Yes, that is correct. The shaft is usually only supported by the Cutless bearing and the reduction gear.
Radial load on the shaft at the gearwheel seems pretty small with toothed belts, certainly not enough to be problem for a 1" diameter shaft closely supported by a thrust bearing.
I tension the belt by moving the motor in slotted mounting holes, as you mentioned. There is much less tension on this belt than on a water pump or alternator.
I have really come to appreciate the simplicity, reliability, and efficiency of the entire installation.
-Tom
--- In electricboats@yahoogroups.com, "John Green" <v_2jgree@...> wrote:
>
> Tom, Thanks. From what you say, there is only one bearing in a regular boat shaft, and that is the cutless or cutlass bearing at the prop end?
> That would make more mechanical sense, as the ICE transmission would form the other bearing. And would make my UJ idea useless, of course.
> Funny how all the books I have read don't make it clear that there is no top (inside) bearing, if that is in fact the case - I hope it is, because if so it just saved a load of future hassle and expense.
> In such a case, of course one bearing at the inside end would be OK provided that the side loads from belt tension were not too high, if a belt was used.
> My two bearing idea is overthinking this whole thing, I assume?
> In my own case, a New Horizons 26 (that was put out of business by the Tartan 27!) I intend trying multiple smaller and cheaper electric motors (to eliminate the controllers and provide the ability to build up the system over time), so I will be able to equalise the side loads by having the motors mounted by slots for adjustment onto a single metal plate, and belts from each one to the shaft pulleys, or preferably one long pulley with teeth. Might be able to use standard automotive parts, maybe recycled cam drives.
>
>
> John
>
> 3b. Re: Tartan 27, setting up bearing
> Posted by: "Tom" boat_works@... boat_works
> Date: Wed Sep 29, 2010 9:21 pm ((PDT))
>
>
>
> Most boats will have self-aligning stuffing boxes (or shaft seals).
> Just remove the stuffing box and shim the shaft to be centered in the
> shaft log. In most boats the unsupported shaft is adequately stiff to
> allow you to accurately place the thrust bearing.
>
> This assumes that you have the boat out of the water.
>
> It's really not difficult. I've shimmed shafts that only had 3/32"
> clearance between the shaft and the log without any trouble.
>
> -Tom
>
> --
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