Monday, May 3, 2010

[Electric Boats] More spam

 

It looks like we've been spammed again. beverlyhillscaviar posted links in the link section that are not e-boat related. Can a moderator please clean those entries out of the site and ban the poster.

Thanks,
Eric

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Re: [Electric Boats] Re: boat designs

 

Dan , you could probably contact the people who have the Kelvin launch , and see what they worked with on their restoration.
Regards Rob J.

From: danbollinger <no_reply@yahoogroups.com>
To: electricboats@yahoogroups.com
Sent: Mon, 3 May, 2010 11:37:27 PM
Subject: [Electric Boats] Re: boat designs

Rob, Thanks for this. There are many launches of medium size that are sure to be efficient hull shapes. All are displacement type. Are the lines drawings still available?


--- In electricboats@yahoogroups.com, Rob Johnson <dopeydriver@...> wrote:
>
> I thought I might post this old Kelvin catalogue , I'm sure there are a number of easily driven and eye catching designs sutable for electric power .
> Go http://www.sky-net.org.uk/kelvin/launches/index.html
> Rob J.
>




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[Electric Boats] Re: boat designs

 

Rob, Thanks for this. There are many launches of medium size that are sure to be efficient hull shapes. All are displacement type. Are the lines drawings still available?

--- In electricboats@yahoogroups.com, Rob Johnson <dopeydriver@...> wrote:
>
> I thought I might post this old Kelvin catalogue , I'm sure there are a number of easily driven and eye catching designs sutable for electric power .
> Go http://www.sky-net.org.uk/kelvin/launches/index.html
> Rob J.
>

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Re: [Electric Boats] controllor for mars brushless 48v

 

On 03/05/10 21:55, dennis wolfe wrote:

The first Sevcon PMAC I had (bought Summer 07) would not go into reverse until it sensed the prop had stopped turning forward.  In my slippery launch this could take up to 15 seconds coasting down from full speed.  Could be pretty scary waiting for the 'brakes' to kick in!  Others reported this same issue.
 
 Back when my boat was powered by a petrol 2 stroke it didn't have reverse at all. It had a clutch and throttle, no gear box. (Direct drive off a 2 cylinder 2 stroke).

 Thus I learned to operate 750kg 5m 'launch' with no effective brakes as there was no reverse gear.

 Turns out it was possible to reverse - by getting the engine to run in reverse. Throttle down to idle, loosen the magneto, press magneto shorting switch (carefully :-), turn magneto 15" to other 'dent', release shorting switch. If you got it right, the engine would fire out of time and reverse direction. (Most of the time you would just stall, it took some practice).
 Even with practice, it you couldn't do it fast enough to use as a braking method and I hate to think what stress the sudden reverse of direction was putting on the crank shaft.


 Being able to flip my electric motor almost instantly into reverse is heaven compared to the 'old way' although out of habit I tend to come in so slowly I don't really need reverse power.

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Re: [Electric Boats] controllor for mars brushless 48v

 

The first Sevcon PMAC I had (bought Summer 07) would not go into reverse until it sensed the prop had stopped turning forward.  In my slippery launch this could take up to 15 seconds coasting down from full speed.  Could be pretty scary waiting for the 'brakes' to kick in!  Others reported this same issue.
 
Sevcon modified the firmware to correct this.  It will now go into reverse immediately, even if the motor is still turning the other direction.  This required returning the controller to Sevcon.
 
These products are designed with land vehicles in mind which have brakes so not having reverse available until the vehicle is stopped is actually a safety feature. On boats, no so much.
 
If the delay is bothersome you might be able to rig a simple brake on the propshaft to stop the free wheel action.  Seems unlikely the Chinese would redo the firmware for you. 
 
 
----- Original Message -----
Sent: Sunday, May 02, 2010 1:22 PM
Subject: Re: [Electric Boats] controllor for mars brushless 48v

 

Denny,
 
I experience a lag when going from forward to reverse in my electric powerboat running my 5KW Golden brushless DC motor and Controller.  Can you explain to me why?  You seem to know about this as you mentioned about the Sevcon Controller.
 
John
 


 
On Sun, May 2, 2010 at 9:22 AM, dennis wolfe <dwolfe@dropsheet.com> wrote:
 

Sevcon PMAC will go from F to R instantly.  Be sure to get the firmware version that has been updated to do this.
 
Denny
 
----- Original Message -----
From: mboucher99
Sent: Sunday, May 02, 2010 6:36 AM
Subject: [Electric Boats] controllor for mars brushless 48v

 

all,
just getting back to my search for a new controller for our mars 48v brushless - powering a 5,600 lbs 27' sloop. (we never hit the water last year)

we have an older controller that requires a delay between forward and reverse, making docking or mooring in our strong currents more adventuresome than the actual sailing. many recent posts seem to touch on this topic, as well as the equally fun one of drive belts riding off of edgeless pulleys) however, my electrical ignorance prevents me from gleaning the info i really need to make a decision. is there a consensus out there as to what might be the best (SIMPLE)option for us?
thanks!
mb in freeport maine


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Posted by at No comments:

[Electric Boats] boat designs

 

I thought I might post this old Kelvin catalogue , I'm sure there are a number of easily driven and eye catching designs sutable for electric power .
Rob J.

 

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Sunday, May 2, 2010

Re: [Electric Boats] 48 volt DC alternator for charging

 

Leese-Neville makes a 48v 100a alternator. 
You might also consider a replacement part from John Deere. I made 48v bldc motors for their commercial turf care greens mowers which had 48v 100a alternators on the Kubota engines 
Find the greens mower using a TCA14327 brushless motor and you'll have the alternator. (The bldc motor is 3200rpm no-load, rated at 2800rpm for 2.5kw continuous. The JD controller is not designed for variable speed operation, however.)  

Be Well,
Arby

On May 3, 2010, at 9:03 AM, "zendodeb" <zendodeb@gmail.com> wrote:

 

Does anyone know of a source for 48 volt alternators?

There is a plan for using a small gas motor and a 12-volt alternator for 12-volt battery charging. I would like to build something similar for 48-volt charging.

I can find 12, 24 and 36, but not 48.

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