Hey Waterfox. Just following up from the other thread with a few questions on your build. Hope you get a chance to reply/confirm a few things:
cooling ESC: I see the motor assembly has a duct to direct water up a hose inside the mast. Is this what you ended up successfully using in the end? Or did you find a passive solution that worked? Couldn’t tell if the earlier (before routing things inside the mast) also had that solution. I’m currently looking into seeing if speccing a different ESC could lead to a more passive option as well. Lots to read/learn there myself at the moment.
related to running things in the mast, did you also end up running cables through a slingshot mast, or was your second mast another brand/solution? Just curious whether you found enough room in there for everything.
cooling gearbox: Do you think this is worth exploring to extend the life of it? Or has that not turned out to be a significant issue. I was thinking I could mill an insert that fits around the gearbox that could sink heat to exterior tube. Not sure if that would dissipate a significant amount though.
I’m assuming the ol’ duct tape method ended up the simplest cable management solution after exiting the side of the mast below the board? I’m trying to think of something removable so I can use the board for kite foiling as well
would love to see a view of your electronics box and details about what you felt worked best there (if you care to share that). Putting a few different ideas together myself here.
Thanks Waterfox and everyone here for putting me on this path.
Cooling ESC: a 1/8in tube sits inside that intake in the nose cone and runs up the mast with the wires and into the control box. I used a little peristaltic pump to keep water moving through it. My calcs indicated water would flow up the mast with dynamic pressure alone, but I wanted cooling even while the board was stopped. It seems to work well.
Yes, I use a 30in slingshot mast and run 3X 12AWG cables + a 1/8" tube
I made all my parts out of aluminum because I thought it would be worth cooling the gearbox. The neugart PLE 40 is rated for 5000rpm IIRC and I am driving it around 22000 RPM. The gearhead on mine sits inside the aluminum “gearbox mount” with thermal paste. The mount is then thermal pasted to the main tube. I also added some thermal paste to my motor.
I’ve now 3D printed a little fairing that covers the cables running out of the mast and the cables and water tube sit in a plastic cable gland that runs to the control box.
Control box: This is just a pelican case that houses the seaking ESC, peristaltic pump and 2X 22V, 16Ah LiPOs.
Thanks Waterfox. Those numbers with the gearbox are what I recall as well. And yes, the gearbox mount you already have is exactly what I was thinking. I’m hoping to 3D print as much of this as possible (unfortunately my little workshop is stuck in storage containers for a while longer and I need to keep things as simple as possible). In fact, I was even thinking of experimenting printing that part with thermally conductive material. There’s some stuff out there that is about 15 W/m-K, and maybe some other untested additives that would be useful as well. How much of this do you feel is printable vs needing to be machined (other than the tube)?
The problem with this design for printing is that the screws thread into the aluminum for the outside. If this was 3D printed, you would be threading into plastic. You could use heat press inserts, but it may be worth making some changes or possibly picking another design to print. I would also print the nose cone + front cap as a single piece. I’m not sure how an O-ring would seal against 3D printing, but it sounds like most other people here are fine with it.
I’ve finished my build here today. Though I went a different way (direct drive, etc.). Still inspired by you since I’m trying to use a similar board. I’m struggling with power though and need to do a very awkward weight shift at full throttle just to plane-ish. I’m curious where you ended up with the prop. Did you use the one at your link or end up elsewhere like you were thinking? Seems like you should be running similar rpms to me with your 16s/500kv/5:1 as I am at 16s/100kv/direct. So I was thinking of scaling up you prop a bit and trying that instead of my large ducted PM design. Next step would be to lose weight and go for more volume
As my board is coming on to plane, I have to shift my weight forward to keep the nose down.
I’m using the 4 blade prop here:
It has been working well but I’m wondering if I can go to 3 blades to save power. I’ve been meaning to print and test a 3 blade prop, but haven’t been on the water much.
I’m at 12S, 500kV, 8:1. So around 2775 RPM. It looks like you’re a little faster at ~5900RPM. You might want to change the pitch a little. I can send you the solidworks file it you like.
My impression is that a duct will add a lot of drag
Thanks @waterfox. Boy, do I ever have to push nose down too Took a battery pack to get that weird move down. Now I’m at the point where I’m at full throttle but barely planing. It doesn’t feel like I’m at a loss of torque (at least by my feel), but likely speed at this point. So I’m going to try a higher pitch 3 blade prop to see how that goes with trading things off in that direction. Feels like I’m so close.
If you don’t mind sharing a solidworks or .step file, that’d be great. Then I can give your design a little scaling and try that out.
The github link has the step files for the propellers. But the SW would be more useful if you are changing the pitch at all. If you PM me your email, I’ll mail you the files.
I’m running the torqeedo 1008 gear which is a neugart 8:1 designed for torqeedo with built in shaft. I use the 750kv 5684 motor (no reason to go bigger as I don’t even max it). I run a very high pitch customised boat prop that I 3D printed. The unit has way more torque and acceleration than any of the direct drives. As I said, I’d shift to an 800kv though just for a bit of extra speed.
Manufoil is currently doing a version with the 1000kv 56104 to get really fast.
If you run 800KV the gearbox rpm will be way above what neugart rate it at… I think the 56104 700KV would be a slightly safer option, it is still going to turn pretty fast! Would be interesting to see how long Manufoils gearbox will last on 1000KV!
Yeah the Neugart is rated for like 5500RPM. I drive mine at 12S / 44.4V, 500kV = 22200RPM. I’ve got it heat sinked as much as possible through metal into the water. So far so good but I wouldn’t expect it to last forever.
yes good point. 18000rpm is the max mechanical rpm it can take with great cooling according to Neugarts website, but 5000rpm with no cooling. I’m in the same situation as you. Under load it doesn’t get over 20k rpm for me. But the theoretical >35k rpm that an 800KV motor would produce would break it very quickly I think. Good stress testing though!
This is no point to worry about. In the past I have built small turboprop units with up to 6KW poweroutput. The second stage Turbine did run at speed up to 60.000 rpm. This was input speed for the PLE 40 1:8. The gearbox did last without any problem. Only difference was lubrication. It was lubricated by a mixture of Jet A1 fuel and 5% oil, constant flow. (like a 2 stroke engine).
So as long as you have a good grease inside your gearbox and the gearbox is anyhow cooled by contact to the outer tube, it will last very long.
