I was reading in different topics on this forum about kill switches / cutting power-disconnecting batteries (and getting zapped).
While the Hall switch looks a simple solution to stop the motor, I was thinking the following solution for a switch for disconnecting the batteries
(seems the huge current is an issue):
I ordered this high current fuse (credits to someone else on this forum / cannot find it back immediately); I did however order
the following rubber waterproof covers which I will glue into the cover of the battery box allowing me to use the fuse as a switch to
cut off the power. Maybe a simple idea to combine a switch and a fuse.
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I had a similar idea but someone mentioned that these “high current” circuit breakers actually cannot handle the current they are rated for, due to the way they are designed. There is some youtube videos of them failing.
I still haven’t tested mine yet. There are lots of people who have mentioned them on there parts list so I assume some are using them. Would be good to get feedback from anyone whether they are using this type of ‘waterproof’ circuit breaker / fuse successfully?
I am using a fuse like this in my battery box. Just for over current protection, not as a switch. So far it didn’t pop on me. I assume it won’t last very long if you use it as switch and close it without pre-charging the esc capacitors.
Thanks, indeed. The waterproof cover would allow me at least to do an emergency disconnect-of-battery without the need to touch anything with wet hands. Closing this fuse is something I could do only after disconnecting the (XT90) connectors on the batteries, e.g. when safely ashore. So not really to be used as a rocker switch but rather as an emergency OFF. Btw, the waterproof cover would not allow me to close the fuse, only to push the button (which I hope is the one to open the fuse - I did not receive it yet)
You precharge the capacitors with a 500 ohm 5-10 watt resistor in parallel with the disconnect switch but with a separate disconnect.
hi, my water pump froze last week here in ireland, i had to rebuild the pump and change a few parts including the ceramic seal, the spring and central seal are on the water side of the pump, probably to keep lubrication between the ceramic face, it was interesting to see, its kind of changed my design of the final drive stage before the prop,
do you think it makes any difference?
having this side of the seal inside would make things a little easier to design
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Hi @keith75, I assume it uses a mechanical face seal? That’s what I got first and planned on using before I learned about the double lip seals most of us use now. Lip seals are simple to install but face seals seem to be more durable, less friction and better sealing. Am not a seal expert but I heard face seals work mostly well with clean liquids and not with abrasive liquids which can damage the hard sealing surfaces. We have a chance for sand, mud or other fine debris in the water and it might impact seal life.
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We use a lot of face seals in the oil industry. And drilling mud is a nasty thing some more than others, it can contain some solids and sometimes be very abrasive.
However, for our uses, lip seal are much easier to put in place.
Face seals needs to be spring loaded, have an oring on the shaft to seal with the rotating part and another one to seal between the housing and the stationary part. Also, they work if the housing is filled with oil and is pressure compensated. That might just be way to high-tech for us 
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yea, true, good point, there is a risk of gritty dirt that would destroy the ceramic seal, i bought one 16mm internal dimension, but a low friction option sounds ideal, ill think about it, maybe the seal to be spring side out, with a fine stainless gauze with an o’ring on the prop shaft in front to keep out grit,
The vanes supporting the duct look to be twisted in the wrong direction. They appear to rotate the water in the same direction the prop is spinning. If you think about the limiting case (water spinning at the same rate as the prop) you would get no thrust at all. If the vanes were twisted in the other direction, they would straighten the flow of water exiting the duct, and may give better thrust at higher board speeds (because of the prop’s fixed angle of attack).
If I am wrong about this, please let me know why.
@pacificmeister
I’ve been studying your Fusion 360 designs & I have a question about what provides the counter torsion against the rotation of the the engine + gear box mount ?
As the engine is basically flush against the aluminium pipe (+ heat paste) and the other end of the tube has the 2 O rings on the seal mount, does this mean that friction & the 3 wire mounts take the rotational force at the front?
I wondered whether there would be 2 or 4 of bolts running through the rear mast clamp into the front of the motor.
Or am I missing something else?
The motor-gearbox mount sits pretty tight in the tube with the 2 o-rings. The thrust pushes into the tube but it’s a good idea to lock rotation. In my first version I did it with a couple small short set screws perpendicular through the the tube into the mount, water side of the o-rings. In a later version I just used tape, worked too. My fit was pretty tight. The wires should not take any force and I have no motor-mount-bolts on the mast clamp side.
What are your thoughts on battery pack size and your current runtime with your 2x 22,000mAh?
Would you prefer more run time like 30,000 or 44,000mAh or would you rather swap battery packs to keep overall board lighter? Thanks in advance
Me personally I’d rather have a not too heavy setup and swap more often. Am happy with my batteries, their weight and runtime right now, they last maybe 30-45min.
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2x Tattu 22000mAh 6S 25C Lipo Batteries in series
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Hi everybody,
Somebody could give me the characteristics of the threat of the sealmont ? I would like to build this in aluminium and this must be compatible with the duct. Thanks
Is 25C the strict minimum ? Or would something like 15C be enough ? The reason behind my question is that now graphene batteries at 8000mAh 6S 15C cost 68 euros… Meaning that 24000 mAh would cost 204 euros, that is less than half price compared to the Tattus. Considering that lipos batteries have to be thrown away 3 times quicker than graphene batteries… That would put Tattu’s price down by 6 times.
Graphene batteries have larger dimensions though, if I am not mistaking.
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How many amps are most people pulling? I’d imagine it would be a lot lower when you’re actually foiling. A lot of batteries have a peak discharge that is higher than the regular discharge which could be used to get foiling.
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