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Antrepat

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4 minutes ago, Alan de Enfield said:

 

 

And then conclude "maybe diesel isn't so bad after all"

 

I'd better state that I didn't start this discussion out of prejudice against diesel - I don't have enough understanding and information to draw a conclusion - I'm doing it because I'm stuck at home for months on end and can't go to my boat and I need something to occupy myself and it may as well be figuring this out for my own satisfaction!

 

As it happens, I wouldn't have access to grid power anyway, nor would I want to use it for propulsion for exactly the reason of the gross inefficiency of the end-to-end system.  In any case, it wouldn't be practical because who can just plug in every night once out the marina?

 

I understand there's an argument that a generator charging a battery can operate at its optimum efficiency all the time, unlike the propulsive engine which is usually running too slowly.  I also understand that charging and taking power from a battery involves losses too, and working out whether there is even a marginal advantage of one over the other in pure efficiency terms strikes me as challenging.  I do know that you can't get free diesel by putting some black panels on your roof, but also that you'd need a lot of panels not to need any diesel at all, and that it's interesting to consider whether the combination of a generator running at optimum efficiency plus some amount of free energy (never mind the capital cost) might be more or less efficient in the long run than a diesel system that doesn't do useful work with 80% of its fuel most of the time.

 

I know I've been talking about electric propulsion more, because it does interest me, but I'm not trying to have the argument about which is best.  I'm just trying to listen and learn.

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29 minutes ago, Alan de Enfield said:

 

 

And then conclude "maybe diesel isn't so bad after all"

What about production losses pollution caused  damage by spillage the list is endless for diesel electric will always be ahead especially if its solar generated 

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12 minutes ago, Antrepat said:

 

I'd better state that I didn't start this discussion out of prejudice against diesel - I don't have enough understanding and information to draw a conclusion - I'm doing it because I'm stuck at home for months on end and can't go to my boat and I need something to occupy myself and it may as well be figuring this out for my own satisfaction!

 

As it happens, I wouldn't have access to grid power anyway, nor would I want to use it for propulsion for exactly the reason of the gross inefficiency of the end-to-end system.  In any case, it wouldn't be practical because who can just plug in every night once out the marina?

 

I understand there's an argument that a generator charging a battery can operate at its optimum efficiency all the time, unlike the propulsive engine which is usually running too slowly.  I also understand that charging and taking power from a battery involves losses too, and working out whether there is even a marginal advantage of one over the other in pure efficiency terms strikes me as challenging.  I do know that you can't get free diesel by putting some black panels on your roof, but also that you'd need a lot of panels not to need any diesel at all, and that it's interesting to consider whether the combination of a generator running at optimum efficiency plus some amount of free energy (never mind the capital cost) might be more or less efficient in the long run than a diesel system that doesn't do useful work with 80% of its fuel most of the time.

 

I know I've been talking about electric propulsion more, because it does interest me, but I'm not trying to have the argument about which is best.  I'm just trying to listen and learn.

There are several long threads on the forum going into all this in interminable detail, I suggest you go and read them ?

 

 

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27 minutes ago, IanD said:

All the numbers I was talking about were power at the prop shaft. Propeller efficiency varies but is usually in the 50%-60% region, so 3kW/4hp at the shaft is just over 1.5kW/2hp power in the water.

 

Lynch's motors are pretty rubbish to be honest, modern brushless PMAC motors are far better with peak efficiency >96%, probably around 94% under actual conditions. Add 4% loss for the controller and you get 90% from battery to motor. On top of 55% typical prop efficiency, this gives you 50% from battery (3kW) to water (1.5kW).

 

For an electric boat you could assume 3kW (from the battery) when cruising on the open canal, 1kW when passing moored boats, and 0kW when sitting in a lock, so your overall power per day depends on how much time you spend doing what. If you take an 8 hour day to be 4 hours cruising/2 hours passing/2hours in locks this means you consume 14kWh. If you do the western part of the Cheshire Ring in a day like I did (25 miles IIRC, no locks) you'll use more, maybe 25kWh or so.

 

You also need to allow for any solar power if you have panels fitted, and any onboard power. Even with as much solar as you can fit on a narrowboat (yielding maybe 8kWh/day in summer, 1kWh/day in winter?), unless you're only going to cruise 2-3 days a week in summer (and not at all in winter) you'll need an onboard diesel generator.

 

Crunch all these numbers and you end up with maybe 40% lower fuel consumption than a diesel, assuming you use the generator a lot. If all the power comes from solar, your direct fuel cost is zero. None of this comes anywhere close to making up the extra cost of installation compared to a diesel even over a long lifetime, but that's not the reason people are choosing electric boats -- or series hybrids to be more accurate -- it's the silence and zero vibration when travelling. In future when/if the canal gets charging points they'll also be much greener, but this is probably many years away.

 

Don't do it for the money, do it because you want to. So long as you have deep pockets...

I like Cedrics motors they are efficient for what they are plus it's DC all the way. It's a simple and cheap way of achieving something that is DIY, controller technology for them is cheaply and readily available and the motors are self cooling. The brushes are long lived as long as they aren't overloaded and really easy to change.  Think of the positives Ian more people can convert to electric so emissions go down? And quieter canals 

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21 minutes ago, IanD said:

All the numbers I was talking about were power at the prop shaft. Propeller efficiency varies but is usually in the 50%-60% region, so 3kW/4hp at the shaft is just over 1.5kW/2hp power in the water.

 

Lynch's motors are pretty rubbish to be honest, modern brushless PMAC motors are far better with peak efficiency >96%, probably around 94% under actual conditions. Add 4% loss for the controller and you get 90% from battery to motor. On top of 55% typical prop efficiency, this gives you 50% from battery (3kW) to water (1.5kW).

 

For an electric boat you could assume 3kW (from the battery) when cruising on the open canal, 1kW when passing moored boats, and 0kW when sitting in a lock, so your overall power per day depends on how much time you spend doing what. If you take an 8 hour day to be 4 hours cruising/2 hours passing/2hours in locks this means you consume 14kWh. If you do the western part of the Cheshire Ring in a day like I did (25 miles IIRC, no locks) you'll use more, maybe 25kWh or so.

 

You also need to allow for any solar power if you have panels fitted, and any onboard power. Even with as much solar as you can fit on a narrowboat (yielding maybe 8kWh/day in summer, 1kWh/day in winter?), unless you're only going to cruise 2-3 days a week in summer (and not at all in winter) you'll need an onboard diesel generator.

 

Crunch all these numbers and you end up with maybe 40% lower fuel consumption than a diesel, assuming you use the generator a lot. If all the power comes from solar, your direct fuel cost is zero. None of this comes anywhere close to making up the extra cost of installation compared to a diesel even over a long lifetime, but that's not the reason people are choosing electric boats -- or series hybrids to be more accurate -- it's the silence and zero vibration when travelling. In future when/if the canal gets charging points they'll also be much greener, but this is probably many years away.

 

Don't do it for the money, do it because you want to. So long as you have deep pockets...

 

This is absolute gold, Ian, thank you.  I've only found the obvious motor suppliers.  Can you suggest where to look for more information about these alternatives you mention?

 

So, this is what my power curve actual-mechanical-output estimate feeds into:

Speed Mechanical power (W) System Efficiency Electrical power (W) Cruise Hours Cruse W-Hr Full P (W) Full P hours Full P W-Hr Dmstc W-Hr Total W-Hr Ah @ 48v Offset Solar Charge W-Hr Net Energy W-Hr
3.0 913 0.4 2282 8 18255 5000 0.5 2500 1147 21901 456 2000 19901
3.5 1449 0.4 3623 8 28988 5000 0.5 2500 1147 32634 680 2000 30634
4.0 2164 0.4 5409 8 43270 5000 0.5 2500 1147 46917 977 2000 44917

 

That's scaling 50% of the drag force by 30/72 to account for skin drag being less with a shorter boat.  The other 50% is factored by the speed squared without alteration, and then of course all multiplied by the speed again to get the power.  Oh, and it's a 30ft boat.  1kW is as much solar as I'm going to fit on!

 

To illustrate how it's coming out, this is the same table unscaled (so using the original 72ft model):

Speed Mechanical power (W) System Efficiency Electrical power (W) Cruise Hours Cruse W-Hr Full P (W) Full P hours Full P W-Hr Dmstc W-Hr Total W-Hr Ah @ 48v Offset Solar Charge W-Hr Net Energy W-Hr
3.0 1289 0.4 3221 8 25771 5000 0.5 2500 1147 29418 613 2000 27418
3.5 2046 0.4 5116 8 40924 5000 0.5 2500 1147 44571 929 2000 42571
4.0 3054 0.4 7636 8 61088 5000 0.5 2500 1147 64734 1349 2000 62734

 

Pie in the sky, perhaps, but fun to work out.

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1 minute ago, Antrepat said:

 

This is absolute gold, Ian, thank you.  I've only found the obvious motor suppliers.  Can you suggest where to look for more information about these alternatives you mention?

 

So, this is what my power curve actual-mechanical-output estimate feeds into:

 

Speed Mechanical power (W) System Efficiency Electrical power (W) Cruise Hours Cruse W-Hr Full P (W) Full P hours Full P W-Hr Dmstc W-Hr Total W-Hr Ah @ 48v Offset Solar Charge W-Hr Net Energy W-Hr
3.0 913 0.4 2282 8 18255 5000 0.5 2500 1147 21901 456 2000 19901
3.5 1449 0.4 3623 8 28988 5000 0.5 2500 1147 32634 680 2000 30634
4.0 2164 0.4 5409 8 43270 5000 0.5 2500 1147 46917 977 2000 44917

 

That's scaling 50% of the drag force by 30/72 to account for skin drag being less with a shorter boat.  The other 50% is factored by the speed squared without alteration, and then of course all multiplied by the speed again to get the power.  Oh, and it's a 30ft boat.  1kW is as much solar as I'm going to fit on!

 

To illustrate how it's coming out, this is the same table unscaled (so using the original 72ft model):

 

Speed Mechanical power (W) System Efficiency Electrical power (W) Cruise Hours Cruse W-Hr Full P (W) Full P hours Full P W-Hr Dmstc W-Hr Total W-Hr Ah @ 48v Offset Solar Charge W-Hr Net Energy W-Hr
3.0 1289 0.4 3221 8 25771 5000 0.5 2500 1147 29418 613 2000 27418
3.5 2046 0.4 5116 8 40924 5000 0.5 2500 1147 44571 929 2000 42571
4.0 3054 0.4 7636 8 61088 5000 0.5 2500 1147 64734 1349 2000 62734

 

Pie in the sky, perhaps, but fun to work out.

Look on plug boats it's a site purely for electric boats 

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31 minutes ago, dmr said:

 

Calling 1500v DC a low voltage suggests you worked in a very different world to many of us ?

 

Electronic engineers regard 3.3 as low, 5 as medium, and 12 as getting dangerous.

 

.............Dave

 

Indeed, I originally studied industrial electronics, where I was used to calculating currents in micro or milliamps, then joined Post Office Telephones on their international power section. I found myself working on DC power plants with up to 10 x 2000 amp 50 volt rectifiers. It was a bit of a culture shock to say the least.

 

The last data centre I worked on at a mains intake at 66kV and 33 x 2000kVA DRUPS (diesel rotary uniterruptible power supplies) for back up genetation.

 

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This whole thing about stopping quickly is quite funny. I suspect that the the operators of boats that were around prior to the invention of propellers (perhaps using ropellers instead, and hanimals) worked out how to deal with this issue. I bet they didn't just whack into each other all the time. It would have all been about anticipation, traveling at a sensible speed etc.  They couldn't stop. It's not possible other than with a strapping post which would normally be near a lock. Did they have strapping posts near bridge holes? More likely a line of sight and limited vegetation. Plus of course the horse goes first so you get to see that a boat is coming before it arrives. 

 

IF canals did end up with electrically propelled boats then perhaps these skills would be learned again. 

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14 minutes ago, magnetman said:

This whole thing about stopping quickly is quite funny. I suspect that the the operators of boats that were around prior to the invention of propellers (perhaps using ropellers instead, and hanimals) worked out how to deal with this issue. I bet they didn't just whack into each other all the time. It would have all been about anticipation, traveling at a sensible speed etc.  They couldn't stop. It's not possible other than with a strapping post which would normally be near a lock. Did they have strapping posts near bridge holes? More likely a line of sight and limited vegetation. Plus of course the horse goes first so you get to see that a boat is coming before it arrives. 

 

IF canals did end up with electrically propelled boats then perhaps these skills would be learned again. 

 

Have you not noticed the huge dents in the fronts of those old working boats ? ?

 

................Dave

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22 minutes ago, peterboat said:

I like Cedrics motors they are efficient for what they are plus it's DC all the way. It's a simple and cheap way of achieving something that is DIY, controller technology for them is cheaply and readily available and the motors are self cooling. The brushes are long lived as long as they aren't overloaded and really easy to change.  Think of the positives Ian more people can convert to electric so emissions go down? And quieter canals 

 

Whst with all those suitcase gennies running to charge the batteries? ??

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23 minutes ago, magnetman said:

This whole thing about stopping quickly is quite funny.

 

We had a recent poster who claimed to regularly need the full stopping power of a Beta 43 when doing unusual manoeuvres like entering locks or going round bends.

 

He's not the only one.

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1 minute ago, TheBiscuits said:

 

We had a recent poster who claimed to regularly need the full stopping power of a Beta 43 when doing unusual manoeuvres like entering locks or going round bends.

 

He's not the only one.

I find going slowly helps me but what do I know?

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1 hour ago, peterboat said:

I like Cedrics motors they are efficient for what they are plus it's DC all the way. It's a simple and cheap way of achieving something that is DIY, controller technology for them is cheaply and readily available and the motors are self cooling. The brushes are long lived as long as they aren't overloaded and really easy to change.  Think of the positives Ian more people can convert to electric so emissions go down? And quieter canals 

Geared Lynch motors whine. All controllers --including the Lynch ones -- are basically fancy switching power supplies, the ones for PMAC motors aren't really any more complex than for DC motors, but both motors and controllers run cooler and there are no brushes to worry about. And the Lynch motors with their controllers weren't much -- if any -- cheaper when I looked recently.

 

Of course there are positives if more people go electric, it's why I'm going to do it. But lower fuel costs aren't the reason. If charging points appeared on the canals this might change...

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28 minutes ago, IanD said:

Geared Lynch motors whine. All controllers --including the Lynch ones -- are basically fancy switching power supplies, the ones for PMAC motors aren't really any more complex than for DC motors, but both motors and controllers run cooler and there are no brushes to worry about. And the Lynch motors with their controllers weren't much -- if any -- cheaper when I looked recently.

 

Of course there are positives if more people go electric, it's why I'm going to do it. But lower fuel costs aren't the reason. If charging points appeared on the canals this might change...

Its the belts that whine Ian without a doubt, I paid 1200 ish squids for my motor and controller the gearbox was 700 squids  so not high money, mine is an Agni motor D135.

A 4QD speed controller isnt big money under 400 squids. As I said I like Cedrics motors simple and reliable the brushes can be advanced for better power forward as well.

A plus fro me is if you get a log caught in the prop it just snaps a belt instead of doing some serious damage to something else, anyway you will have the Rolls Royce of systems on your new boat and I am envious of it

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2 hours ago, peterboat said:

Its the belts that whine Ian without a doubt, I paid 1200 ish squids for my motor and controller the gearbox was 700 squids  so not high money, mine is an Agni motor D135.

A 4QD speed controller isnt big money under 400 squids. As I said I like Cedrics motors simple and reliable the brushes can be advanced for better power forward as well.

A plus fro me is if you get a log caught in the prop it just snaps a belt instead of doing some serious damage to something else, anyway you will have the Rolls Royce of systems on your new boat and I am envious of it

 

To be honest my pockets aren't very deep so gold-plated equipment is not an option anyway.  Buy the best you can afford, that's what people say.

 

That's, what, £2,300?  Plus a control handle, switches and instruments but I suppose that can be anything that delivers the right electrical signal, doesn't have to look like a classic marine throttle handle, and I'm interested in affordable and effective, not looking fancy.

 

I was confused - why would you need a gearbox, isn't reduction what the belt's for? - but then I thought maybe you bought the motor on its own without the Marlin marine rig?  But then, you refer to the belt's advantage if the propeller gets fouled, so I'm still not sure.

 

I was confused again, momentarily, as I hadn't heard the name Agni, but I see it's the Lynch LEM series.  I've had trouble finding a uk seller, so I must be looking for the wrong terms.  I found the Marlin 5 at Gecko Energy for £5,400 - four grand more than Peter has said (without gearbox, but with controller and instruments etc.), so I must be missing something here - but otherwise I found a US supplier and a French one, whilst just looking for the motor alone.  Given that it's a UK product (as far as I can tell), it would seem daft to re-import one from abroad, and those aren't in the marine rig anyway.

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4 minutes ago, Antrepat said:

I found a US supplier and a French one, whilst just looking for the motor alone.  Given that it's a UK product (as far as I can tell), it would seem daft to re-import one from abroad, and those aren't in the marine rig anyway.

 

And, have to add on freight, duty, and 20% VAT.

It all bumps up the price.

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2 hours ago, Antrepat said:

 

To be honest my pockets aren't very deep so gold-plated equipment is not an option anyway.  Buy the best you can afford, that's what people say.

 

That's, what, £2,300?  Plus a control handle, switches and instruments but I suppose that can be anything that delivers the right electrical signal, doesn't have to look like a classic marine throttle handle, and I'm interested in affordable and effective, not looking fancy.

 

I was confused - why would you need a gearbox, isn't reduction what the belt's for? - but then I thought maybe you bought the motor on its own without the Marlin marine rig?  But then, you refer to the belt's advantage if the propeller gets fouled, so I'm still not sure.

 

I was confused again, momentarily, as I hadn't heard the name Agni, but I see it's the Lynch LEM series.  I've had trouble finding a uk seller, so I must be looking for the wrong terms.  I found the Marlin 5 at Gecko Energy for £5,400 - four grand more than Peter has said (without gearbox, but with controller and instruments etc.), so I must be missing something here - but otherwise I found a US supplier and a French one, whilst just looking for the motor alone.  Given that it's a UK product (as far as I can tell), it would seem daft to re-import one from abroad, and those aren't in the marine rig anyway.

If you want to install a new ready-to-go drive system (including throttle, controller, display etc) instead of building it yourself, the best option is probably Waterworld:

 

https://www.energy-solutions.co.uk/products/waterworld

 

They did send me a quotation which I can't find, from memory it was just over £5k for the 15kW version.

 

If you think that's expensive, it's less than half the price of the comparable Bell-Marine and Fischer-Panda solutions...

 

Of course you can do it cheaper if you find all the bits yourself and put them together, especially if some are second-hand -- which is what Peter did. Same applies to batteries, and battery management/protection/charging system.

 

Just be aware that if you're going to put all this together with an expensive (even second-hand) LiFePO4 battery bank, you really need to know what you're doing, especially with charging and battery protection, to avoid reducing battery lifetime or in the extreme destroying them. There are people on this forum who have done this successfully (you can find many threads about this by searching), but if you're thinking of going down this route here's some strongly recommended reading (in case you haven't already):

 

https://marinehowto.com/lifepo4-batteries-on-boats/

 

http://nordkyndesign.com/category/marine-engineering/electrical/lithium-battery-systems/

 

The marinehowto site is written by a guy with a commercial side, but his advice about LiFePO4 is based on a lot of experience and there's some gold dust in there. The Nordkyn site is by a guy who designed and built his own aluminium-hulled yacht from scratch together with most of the systems in it (there's some fascinating stuff on here, you can waste hours reading about it) and is generally reckoned to be one of the best information sources about LiFePO4 and using them on boats.

 

Have fun ?

Edited by IanD
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1 hour ago, Antrepat said:

 

To be honest my pockets aren't very deep so gold-plated equipment is not an option anyway.  Buy the best you can afford, that's what people say.

 

That's, what, £2,300?  Plus a control handle, switches and instruments but I suppose that can be anything that delivers the right electrical signal, doesn't have to look like a classic marine throttle handle, and I'm interested in affordable and effective, not looking fancy.

 

I was confused - why would you need a gearbox, isn't reduction what the belt's for? - but then I thought maybe you bought the motor on its own without the Marlin marine rig?  But then, you refer to the belt's advantage if the propeller gets fouled, so I'm still not sure.

 

I was confused again, momentarily, as I hadn't heard the name Agni, but I see it's the Lynch LEM series.  I've had trouble finding a uk seller, so I must be looking for the wrong terms.  I found the Marlin 5 at Gecko Energy for £5,400 - four grand more than Peter has said (without gearbox, but with controller and instruments etc.), so I must be missing something here - but otherwise I found a US supplier and a French one, whilst just looking for the motor alone.  Given that it's a UK product (as far as I can tell), it would seem daft to re-import one from abroad, and those aren't in the marine rig anyway.

It's a long story Google Cedric lynch and then keep on working forward from there, Agni motors were made in India, it then became saitta, but as I said Google Cedric for the full story. 

The belt drive is a gearbox because it alters the ratios increasing torque in most cases at the loss of RPM 

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9 minutes ago, IanD said:

If you want to install a new ready-to-go drive system (including throttle, controller, display etc) instead of building it yourself, the best option is probably Waterworld:

 

https://www.energy-solutions.co.uk/products/waterworld

 

They did send me a quotation which I can't find, from memory it was just over £5k for the 15kW version.

 

If you think that's expensive, it's less than half the price of the comparable Bell-Marine and Fischer-Panda solutions...

 

Of course you can do it cheaper if you find all the bits yourself and put them together, especially if some are second-hand -- which is what Peter did. Same applies to batteries, and battery management/protection/charging system.

 

Just be aware that if you're going to put all this together with an expensive (even second-hand) LiFePO4 battery bank, you really need to know what you're doing, especially with charging and battery protection, to avoid reducing battery lifetime or in the extreme destroying them. There are people on this forum who have done this successfully (you can find many threads about this by searching), but if you're thinking of going down this route here's some strongly recommended reading (in case you haven't already):

 

https://marinehowto.com/lifepo4-batteries-on-boats/

 

http://nordkyndesign.com/category/marine-engineering/electrical/lithium-battery-systems/

 

The marinehowto site is written by a guy with a commercial side, but his advice about LiFePO4 is based on a lot of experience and there's some gold dust in there. The Nordkyn site is by a guy who desinged and built his own aluminium-hulled yacht from scratch together with most of the systems in it (there's some fascinating stuff on here, you can waste hours reading about it) and is generally reckoned to be one of the best information sources about LiFePO4 and using them on boats.

 

Have fun ?

I had lots of fun sourcing all the stuff Ian, all the Cedric lynch stuff was brand new, the big boat stuff was all secondhand, I am thinking of installing it in the big boat after regearing it so I will report back if I do

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55 minutes ago, peterboat said:

It's a long story Google Cedric lynch and then keep on working forward from there, Agni motors were made in India, it then became saitta, but as I said Google Cedric for the full story. 

The belt drive is a gearbox because it alters the ratios increasing torque in most cases at the loss of RPM 

One issue with direct drive motors is that they often want to run at rather higher speeds than is best for propellor sizing, typically 1500rpm or so, and running more slowly also reduces the power for a given size (cost) motor.

 

Antrepat asked about motors, the best I found (which Finesse are using) are from Engiro, UK source is voltsport.co.uk

 

https://www.voltsport.co.uk/voltsport-motors/engiro-motors-all

https://www.engiro.de/en/products/motors-and-generators

 

Best off-the-shelf choice for a narrowboat is probably the 205W_12013_ABC, 15kW/48V at 1080rpm means a nice-sized prop. The only slight problem is that this needs a 3-phase PMAC controller that can supply 380A rms which is too high for the biggest easily available reasonably-priced controller (Sevcon Gen 4 Size 6 which is 280A long-term) -- there's a not-quite-released-yet Curtis 1238SE-5971 which is rated at 390A rms but it's a lot more expensive and difficult to find.

 

For more power (e.g. wideboat, rivers) Engiro also do a 6-phase motor which can be driven by 2 48V Sevcon 3-phase controllers (205W_12202_ABC) which is 24.5kW/48V/1780rpm (49kW/96V/3550rpm -- power/voltage/rpm are proportional), but this is a bit too much power for a narrowboat (also 308A rms per phase) and the rpm are really too high, which means the prop ends up as a bit of an egg-beater. Finesse are having a custom version made with different windings to drop the power/current/rpm a bit to make it more suitable for a boat, this is what I'll be getting.

 

Belts do give some protection to the motor at first sight but I'm not convinced they're needed. With a direct-drive motor the prop has a far bigger inertia than the motor (which is far smaller inertia than a diesel engine) so if the prop gets jammed almost all the force is used to stop the prop, the motor will just stop together with it and shouldn't be damaged (though the prop might be). With a belt drive the motor spins several times faster so it's much harder to stop (typical 2.8:1 ratio means 8x more force needed to stop it) -- which means the belt is very likely to break if you're travelling at any speed when a jam happens. I'd rather have a direct-drive motor which just stops (maybe with some damage to the prop) than a belt drive where the prop is still damaged but the belt also breaks...

 

And I've heard belt drive boats (with brushed motors) and they whine, fine if you want to sound like a quiet milk float, but I'd rather have an almost silent (except for prop noise) direct-drive brushless motor.

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2 hours ago, IanD said:

One issue with direct drive motors is that they often want to run at rather higher speeds than is best for propellor sizing, typically 1500rpm or so, and running more slowly also reduces the power for a given size (cost) motor.

 

Antrepat asked about motors, the best I found (which Finesse are using) are from Engiro, UK source is voltsport.co.uk

 

https://www.voltsport.co.uk/voltsport-motors/engiro-motors-all

https://www.engiro.de/en/products/motors-and-generators

 

Best off-the-shelf choice for a narrowboat is probably the 205W_12013_ABC, 15kW/48V at 1080rpm means a nice-sized prop. The only slight problem is that this needs a 3-phase PMAC controller that can supply 380A rms which is too high for the biggest easily available reasonably-priced controller (Sevcon Gen 4 Size 6 which is 280A long-term) -- there's a not-quite-released-yet Curtis 1238SE-5971 which is rated at 390A rms but it's a lot more expensive and difficult to find.

 

For more power (e.g. wideboat, rivers) Engiro also do a 6-phase motor which can be driven by 2 48V Sevcon 3-phase controllers (205W_12202_ABC) which is 24.5kW/48V/1780rpm (49kW/96V/3550rpm -- power/voltage/rpm are proportional), but this is a bit too much power for a narrowboat (also 308A rms per phase) and the rpm are really too high, which means the prop ends up as a bit of an egg-beater. Finesse are having a custom version made with different windings to drop the power/current/rpm a bit to make it more suitable for a boat, this is what I'll be getting.

 

Belts do give some protection to the motor at first sight but I'm not convinced they're needed. With a direct-drive motor the prop has a far bigger inertia than the motor (which is far smaller inertia than a diesel engine) so if the prop gets jammed almost all the force is used to stop the prop, the motor will just stop together with it and shouldn't be damaged (though the prop might be). With a belt drive the motor spins several times faster so it's much harder to stop (typical 2.8:1 ratio means 8x more force needed to stop it) -- which means the belt is very likely to break if you're travelling at any speed when a jam happens. I'd rather have a direct-drive motor which just stops (maybe with some damage to the prop) than a belt drive where the prop is still damaged but the belt also breaks...

 

And I've heard belt drive boats (with brushed motors) and they whine, fine if you want to sound like a quiet milk float, but I'd rather have an almost silent (except for prop noise) direct-drive brushless motor.

My big boat is direct drive currently brushed because it was 300 squids and air cooled it can if it gets a bit of wood caught chop it in half! So much torque, but I am going to have a play with the agni/lynch motor which is ideal at 72 volts and the belt gearbox gets the RPM to the right numbers, I am after the better efficiency of Cedrics motors and better cooling the 4QD controller can be air or water cooled and it will tidy the wiring up getting rid of the reversing contractor. Because of my battery voltage I am stuck with what I have!

Starting again I would use a BMW I3 battery pack which is robust and very long lived, its also well priced secondhand 

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