Flying Nemo from North Queensland Australia


#21

Same story this weekend. I lost the shaft and the propeller after 1 hour of testing but not lost the duct. After disassembly, all the tightenings are ok and glued. Same result as @rogjalon : a complete rebuild of the motor pod but I need to find solution.
Have you had this type of problem? What solutions?


#22

Maybe it would help to reverse the thread direction so the water pressure would tighten the duct.


#23

I got shat failure as well… I thougt everything was lost when I heard the motor revving but I fallen off the nose of the board but no, luky me shaft and joint stayed together, no water in.
Plastic printed parts shoulg screw in very tight, with no play (they can’t work like a metal thread!), If they’re not, a little silicone as thread locker would work, like Hiorth said.
The solution, for me, is this type of shaft:


Not easy to realize, even on a lathe, because of the key slot…


#24

I plan to use the clamp style coupling this time. I don’t think the couplings with grub screws clamp well enough.
It would be great to have a motor that can easily dismantle for servicing. I just don’t have the skills to design it.


#25


I purchased the whole family of these… but I don’t trust too much that plastic coupler. It clamp very firmly though. I’ll try the one piece part with key slot.


#26

I have one of those clamping jaw couplings in my setup. Mine did always slide eventually. Especially on my custom shaft as it was not exactly 8mm. I just drilled through the coupler and shaft and pinned it. It’s a quick and dirty solution, but still removable. Just a little bit more work.


#27

…designing parts on cad software it’s not a problem, the huge task is to draw something doable first… and to find somebody kind enought to lathe or mill your pieces for free or for pizza&beer! With 3d prints you won’t go too far, if waterproof, thin and serviceable pod are your goals, using prototyping factory makes the purchase of a Lift efoil more convenient!!


#28

F7006910-01

I like the look of this type


#29

This looks better. There still one thing that doesn’t convince me, other than the bulkiness of the joint itself, which is the thrust force all on the gearbox axel. No matter how much you “pre-load” that against the thrust bearing, the thrust power will squeeze your gearbox. if no…the joint will slip on the planetary shaft. Thrust should be transmitted by keys, which are designed for the purpose.
My failed coupling was like that, only I used a grub screw as “key”, tightened down into the 12mm key slot of the gearbox shaft. It was sligtly free to slide in and out a mm, but grub screw got sliced as soon as…


#30

Ah sorry to hear. Did you use the first version of the duckt with the angled struts? I think that causes it to twist off at faster speeds. My 2nd duct version has straight struts and has a more efficient NACA0012 profile. It stayed on ok for me so far, I need to update my post because I think it still says untested. H


#31

These are pretty much useless for any precise rotation because you cannot clamp two shafts in such a way that they perfectly align. If they don’t align, they will bind and block the motor, or just create heat, damage the bearings, or make everything vibrate.


#32

We have used the same coupler (from roland)in v1 design for 9months now( maybe 30 times in the water) , still working fine. But you need to balance it! by grinding it down. Also use a very strong loctite:) also if your shafts is polished slight sanding wil help.


#33

If we are using two bearings on the output shaft this jaw coupler should be fine? I thought this coupler is designed to join two shafts which might be slightly mis-aligned?

I guess the speed might be an issue.

Edit: I see you were referring to the solid coupler sorry.


#34

Yes, I used the first version with angled struts. I should have added screws or secured it better. Thankyou for all your help


#35

Any flexible coupler is fine (if it is strong enough). I was refering to the fixed coupler posted above.


#36

Nice build … thanks for sharing … have been looking everywhere for suitable batteries … where do you get yours please … I’m residing in Australia … cheers … Tony


#37

Hi @tony I got the from Hobby King Sydney. Occasionally they have them on sale. Here’s the link
Cheers


#38

I got very lucky and bought 6 of these before they sold out:

There was also a sale on 6s packs. If it doesn’t let you ship a large quantity, order in two parts. There are legal restrictions on selling large batteries.