this 80100 is the one i will be printing out soon. ill let you know how it prints
do you have any pictures of your broken gearbox? And can you explain a little more what you think was the issue. I am pretty sure a lot of people might be interested to avoid it for theirs own build, including me. Thanks in advance.
2 Likes
Today I had to cut the motor pod in pieces to get gearbox out… I still have to open it but I’m afraid that to blame is the prop shaft pushing into the gearbox an not loading the thrust bearing. Will take pictures of it.
This prop is absolutely gorgeous, well done @MaB . Now I have the dilemna of either printing a larger duct than Pacificmeister’s (more drag), or scaling your prop down to fit PMs duct (less torque). That’s for a 500 KV SSS
I don’t know exactly which size of my prop you printed, but I remember to have one filed down a little to fit my duct… which should be wider than Pacificmeister one, apparently…
The problem could arise because I designed all the pod parts taking Pacificmeister as big inspiration but basically from zero, so you might have to modify my duct collar, probably…
After all this destruction…
It will reborn from its dust!! New joint and double bearing/seals is arriving!
3 Likes
Is that a new gearbox? Whats the brass piece on the gearbox output shaft?
A coupling joint with slot for the key. Taken from a small bow thruster for boat. I will reduce it a little in length and diameter and add the 8mm stainless steel shaft. This time I want a proper shaft, sliding on its key slot to force only against the thrust bearing.
Very frustrated now.
I rebuilt my pod, after first gearbox failure and motor stuck on the tube.
Then I managed to build a better joint and add also a second bush bearing (ceramic) inside of the pod, so now it’s prop, bearing, oilseal, oilseal, bearing, coupling, thrust bearing, gearbox.
The problem have been a difficult soldering on motor cable (last time I used acid for the enamel, now copper seems oxidized, solder don’t stick too well), the axel is quite long and not perfectly straight or balanced. Cables are bulky (soldering too big).
I assembled everything, silicone on the cables, grease…internal bearing won’t stay in, the cave is too wide… I added 4 small dots of silicone without degreasing the part, then I fit the tube end. Air won’t escape so I played in and out waiting for the pressure to purge. Oilseal behind bearing can’t be accessed.
Seatrial, damn fast and smooth!! Never gone above 2/³ throttle, board won’t stay wet, it lift itself with speed!!! I knew it, 4:1 and less pitch prop is better!! 3 minutes of joy than I slow down and stand up on board, push the gas but the board stall…what the heck! Something slipping…noooo! I had to get back closer to the beach slower and slower and then paddle, something spin free as soon as I accellerate a little.
Back home, totally mad. Try motor pod on a bath tube…nothing, it slip and the prop stops right there. I open the tube, 3 oring hold very firmly… then I see some water dripping from the tube… little amount but salt! The second bearing is out of its seat, useless. The water come in from oilseal because the shaft moves sideway. F…k!
Cut wires, pulled motor out…the cables were almost detached and solderings with melted or bruised shrink tube were ready to short circuit!!!
I’ve a new motor coming now, I will do soldering out of the. The other major problem is that Neugart did not hold the motor shaft, despite tightened very hard.
If possible I will have the bew shaft lathed a tenth thicker… if not, I will reutilize old rotor but should I put Loctite?
At the end of story: gearbox ok, shaft probably to be rebuilt in one single piece, new 236mm pitch 145mm diameter prop ok… still no foiling and summer holidays are next week only… Ask me if I’m happy now
2 Likes
The water Gods stopped you before cables short and before your whole investment explode, burn, and potentially injure you. Your calculations proved to be true and you experienced 3 mn of intense pleasure. You can be happy. 
Do you know the cause? Axial movement of the shaft forcing the bearing to pop out of is seat?
I guess it should be: prop, bearing, oilseal, (maybe some marine grease, put in by grease gun), oilseal, thrust bearing, coupling, gearbox. So the thrust bearing takes the load of the coupling and the gearbox shaft can move freely. Also some grease between the lips, so even they dont work 100% still it is water repellent and keeps the pot dry.
I understand completely , but you got 30s more riding than i did ! For the shaft and the gearbix , maybe you can try the same as gobbia setup for his coupler: washer 90 angle in shaft cut …
No, the shaft moves free and push against the thrust bearing. Grease between oilseals.
The bearing had a lose fit on its seat, 3d printed part with too much tolerance.
Like @philgib say…it would have ended worst!
Keyways are the only reliable way I found to connect a shaft. So if you can add them that is probably the most secure connection.
I had to use loctite on my 8mm CNC shafts and I clamped them so hard that the internal hex almost stripped. I learned after a few messed up cuts when one axis stopped moving. If I had to build a new CNC, I would only use keys.
1 Like
I agree, on propeller shaft I used a joint with key slot, to utilize the Neugart key.
But the probl now is between motor and Neugart, no key here just round shaft and collar.
On CNC key could be a problem because of mechanical play
Its the first time Ive heard of one of those neugart collars slipping. I will be running the same motor/ gearbox, so Im a bit worried now!
I was going to machine my motor shaft down to 8.05 mm. What size is yours slipping at?
Maybe when the bearing moved it caused an imbalanced shaft to send forces all the way back to the motor. Did it vibrate much when it failed?
Im glad to here your prop is kicking ass. You might need to put on some weight to control it. Like me!
My motor shaft is 8.0, the coupler motor to Neugart is made in two pieces, aluminum, very tight fit, so it should not bend or cause misalignment.
The fact that the propulsion became a little jerky and then worsen really fast when slowed down and tried to speed up again, make me think about the water infiltration…2 of the wires where “naked” and even if not in touch to each other, water could conduce.
Once tried in a bathtube, the motor was holding transmission only at very low speed and behaving exactly the same in water and in air, where resistance from prop is almost nothing. I spun prop by hand, it seemed connected to motor and free to move.
New motor should arrive tomorrow but I don’t trust that prop shaft anymore, I must have that reworked to be sure oilseal won’t leak.
I machined my motor shaft down yesterday, but I could not get the motor shaft to go in to the gearbox at 8.1mm. It ended up at 8.03-8.05mm. The motor shaft is very, very hard. Tough work! burnt through a couple of inserts!
I cleaned the motor cables with vinagre salt and then baking soda, as suggested by @Hiorth and despite not as shine as new, wires resulted good enought for soldering.
Measured motor shaft: 7.98, fit with no effort into the Neugart.
I did an “old school” metalshop trick, don’t know if it would work… take the metal powder from a grinder bench, using a dirt finger, stick some onto your shaft, then couple it tight. We used this to held drill press chuck shaft, I wish will add that extra hold I need.
Tested the motor pod in a big bucket, doesn’t slip, now the shaft is held by two bearings and the prop seems more stable and oilseals might work, but I feel the motor moving slightly, vibrating, at each turn of propeller. Very subtle movement but it indicates that the shaft is not ok at all. Next week I wish to redo it. I sealed the motor pod, maybe tomorrow morning, if the swell give up, I’ll do a test run!
1 Like
This morning I enjoyed a very fast, too fast, 40 minutes run, foiling stand up and foiling also on my knees (first time I managed that, fun!!). Neugart with 2 ceramic bearings and the thrust bearing felt incredibly smooth and silent… For more than half hour, then… I got water into the pod, again. But this time the motor jerked a little and at the end… it stopped, dead.
I disassembled the pod, 2 cables had cut sleeve near the pod, there was little water inside, gearbox was all greased and still ok.
Water comes from oilseals, for sure, due to the prop shaft not really straight.
But why the motor died like this? I cleaned it, little oxide on stator but nothing really, my fear now is for the ESC… I’ve not opened the esc box, anyway, current absorption have been really on the low side today, foiling at 27-35 and some fast run at less than 50A, never squeezed the gas! I don’t dare to check the ESC
1 Like