Nooo, did the propulsion unit survive?
It looks fine. But all 3 prop blades broke off. Surprised me because nothing touched them, just the sudden stop of waterflow must have caused that. Hope the gear wasn’t impacted, haven’t tested yet.
That might be one of the perks with a 3d printed prop, the prop might break before the gearbox. We are looking into building an inserts in the prop that will break before the gearbox so the gearbox survives if there is something (jellyfish, wood or trash) entering the prop). It’s a mechanical safety in a way.
It’s a feature we have seen in our Mercury 40hp outboard motor, it’s like a small plastic cup that disconnects the prop shaft if the prop hits a rock. It saves the gearbox, and you can still drive slowly.
ohhh, Merten, you can repair that easily!
In my opinion prop and elements near the gearbox should be built on very solid, strong materials, carbon fiber, aluminium. I think 3d printer is good for initiate but not for progression. I want to see you flying over the rocks again!!
yesterday i hit with the sand reef i only had a little scratch on my front wing, I´m really happy with my carbon fiber parts.
how about the magnetic coupling as the stress relief?
Yes that would work, have looked into building a custome one, but seems like it needs to be pretty long to transfer sufficient amount of torque at Ø60mm, but we will try to design one to test either way.
What do you think how much torque you need? It is not very easy to find a very thin and non conductive but also stress resistant material for the boundary between the wet and the dry area.
We would like to design the system for around 12Nm torque. Nominal torque rating for the PLE 5:1 gearbox is around 14Nm max torque 24Nm and emergency stop torque 36Nm, when the system operates at 12Nm, we have a safety factor of 3 against emergency stop torque, which is nice to prevent gearbox failure.
A plastic material such as Nylon SLS should have sufficient strength as a boundary material.
Are people epoxy’ing the lip seals and thrust/ceramic bearings into the mounts?
I believe the lip seals are just held in there with the marine lubricant. The ceramic bearing is friction fit (mine is super tight). And the thrust bearing is just seated in the indent on the thrust bearing printed part.
Did you end up using a headless m8 bolt for the prop shaft? Or how did you get the threads onto the tip?
Also- any tips for drilling the hardened steel rods?
I’ve got the 8mm shaft as per the list of materials list. I believe you manually use a tap and die set to cut the thread onto the shaft. Also worried about drilling the shaft for the 3mm pins. Will use a dremel to make a notch for the coupler.
Yeah that sounds complicated and annoying.
I’m going to try and avoid as much as that as I can, especially since I don’t have a drill press… instead… I’ll attach an 8mm to 8mm coupler on the end of the prop shaft, use the two grub screws on the coupler closest to the motor to hold the coupler into the shaft. Then redesign the prop to fit the coupler perfectly into the prop body, add 2 holes through the prop body, 180 degrees from each other to slot m3 bolts through the prop body, into the threads for the grub screws further away from the motor and secured to notches made in the prop shaft itself.
Yes, tapped it. My shaft was not super hard… wait that sounds wrong… anyways, no problem tapping or drilling. Need to find harder pins, mine bend after a while. Or M4.
I believe that most outboard motor props have that rubber insert that is pressed into them called a hub. When the prop hits an object in the water it allows the shaft to continue to spin but the prop can only spin slowly. I believe that is the part that you are referring to @Hiorth. Since many are printing props I’m not sure that finding the right sized rubber “hub” and then pressing it tightly into the prop will work.
@pacificmeister and @morgansteven1970, Im new here but have been lurking on youtube for a while. Thank you pacificmeister for all of your help/documentation and making your designs open source! I have extensive time in inboard ski boats and the topic of propellers comes up on those forums often. Back in the 80s a lot of nautiques were direct drive with no gear reduction. In 1989 that switched and they put a 2:1 gear reduction on them. What is interesting is that one of the top aftermarket prop manufacturers (Acme) recommends 3 blade props for direct drive and 4 blade props for boats with gear reductions. The forum this was discussed at length on and the reasons why is no longer online but its something that I haven’t forgotten as I was switching props on a non-gear reduction direct drive boat and everyone was adamant about going 3 blade. I wonder if the same would be true on the efoils? I have an interest in trying direct drive without the gear reduction to help save on cost and to keep things simple. Do you think the latest drawings for Rev 2 would work without a neugart gear reduction? I like the stabilizing bearing aspect. I also think the talk on balancing the prop is valid. Really nice cnc props still come with scuff marks on them from balancing even though they should be close to balanced with a cmc machine.
Buy a 100€ drillpress! It makes life much easier.
Hey pacificmesiter, on the baseplate of your liquidforce mast that attaches to the board, did you have to cut a hole in the top to route the phase cables through? And what about the endcap of the mast itself? From images that I’ve seen of baseplates, theyre all completely solid and the mast endcap is mostly solid as well.
the 2017+ LF masts are covered on top and on bottom with a thin 1/2" layer of foam and then a 1/4" epoxy layer. Both can be drilled and removed VERY easily.