# Motor identification/suitability?



## Squidlings (Aug 1, 2019)

Im no expert but thats an AC motor and as i understand it, you need the correct controller to run that thing properly. 

I think you could be looking for a dc series wound motor perhaps? 

20kw sounds a bit overkill for a narrowboat. I thought they ran on old 10hp diesels? 

Also i thought narrowboats ran on 12v so perhaps finding a 12v would be best to save u having 2 battery packs. Unsure if thats possible. Question to the gurus...can u a 12v with high amp motors? 

My friend has a narrow boat so im interested in this.


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## Squidlings (Aug 1, 2019)

Ahhh.... your in uk, barnsley. 

I went to see a 48v dc series wound today. It was in radcliff north Manchester. Much cheaper than this motor. I needed it for , a car conversion so it to small for me. But im sure itd be great for a narrow boat unless there is an issue with dc motors and water 🙂 let me google it.


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## JPac (Sep 6, 2019)

Thanks Squidlings
I'm fitting a whole new lead-acid battery bank etc, so going maybe with 72v.
Found an AC motor near me (I'm in Bristol) - a Juli 28V 174A 6kW AC motor. 1535rpm, S2=60min. £350, so quite expensive still. 



Wanting to go AC for efficiency and reliability... thinking of using a Sevcon Gen4.



Does you know (or can point me to the right thread/member who does) about over-volting forklift motors? The potential issue is cooling I guess, but 72v shoud give ~4000rpm and ~12kW peak (for stopping, turning etc)


A 60' Narrowboat needs 3kW at 3mph and 6kW at 3.5mph apparently, big difference!


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## Squidlings (Aug 1, 2019)

Im not sure an ac motor would be much more efficent in a narrowboat. You cant use regen braking. Thinking about it. You need high rpm not torque.

4000rpm sounds inline to replace a diesel. 

Wonder if you could have a lower rpm and have a long gear. Then the torque would come into play.


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## JPac (Sep 6, 2019)

We're looking at 1000rpm max at the prop, so usually there's a reduction for electric boats.... 2:1 or 3:1 is common.


There's a good breaker in Chesterfield, miles away from me though.... they have quite a few DC motors if you're still looking.


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## Squidlings (Aug 1, 2019)

I went to the chesterfield breakers the other week. They have a lot of 8" dc motors. I think theyll be rated at 4kw. Theyd be easily over volted i think. 

Not great for a car but id say perfect for a narrow boat. Plus a controller would be dirt cheap too. 

Looking at £200 motor £350 controller.


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## brian_ (Feb 7, 2017)

Squidlings said:


> 4000rpm sounds inline to replace a diesel.


4000 RPM sounds very high to me for a marine diesel. Even a light truck diesel rarely runs that fast.



JPac said:


> We're looking at 1000rpm max at the prop, so usually there's a reduction for electric boats.... 2:1 or 3:1 is common.


That does seem in line with diesel engine operating speeds.


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## Squidlings (Aug 1, 2019)

I thought diesel engines usually have a range of 450-6000 rpm right?

With the efficency (cruise speed) range between 1500 -2500

Not sure how this translates to marine engines. 

Again i suppose it depends on the gears...if gears are being used.


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## Squidlings (Aug 1, 2019)

Why go for 4000rpm with a reduction gear ratio? You could just go direct to the prop with a 1000rpm motor? Seems more logical to me.


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## summetj (Mar 30, 2011)

Squidlings said:


> Not great for a car but id say perfect for a narrow boat. Plus a controller would be dirt cheap too.



You might not even need a controller for a DC motor connected to a propeller, just an on/off and a reversing contactor. I imagine the mass of the narrow boat would give you plenty of time to turn the motor on/off to speed up or slow down over time.



If you wanted a high/low speed for cruising vs maneuvering you could put two halfs of your pack your pack in series/parallel. 



On the other hand, PWM DC motor controllers are quite cheap, so it's probably not worth going old school.


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## brian_ (Feb 7, 2017)

Squidlings said:


> I thought diesel engines usually have a range of 450-6000 rpm right?
> 
> With the efficency (cruise speed) range between 1500 -2500
> 
> Not sure how this translates to marine engines.


Only small diesels used in cars would ever run 6000 RPM. A large (14 litre) truck engine will have a _maximum_ operating speed around 2000 RPM, and even a pickup truck engine would cruise at the low end of that 1500 - 2500 RPM range. Marine diesels tend to be designed run more slowly than truck engines, because they are expected to run at well up in their power range for very long periods.

In some big (ship-sized) diesels you can count the engine revolutions by watching valvetrain parts move, because they only turn 300 RPM. Of course a canal boat wouldn't have an engine that slow, because it would be small.


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## Squidlings (Aug 1, 2019)

Thx. Brian. Nice info.


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## Duncan (Dec 8, 2008)

Sorry Brian but you are about 50 years behind the times
A 14 or 16 litre engine will have max power at about 4,000 rpm or higher

_In some big (ship-sized) diesels you can count the engine revolutions by watching valvetrain parts move, because they only turn 3000 RPM. Of course a canal boat wouldn't have an engine that slow, because it would be small._

3,000 rpm is NOT NOT NOT slow -

And again the times of the really slow "Cathedral" engines have gone today's big engines run faster than they used to - as in 1500 rom


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## brian_ (Feb 7, 2017)

Duncan said:


> _In some big (ship-sized) diesels you can count the engine revolutions by watching valvetrain parts move, because they only turn 3000 RPM. Of course a canal boat wouldn't have an engine that slow, because it would be small._
> 
> 3,000 rpm is NOT NOT NOT slow...


Sorry, that was a typo (now corrected in my original post) - it was supposed to be 300 (three hundred) RPM. Yeah, 3,000 RPM would be terrifying for an engine like that! 

Yes, the really slow engines are no longer current - it was just an extreme example.


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## brian_ (Feb 7, 2017)

Duncan said:


> Sorry Brian but you are about 50 years behind the times
> A 14 or 16 litre engine will have max power at about 4,000 rpm or higher


I just search quickly for a spec for a 14 litre engine and found a Cummins N14, forgetting that it is not current... but it's not half a century old, either. A current Cummins X15 "efficiency series" is governed to 2000 RPM in the higher-output 500 hp version (1800 in the 400 hp version). The up to 605 hp X15 "productivity series" positively screams along at... 2000 RPM. Other brands may run faster, I suppose.

Diesels in general are more suitable for low-speed operation due to their combustion process, but more importantly heavy-duty engines - including those in many kinds of boats - run slowly for durability. A ski boat engine spins fast, but a canal boat engine is going to be slow, so an electric motor replacing it would a change in prop or gearing is going to be slow.


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## Jonisingt35r (Sep 5, 2019)

hello
im hunting also for a dc forkift motor, im in the uk can anybody help me 
thanks im situatee in cornwall
cheers jon


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