Small inboard gas engine

[alan white]

Originally Posted by TollyWally

When I think of suitcase gensets I usually picture one of the Honda units, very quiet nice little units.

Is this similar to what you are thinking about?

I don't know the rating but I have twin 4D batteries, how much more capacity is needed for manuevering and in harbor work?

Imagine one of those units putting out 48 or 72 volts, with insulation to reduce noise, hung off the stern in a neat box.
Any calculation would include variables such as hp or kw required (a thirty foot boat could require an average of anywhere from 3 to 15 for harbor work depending on displacement. If, say, your average is 5 hp, that's about 3.7 kw.
With two batteries, you can get 24 volts, and so dividing 3700 watts by 24, Your amperage requirement is 154 AH. At that rate, the average set of 80 AH batteries will be depleted in an hour.
Better to istall six batteries and run 72 volts, which is higher efficiency (maybe 92% for the motor) and can use smaller cables as well.
That will give you three hours at a decent speed of say 5-6 kts.
Recharging would take maybe 5 hours if the genset puts out about 3.5 hp.
Or, the genset can run the motor direct and you'll see about 3 hp output at the prop for a speed of maybe 4-4.5 kts continuous.
The bigger the battery bank, the more voltage options, the longer the run time at higher rates, the greater the weight, the longer charge time.
I think four batteries is a good start for a small (3000#) cruiser that just needs to motor for steerageway or harbor work up to the mooring. A 6 hp continuous rated (15 hp max) motor would be fine, and a 2500 watt 48 volt genset. The controller could be a 300 amp max unit, which would allow 30 second spurts at up to 15 hp in emergency use.

Alan

[dskira]

Hi Fast Fred,
The rorotiller engine is quite a good idea.
By the way thank you all for your very enlighted comment. You gave a lot of ideas to work with.
The small genset and electric motor is quite also a great solution.
Diesel is so overprice and not as efficient we can think, there life is around 5000 hours against 2000 hours for the gas, but the price is almost five time. A rototiller engine 12 hp is around $800, a diesel is $7000, for marine use, $5000 bobtail configuration.
Perhaps sombody has better infos about pricing, it is what I see around, and I admit without going in to deep in details. But I like gas, so silent, light, smooth, and it's like sailing without sail.
Kengrome, perhaps you can take apart an outboard and reconfigure all the element in a different position making them an inboard. It will be a cheaper start. I just tossed an idea without real knoveldge.
Daniel

[Guest625101138]

Originally Posted by alan white

Could be the Perm motor is higher torque (they claim 40% higher), Rick. B&S has the new high torque model as well, but I haven't researched it. I'm building an ultralight three-wheeled car right now so I'll very soon be choosing and buying a motor. Of course, I'd have a chain drive, so ratios are going to be easy to get.
The B&S have brushes, yes, but 1000 hrs is practically a lifetime aboard a small cruiser and then when it's time, how long could the job take? I suppose it all depends on the architecture of the boat.

Alan

Alan
I bought two Mars PMAC motors and 100A continuous, 48V controllers from Kelly controls. Apart from an error in their connection diagram for the hall sensors the motor works brilliantly. I have not yet tried in regeneration mode but it should not be any problem.

http://www.kellycontroller.com/

Kelly offered the best overall price including delivery cost. Both motor and controller were also best price I could find.

The combined motor controller efficiency is 88%. The controller takes 60mA at rest so I just make a mechanical connection when I start up. I have not even bothered with a fuse because I am only using small batteries for testing and they give out around 15A. The main wiring is good for 200A and I believe the controller has a fuse on the input circuit.

The wiring is more complex than a PMDC set up and quite fiddly but you need a 4 quadrant drive to give contactorless reversal using the PMDC. You also have to contend with brush life.

I found Kelly gave excellent service and support but may not have your selected controller on the shelf and this could delay by a week or so. I got one controller in a week and the motors and second controller came two weeks after.

Rick W.

[alan white]

Originally Posted by Rick Willoughby

Alan
I bought two Mars PMAC motors and 100A continuous, 48V controllers from Kelly controls. Apart from an error in their connection diagram for the hall sensors the motor works brilliantly. I have not yet tried in regeneration mode but it should not be any problem.

http://www.kellycontroller.com/

Kelly offered the best overall price including delivery cost. Both motor and controller were also best price I could find.

The combined motor controller efficiency is 88%. The controller takes 60mA at rest so I just make a mechanical connection when I start up. I have not even bothered with a fuse because I am only using small batteries for testing and they give out around 15A. The main wiring is good for 200A and I believe the controller has a fuse on the input circuit.

The wiring is more complex than a PMDC set up and quite fiddly but you need a 4 quadrant drive to give contactorless reversal using the PMDC. You also have to contend with brush life.

I found Kelly gave excellent service and support but may not have your selected controller on the shelf and this could delay by a week or so. I got one controller in a week and the motors and second controller came two weeks after.

Rick W.

Thanks much, Rick. I'm welding up the aft end of the vehicle now and so the bracket for the motor needs a motor to fit everything in correctly.
Then I'll be broke for a while but I'm going to bookmark and research Kelly.
I'm a bit slow when it comes to wiring and electronics in general.
I may bug you for some support when the time comes.

Alan

[Guest625101138]

Originally Posted by alan white

Thanks much, Rick. I'm welding up the aft end of the vehicle now and so the bracket for the motor needs a motor to fit everything in correctly.
Then I'll be broke for a while but I'm going to bookmark and research Kelly.
I'm a bit slow when it comes to wiring and electronics in general.
I may bug you for some support when the time comes.

Alan

Alan
The plug used to connect the control wiring requires a small soldering iron with a fine tip. I soldered the wire and then placed heatshrink tubing over the individual cores. It was finer work than I have done in quite a while. It tests my aging eyes and unsteady hands.

I have not found a supplier of the ideal multicore cable either. In years past I used Dekron cable but have not been able to find a local supplier of this. It is these things that cause a bit of frustration. The heavy conductors and lugs were easy to get. I also purchased a new heavy duty crimper as I expect I will be doing a reasonable amount of heavy duty wiring.

Rick W

[alan white]

Incidentally, Rick, I think I am going to be adding another motor (so I'll have two) and a total hp for accelleration of about 38 hp.
I would therefore need an oversized controller to begin with in anticipation of the load of maybe 600A or more. The machine should weigh, all up, about 700 lbs, so it ought to accellerate briskly with the two motors.
I see that the controllers shown are priced in dollars, but I couldn't see if those were American or Australian dollars. Where's the company based?

[alan white]

Originally Posted by Rick Willoughby

Alan
The plug used to connect the control wiring requires a small soldering iron with a fine tip. I soldered the wire and then placed heatshrink tubing over the individual cores. It was finer work than I have done in quite a while. It tests my aging eyes and unsteady hands.

I have not found a supplier of the ideal multicore cable either. In years past I used Dekron cable but have not been able to find a local supplier of this. It is these things that cause a bit of frustration. The heavy conductors and lugs were easy to get. I also purchased a new heavy duty crimper as I expect I will be doing a reasonable amount of heavy duty wiring.

Rick W

I guess a lot of connecting and switching devices are similar if not the same part number as common industrial controls, which are always comparatvely cheap. I can solder okay. That Kelly site is a real find for me. i'm on it right now.

[Guest625101138]

Alan
When you deal on the web it is hard to know where the company is based. I believe I was dealing with Chinese who had perfect written english. The Mars motors are US designed but manufactured in China. The controller does not show place of manufacture. All prices are USD. AUD, CAD and USD are very nearly the same value right now so it does not make much difference.

I think all this stuff is manufactured in China and the mailing cost is lower for me if it comes direct from China. There is huge growth in electric scooters in China and I think they will soon lead with this technology. A friend working there said it is all very low cost and good value. I visited last year but did not have time to shop for such items. You can find it direct on the web but most of it requires quantity purchase.

I think Kelly are working hard to beat Sevcon and other popular controller makers.

If you use two motors then I think you would have difficulty synchronising two PMAC motors. You may be better off using the PMDC with a single controller.

Rick W

[alan white]

Originally Posted by Rick Willoughby

Alan
When you deal on the web it is hard to know where the company is based. I believe I was dealing with Chinese who had perfect written english. The Mars motors are US designed but manufactured in China. The controller does not show place of manufacture. All prices are USD. AUD, CAD and USD are very nearly the same value right now so it does not make much difference.

I think all this stuff is manufactured in China and the mailing cost is lower for me if it comes direct from China. There is huge growth in electric scooters in China and I think they will soon lead with this technology. A friend working there said it is all very low cost and good value. I visited last year but did not have time to shop for such items. You can find it direct on the web but most of it requires quantity purchase.

I think Kelly are working hard to beat Sevcon and other popular controller makers.

If you use two motors then I think you would have difficulty synchronising two PMAC motors. You may be better off using the PMDC with a single controller.

Rick W

I don't know much about the synchronization aspect. I also am considering the generating options of two motors, where the gas engine spins one motor as a generator, which allows for the omission of a 48 volt generator seperate from the motors. On accelleration, the role of generating motor would simply be reversed and I'd have both motors pulling. So maybe two controllers is an absolute requirement for that reason too. That setup also allows direct gas power at top speed.

A.

[FAST FRED]

Since an electric motor drive can function as a generator while sailing, those who sail a lot more than motor need no genset at all.

Yes BUT , (always that BUT!) to generate electric the prop will be rotating slowly under load, exactaly the formula for MAXIMUM drag from the prop.

So if you are willing to loose a K while charging at top speed and an even higher speed loss (as percentage of speed thru water) its fine.

The ocean folks I have known have all trailed small OB props hooked to very small alternators, after trying the speed brake of using the vessels prop.

IF one can put up with the unique operation of the rotor tiller engine , there is no equal in terms of costs over the boats lifetime , even with gas at $20 a gal.

FF

[alan white]

Originally Posted by FAST FRED

Since an electric motor drive can function as a generator while sailing, those who sail a lot more than motor need no genset at all.

Yes BUT , (always that BUT!) to generate electric the prop will be rotating slowly under load, exactaly the formula for MAXIMUM drag from the prop.

So if you are willing to loose a K while charging at top speed and an even higher speed loss (as percentage of speed thru water) its fine.

The ocean folks I have known have all trailed small OB props hooked to very small alternators, after trying the speed brake of using the vessels prop.

IF one can put up with the unique operation of the rotor tiller engine , there is no equal in terms of costs over the boats lifetime , even with gas at $20 a gal.

FF

Thanks for the thoughts. I wonder if a variable pitch prop would be an improvment.
Your point regarding the small utility engine is well taken and I appreciate the philosophy behind it. Yachting has gotten so expensive that it's bordering on the ridiculous in my opinion. With modern sniffers and fire systems, there's no reason that a gas engine couldn't be a best choice for a lot of sailors.
Air cooled machines do have to have air supplied, however. They should also have fuel pumps built in and possibly diaphragm carburators to deal with motion and heeling.

Alan

[kirtley]

I wonder what you think of this small Chinese-British joint venture gas engine:

http://www.cqwolei.com/ProductShow.asp?ArticleID=134

Do you think it would work as an inboard?

[Frosty]

But -but --its air cooled, if you really want to challenge your mechanical ability that would do it.

Sorry that should read,if you really really want to waste your time and money.

[kirtley]

Oh! Thanks for saving me the time & money!

[PAR]

I'm seeing $450 and up per KW once you count up everything (4.5 KW 72V motor, 72V/8A charger, 0-5K throttle, meter, converter, control box, cable, etc.) Priced through Kelly about $2,500. Seems fairly steep for 5.6 HP and no battery bank yet. Would this be typical currently as far as KW pricing?

In other words, lets assume a reasonably designed system, brushless motor, good charger, controller, batteries, etc. an average per KW or converted to HP would be possible. At least a range to work with. A 6 HP (4.4 KW) gas outboard is about $220 per HP ($165 per KW).