Continuously Variable Transmissions

[apex1]

One question was not asked here. How often do we change the load conditions, speeds on our average boats?
A bluewater cruiser (motor of course) has a real demand on variable propulsion (which so ever), because he needs just a handful of horses under nice conditions to go faaar away and do that with the given tank capacity. But he needs much more power when in a hurry (to escape weather), or when going uphill in adverse conditions. Any unflexible propulsion, like the conventional, leaves to a noticeable underloaded engine in nice weather.
But there are about 10.000 boats underway on the barefoot routes around the globe, thats about the number of some larger marinas. Joe sixpack does´nt have this problem.

 

[kroberts]

Richard,

I confess to not having read your reference on electric transmissions, but IMO the thing you describe seems like just exactly the application for it.

 

[apex1]

Ken, if you want my opinion?!?


My next (probably last) own boat, has a single engine (a very beefy one), and a controllable pitch propeller. And I could afford every other propulsion as well (except maybe "U 235 / Electric").

best regards
Richard

 

[kroberts]

Richard,

Of course I want your opinion!

Seriously though, the CPP is probably much more practical, but I have a fascination with modern electric transmissions. To the point that I'm contemplating a bicycle with one. I know it will never be practical (especially if I do it myself) but it seems like it would be so neat.

 

[ancient kayaker]

Interesting discussion; there seems to be a consensus that a constant engine speed gear is wasted on a typical power boat, with perhaps a variable pitch feathering prop for a motor-sailer.

The infinitely-variable transmission is ideal for an auto allowing the engine to run at its ideal speed while the vehicle can adjust its speed over a wide range. An even better arrangement would be one that allowed the engine to run at its optimum power level.

A diesel-electric system allows the primary power source to be located remotely from the final drive element, connected by a copper cable and maybe a computer-controlled electronic transmission. In locomotives it allows the power to be applied to the rails through multiple axles on the locomotive and even through motors on a carriage.

In a large vessel the ability to use multiple, redundant electric power pods and/or bow thrusters has an obvious utility, especially for ferries and suchlike which spend a lot of time docking/undocking and must frequently maneuver in restricted waters.

 

[marshmat]

The infinitely-variable transmission is ideal for an auto allowing the engine to run at its ideal speed while the vehicle can adjust its speed over a wide range. An even better arrangement would be one that allowed the engine to run at its optimum power level.

Some of the carmakers that are using CVTs do have them set up this way, the engine choosing its RPM according to the required power, and the CVT adjusting to suit the speed. Drivers sometimes complain that this is quite weird (the engine will quickly rev up when the pedal is pushed, and will slow down as the car accelerates).

While we're on the subject of variable drives, we ought to at least mention variable-displacement hydrostatic transmissions. They're common on industrial equipment, tractors, ATVs and many other machines, but for some reason are rarely seen on boats. They give the same effect as a CVT or electric transmission (decoupling engine speed from prop speed) and, like electric, allow arbitrary location of the engine room. A well-matched hydrostatic setup should have losses comparable to an electric equivalent. I'm not advocating them as a universal solution, but if unusual transmissions are being considered, they're worth a look.

 

[WestVanHan]

Just for interest's sake,and not applicable to boats,but CVT s can take a lot of hp.

ie: Skidoo Mach Z 170 hp stock,with minor mods to 220 hp.
Kevlar woven into the belt.
Yes ,I know it's not too heavy.

Mine puts out 340hp,yes for intermittent use


Willams F1 team tried a twin belt version in '92 (?) and the car was much quicker around a course.Was banned.
In '92 I think F1 cars put out about 770 hp,so 380 a belt


Unless you're racing offshore cats with surface drives,why?

 

[apex1]

Terry
that >>>>>>>>located remotely from the final drive element<<<<<<< of course is a real advantage (at least for sailing vessels, in a motoryacht I do´nt see much). But we should not forget, that D/E in a motorcruiser starts being attractive when there are a minimum of three different sized generators installed. Due to the fact that a genny runs always at constant speed (AC) you again will fight hughe losses in inefficient operation when you try to operate just two of them! I calculated and recalculated these scenarios again and again and ended up with........................ well, guess.

 

[kroberts]

Terry
that >>>>>>>>located remotely from the final drive element<<<<<<< of course is a real advantage (at least for sailing vessels, in a motoryacht I do´nt see much). But we should not forget, that D/E in a motorcruiser starts being attractive when there are a minimum of three different sized generators installed. Due to the fact that a genny runs always at constant speed (AC) you again will fight hughe losses in inefficient operation when you try to operate just two of them! I calculated and recalculated these scenarios again and again and ended up with........................ well, guess.

Richard,

I hate to start this up again, but you seem to have a different impression of D/E than I do.

A modern D/E installation, the generator does not run at constant speed. It is throttled according to load required by the inverter.

For as long as I can remember, the D/E train engines changed RPM at will. I grew up near a "slow zone" and I heard it all the time.

The generator's RPM really doesn't matter. It gets converted directly to DC, then is fed into a 3-phase inverter which drives the traction motors. There is absolutely no reason why you need to run the generator at a constant speed, and while I could see the use for 2 generators (one for docking, one for under-way) I really can't see why you would want more, unless maybe if you intend to make slow headway at full throttle on one generator for a long time.

 

[ancient kayaker]

Ken, I think Richard is thinking of a generator set, in which the engine would normally run at constant speed. A more sophisticated (read bigger) installation such as a D/E your concept would provide more flexibility to allow for optimization, usually of economy.

 

[kroberts]

Dances with Turkeys,

I'm sure you're right.

I'm convinced that D/E is not economical for anything that small. I'm thinking that if you can't do it right, it will never pay off. Even if you CAN do it right, it won't pay off for years. I don't think a half-assed solution would be rewarding at all.

I kind of wonder if you couldn't make a simple (to use) throttle, where you throttle the engine and the controller simply uses all the available torque as best it can. As I understand it, the locomotives do it the other way, where the throttle powers the motor and the controller sets the diesel throttle based on demand.

BTW, is that an earned name or did you just make it up? I got one, "He who runs from distant coyote" from an Eskimo once. I earned it, unfortunately.

 

[apex1]

Ken, I think Richard is thinking of a generator set, in which the engine would normally run at constant speed. A more sophisticated (read bigger) installation such as a D/E your concept would provide more flexibility to allow for optimization, usually of economy.

Ken I do´nt have impressions I have experience! Or I keep my stupid mouth shut. (well usually)

Of course I was talking AC setup what else? No matter how big. A DC installation is already a hybrid propulsion (if you want at least a little power left after all losses). And than we have the same trouble again, when you do not run the genny diesel at sufficient load you waste just more money.
We should understand direct driven D/E setups (where you have at least two, better three different sized genny´s) they are AC and are very sensible when Hotel loads are high and constant. And the so called hybrid, where we use DC generation and Battery Inverter technology to get our junk running. In both cases we waste much money to save some pennies or to fulfil a mentally ill dream of "green" energy.

I strongly recommend to read the Nigel calder articles at Proboat last year:http://www.proboat-digital.com/proboat/20070607/
and to read "achieving the impossible" from "Victron Energy" (search under whitepapers, downloads)! http://www.victronenergy.com/support-and-downloads/white-papers/
When that is consumed and understood you immediately go and buy a CPP, although that technology is not mentioned there.

Regards
Richard

 

[kroberts]

Richard,

I assure you I am talking about something completely different than you are. I haven't read much of your articles, but I've read enough to see where they're headed.

On the surface, a 3-phase motor controller driving a generator, yes they are the same.

Your references are, first of all, using batteries. My reference is a diesel locomotive. The only batteries in there are to start the engine. This is mature technology, and it is pervasive throughout nearly every type of industry requiring efficient, highly controlled power from electricity.

Second thing, you are looking at consumer products that MIGHT power an electric golf cart. A decent electric car, for commuting at sub-speed-limit, is going to use WAY more power than your "Achieving the impossible" article references. Using these articles to describe a commercially viable D/E setup

I've been on DIY electric car forums for a while now. (Surprised? Probably not) They generally have more than 100A available for anything that could come sort-of close to highway speeds, and often more than twice that. Your references are quoting 16A. I have a flashlight that probably draws that much.

Stop looking at toys. Start looking at industrial motors, 300 kW and higher, and the industrial 3-phase controllers that drive them. Common sense practicality drives the technology here. Controlling start-up torque, handling power fluctuations and avoiding overloads on circuits started the controller technology on its current path, and robotics finished it. Running something like this from batteries would cost more than the gross national product of a small nation to buy the hardware!

First thing, the advances in motor technology has gone fairly far recently. You can get light weight, strong motors which weigh very little now. You have to pay for them, but they're out there.

Second thing, a serious 3-phase motor controller makes extremely good use of available power, and can control a generator such that the engine wastes very little fuel.

The articles you point to are vapor. It's similar to using hydrogen fuel cells as a power source: Hydrogen does not exist in a high energy state in nature, so it is not a power source at all, it's an energy storage mechanism. Politicians use it as a buzzword to make people think they're doing something important.

Most of the industrial controllers assume line power, but some have controls for a generator. Get them from Siemens or any other respected motor manufacturer.

 

[apex1]

I assure you I am talking about something completely different than you are. I haven't read much of your articles, but I've read enough to see where they're headed.

Ken I do´nt know why, but you WILL misunderstand me. We are NOT talking about different things. And I NEVER talk about toys, that was just principles, not installations, and principles are the same, no matter 10 or 10000 kw.

Your references are, first of all, using batteries.

Thats not my reference, thats a article about diesel electric propulsion, I have nothing to do with it.

This is mature technology,

There was never a doubt about! But there is absolutely no NO NO sensible way to use that on a yacht.

Second thing, you are looking at consumer products that MIGHT power an electric golf cart.

That is already a bit offensive right? I refer to some articles, I did neither recommend to buy some of these products nor was I looking for them!
And btw. Victron power management is at present the most sophisticated you can find on the market!

Stop looking at toys.

Stop talking nonsense!

First thing, the advances in motor technology has gone fairly far recently. You can get light weight, strong motors which weigh very little now. You have to pay for them, but they're out there.

Please do not try to tell me anything about Diesel engines, please do not!!!

The articles you point to are vapor.

Well you do´nt like to read them, that your thing, but then please stop talking nonsense here, you would have understood what I was pointing towards. And after all we are discussing yacht installations in general, not battleships.
I must say I´m definitely disappointed how stubborn you try to fight a senseless battle, and I know you know how senseless it is.

 

[wardd]

i have it, a rotary magazine of several props that can be auto changed for max performance

ok, thats the outline, ill leave the details up to the experts