Interesting video - Narrowboat with azimuth pod drive

[IanD]

7 minutes ago, magnetman said:

I realise that is what you think.

 

However in a real situation where someone has a diesel engine installed and does not want to remove it there are not all that many ways to get electric propulsion..

 

I also considered having a pod each side of the uxter plate on retractable mounts with tubes to deck level fir servicing and prop cleaning. You could wind them up and down or use actuators. 

 

I spend most of my time in an 18ft electric canoe which I have put a trolling motor on the back of and steer with strings so I know about quiet electric boating. Its great but best to keep the diesel engine on a heavy boat. Diesel-gearbox-prop is actually very reliable. Yes one gets fuel issues but this is a sign of neglect not a design feature. Use a day tank and have good filters. 

 

Wing engines in the form of pod motors may be a better solution than a udder mounted pod. 

 

I haven't seen the video but in the image shown it appears too complex as the pod is separate but seems to be steerable. 

 

That is definitely overcomplicating things. 

 

 

You don't see the contradiction here? 😉

[magnetman]

A couple of pods one each side would be pretty easy to arrange. 

 

I'm talking about adding electric drive to a diesel boat. 

 

Having weed hatches could be useful. 

 

 

You could just weld in a couple of tubes big enough to accommodate the pods then mount them on cylinders which slide up and down inside the tubes. Not rocket science and if you had two pods you could use small ones. 

 

 

A couple of these would do 

 

[IanD]

17 minutes ago, magnetman said:

A couple of pods one each side would be pretty easy to arrange. 

 

I'm talking about adding electric drive to a diesel boat. 

 

Having weed hatches could be useful. 

 

You could just weld in a couple of tubes big enough to accommodate the pods then mount them on cylinders which slide up and down inside the tubes. Not rocket science and if you had two pods you could use small ones.

 

A couple of these would do 

 

 

If added electric drive is all you want, wouldn't it be far easier to do what parallel hybrids do and add a toothed-belt drive from an electric motor onto the gearbox output shaft?

 

Far simpler and cheaper and doesn't involve cutting big holes into the hull, or adding on possibly vulnerable pods...

[magnetman]

3 minutes ago, IanD said:

 

If added electric drive is all you want, wouldn't it be far easier to do what parallel hybrids do and add a toothed-belt drive from an electric motor onto the gearbox output shaft?

 

Far simpler and cheaper and doesn't involve cutting big holes into the hull, or adding on possibly vulnerable pods...

Parallel hybrids seem to have problems. Yes it would be easier to do that but it won't be properly quiet.

 

If doing an electric boat I would be very upset if the boat was noisy. 

 

 

[IanD]

15 minutes ago, magnetman said:

Parallel hybrids seem to have problems. Yes it would be easier to do that but it won't be properly quiet.

 

If doing an electric boat I would be very upset if the boat was noisy. 

 

 

The problems of parallel hybrids are mostly to do with inefficiency when charging or propelling the boat (big engine running at low power, inefficient alternators/charging), plus not being as quiet as (direct-drive) series hybrids under electric power. Also to save money most of them currently use lead-acid or lead-carbon batteries, with lower efficiency and lifetime than LFP.

 

Why is a parallel hybrid "not properly quiet" with the diesel engine off? If you mean high-frequency noise/whine from the belt drive and the higher-speed motor, don't forget that pods with small fast-turning props are also noisier than a bigger slower prop like in a series (or parallel) hybrid -- the ones like you showed are really intended for lighter faster small boats, not big heavy slow narrowboats, the high rpm and tip speeds will reduce efficiency and generate noise... 😞

Edited October 2, 2023 by IanD

[magnetman]

It seems likely the pod will be quieter. 

 

I want two propellers. 3 would be even nicer. 

 

 

[IanD]

3 minutes ago, magnetman said:

It seems likely the pod will be quieter. 

 

I want two propellers. 3 would be even nicer. 

 

 

Or not. What's the rpm and prop size? Small high-speed props are *not* quiet, and are inefficient when propelling slow boats -- the prop speed (diameter/pitch/rpm) needs to be matched to the boat speed, which is why narrowboats use relatively large slow-turning props.

 

More propellers = more opportunity to foul/damage them, especially if not designed for canal use... 😉

[booke23]

6 hours ago, IanD said:

 

A clever idea, but a couple of things don't seem to work very well --- the first is the non-intuitive motor speed control method (buttons rather than a lever), but the bigger one is that with the motor running the tiller is very heavy and difficult to move and vibrates a lot, which is exactly what you don't want on an electric drive boat... 😞

 

 

5 hours ago, IanD said:

And that might be part of the reason for the very heavy rudder if the bearings used were not up to the job -- which I'd be surprised given the aerospace engineering background of the designer.

 

I did toy with the idea of pod drive a couple of years ago, but on further investigation decided it wasn't really suitable for a narrowboat -- too expensive and fragile for canals/locks, and not good with a tiller. For their intended application -- deep-water use in ships like ferries with powered wheel steering where extreme manoeuvrability is vital -- they can be a good solution.

 

Indeed. With development I'm sure it could be much improved....I've seen these pods made by mainstream manufacturers (Volvo IPS pod drive) for sea going pleasure craft, but as you say steered hydraulically and in the case of the Volvo versions, computer controlled. And they would certainly be prone to damage on the inland waterways.  

[ditchcrawler]

Didn't the gravel boats on the GU have pods and no reverse, just swivel the pod

[booke23]

14 minutes ago, ditchcrawler said:

Didn't the gravel boats on the GU have pods and no reverse, just swivel the pod

 

My old Johnson 2hp outboard was like that.....no gearbox at all, just swivel it for astern and stop the engine for neutral! 

[magnetman]

Nato tugs have steerable schottel drives with no reverse gear.

 

As for the small propeller story it would only be possible to test this by actually fitting one. Generally small props are for lighter boats but if you look at large azimuth thrusters on ships the propellers are not all that large. 

 

 

 

 

Of course if it is a upstream propeller the water flow in won't be negatively impacted by the motor housing. Most pod motors have downstream propellers. 

 

 

[IanD]

12 minutes ago, magnetman said:

Nato tugs have steerable schottel drives with no reverse gear.

 

As for the small propeller story it would only be possible to test this by actually fitting one. Generally small props are for lighter boats but if you look at large azimuth thrusters on ships the propellers are not all that large. 

 

 

 

 

Of course if it is a upstream propeller the water flow in won't be negatively impacted by the motor housing. Most pod motors have downstream propellers. 

 

 

You really need to do some more in-depth research into how propellers work and how they're matched to a motor/hull...

 

Azimuth thrusters -- like bow thrusters -- have small relatively high-speed propellers because -- unlike propulsion ones -- they don't have to provide much thrust, and noise doesn't really matter.

 

If you want a quiet propulsion propeller on a low-speed boat -- like an electrically-propelled narrowboat -- you need to keep the rpm and tip speed down, the usual rule-of-thumb is to try and not exceed 1000rpm and 25m/s tip speed at full power. You also need to take into account how much power the prop needs to absorb, and also what the hull speed will be -- there's an optimum speed for the prop wash, too slow or too fast wastes power.

 

The prop calculators like Vicprop can give a good insight into this if you play around with power/rpm for a narrowboat-sized hull, but the sizes/rpm they come up with are nowhere near those used by the smaller high-speed pods you keep giving as examples, or similar ones used on electric outboards -- these are all targeted at much smaller lighter faster boats, and are just not appropriate for narrowboats.

 

The propulsion/steering pods used by tugs have big lower-speed props driven by big -- usually geared -- motors, and are *extremely* expensive as a result. Something similar but much smaller could in theory be developed for narrowboats, but nobody's going to do it because the market is tiny -- and even fewer boaters would be willing to pay the resulting cost, which would probably start at something like £10k per pod going by the cost of marine electric propulsion systems from suppliers like BellMarine... ;-(

[magnetman]

Does Vicprop have a setting for boats with such a high Bc (block coefficient)? 

 

Never looked at it but I did wonder if it was made around the assumption that a boat would usually have quite a low Bc whereas the average canal boat if it has slab sides has a very high Bc. 

 

 

 

I've always been of the view that the initials Bc when referring to a narrow boat actually stand for Brick comparison.

[ditchcrawler]

These boats have two pods, one each end

 

[IanD]

40 minutes ago, magnetman said:

Does Vicprop have a setting for boats with such a high Bc (block coefficient)? 

 

Never looked at it but I did wonder if it was made around the assumption that a boat would usually have quite a low Bc whereas the average canal boat if it has slab sides has a very high Bc. 

 

I've always been of the view that the initials Bc when referring to a narrow boat actually stand for Brick comparison.

Vicprop allows you to enter length/width/draught and displacement (weight) so it should take account of this, but anyway the BC only has a weak effect on prop size, power and rpm have by far the biggest effect.

 

Go and play with some numbers and see what happens, including to predicted boat speed in deep water, you should get a feel for how this works quite quickly... 😉

[magnetman]

I've got too many boats to play with! No time for computer programs also no working computer available even if immersion was attractive. 

 

Just the Xiaomi Redmi9 fone keeping me in touch with what is presumably a reality, of sorts. 

 

 

[JungleJames]

8 hours ago, magnetman said:

I realise that is what you think.

 

However in a real situation where someone has a diesel engine installed and does not want to remove it there are not all that many ways to get electric propulsion..

 

 

If you don't remove the diesel engine, and that is what producing your elektrikery, then you don't have electric propulsion.

You have a diesel electric drive train with added batteries.

 

So you have a 2 blade prop (bad vibration) which will usually sit adding to the drag when your pod is doing the work. 

 

Your pod, which should normally be more efficient if the hull and drivetrain is designed around it, probably ends up being less efficient with its 2 bladed brake.

I can see what you are thinking, I think, but aren't you guilty of trying to redesign the wheel when there is nothing wrong with it? 

 

For the small amount of fuel a narrow boat uses, trying to convert something to this magnitude doesn't seem worth while, and certainly not if you keep the initial drive train as well.

 

Of course, your money, your choice. Go for it. 

 

[ditchcrawler]

9 minutes ago, JungleJames said:

 

I can see what you are thinking, I think, but aren't you guilty of trying to redesign the wheel when there is nothing wrong with it? 

 

 

Isn't that what this forum is all about, solving problems that don't exist 😁

[JungleJames]

5 hours ago, ditchcrawler said:

Isn't that what this forum is all about, solving problems that don't exist 😁

I suppose everybody does it from time to time.

[john.k]

I didnt see from the waffle laden video,but they may have cooling  water flowing thru the electric motor ,which increases the power output /size  ........theoretically ,a 20+ hp motor would be possible .....I have made these kinds of drives for barges,but always hydrostatic with a roller stator motor ,which has low revs ,high torque,and can take prop loads directly coupled ............It seems the only reason for a front mount prop is access from inside the boat 

[magnetman]

10 hours ago, JungleJames said:

If you don't remove the diesel engine, and that is what producing your elektrikery, then you don't have electric propulsion.

You have a diesel electric drive train with added batteries.

 

So you have a 2 blade prop (bad vibration) which will usually sit adding to the drag when your pod is doing the work. 

 

Your pod, which should normally be more efficient if the hull and drivetrain is designed around it, probably ends up being less efficient with its 2 bladed brake.

I can see what you are thinking, I think, but aren't you guilty of trying to redesign the wheel when there is nothing wrong with it? 

 

For the small amount of fuel a narrow boat uses, trying to convert something to this magnitude doesn't seem worth while, and certainly not if you keep the initial drive train as well.

 

Of course, your money, your choice. Go for it. 

 

 

It isn't about having an electric boat. All electric canal boats are rather impractical unless going for short runs and back to base..

 

For me the reason would be the option of silent running. Stealth mode. 

As I said the two blade prop can be parked using a sensored brushless motor. I run a two blade rc aircraft prop on my electric canoe and it has no vibration problems at all. Much smaller yes but its long and thin like a canal boat. 

 

The main engine prop which is of course a normal 3 blade bronze type would not be a problem in terms of drag at low speeds. 

Look how easy it is to bowhaul a canal boat and how long it takes to stop when the engine is put in neutral. 

 

Its not an electric boat but neither is a series hybrid an electric boat. 

 

My design would be a diesel boat with stealth mode as well as two entirely independent means of propulsion.

 

I would not consider removing the diesel engine from a conventional driveline for reliability and range reasons but the addition of a silent running option seems quite interesting and having steerable thrust is also quite appealing. 

 

 

 

[JungleJames]

17 minutes ago, magnetman said:

 

It isn't about having an electric boat. All electric canal boats are rather impractical unless going for short runs and back to base..

 

For me the reason would be the option of silent running. Stealth mode. 

As I said the two blade prop can be parked using a sensored brushless motor. I run a two blade rc aircraft prop on my electric canoe and it has no vibration problems at all. Much smaller yes but its long and thin like a canal boat. 

 

The main engine prop which is of course a normal 3 blade bronze type would not be a problem in terms of drag at low speeds. 

Look how easy it is to bowhaul a canal boat and how long it takes to stop when the engine is put in neutral. 

 

Its not an electric boat but neither is a series hybrid an electric boat. 

 

My design would be a diesel boat with stealth mode as well as two entirely independent means of propulsion.

 

I would not consider removing the diesel engine from a conventional driveline for reliability and range reasons but the addition of a silent running option seems quite interesting and having steerable thrust is also quite appealing. 

 

 

 

I was just going by your initial 'electric propulsion' quote. 

Hence why I said what I did.

Clearly you know something with a diesel engine or generator isn't electric.

 

Unfortunately plenty still seem to call them electric!

[magnetman]

My understanding of the term 'electric propulsion' is where a propeller is turned by an electric motor. This could be a part time or full time solution to the problem of moving the boat across water. 

 

I like the solution as it is quiet. I like underwater drive pods as it seems to me to be the best arrangement. 

 

An 'electric boat' would need to have no fuel burning engine aboard otherwise it is not an electric boat.

 

It seems obvious. A boat with a diesel engine in it is never going to be an electric boat but it may have electric propulsion. 

 

 

[IanD]

2 hours ago, magnetman said:

My understanding of the term 'electric propulsion' is where a propeller is turned by an electric motor. This could be a part time or full time solution to the problem of moving the boat across water. 

 

I like the solution as it is quiet. I like underwater drive pods as it seems to me to be the best arrangement. 

 

An 'electric boat' would need to have no fuel burning engine aboard otherwise it is not an electric boat.

 

It seems obvious. A boat with a diesel engine in it is never going to be an electric boat but it may have electric propulsion. 

 

 

For many people a series hybrid with a lot of solar on the roof doesn't need to run the (diesel) generator at all in summer, unless you cruise for several long days in a row which many people don't. That makes it an electric boat.

 

In winter this is of course not the case, and a generator is needed unless you have a shoreline plug-in, so it's a series hybrid.

[magnetman]

I know. 

 

I was responding to the other poster who seemed to be confused between the terms 'electric boat' and 'electric propulsion'. 

 

A boat with a diesel engine installed is not an electric boat.