That's a good point I forgot about the reversing reduction gear. My Kansaki gear box has a reduction of 2.14 in forward and 2.5 in reverse. The motor will run either direction with the flick of a switch, so I essentially have a two-speed close-ratio transmission. Each gear might work better in certain circumstances but I'll probably just figure out which one gives the greatest efficiency with a particular prop and leave it at that.
Part of the appeal of a gear box like this is the built in thrust bearings. From what I can tell of those projects using pillow blocks all the thrust is taken by set screws, that's something I'm just not comfortable with from a durability and reliability stand point; though it doesn't seem to have been a problem for anyone so I'm probably just over thinking it.
Not having a bell housing won't be a deal killer, it just means you'll have some more fabrication work to do to get your motor in the right place for mounting. I'm sure if you post some pictures the group would have some recommendations.
David
I've got a PMDC 5KW Golden motor that I intend to match via a spider, to a Hurth ZF boat gearbox too. It also has the enefit of a forward or reverse gear if one becomes noisy or clutch slipping (manually change gearbox but use motor forward/reverse function.
Unlike you, I don't have a bell housing, so it will be a bit more work to combine the motor to the gearbox and two shaft drives. I'll be very interested in how you find your system.
I've used liquid teflon (Nulon) in gearboxes before but that's without clutches. So I'll stick to normal fluid.
Like you I think the slight losses will be made up for by designed thrust bearings and easier remounting to shaft.
All the best and keep us informed - interesting project> I just uploaded a couple of pictures of my MARS PMAC motor mated up to a Kanzaki transmission from the Yanmar 2QM removed from the boat. I cleaned up the transmission, painted it and used an aluminum plate to mount the motor to the bell housing in such a way that a spider coupler on the transmission input mates to the motor drive shaft.
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> I have a Kelly controller and controls on order. I'm planning on installing it in a case mounted on top of the back of the gear box, so the whole drive is in one more or less self contained unit.
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> My thinking in using the gearbox is it will be a very robust and reliable reduction gear and installation should be the same as any engine. I replaced the engine beds with similar but much shorter ones in the boat.
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> I do have a question about efficiency. There is some effort in turning the transmission. I've been inside this type of gear box and its pretty much just two shafts with gears, nothing to it. The efficiency of mechanical gearboxes should be very high, in the 90% and up range, comparable to belt reduction, but the initial effort in turning the output shaft makes me wonder. Is it just that once the gears get running they are very efficient? Is there a fly wheel effect going on?
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> I'll update with pictures of the controller installed and installation in the boat when the time comes.
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> David
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