Chain drives are cheap but noisy and messy. If you figuring on playing around with reduction ratios a lot, their cheapness makes them attractive. Timing belts are a much better choice for a permanent installation IMO.
Since the batteries are often the limiting factor, I like to set the pulley ratio to limit the max continuous amps to a level that will keep them happy.
For 220AH 6V golf car batteries 100A or so is about right, for 110AH group 31 batteries, 50 to 60 amps seems reasonable. This is for conventional flooded lead-acid batteries, and I think it is fairly conservative.
This should get you pretty close to best efficiency as well since, generally speaking, the lighter you load it the more efficient it will be.
On the bearings, keep in mind the thrust load is only likely to be a few hundred pounds. Angular contact ball bearings work fine. If you get the "food grade" ones that are mounted in plastic housings together with a belt drive you can get electrical isolation between the prop shaft and the motor, which will help reduce corrosion and could provide safety benefits as well.
Cheers,
Jim
--- In electricboats@yahoogroups.com, "Andrew Gilchrist" <andrew@...> wrote:
>
> Maximise performance in terms of efficiency, power or economy?
>
>
>
> One good setup will enable you to change ratios so you can have the motor
> running at its peak efficiency current rpms at full throttle given the
> voltage you are applying.
>
> Another more economical would have it running out past the rpms at peak
> efficiency so that sort of power is only used under WOT acceleration or
> turns and lower current crusing at WOT - ie so any part throttle setting has
> the advantage of lower current draw but higher efficiency
>
> Another would see the motor loading a little more heavily than peak
> efficiency so the potential thrust is greater this is not as economical but
> can be very good.
>
>
>
> A practical ideal is probably a set of pulleys like a drill press or a motor
> cycle gearbox
>
>
>
> Electric motor performance is maximized at any given voltage by setting it
> to run WOT at the rpm/current (in practice the same point) at which the
> motor specs show it to be most efficient. From there you can go either way
> by say +or -5 percent to get an efficient setup. Most people are running
> very innefficient setups and not realising the potential of the system used
>
>
>
>
>
>
> Andrew Gilchrist
>
> www.fastelectrics.com
>
> 612 4982 5481
>
> Australia
>
> _____
>
> From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com]
> On Behalf Of RandyB
> Sent: Monday, 19 September 2011 12:55 PM
> To: electricboats@yahoogroups.com
> Subject: [Electric Boats] Re: reduction drives
>
>
>
>
>
> I got everything I needed pretty cheap at www.surpluscenter.com
>
> Your gear ratio depends a lot on your prop. I went with 1:2.7 and wish I had
> gone more.
>
> RandyB
>
> --- In electricboats@yahoogroups.com
> <mailto:electricboats%40yahoogroups.com> , "svcabernet" <bsmisner@>
> wrote:
> >
> > Hello all,
> >
> > I've been lurking here for a while, which has paid great benefits as I've
> been putting together a parts list for an electric drive for my Cascade 29.
> >
> > Given the limited budget I've decided to "build" the system myself rather
> than go with one of the tried and true manufacturer's assemblies.
> >
> > The one component(s) I've been having trouble with is the reduction drive.
> I've decided to use timing pulley's/belts or sprockets and chain along with
> captured roller/thrust bearings but am having a tough time sourcing them. I
> wouldn't be opposed to a gear reduction either provided a "bullet proof"
> reputation. The motor of choice is the ME0907 for it's lack of brushes,
> performance, and affordability. By my calc's a 2:1 to 2.5:1 reduction will
> be needed to maximize performance. Any ideas would be appreciated.
> >
> > Thanks,
> >
>
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