them together to have to leavers… No luck. Not even with a new silicon seal!
The board is from where I have the jet box till past the battery compartment 90 mm thick.
The aluminum box we got made is 100 mm thick. So it was standing 10 mm above the board.
If we would have known that the hatches were as useless as an ashtray on a motor bike we could have got the box made flush with the board, and use a perspex plate as cover.
Here is a picture of the PVC drainage hatch. It does also show the thickness of the board…
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Running time with me is about 13 minutes at WOT.
I’m using 6 “old” Zippy Compact: 6S 4500mah 40C.
3 parallel per motor.
Some more pictures
When V2 is done (will take some time) we will for sure mention it here.
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