By logic and reasoning and conventional wisdom it is better to have a reduction gear. Well, let's just see about that. I can always reinstall the 2:1 gearbox if I am not seeing increased RPM/KW.
I had to buy a new piece of shaft... the stub shaft I used just to position the thrust bearing is actually a couple inches short of reaching the coupling. So to get it immediately I ordered online from Grainger, for pickup. They have two warehouses here in New Orleans. My usual supplier of such things, McMaster Carr, is cheaper but they have no outlet here locally. Anyway, the shaft turned out to be maybe .002 oversize and these couplings and the thrust bearing don't like them one bit. I hand sanded to get the stub shaft through the thrust bearing, not having any super duper cold stuff like liquid nitrogen handy, and not wanting to heat a bearing that cost me the better part of $100 with housing, or get too medieval on it with a hammer. After much wrestling and banging of knuckles, after the 3rd attempt I got the assembly bolted up in the mount and the shaft doesn't fit into the u joint. Also the alignment is a good bit off because the angle irons supporting the thrust plate are too close together by maybe 1/8" for the motor to fit between them without cumbrance. Before, the reduction gearbox had the motor mounted on it in a position above the axis of the prop shaft and above the angle irons so it didnt have to fit between them. I will just turn the motor over and sand the shaft enough to fit the ujoint coupling, then remove the assembly yet another time and do a little cutting on the angle iron, just enough so that it doesn't touch the motor and influence the final alignment. But first I have to hook up the controller. The motor now occupies the space where once I had the controller, so I need to make up some new cables for either the phase wires, or DC supply, or both, to have enough length. Right now it is raining and I am stuck here below, so all work is on hold for now. I had hoped to be able to dock test the motor this morning. The motor does spin more easily by hand with just the thrust bearing and no gearbox of course, which is to be expected. Prop is 14 x 10 3 blade, which is a bit large but the low pitch might just be the thing that makes this work out okay.
I could just use one of my 5kw motors, which will easily fit with no cutting, but I think I would feel better with the heat dissapation capability of the big motor. And I still need to turn down that new piece of shaft anyhow.
Honestly I am not sure at all that there will be any significant heating, because of the low-ish prop pitch. I can crunch numbers and do modeling and massage spreadsheets, and trust them to be right when they say it is a go or a no go. Or I can just do the thing and see for myself.
But due to weather, this will be a beer and movie day, I think.
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