Diesel Electric Propulsion

Hi,

If I recall an article I once read correctly, the reason the Computers stayed so "old" was the use of x86 type Processors and these could not be upgraded to anything with a bigger data path.

I also remember a story that NASA were buying new still boxed chips off e bay

Volkswagen Marine is a great example. They convert those VW / Audi 4, 5, V6 and V8 diesel car engines into perfect boat engines. The engines run on less fuel, run much cleaner, more quiet and with less vibration than most of their competitors. Not because they are better than Volvo Penta, Yanmar or any other. Their basic engine is of much newer design (state of the art).

Example: The VW marine, 4 Zyl. 55 HP sailboat engine with saildrive has electronic fuel control and engine management, overhead camshaft, very low fuel consumption, runs very clean (Tier 3), runs very quiet and with very low vibration. It is the VW Golf (Rabbit) engine.

But sailors in Europe rather buy this ancient Volvo Penta D2-55 mechanical controlled engine, whose basis probably is the 50 years old Perkins London Taxi engine

Just an example, the Austrian company Steyr Marine with their modern engines would be one more great example.

Only the power of the buyer can control it.

Hardly. Spend about a minute following some Google leads to Z-drives and you will see that it is a long used and very successful technology that is among the least of things that a generation of boat drivers and engineers lose sleep over.

I think Brian's suggestion of the Reintje is very excellent for a displacement yacht.

Now for some educated comments and guesses:
I doubt any of these make a huge difference from a single propellor system like the Azipod or Rolls Mermaid. Both of those are electric by the way.

The closer the counter rotating propellors are the more efficient the system as the swirl losses are more directly recovered. However, this complicates the drive... and makes the inter-shaft seal more critical. Strangely the Schottel has the higher gear loads than the Reintje but is also used for lower speed applications. In fact of the internal drive layouts the Reintje has the most balanced design and likely the most reliable of the lot.

I would guess as far as hydrodynamic efficiency best to worse is:
1. Volvo
2. ZF
3. Reintje
4. Schottel
This is easy Volvo tractor arrangement with closely spaced counter rotating propellors... ZF with closely spaced counter rotating propellors but pusher propellors... Reintje with counter rotating propellors but space far apart but with with the fin in between to disrupt the swirl flow... Schottel one direction rotating propellors spaced far apart... and swirl reducing fins between... basically simply reduces propellor loadings.

I would say / guess mechanical design wise the most balanced and likely reliable are best to worse:
1. Reintje
2. ZF
3. Volvo
4. Schottel
ZF and Volvo are almost interchangeable in my opinion on this score. But I am almost sure everyone will disagree with putting Schottel last... as it seems simpler and it does win on that score... but the bearings and gears are under high and more unbalanced forces than the others. Reintje wins hands down on those scores.

None are factory electric drive except the Schottel but it can easily be applied to any of them.

I prefer the Reintje due to better mechanical design and the lack of the complication of steering... nice to have rudders if the drive goes out... . The ZF has the best break away deal.

Could you use the high speed drives for a displacement application (all the others than Schottel) yes but the props would be different and the you would end up with a larger drive as the torque situation has to be considered.

Now on Brian's web site there is a right-angle hydraulic pump/motor system that could be adapted to a pod drive (best fixed with rudders) and if arranged in a tee and two motors used it could be a twin propellor counter rotating pod and an electric motor could be used for drive... but it is a only in the proof of concept stage needing engineering development and "money"... so it is little bit of a venture capital deal.

Average scores Volvo - 2, ZF - 2, Reintje - 2, Schottel - 4

The ZF being rated 2 twice likely makes it the most reliable scoring choice but based on average score...

clearly we can eliminate Schottel... and leave the rest to personal preference!

Big Torque over 90 Degree Gears?, perhaps 'Belt drive'

On this other subject thread I had advanced the idea of belt or chain drive arrangements:
http://www.yachtforums.com/forums/technical-discussion/2232-new-drive-system-volvo-penta.html

"Other than direct straight-shaft drive of propellers, most marine drives today involve some sort of 90 degree arrangement, ie.sail drives, stern outdrives, outboards, etc. The 90 degree gear set (and there are usually two sets) is the potential weak link in the system. All the power is being transferred over a very physical small contact area between two bevel gears. This contact patch can be nothing more than a thin line on the opposing two teeth! Special hardened gears and maintaining close-fit tolerances permit the horsepowers of today. But when it comes to diesel engines, the situation gets worst. The diesel is by its nature a much more torque'y beast. Gears to handle an even modest horsepower diesel are extra hard pressed. Teeth can break or get worn so quickly as to loose all tolerance."

Big torque on 90 degree gears is not the biggest problem for modern engineers any more. They are quite good in handling the construction of what they call the "Kings Shaft", the vertical shaft in those drives or gears. The problem with large gears and large vertical distances between input and output shaft can only be solved by either a set of cogwheels or this type of going around the corner twice, by means of a vertical shaft. Both versions are causing friction and loss of efficiency.

That makes the Schottel SCD so efficient, no gear in the upper part of the drive.

B.t.w, in the sixtees we had two cargo vessels in our fleet with belt driven gear. They had two engines working with fixed reduction ratio, driving one prop shaft with VPP via multiple belts. That transmission solved the problem of the great standoff distance from the engines to the prop shaft, was light and very quiet and did not need any lubrication and cooling. It transmitted several tausend HP. As far as I remember, it worked flawless for years.

I like that Reintje Fortjes pod drive. But it needs additional rudders and reverse gear. A mechanical pod drive is always more heavy than conventional shaft. By eliminating reverse gear and rudder(s), you can compensate for some of that extra weight.

A mechanical or DE pod drive opens a lot of new internal design possibilities by moving the engineroom towards the stern. See picture of a Reintje Fortjes setup for a typical yacht.

HTM09 and Brian:
Proves the point on the belt drive and that does make for a quieter, less vibration and less expensive situation! I guess that might be the fix to solve the mass and complication issues with diesel electric and yet gain the quiet enjoyment benefit. Amassing simple and cheap somehow with good engineering always trumps complicated and expensive. Maybe a new thread on that!

The Schottel as it in direct drive form has a spiral bevel gear in the mix... as does the Reintje Fortjes for attachment to the drive from a horizontal engine. Reintje tries to add the transmission to the drive rather than the engine giving you the choice of engine mounted transmission and big slow turning driveshaft or direct drive from engine to the pod transmission... small high speed direct drive shaft. I think maybe they are trying to up the sale dollars and horn in on the transmission business end. Unless one used a Norberg horizontal radial engine!

In the electric drive form the Reintje Fortjes it has no such gear as you pointed out. This would be a custom design I suppose but if the Reintje Fortjes was made or adapted to the same electric drive with a vertical shaft motor then it is better because of what is down below and that it does not rotate... and you still have conventional rudders... which are simpler and more reliable... than rotating PODS.

The issue is aways the shaft driven prop is simpler, lighter, cheaper and more reliable. So hard to make an argument with an experienced yacht builder what you suggest is better... and it becomes a boutique type choice. But this same is faced with the diesel electric. Now I happen to like enclosed oil bathed shaft drives... over strut drive situations. But unless that is specified up front most will go with the strut as it is cheaper. So I think the pod actually is more a personal preference situation... to give the mechanically interested yacht owner something different to occupy himself with.

So what is learned and what am I left with... I should be dreaming of a belt drive arrangement with a convention drive.... and maybe the boutique choice of a variable pitch prop without reverse gear to simplify the thing....

Eureka... maybe it could be a belt drive pod... with a horizontal shaft electric motor up top and a horizontal shaft and Schottel like twin props down below... and the belt between... driven by cycloconverter / variable frequency drives that may not be a bad idea except for changing the belt requires disassembly of the underwater drive... bad to the idea tank...

Oh... maybe a silent chain type oil bath drive solves that one... as the chain can be broken and replaced... actually really like this one the best!

Or perhaps.... use two cantilever shafts attached to the two props down below... and two chains and motors so I can have two props...!

Hi,

Reintjes are already a well established gearbox manufacturer who know how to charge exorbitant prices both initially and when you need anything to maintain their products afterwards.

Chain gear

A chain gear is nothing extraordinary. The bicycle is the most simple example. But chain gear can transmit large torque and offset distances. On most modern cars, the camshaft and other subsystems of the engine are chain driven. Even shifting gears can be chain driven (motorbyces).

On the famous old VW Beetle the cooling fan of the air cooled engine and the alternator were driven by a single belt. This belt did not last very long. So, if during an excursion with your girl friend, the charging light came on, the belt was gone. In this case, the girl friend had to sacrifice her nylons and the car was repaired (at least up to the next filling station with spare parts)

Example of manual shifting motorbyce gear below

This is far from cutting edge technology, Brian. Do a minimal review of the literature on gear design and loading and you will see that the issues that seem to cause your distress were virtually eliminated a century ago.

Any good textbook or design guide for power transmission products explains how and why those scary drives have been used with great reliability for generations of marine engineering products from reciprocating steam engines to great thumping low and medium speed (read as torque with a capital T) diesels.

Been a long day... I think everyone is happy... anyway can now find a little time to myself.

This thread is "diesel electric" and because that is in yachting right now "avant garde" it draws those of us technically interested in and then the "idea" yacht is discussed which includes many other ideas particularly in propulsion. I suppose it is the hobby nature. This issue is putting anything new or different than industry standard in use is hard and risky.

The two major electrically powered pod drives the ABB group Azipod azimuthing pod and the Rolls Royce Marine Merlin azimuthing pod both have had major problems in first entering the cruise ship business. Mainly having to do with "bearings" and particularly as they are azimuthing pods or can be steered my moving the whole pod to thrust in any direction needed. The costs for development are around 1 Billion dollars US and one incident of failure costs in the area of 65-100 million dollars. No yacht owner or yard can afford such costs. The are very few electrically driven azimuthing pods in use in large yachts over 60 m in length... that also have diesel electric power plants.... Lurssen and Benetti yachts. Why is basically the commercially available sizing of the pods and diesel electric power plants is for larger applications. Its like the Voith Schneider propellor... if you tried to retrofit that on any existing yacht other than over 60m it would sink the stern and flood the garage... and then maybe sink the yacht.

The idea of cobbling together something on a smaller scale seems attractive. I have run many many engineering development programs in my younger days... and am humbly exceptional at it: 99.9% are not. I can tell you its a lot of hard work and very expensive... you need a very talented carefully chosen team and very close technical and budget control. But that is very rare now-a-days. And with the "global supply strategy" most companies pursue not possible or affordable... you really need tight control... and to try that across several companies is a management nightmare. And, the costs are out of control... sending one man on a trip from Europe to USA to sort out one problem... is on equivalent in cost of 1 man-week on the shop floor. But it is more than that its delay so it might really be 10 or more worse. And, with several companies involved it multiplies.

So really you are stuck with existing technology...

Unless you are willing to pay the price...

SO a little sea story... which is so old maybe I can tell now... which perhaps is applicable here.

When I was young I was very interested in nuclear technology. I remember after an incident board I was involved in, Adm. Rickover came up to me and we talked for a few minutes. Being young I mentioned a couple new things, including: about the Thorium idea... which is popular today... and hinted assignment to the S7G plant (a plant without control rods but a whole lot more new ideas), he did not give me the any answer I would expect, perhaps "no" or one of his famous quotes such as follows:

"An academic reactor or reactor plant almost always has the following basic characteristics: (1) It is simple. (2) It is small. (3) It is cheap. (4) It is light. (5) It can be built very quickly. (6) It is very flexible in purpose (“omnibus reactor”). (7) Very little development is required. It will use mostly “off-the-shelf” components. (8) The reactor is in the study phases. It is not being built now.

On the other hand, a practical reactor plant can be distinguished by the following characteristics: (1) It is being built now. (2) It is behind schedule. (3) It is requiring an immense amount of development on apparently trivial items. Corrosion, in particular, is a problem. (4) It is very expensive. (5) It takes a long time to build because of the engineering development problems. (6) It is large. (7) It is heavy. (8) It is complicated."

What he said to was simply on that issue, "besides me... you are the only one that would dare tell the truth... you already know it cannot be cheated."

A couple weeks later I was taken by my boss into a room and left by myself for an hour. My boss presented me with my ultra top secret "personal record," and made promise not to tell anyone that these were kept or that they were for use only by the KOG (Kindly Old Gentleman) OR the fact they even existed... and told he from the highest level I was ordered to read the complete book. It was a journal with hand written weekly statements from every instructor during my training; my direct supervisors and afterwards personal reviews from everyone in any board of qualification; same for incident boards; and other entries in chronological order of review or comment about literally anything.
My "book" was about 100 pages of this... and I learned something that holds true to this day... and reflects the KOG answer to me.

At the end of the hour, I was asked if I needed more time, then I was given a sealed note that I had to give back in a sealed envelope... I was to read the note privately in the room, but before my boss left me along he gave me the offer of an instructor position at the yet to be constructed S8G plant... .

About a couple three weeks later I gave my answer back...
"I want to be assigned sea duty."

Just been in the explorer thread and and lots of SWATH comments going on... maybe this solves the pod problem.... Just make them big!

http://www.yachtforums.com/forums/g...n/20483-what-defines-expedition-yacht-16.html

Why do I seem to recall a significant 'durability issue' with big HP gas engines, and diesel engines powering inboard-outboard drive units?? Perhaps I just don't fool around with many of these powerboats enough to have seen those big improvements, but I do remember visiting lots of shops with lots of discarded I-O units sitting around.....and lots of manufacturers selling replacement/rebuilt units.

Did they improve the 'contact patch' that much, or just much more 'hardened teeth', or new tooth/gear style. ??

I guess I'm just 'old school' here ?

Slient Chains

That is older style chain technology.

Here is the latest chain technology I'm familiar with, referred to as 'silent chains'.
Fundamentals
Ramsey Products | Silent Chain Fundamentals

Advantages
Ramsey Products | Advantages of Ramsey Silent Chain





....some chain efficiency discussions
Transmission, Driveline, Hybrid Drive engineering - roller chain efficiency

The stuff you just described is cheap consumer recreational crap for the most part. Most of them probably corroded away from electrolysis or saltwater intrusion through seals cut by fishing lines, running aground or other abuse, or simply by lack of maintenance.

Some of the "harbormaster" units built and used in WW2 are still in regular use. Lots of Z-drive tugs are pushing ships around all over the world every day.

Don't fall in the trap of comparing lemons to Yubari melons.

Brian:
Yes that is they type of chain referred to "silent chain". It is commonly used in large power and torque transmission application. In automotive it is usually a 4wd transfer case chain main drive... very heavy duty.... or in fwd. transmissions. Industrially it is in the really high horsepower; shock loading applications, and; long term durability challenged applications where it finds its place. It is the most reliable and efficient of all chain drives... and that includes roller... and that is commonly misunderstood by non engineers.

In many cases it is very much superior to gear drives as to durability, efficiency, and shock absorption... as well as cost. It is also tolerant of misalignments.

I understand what you are explaining to me, but then they sure used an awful lot of that 'cheap consumer recreation crap" on some pretty powerful expensive offshore racing boats if I remember correctly. ....And a GREAT deal of the recreational power boats produced.

Yes I mentioned that back on this old tread that is closed now.
"I know such a 'chain' was utilized on the older Olds Toronado automobile."

http://www.yachtforums.com/forums/technical-discussion/2232-new-drive-system-volvo-penta.html#post15453




PS:
1) There is also a photo of a Schottel Twin Prop there.

2) And my early suggestion about a 'pulling counter-rotating prop' arrangement.

Interesting story Karo

Adm Rickover was a tough old guy, but without his straight forward resolve, we would have likely not spurted past the Russians so quickly with our nuclear submarine fleet capabilities.

And speaking of youth, with new ideas. I was working on the torpedo systems, and offered up the idea of placing the wire-guided weapons on a cylindrical launching apparatus surrounding the pressure hull so you wouldn't need torpedo tubes piercing the pressure hull.... ...that wasn't boldy received....ha...ha

Rickover was likely the reason that we did NOT go off on multiple types of sub designs that the Russians did. We kept developing the 'class'

On another theme, it does appear that the French have adopted a similar program with their nuclear reactors....most are the same design, tweaked and perfected to give them consistancy. On the other hand we (the USA)have too much variety, and thus a 'less stable' collection of nuclear plant energy production.