Hi Myles;
I am still thinking of all things EV and while thinking I have acquired a 60V 40Ah scooter. As I play with this, I bump into electric bikes, trikes and they in turn have other interesting projects. Some fellows are building altermotors from large vehicle alternators. To control the 3 phases they are using Hall sensors, 120 electrical degrees apart. Frugal builders from 3rd world counties, with much more brains than money, have discovered there are Hall sensors in desktop computer fans, and are using these in their altermotors. They have also found that one can either use field weakening in the rotor by applying a maximum of 5V to the brushes or advance the Hall sensor signal with the controller to increase the rpm when maximum torque is not needed. Some are running 10KW to an automotive alternator. I'm am sure many are thinking, what about the efficiency? These altermotors are not as efficient as a hubmotor, but they are very close to that of the RC and B&S motors, at a fraction of the cost.
One of the other projects I stumbled onto in the shop of the owner of the world's fastest 100V BMX bike, is a very hairy 440 Dodge complete with homemade port fuel injection which is triggered by a standard Hall sensor off of a trigger wheel. The trigger wheel is a standard motorcycle sprocket, with the correct number of teeth. There are many sizes of two piece sprockets available from industrial suppliers, that can be clamped to the prop shaft of a boat, which in conjunction with a Hall sensor, will provide an output for a tach. Use any sprocket with a given multiple of teeth for a tach with a 4,6,8 cylinder switch on it. i.e. with a 24 tooth sprocket, you grind off all but 8 teeth, (grind 2, skip 1) and set the tach switch to 8 cylinder. This will give you accurate rpm.
--- In electricboats@yahoogroups.com, "Myles Twete" <matwete@...> wrote:
>
> Pat-
>
>
>
> Regarding the tach, it's hard to say.
>
> Some tachs have a switch on the back to select multiple cylinder engines.
>
> If you can get a hall effect or other type of switch sensor that has the
> sensed element spinning on the motor shaft, you could at least sense motor
> speed or some fraction or multiple of it. If you were real lucky it might
> give you prop speed at proper scaling.
>
>
>
> -MT
>
>
>
> From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com]
> On Behalf Of greenpjs04
> Sent: Saturday, May 22, 2010 6:58 AM
> To: electricboats@yahoogroups.com
> Subject: [Electric Boats] Re-use of gauges
>
>
>
>
>
> After removing the 40 hp mercury engine from my pontoon boat and replacing
> it with a Torqeedo, I find myself with three perfectly good gauges on the
> console that do nothing. Does anyone have any good ideas for using them in
> some useful way?
>
> The volt meter is easiest. I connected it to the separate 12 volt battery I
> use for the navigation lights and horn.
>
> The fuel gauge is next. I thought about recommissioning it as a volt meter
> for the 48 volt pack. I could create a set-up that causes it to go from
> empty to full as the battery bank goes from 48 to 51 volts (or whatever the
> right numbers are).
>
> The third gauge is a tach. It would be nice if it could measure prop rpm's,
> but I can't think of any easy way sense that.
>
> Any ideas for using the current gauges or replacing them with other gauges
> of the same size? (The tach uses a 3-3/8" hole while the other two use
> 2-1/8" holes).
>
> Thanks,
> Pat
>
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