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Old 18-12-2018, 15:09   #1771
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Re: Oceanvolt Hybrid Motor

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Originally Posted by bridaus View Post
No. You are imagining the scenario you want. We don't know this at all. We know that at that RPM per the manual it is supposed to supply 17kW with a certain prop and gearing. The gearing and prop you are choosing for your example might allow it to decrease fuel, or it could just as well increase it. How do we know? We can't pretend it's a prop that happens to output the same 14.25kW at the same RPM just because we want it to be true!



Unfortunately I respectfully do not agree at all. You've used the output power of the OV as evidence that the Yanmar is producing less than what the specs state and introduced a theoretical prop/gearing combo that will support your argument that is different than Yanmar's manual states. Yes you could be right, but we could pick 20 other prop/gearing combos, 10 to prove you right, and 10 to prove you wrong. That's the point of holding variables constant, so you don't invalidate the other input. We could play "what if" with the unknowns all day long. What if the hull the Yanmar is driving has a lot more drag? What if the OV's does? What if I use this prop? What if...

I apologize, I have to be finished with this particular exercise, I am not qualified to explain this over the internet, no matter how much I want to or try. Maybe someone else can try/explain?

No, I used the OV as the baseline. All I'm saying is if the OV can push the boat at 7kts with 14.25KW at the prop, so can the 4JH5E. Period!

Same boat, same prop, same weight, same speed equates to same power required at the prop.
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Old 18-12-2018, 15:36   #1772
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Re: Oceanvolt Hybrid Motor

In the interests of keeping the thread alive can we please leave that point there? Thanks
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Old 18-12-2018, 15:42   #1773
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Re: Oceanvolt Hybrid Motor

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Originally Posted by OldMan View Post
No, I used the OV as the baseline. All I'm saying is if the OV can push the boat at 7kts with 14.25KW at the prop, so can the 4JH5E. Period!

Same boat, same prop, same weight, same speed equates to same power required at the prop.
I agree!
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Old 19-12-2018, 04:58   #1774
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Re: Oceanvolt Hybrid Motor

Ok, my next contribution requires answers to questions about transmissions. Does anyone know what the transmission used with the Yanmar 4JH5E in the Freeflow 46 is? Or a really typical transmission for it? Then I need to find (unless someone has it) schematics for that transmission to calculate the losses.

BTW, I feel that Gerr's high efficiency 3% is too optimistic (for almost any transmission), and the low efficiency (15%) may be arbitrary OR for a more complicated transmission than used in the application being discussed here. May be starting to split hairs here, but I wanted to take a break from the bsfc discussion, because I don't have data on whether generator manufacturers are accessing that part of the ICE map because no one publishes bsfc maps anymore (or maybe they never did). So I feel like that will be guessing too unless someone here has an inside source, or knowledge where to get these. If someone has a bsfc map for an engine used in a 10-20kW diesel generator (OR similar, we may not get to be picky) that would be useful too.

PS: I really like using the real life example we have here, because it makes it, well, real. It can get very time consuming to discuss total theory on the internet. Too many what if's.
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Old 19-12-2018, 08:00   #1775
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Re: Oceanvolt Hybrid Motor

Ignoring Oldman’s discussion point is an error in logic. He is exactly correct as anyone who ever actually sails a boat knows. You cannot use the propeller curve to determine fuel usage at any RPM. But you can estimate fuel burn pretty well if you know the power delivered by the engine (or used by the prop).

The propeller curve is provided so the engine maker can fault the system designer when an engine makes lots of black smoke and the customer is unhappy. That curve is the boundary between no smoke and dark smoke. Almost no one runs their boat on that curve at all RPMs.

The governor adjusts the injector fuel per power stroke to maintain a certain RPM as set by the throttle linkage. Thus fuel burned is closely related to power produced. Remember, the throttle adjusts desired RPM. Governor regulates fuel flow to maintain that RPM. Thus fuel flow determines power not RPM. More fuel means more power until you hit the propeller curve.
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Old 19-12-2018, 08:07   #1776
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Re: Oceanvolt Hybrid Motor

Transmission efficiency of ZF-15 is about 90-95%. It needs a bit of external cooling at 30kW input power. It only loses a few hundred watts at that input level.
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Old 19-12-2018, 09:17   #1777
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Re: Oceanvolt Hybrid Motor

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Transmission efficiency of ZF-15 is about 90-95%. It needs a bit of external cooling at 30kW input power. It only loses a few hundred watts at that input level.
Do you have a source for that number by chance?

30kW is higher than we are working at, but transmissions are mostly more efficient at higher loads in any case.

We'll target cruise speed which seems to need 15kW or so.

Are people running oil coolers on these when less than 25kW? Literature I'm reading says you don't have to...
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Old 19-12-2018, 10:23   #1778
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Re: Oceanvolt Hybrid Motor

My HBW150V transmission has a very tiny seawater heatsink. I can tell by the temperature that the power dissipated is <1kW at 35HP. These are very simple devices and do not have poor efficiency. They would burn up rapidly if so.
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Old 19-12-2018, 10:45   #1779
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Re: Oceanvolt Hybrid Motor

Agree they are simple, agree they don't lose a lot, but if they have a heatsink of any kind especially to seawater, they might lose more than you think.

The thing about heat, is the more you spread it, the less hot it has to be. So a lot of oil, heavy case, heatsink, etc. can dull the temperature it feels when putting your hand on it. All can be calculated.

Happen to know how many shafts it has, and how many gear engagements when running in forward? Shafts is probably 2, and gear engagements is probably 1 or 2, but I'm looking for schematics and confirmation.
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Old 19-12-2018, 12:26   #1780
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Re: Oceanvolt Hybrid Motor

The 4JH5E on the Freeflow 46 is shaft drive, not saildrive. I do not know the specific transmission. It would have been whatever was standard back in 2010 -2011.


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Old 19-12-2018, 13:03   #1781
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Re: Oceanvolt Hybrid Motor

My quick calculations on the V drive unit (HBW150V) without churning losses is 2.5kW, about 9.6%. I'm estimating another 1% in churning. Turns out supporting data that is current for bearing, gear, seal and churning loss is stingy online. I'm sure it's well protected information. If anyone has any sources, feel free to point. I don't know how I feel about dusting off old textbooks...

Without any other info, absolute best case on the 4JH5E shaft drive is about 4% without churning losses. This is the most efficient a transmission can be without exotic materials near as I can tell (2 shafts, 1 engagement, 4 bearings). Again, the data is sparse, I'm open to new sources and improving the calculations and I'm also working on it in spare time...
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Old 20-12-2018, 14:02   #1782
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Re: Oceanvolt Hybrid Motor

ZF-15 more info: Helical gears. Two engagements not one. 5 bearings rolling during use. Churning approximately 1-10% based on research (still hard to pin down) depending on viscosity/temp/etc. I'm going to keep it low at 2% estimate for now just from intuition (using low viscosity tf, lower RPM's, bottom shaft submerged 50%) but it may climb. I wish I could find some more relevant sources. There was talk of 5-10% for this specific transmission, but with no source. A source would be helpful.

Right now that puts ZF-15 at an estimated 10.5% loss.

Therefore with current estimates 16.75kW shaft input is required to output 15kW to prop.

PS: Clearly the HBW estimates I did are low, but I'm not going to dig into bevel gears, and how many shafts are fully submerged in that drive etc. It's going to be higher than 11-12% for sure.
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Old 21-12-2018, 10:06   #1783
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Re: Oceanvolt Hybrid Motor

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Originally Posted by bridaus View Post
ZF-15 more info: Helical gears. Two engagements not one. 5 bearings rolling during use. Churning approximately 1-10% based on research (still hard to pin down) depending on viscosity/temp/etc. I'm going to keep it low at 2% estimate for now just from intuition (using low viscosity tf, lower RPM's, bottom shaft submerged 50%) but it may climb. I wish I could find some more relevant sources. There was talk of 5-10% for this specific transmission, but with no source. A source would be helpful.

Right now that puts ZF-15 at an estimated 10.5% loss.

Therefore with current estimates 16.75kW shaft input is required to output 15kW to prop.

PS: Clearly the HBW estimates I did are low, but I'm not going to dig into bevel gears, and how many shafts are fully submerged in that drive etc. It's going to be higher than 11-12% for sure.

That seems to disagree with both Yanmar and Gerr.

Yanmar power curve on this:

https://www.yanmarmarine.com/theme/y...heet_4JH5E.pdf

The dotted line on the power curve includes the transmission (the solid line does not).

Gerr states in this:

https://www.gerrmarine.com/Articles/...owerCurves.pdf

Quote:
Standard marine gears fritter away about 3 percent of power as they do their required job.
BTW, it may be worth reading the whole Gerr document referenced.
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Old 21-12-2018, 10:43   #1784
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Re: Oceanvolt Hybrid Motor

I agree, our 4JH3E should produce about 36kW at 3650RPM. I have run there for a while and there is no way the transmission is burning up 4kW of heat. It would be smoking hot and burn the fluid. The heat sink is very small and just bolts on the outside with no direct contact to the fluid. I doubt it can carry away 4kW of heat.

And I seem to recall that transmission efficiency is not linear. Slower is more efficient. At 15kW from the engine I am sure the efficiency is much better than 90%.
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Old 21-12-2018, 14:13   #1785
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Re: Oceanvolt Hybrid Motor

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Originally Posted by OldMan View Post
That seems to disagree with both Yanmar and Gerr.

Yanmar power curve on this:

https://www.yanmarmarine.com/theme/y...heet_4JH5E.pdf

The dotted line on the power curve includes the transmission (the solid line does not).

Gerr states in this:

https://www.gerrmarine.com/Articles/...owerCurves.pdf

BTW, it may be worth reading the whole Gerr document referenced.
Reading the Yanmar manual: 5%. This is what they'll admit to, not actual. Ratings are funny like that.

I've read the Gerr article multiple times, great article and I count it as a source, but I believe he's off. Even the manufacturer says at the lowest it's 5%.

And if you want to believe him 100% then you have to include this gem: "This isn't because the conversion is difficult (it isn't) but because almost every engine's specific fuel consumption curve seems to understate the real-world, in-the-boat fuel consumption." I wonder where is all that fuel going? Magic?

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Originally Posted by transmitterdan View Post
I agree, our 4JH3E should produce about 36kW at 3650RPM. I have run there for a while and there is no way the transmission is burning up 4kW of heat. It would be smoking hot and burn the fluid. The heat sink is very small and just bolts on the outside with no direct contact to the fluid. I doubt it can carry away 4kW of heat.

And I seem to recall that transmission efficiency is not linear. Slower is more efficient. At 15kW from the engine I am sure the efficiency is much better than 90%.
"There is no way", "I doubt" and "I am sure" are nice, but they are not science.

Per the manual the normal operating temp of the transmission oil in these are 50C to 80C and can hit 100C for short periods. ATF auto ignition temperature is 210C (110C is highest recommended generally), it's not even close to burning up. Maybe your transmission is special, but these could output 4kW with no problem especially in an aluminum case.

Even if you assume (incorrectly) the ABSOLUTE best efficiency for every component (5 bearings, two engagements, lowest churning) all at 99% efficiency, the transmission still has 8% losses. Do we think a marine transmission is made with the best most efficient transmission technology available? More magic?
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