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Antrepat

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Cost was 6d per boat for the electric tug (equivalent to a couple of quid today). Cost to install was the equivalent of a couple of hundred grand today...

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18 hours ago, Antrepat said:

 

Incidentally, if the suggestion made that a diesel at full power does 30% efficiency at the prop shaft, wouldn't that mean you'd need a 67hp engine to achieve 20hp actual...?

A diesel engine's rating is quoted at the output shaft. So a 20bhp diesel produces 20hp at the input to the gearbox. Ancillaries such as alternator and maybe water pump will take a little, as will the gearbox and prop shaft bearings and stern tube, meaning the prop will see around 10% less than the 20hp.  Of the energy in the fuel about a third comes out as motive power, a third is lost in the cooling air or water and the other third goes out of the exhaust as the latent heat of water vapour, hot air and unburned fuel.  So yes, to get 20hp at the prop you do need a fuel input equivalent to over 60hp.

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1 hour ago, TheBiscuits said:

 

 

Surely you'd assemble the next train of boats while the current one is in the tunnel, then just connect the tug and set off again.

 

The tug doesn't need to wait while the towed boats sort themselves out after leaving the tunnel, neither does it need to wait while the next train is being assembled.

 

Fair comment.  It was just a bit of fun.

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  • 2 months later...

I am suprised at the lack of discussion, in regard to electric boat propulsion, of torque and propellor design, not size or pitch but efficient design.

 

I have always been sceptical of the Lynch motor concept and those belt driven copies, purely on the low torque numbers given. It seems they are designed to spin fast like existing props, allowing for lots of slip to achieve forward motion. What's with the tiny shaft diameters too? It goes against everything I ever learned at marine eng school.

 

To be fair, my experience goes to direct shaft drive, on large marine ship instalations, some with variable controlled pitch propellor systems, some with specific propellor designs BUT, in any boat, the highest power / torque would be used to either intiate forward motion or to arrest it. Normal cruising at a fixed speed, allowing for supplimental momentum  results is a great drop in amps to the motor and thus greater overall longevity of the battery capacity. Some "boats" I have experience of can move 20,000 tons at 5 RPM at 4 knots for a month at a time, in a seaway.

 

I would point my real world finger at the propeller as the culprit.  In the "real" marine world, there has been a huge investment in low rev, high thrust models, giving (near ) low cavitation in a submerged environment. Those VLBC / VLCC you often see running unloaded and high in the water with the prop 2/3rds submerged are wasting SO MUCH energy!! Also canal boats rely on traditional calculations with an ICE, measured in litres of diesel a day and accepting high slipage in a design dating back 100 years. In the new age of conserving energy in a non ICE environment there needs to be , IMHO, a new design philosophy in this area. In the same way that outboards were improved when it became viable to race them and so they got huge prop R&D investment and actually use cavitation as an additon to thrust. NOT suitable for canals and rivers, before you all start shouting at me. 

 

So can we have a shaft drive, high torque EM, with a prop specifically designed for its ability to operate at lower shaft speeds ( iE Crawl ) to provide low amp forward thrust, suitable for 2 - 5 mph, using suplimental momentum of a 17.5 tonne object and also being capable of operating against a current on river excusions? I doubt a CPP system would be anything like affordable in this market but I live in hope because if I can do it in Lego then surely it's possible in the real world? Again in the real world, unlikely when prop manufacturers in this market seem to be low quality sand pattern casters who then just polish to finish, when what is needed is a billet CNC machined thing of beauty.  Yes, I accept the expense but when people buy those nice new yellow sprayed engine sets and fit those lovely blue electrical boxes in their boats, higher expense is already accepted. Don't get me started on the robbery that are hybrid engines.

 

FYI - I have lived outside the UK in the Far East for nearly 20 years and will return to the UK shortly because of the local political situation and to build two 57s. I am shocked and stunned at the rise in prices in the UK that are now accepted for "stuff", as I have always been a cheapskate, but times change and technology too.

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Much sense in HK's post (and some that I don't understand) but I don't know why variable pitch props are not found more often in our world. OK, there are issues with expense and doubtless other things that I don't know but if we are going to be stuck with electric motors with probably exaggerated green credentials (all that copper, all those nasty batteries)  then there must be a a better way of shoving a boat along than the heap of compromises that most propellers are.

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34 minutes ago, Bee said:

Much sense in HK's post (and some that I don't understand) but I don't know why variable pitch props are not found more often in our world. OK, there are issues with expense and doubtless other things that I don't know but if we are going to be stuck with electric motors with probably exaggerated green credentials (all that copper, all those nasty batteries)  then there must be a a better way of shoving a boat along than the heap of compromises that most propellers are.

You can buy variable props  it's just their life expectations are very short! The issue is the bottom is to close to the top so that they would hit something and break also they would be running in a mud slush!

 

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2 hours ago, David HK said:

I am suprised at the lack of discussion, in regard to electric boat propulsion, of torque and propellor design, not size or pitch but efficient design.

 

I have always been sceptical of the Lynch motor concept and those belt driven copies, purely on the low torque numbers given. It seems they are designed to spin fast like existing props, allowing for lots of slip to achieve forward motion. What's with the tiny shaft diameters too? It goes against everything I ever learned at marine eng school.

 

To be fair, my experience goes to direct shaft drive, on large marine ship instalations, some with variable controlled pitch propellor systems, some with specific propellor designs BUT, in any boat, the highest power / torque would be used to either intiate forward motion or to arrest it. Normal cruising at a fixed speed, allowing for supplimental momentum  results is a great drop in amps to the motor and thus greater overall longevity of the battery capacity. Some "boats" I have experience of can move 20,000 tons at 5 RPM at 4 knots for a month at a time, in a seaway.

 

I would point my real world finger at the propeller as the culprit.  In the "real" marine world, there has been a huge investment in low rev, high thrust models, giving (near ) low cavitation in a submerged environment. Those VLBC / VLCC you often see running unloaded and high in the water with the prop 2/3rds submerged are wasting SO MUCH energy!! Also canal boats rely on traditional calculations with an ICE, measured in litres of diesel a day and accepting high slipage in a design dating back 100 years. In the new age of conserving energy in a non ICE environment there needs to be , IMHO, a new design philosophy in this area. In the same way that outboards were improved when it became viable to race them and so they got huge prop R&D investment and actually use cavitation as an additon to thrust. NOT suitable for canals and rivers, before you all start shouting at me. 

 

So can we have a shaft drive, high torque EM, with a prop specifically designed for its ability to operate at lower shaft speeds ( iE Crawl ) to provide low amp forward thrust, suitable for 2 - 5 mph, using suplimental momentum of a 17.5 tonne object and also being capable of operating against a current on river excusions? I doubt a CPP system would be anything like affordable in this market but I live in hope because if I can do it in Lego then surely it's possible in the real world? Again in the real world, unlikely when prop manufacturers in this market seem to be low quality sand pattern casters who then just polish to finish, when what is needed is a billet CNC machined thing of beauty.  Yes, I accept the expense but when people buy those nice new yellow sprayed engine sets and fit those lovely blue electrical boxes in their boats, higher expense is already accepted. Don't get me started on the robbery that are hybrid engines.

 

FYI - I have lived outside the UK in the Far East for nearly 20 years and will return to the UK shortly because of the local political situation and to build two 57s. I am shocked and stunned at the rise in prices in the UK that are now accepted for "stuff", as I have always been a cheapskate, but times change and technology too.

We used to run slow revving high torque engines like electric motors can do, but our canals are to shallow for those propellers required for them I have a lynch motor 3 2 1 gearing works fine, you need to see what we have to work with before trying something that will work in deep water but will  e destroyed in days on our shallow muddy ditches 

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2 minutes ago, peterboat said:

You can buy variable props  it's just their life expectations are very short! The issue is the bottom is to close to the top so that they would hit something and break also they would be running in a mud slush!

 

So why dont cannal boats have ducted / cowled props?

 

Back in my navy days we had ships boats with " bucket drives".  The prop just spun in one dircction and two halves of a bucket produced direction.  Hand opperated but with todays tech may be easy to incorporate?

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18 minutes ago, David HK said:

So why dont cannal boats have ducted / cowled props?

 

Back in my navy days we had ships boats with " bucket drives".  The prop just spun in one dircction and two halves of a bucket produced direction.  Hand opperated but with todays tech may be easy to incorporate?

How would you clean the prop of weed? I am on deep water (over 9 foot deep) and yet I still get stuff on my prop! Most of our canals are very shallow with the bottom full of rubbish that we constantly stir up, just accept that for our conditions what we have works, if the canals were deeper as designed and cleaned of crap your ideas would work ie big slow spinning propellers. 

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25 minutes ago, peterboat said:

We used to run slow revving high torque engines like electric motors can do, but our canals are to shallow for those propellers required for them I have a lynch motor 3 2 1 gearing works fine, you need to see what we have to work with before trying something that will work in deep water but will  e destroyed in days on our shallow muddy ditches 

I see your point. Thanks.

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20 minutes ago, David HK said:

So why dont cannal boats have ducted / cowled props?

 

Back in my navy days we had ships boats with " bucket drives".  The prop just spun in one dircction and two halves of a bucket produced direction.  Hand opperated but with todays tech may be easy to incorporate?

 

They have been tried and failed - as they cannot withstand hitting supermarket trolleys, bicycles, safes, etc etc. The cups get dented and fail to work. or fouled up with rubbish, weeds etc.

 

Remember that out canals are in the main 2' 6" - 3' deep and many boats have similar draft and polish the base plate every time they move.

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33 minutes ago, peterboat said:

We used to run slow revving high torque engines like electric motors can do, but our canals are to shallow for those propellers required for them

We still do. Plenty of ex-working narrow boats about on both wide and narrow canals, drawing 3 ft or so, propelled by large diameter slow running props, and mostly driven by lower powered engines than the majority of modern boats. If it works for vintage diesel engines I don't see why electric motors can't do the same.

37 minutes ago, David HK said:

 

Back in my navy days we had ships boats with " bucket drives".  The prop just spun in one dircction and two halves of a bucket produced direction.  Hand opperated but with todays tech may be easy to incorporate?

 

Why would you need this with electric propulsion? Reversing an electric motor is far easier than a mechanical reversing gearbox or a bucket contraption.

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This boils down to the same thing as hovering aircraft: There are two approaches; move a lot of water  (air).slowly, the helicopter approach or a smaller bit much faster.  The Harrier/Elon Musk reusable rocket landing  approach.  The experts talk about momentum change and energy.

 

Practically, for a canal boat, moving a smaller amount of water has other benefits:

Less underwater space is needed by the prop, so draught can be decreased;

Moving less water means less opportunity for the weed etc. to find a new home on the blade.

A faster rotating prop may be better at throwing  off crap and is easier to match to a modern engine.

 

There are downsides though:

At low speeds a fast turning prop is less efficient.

Hitting something solid with a high speed prop can do real damage.

 

 

The kitchen rudder (buckets round the prop) is the invention of the devil.  It was  very manoeuverable once you had the skill but getting the skill took ages, and it still need a clutch for when you wanted to stop.

 

N

 

 

 

 

 

 

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8 minutes ago, BEngo said:

 

The kitchen rudder (buckets round the prop) is the invention of the devil.  It was  very manoeuverable once you had the skill but getting the skill took ages, and it still need a clutch for when you wanted to stop.

 

Quote

Kitchener gear not Kitchen,  but once you posted my brain woke up from a 30 year leep. i was a motor boat mechanic as one job and the boats with this were normally big MF load luggers. Not officer boats and I agree with your comments. Would be a lot easier controlled by a micro controller these days. As someone has already commented the shollow bottom a detritis may cause more problems than provide benefits.

 

 

Edited by David HK
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1 hour ago, David Mack said:

We still do. Plenty of ex-working narrow boats about on both wide and narrow canals, drawing 3 ft or so, propelled by large diameter slow running props, and mostly driven by lower powered engines than the majority of modern boats. If it works for vintage diesel engines I don't see why electric motors can't do the same.

 

Why would you need this with electric propulsion? Reversing an electric motor is far easier than a mechanical reversing gearbox or a bucket contraption.

I know David but we both know the reality of some canals only having two foot six of depth! I could easily regear my motor for a bigger prop but the stern is another story! ? big slow spinning propeller is the most effective setup

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12 minutes ago, peterboat said:

I know David but we both know the reality of some canals only having two foot six of depth!

Which canals are those then? Boats drawing 3 feet navigate over the whole of the connected system with very few serious difficulties.

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13 minutes ago, David Mack said:

Which canals are those then? Boats drawing 3 feet navigate over the whole of the connected system with very few serious difficulties.

 

C&RTs own figure say they maintain the Llangollen & the Ribble Link to 2' 3", with the Mon & Brec and parts of the HNC to 2' 6"

 

 

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35 minutes ago, David Mack said:

Which canals are those then? Boats drawing 3 feet navigate over the whole of the connected system with very few serious difficulties.

Years ago I towed an old boat off near black country living museum he drew 3 foot and was on the bottom!

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1 hour ago, Alan de Enfield said:

 

C&RTs own figure say they maintain the Llangollen & the Ribble Link to 2' 3", with the Mon & Brec and parts of the HNC to 2' 6"

 

 

3 ft deep boats can get to Llangollen. Ribble Link is a new waterway, although I'm surprised they built it that shallow, likewise the restored HNC. And the Mon and Brec is not part of the connected waterway network.

55 minutes ago, peterboat said:

Years ago I towed an old boat off near black country living museum he drew 3 foot and was on the bottom!

Well any boat can go aground in shallower parts of the canal. Doesn't mean there isn't a perfectly good 3 ft+ deep channel though.

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Just now, David Mack said:

3 ft deep boats can get to Llangollen.

 

 

I know, and they are 'ploughing their own furrow'.

C&RT will only guarantee depths of 2' 3" (I guess it is actually dredged to a greater depth to allow for infill over time)

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There's actually an optimum speed/diameter/pitch/rpm for a propeller at a given power level which gives maximum efficiency; too small ("egg-whisk") and the prop speed is too high and losses go up (with cavitation in extreme cases), too large and the pitch is too small compared to diameter and losses go up. A good start to getting close to this optimum is the displacement hull prop size calculator at https://www.vicprop.com/free-propeller-sizing-calculators.

 

Another "rule-of-thumb" for slow-speed boats like narrowboats is that the tip speed should be about 25m/s, which means the diameter in inches multiplied by propellor rpm should be about 19000. Another rule-of-thumb is that diameter^2/bhp=15 -- in other words, a given power per square inch of propeller area, which I think comes out with the same answer. Yet another "rule-of-thumb" is that optimum diameter/pitch is around 0.6-0.8 for slow high-pulling-power boats.

 

To take an example, put the numbers for an Engiro 12013 electric motor in (15kW/20bhp at 1080rpm), the tip speed "rule-of-thumb" gives a diameter of 17.4", diameter^2/bhp gives 17.3", propcalc suggest a 17.6" x 11.8" prop, all of which suggests this is close to an optimum design for 15kW/20hp -- this is true regardless of whether the engine is electric or diesel (or steam...). Most direct-drive electric motors at these power levels used in narrowboats run at 1500rpm or even higher which gives a 14.4" x 8.5" prop -- the classic "egg-beater", too small and turning too fast. Geared motors can choose the optimum prop speed/size but need belts which whine and break...

 

What is obvious is that as power levels go up so should prop diameter, but this often doesn't happen on modern narrowboats because a "right-sized" prop is too big diameter to fit in. For example, for a Beta 43 with the standard 2:1 gearbox (43bhp/1400rpm at prop) propcalc suggests 17.4" x 11.1" which is pretty close to the size Beta recommend (18" x 12"), but it's actually going a bit too fast (tip speed is 33m/s). Note that this is almost exactly the same size as the 20bhp electric one above, but turning faster to absorb more power. The optional 2.8:1 gearbox would be a better choice (43bhp/1000rpm at prop) but would need a 21.3" x 15.5" prop (3-bladed) which is too big for most modern hulls, and still has tip speed of 28m/s.

 

To the best "pulling power" and lowest wake noise with 40bhp would need a 25.3" x 20.7" prop turning at 750rpm -- which is probably very close to what would have been used for deep-drafted boats in "the old days", but needs a swim at least 30" deep which modern hulls just don't have.

Edited by IanD
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32 minutes ago, IanD said:

There's actually an optimum speed/diameter/pitch/rpm for a propeller at a given power level which gives maximum efficiency; too small ("egg-whisk") and the prop speed is too high and losses go up (with cavitation in extreme cases), too large and the pitch is too small compared to diameter and losses go up. A good start to getting close to this optimum is the displacement hull prop size calculator at https://www.vicprop.com/free-propeller-sizing-calculators.

 

Another "rule-of-thumb" for slow-speed boats like narrowboats is that the tip speed should be about 25m/s, which means the diameter in inches multiplied by propellor rpm should be about 19000. Another rule-of-thumb is that diameter^2/bhp=15 -- in other words, a given power per square inch of propeller area, which I think comes out with the same answer. Yet another "rule-of-thumb" is that optimum diameter/pitch is around 0.6-0.8 for slow high-pulling-power boats.

 

To take an example, put the numbers for an Engiro 12013 electric motor in (15kW/20bhp at 1080rpm), the tip speed "rule-of-thumb" gives a diameter of 17.4", diameter^2/bhp gives 17.3", propcalc suggest a 17.6" x 11.8" prop, all of which suggests this is close to an optimum design for 15kW/20hp -- this is true regardless of whether the engine is electric or diesel (or steam...). Most direct-drive electric motors at these power levels used in narrowboats run at 1500rpm or even higher which gives a 14.4" x 8.5" prop -- the classic "egg-beater", too small and turning too fast. Geared motors can choose the optimum prop speed/size but need belts which whine and break...

 

What is obvious is that as power levels go up so should prop diameter, but this often doesn't happen on modern narrowboats because a "right-sized" prop is too big diameter to fit in. For example, for a Beta 43 with the standard 2:1 gearbox (43bhp/1400rpm at prop) propcalc suggests 17.4" x 11.1" which is pretty close to the size Beta recommend (18" x 12"), but it's actually going a bit too fast (tip speed is 33m/s). Note that this is almost exactly the same size as the 20bhp electric one above, but turning faster to absorb more power. The optional 2.8:1 gearbox would be a better choice (43bhp/1000rpm at prop) but would need a 21.3" x 15.5" prop (3-bladed) which is too big for most modern hulls, and still has tip speed of 28m/s.

 

To the best "pulling power" and lowest wake noise with 40bhp would need a 25.3" x 20.7" prop turning at 750rpm -- which is probably very close to what would have been used for deep-drafted boats in "the old days", but needs a swim at least 30" deep which modern hulls just don't have.

I have fitted the lynch motor in Ian its peak power is 26kw but I  reality 13kw continues is the most I expect to use. When the new controller arrives I will know better what its using, but I expect it to be better than the old series motor.  Its running 30 teeth to 80 teeth which  is 2.666666 to 1 which seems to work ok, the belt is a high quality item which should do ok, I do have spares though 

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3 minutes ago, peterboat said:

I have fitted the lynch motor in Ian its peak power is 26kw but I  reality 13kw continues is the most I expect to use. When the new controller arrives I will know better what its using, but I expect it to be better than the old series motor.  Its running 30 teeth to 80 teeth which  is 2.666666 to 1 which seems to work ok, the belt is a high quality item which should do ok, I do have spares though 

Those power figures look, on paper, horrendous. It runs 48v so how many amps does it actually suck out of the 

battery bank every hour for you?

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2 hours ago, David HK said:

Those power figures look, on paper, horrendous. It runs 48v so how many amps does it actually suck out of the 

battery bank every hour for you?

Mine runs at a nominal 72 volts is over 90% efficient, given that the motor holds a few world records on water and in motorbikes they are way better than you think, I would think on my widebeam it will be similar or slightly better than my old motor at 3.3kwh at 3 mph, it can run up to 400 amps flat out but the question is why?

Last week I was playing with it and after 1,5 hours it was 40 degrees C on the body and 55 C on the rotor its not creating heat its creating power the controller was sitting at 29 C.

I am awaiting a new all singing controller from 4QD with much more info available, designed for these motors really, so I will know better then how its doing

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On 18/05/2021 at 06:59, David HK said:

Again in the real world, unlikely when prop manufacturers in this market seem to be low quality sand pattern casters who then just polish to finish, when what is needed is a billet CNC machined thing of beauty.  Yes, I accept the expense but

I think you're missing the fact that the typical canal boat burns about 1.25 litres of red diesel per hour. Even if you could halve fuel consumption with a better prop, the annual saving would be too small to justify the expense for the user to buy one. Canal boat props are such a tiny market that there's really no incentive for the manufacturer's to invest. There may be some imperative to improve prop efficiency with electric drive canal boats, but even now that's still a very tiny fraction of an already tiny market. If more efficient propellors do become available for canal boats, they'll be as a result of the R&D for markets other than ours..

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