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Old 30-11-2016, 05:19   #496
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Re: Oceanvolt Hybrid Motor

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Originally Posted by BigBeakie View Post

But even so, what is the max torque on the electric vs the diesel?
Whatever you want it to be. Just run it thru the proper gearing. Tell me what torque you are getting from the electric motor at the prop and I can get you 50% better torque at the prop from the diesel.

You'll notice from octopus' well described operations, that he is using large props with a lot of torque available. With the exception of instantly going from hard forward to hard reverse, you could achieve the same thing with a reduction gear and big props on a diesel. Given the twin engine catamarans are typically considered to be the most maneuverable type of boat available, it's an improvement on something that is already the best.

"The hybrid is far more manoeuvrable than a conventional diesel. I've waited my turn watching a 440 make a complete pigs-ear of berthing in gusty cross-winds and then followed in and parked perfectly. The electric motors connected to their large props have far more grip on the water and I can push through from full ahead to full astern without even pausing in the middle."

But hey, I'm just a hater for calling out marketers claiming they can break the laws of physics, so don't mind me.
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Old 30-11-2016, 05:22   #497
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Electronic Diesel Engine Control

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Rob

Finally, it is all very well to quote the capability of ocean volt engineers, but when you are 500Km from anywhere - say between Vanuatu and Aus, there will not be an Ocean Volt engineer to be seen. You will be dependant on one generator, with all of its attendant issues, as compared to two diesels which are independent other than fuel supply. In two years my generator has failed a few times for various reasons. My diesels have never failed and if they did I pretty much know how to get them going again. A generator is a black box with a lot of electronics, and Murphies law dictates that it can and will fail at the worst of times. A clear example of this to me is the Autopilot which I have had fail on me on numerous occasions. On this basis alone I would not equip EP unless I had two generators.
Just wondering what your opinion is of the electronic controls being placed on ALL new diesel engines??
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The mechanical fly-weight governors of inline and distributor diesel fuel injection pumps used to control fuel delivery under a variety of engine loads and conditions could no longer deal with the ever increasing demands for efficiency, emission control, power and fuel consumption. These demands are now primarily fulfilled by the Electronic Control, the system which provides greater ability for precise measuring, data processing, operating environment flexibility and analysis to ensure efficient diesel engine operation. The EDC replaces the mechanical control governor with an electro-magnetic control device.
The real problem I have with this technology is its susceptibility to failure by lighting strikes, etc, that might damage that little 'electronic brain', and render the engine(s) useless. If that happens you can no longer get these engines to operate, at all. (brain replacement is only solution I know of at the moment)
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Old 30-11-2016, 05:44   #498
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Re: Oceanvolt Hybrid Motor

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Originally Posted by valhalla360 View Post
Whatever you want it to be. Just run it thru the proper gearing. Tell me what torque you are getting from the electric motor at the prop and I can get you 50% better torque at the prop from the diesel.
But at set RPM's, not the whole range...
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Old 30-11-2016, 05:54   #499
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Re: Oceanvolt Hybrid Motor

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Originally Posted by BigBeakie
OK, I'll ask again in case we have missed something. What is the single killer reason that EP is completely the wrong decision for bluewater cruising? Fire away.
Rob

I guess you have it all sorted then. Best of luck on the build of the new boat.
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Old 30-11-2016, 06:00   #500
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Re: Electronic Diesel Engine Control

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Just wondering what your opinion is of the electronic controls being placed on ALL new diesel engines??
The real problem I have with this technology is its susceptibility to failure by lighting strikes, etc, that might damage that little 'electronic brain', and render the engine(s) useless. If that happens you can no longer get these engines to operate, at all. (brain replacement is only solution I know of at the moment)
Very good question. I guess we all had to swallow the introduction of EFI into motor vehicles, but with a MV EFI failure I can simply ease to the side of the road and call a tow. Not so easy when you are at Minerva Reef.

Lightning is only one of the problems. Water intrusion and salt corrosion are others.

My current diesels do not have these controls and I am not interested in a new boat going forward so I hope to avoid the problem for the foreseeable future, but eventually it will be a universal on most boats.

I guess you have to pray that any issue is within 200nm of land, where you can get effective help should you need it and chalk it down to the cost of progress.
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Old 30-11-2016, 06:57   #501
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Re: Oceanvolt Hybrid Motor

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But at set RPM's, not the whole range...
Actually, you can have it over the entire RPM range though at RPM that generates peak torque, it may be 100-200% more than the electric motor.
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Old 30-11-2016, 09:24   #502
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Re: Oceanvolt Hybrid Motor

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Actually, you can have it over the entire RPM range though at RPM that generates peak torque, it may be 100-200% more than the electric motor.
Well said and quite true (ish). For comparison of this blatantly disingenuous claim, let's compare your hypothetical engine with the corresponding electric motor power in a production P90D passenger car. You would then need a engine that generated 1,428-2,139 lb/ft of torque, taking said motor out of the realm of practical daily use and placing it into the category of race-car technology or commercial shipping. Regardless, hardly equivalent use to a passenger vehicle or small boat.

But then again, you did say Elon Musk is not innovative, so your comments never really surprise.
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Old 30-11-2016, 09:29   #503
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Re: Oceanvolt Hybrid Motor

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Originally Posted by cwjohm View Post
Octopus states that he is typically only one hour from anchor. In that instance I would also seriously consider EP.
Err, that's not what I said. I said that I felt one hour of of motoring on batteries alone was sufficient to get you out of trouble:
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An hour is plenty. Twice our genset has failed at critical moments and each time we were safely anchored or moored within ten minutes.
In response to Rob's query
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Originally Posted by BigBeakie View Post
... our thinking for planning our system was that there are 2 basic scenarios to be able to handle for offshore cruising and liveaboard. One is the max power for short duration, the "get out of Dodge" emergency like having to pick up the hook in a big blow. We have sized our LFP bank to be able to motor at full power for an hour... Your thoughts on the above?
Actually, I think diesel-electric propulsion (I refuse to call it EP) is ideally suited to long-distance passage-making and liveaboard life on the hook.

Much of my sailing has been long-distance passage-making and on-the-hook island hopping, where our hybrid diesel electric propulsion has proved its worth, simply because the abundance of electrical energy has improved our quality of life.

Regards

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Old 30-11-2016, 11:18   #504
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Re: Oceanvolt Hybrid Motor

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Yeah but that is the Torqeedo 30kW Deep Blue motor., as myocean stated.
That drop is just one of the things that led me to another vendor. We saw some strange things with the Deep Blue that didn't add up.
The drop you see there is the result of not limiting the RPMs to go higher than the point of maximum power. (which is at 700 rpm here)
Every electric motor can operate with maximum torque over the whole range up to the speed where the maximum power is reached - not further! In this example at 700 rpm max power is reached.
Vendors may limit the speed, so it can not exceed this point (and then the line is just flat) or they just leave this open. In this case this rpm limit is not set.

For an efficient prop solution you would probably target the 700 rpm for max. power, so you do not really need the higher rpms.
This is a big difference to diesel engines where you have the maximum power available only when going to the highest rpm.
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Old 30-11-2016, 11:29   #505
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Re: Oceanvolt Hybrid Motor

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Originally Posted by SDChristian View Post
Well said and quite true (ish). For comparison of this blatantly disingenuous claim, let's compare your hypothetical engine with the corresponding electric motor power in a production P90D passenger car. You would then need a engine that generated 1,428-2,139 lb/ft of torque, taking said motor out of the realm of practical daily use and placing it into the category of race-car technology or commercial shipping. Regardless, hardly equivalent use to a passenger vehicle or small boat.

But then again, you did say Elon Musk is not innovative, so your comments never really surprise.
Nothing disingenuous about it.

Let's say it's a 2000lb-ft (not lb/ft) torque tesla engine with no reduction gearing. (no idea what the actual gearing is but since you want to talk torque without a use case...).

16-1 is fairly typical for a pickup 1st gear. A V6 in the Ford (The weakest available engine and not the turbo)has about 230lb-ft of torque from idle, so in first gear it's putting out around 3700lb-ft of torque at the wheels from idle. If you have a low range gear box, it can push upwards of 30-1 to 40-1 or around 6000-8000lb-ft of torque at the wheel.

In an automotive situation, you can't run a single deep gear because you will run out of RPM long before you hit 70mph. That's why they use transmissions with multiple gears because you really don't need 8000lb-ft of torque once you get a load rolling.

For a displacement boat that only needs to do 0-8mph, you can put in a fairly deep gear ratio and still stay well within a reasonable RPM range for the engine. Also the propeller pitch acts as an additional gear ratio.

Given Oceanvolt says to replace a 45hp diesel with a 15hp electric, the example of getting the same torque from idle (at the propshaft) is very realistic but totally unnecessary. What low end torque gives you is better acceleration but that's not a major consideration when designing a drivetrain for a displacement vessel. For a displacement vessel, matching the drivetrain to typical cruising speed with enough extra power to handle adverse conditions, is the primary consideration. If it was all about having a big low pitch prop, you could put a 15hp diesel in with a reduction gear and match the acceleration of the electric boat.

But I guess you are too busy gushing of musk to bother learning about the physics behind the problem.

Edit: Oops, math error, that's 6900-9200lb-ft of torque for a weak non-turbo V6.

Also, checked it out and tesla model S doesn't put out anything close to 1400ft-lb, let alone 2000ft-lb. Maybe you were thinking of the torque at the wheel after the gear reductions?
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Old 30-11-2016, 11:29   #506
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Re: Oceanvolt Hybrid Motor

Here for better understanding the same diagram but with an additional power-curve.
If compare this with the power-curve of a diesel it is very different.
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Old 30-11-2016, 11:31   #507
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Re: Oceanvolt Hybrid Motor

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Originally Posted by myocean View Post
The drop you see there is the result of not limiting the RPMs to go higher than the point of maximum power. (which is at 700 rpm here)
Every electric motor can operate with maximum torque over the whole range up to the speed where the maximum power is reached - not further! In this example at 700 rpm max power is reached.
Vendors may limit the speed, so it can not exceed this point (and then the line is just flat) or they just leave this open. In this case this rpm limit is not set.

For an efficient prop solution you would probably target the 700 rpm for max. power, so you do not really need the higher rpms.
This is a big difference to diesel engines where you have the maximum power available only when going to the highest rpm.
Attachment 137227
Thanks myocean

Can you shed some light on this intractable disagreement about the electric carrying it's torque throughout the rev range, and the So What?, of this? In plain English, does the electric provide a notable advantage in pushing power against wind and waves?
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Old 30-11-2016, 11:53   #508
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Re: Oceanvolt Hybrid Motor

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Originally Posted by myocean View Post
Here for better understanding the same diagram but with an additional power-curve.
If compare this with the power-curve of a diesel it is very different.
Attachment 137228
And the so what is?? What is the effect?
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Old 30-11-2016, 14:06   #509
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Re: Oceanvolt Hybrid Motor

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Originally Posted by Octopus View Post

Much of my sailing has been long-distance passage-making and on-the-hook island hopping, where our hybrid diesel electric propulsion has proved its worth, simply because the abundance of electrical energy has improved our quality of life.
I presume this abundance of electrical energy is because of your large diesel generator?
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Old 30-11-2016, 14:09   #510
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Re: Oceanvolt Hybrid Motor

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This thread brings an anonymous quote to mind, "people who claim it cannot be done should not interrupt those who are doing it."
So you believe the claims that by running one electric motor in propulsion, using the power generated by the other in regen mode, a boat can be made to go faster than by sail power alone?

So therefore a boat in zero wind can go faster than zero knots....


And that people are actually doing this?
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