[Electric Boats] Re: In-line electric motor as backup power

 

Hi- I am in the process of doing something similar on my 38 ft diesel powered sailboat.  I purchased an ME0709 brushed PM motor for the project.  The motor is mounted right above the transmission, and is firmly bolted to rear of the transmission using an aluminum bracket and existing unused threaded holes. The bracket also bolted to the engine block. For now I have a #50 chain drive between a 10 tooth sprocket on the motor and a 30 tooth sprocket mounted directly over the shaft half of the coupling. The large sprocket can actually be disengaged from the coupling and be made to freewheel on a delrin hub. Its a neat installation, but it took a tremendous amount of machine shop work and trial fitting. Fortunately I have the equipment, time, and consider it a "fun hobby" and not work. 

So far I have only tried it with the boat tied to the dock. The motor is rated 8HP continuous and 18 HP intermittent and uses a voltage of 24-72 per spec. sheet.  I tried running it on 12 VDC in forward and reverse (diesel off  and transmission in neutral) and it  slowly turned the 3 blade prop moving the boat forward and back until the docking lines tightened. At 12 volts, with the prop turning against water resistance, it drew about 12 amps (144 watts). So it seems like the system (obviously with more voltage) will work fine for low speed usage (3-4 kts) which is 95% of my motoring needs. Next I tried running the diesel at idle, in gear, with no battery connection,(prop driving the motor) and measured 26 VDC open circuit voltage generation at the motor terminals. 

That all I have done so far, but my sense is that the chain drive is much too noisy and will probably consider a belt drive after I get some data.  The diesel engine is an old but running Perkins 4-108 rated 50 HP, but probably not producing more than 35HP. It's a work in progress.

Art

SV Sh-Boom Sh-Boom

Barnegat Bay NJ

--- In electricboats@yahoogroups.com, "DRHitch" <drhitch@...> wrote:
>
> Bear with me if this sounds strange:
>
> Has anyone created a "swing-in" motor mount that is PARALLEL to the prop shaft and pivots in to engage a gear tooth in the prop shaft?
>
> Assume your main power plant fails.
> In the prop shaft, there is a coupling between the aft stuffing box and the motor/transmission.
>
> I am considering the following scenario.
>
> 1) Open the shaft coupling, and remove the aft-facing half of the coupling. Slide a gear over the shaft, and re-attach the motor coupling to the shaft. Re-attach the two halves of the coupling together...At this point you have a spinning gear tooth on your prop shaft.
>
> 2) Now, in parallel to the shaft, install an electric motor that pivots/tilts inwards towards the shaft and engages the gear.
>
> 3) In case of main power plant failure, you just undo the motor coupling, pivot in the electric drive, and the prop shaft now turns through this gear system....Or maybe the backup electric motor is coupled to the gear on the prop shaft via chain/belt?
>
> The reason for all this is that the main power is a steam engine and if it stops operating, I'm considering a backup electric drive system. There is no opportunity to simply drop a Torquedo outboard alongside the hull (round fantail)....sound plausible or just too weird?
>

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