I am a bit confused though, after my query to the group on bearings a while back, I had the understanding that there was only one bearing required, and you set it up to support the top end of the shaft central in the tube.
Now, for experimentation, I might need two plates, and therefore two bearings to replicate the ICE setup, and to allow side loads from the belts. Also, the prop shaft end is a bit short to allow easy access, and is under the cockpit.
The final ideal for me would be one self aligning bearing, with enough of the shaft at the front side of the plate, to allow room for a pulley. I still have to juggle things around to mount the motors, which for now, although I still have to test them, will be old style automotive generators. I don't want to reinvent the wheel, but I do not like the way that boat ICE's are mounted, with no universal joint. It is more difficult to get bearings in line when there are more than 2 of them, and there is already the cutlass (cutless?) bearing at the bottom of the shaft near the prop. Anyway, up to me! Minor details. The less parts to go wrong, the better. I will look and see if the top end of the current shaft would be in good enough condition to use a solid coupling, to extend the shaft up to where access is better. Even with 2 bearings total, I don't see side loads on the cutlass bearing as an issue, because of the 'leverage' length of the shaft, and also the opposing pulling from having 2 motors. Could be wrong on that one though, bearing in mind most electric drives presumably have the solitary motor aligned with the shaft, and therefore no side loads are created.
As far as the power goes, mine is a longish and hollow lead ballasted keeled 26 footer, 6500 pounds, and the hull speed, I was told, should be around 6 knots. So I was figuring about the same as your numbers, that I would need a total of 6 HP or so. Now, the difference for me is that I would want to use an ICE as emergency long distance power, simply because a gas tank costs less than batteries, and I already have the gas tank. I would want it to charge the batteries at the same time, and preferably supply hot water also, after all, why not? So my combo would be maybe 2 or 3 HP electric, and maybe up to 10 HP ICE. But at least a 6 HP ICE. I am figuring maybe 2 to 5 HP consumed for charging. For emergency use, run both, remembering that sails are primary power. And that the ultimate plan is a windmill charger. With the right plate setup, as in allowing for more fiddling around, I could add more electric motors if needed.
My reality is different from my dreams though.
I already have a 25 HP outboard, I think that I have the power correct there, and I don't know if it has charging on it, I bought it a few months back, and stored it the same day. But if using an outboard, I would prefer it in a well, and set up to lift up when not in use.
So, in my case, the electric thrust will be a guesstimate of about 100 pounds, based on your figures.
Obviously, my thrust will be about the same as yours if I use the original shaft and prop. , and then feed both power sources to it somehow. 200 pounds is quite low really.
Another possibility for the final goal might be a small gas or diesel gennie, mounted outside the cabin, and a small directly driven AC motor to add to the DC ones.
During all this fiddling, if I can never have to start/use an ICE, then that would be great.
My own thinking is to forget the plastic, just use regular ferrous industrial bearings - I don't even think a spare would need to be carried, they are very rugged, and can run for many hours even once getting noisy and loose. Although speaking of electrical isolation, I might need my motors isolated electrically, as well, to allow circuit combinations for speed variations - but for now, I will just try stuff, and see what happens.
Thanks for the figures, especially the 200 pound one.
John, re the pic link, it would not work for me, I have sent you separate email.
Thanks,
John
Re: Re -Main mounting plate needs.
Posted by: "luv2bsailin" luv2bsailin@yahoo.com luv2bsailin
Date: Sun Jan 16, 2011 4:46 am ((PST))
Here's an example of a type of bearing that works:
http://www.mcmaster.com/#flange-mounted-ball-bearings/=am3si1
There's no rating listed for thrust loads, but they can handle a
significant amount due to their grooved races. You would normally use
two of them to hold the shaft rigid and parallel to the motor shaft.
I forgot to mention thrust loads in my previous post. I don't think
you mentioned what kind of boat you've got, but a typical 25-30 ft.
displacement boat at hull speed will top out at a maybe few hundred
pounds. For example my Albin 25 takes a little over 200lb to push at
6.3kt. She'll do that pulling 5.28KW (7hp) from the batteries. As for
lubrication, a good sealed bearing as above will last for years
without any maintenance, but they do have zerks so you can give them
a squirt once in a while if it makes you feel better.
I've used food-grade bearings with plastic flanges, but for their
electrical isolation properties rather than corrosion resistance. If
you go that route, look carefully at the rpm and load ratings. Some
are pretty low. Not sure why, but perhaps it's due to the plastic
getting soft as they warm up.
Cheers,
Jim McMillan
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