Single engine / dual shafts?

Pacific Yachting recently did an article about a guy who had a system installed, pulled 2 diesels, put in a bigger and it worked fine, Less weight more engine room space.
Bracewell Marine in Vancouver did the work, The main reason that you would not want to run hydraulics is the horsepower lost in hydraulic pumps and motors as compared to helical gears. Dont hold me to it but you may lose up to 30% for hydraulics and say 8% for gears, Anyway and interesting article. though you would still need rudders.

 

It's done in the R/C world sometimes. They tend to use up to 5HP motors. I read an article back at christmas about a US company who was manufacturing a form of "splitter" drive. The idea was that it could use one engine to power two props independantly or two engines to pust four props.

 

There is an off the shelf system availible. Philbrook's Boat Yard LTD. (Sidney BC Canada) installs them. philbrooks.com There is an article in Passage Maker Magazine .. Feb 05 pg 112.

Easy Rider

 

but the better idea from all this I think is to dispose of the big main engineand seperate gen set and install two smaller engines driving one shaft with a cpp

 

the only advanatage i see is that you reduce draft. and can get away with smaller props. better to go with two engines ...here is a youtube of the same system- twin props one engine...
http://www.youtube.com/watch?v=tX2PSot7PE4&feature=related

 

a same boat here but longe vid http://www.youtube.com/watch?v=LhtB5fRDSV4&feature=related he explains somewhere how its done..

 

Add in the fuel economy of one engine and coupled with having that one engine sitting in the very bottom of the boat to lower the COG, and you'll see there are lots of advantages to this system. I have no first hand experience with it, but I'm sure there are people on here who do. No one system works for every boat, but for someone this design could be exactly what they need.

 

Some mad ideas will never die..............

 

And why is that??

So why is it a mad idea? Have you installed or used this system of one engine having two drives and know something the rest of us don't? If so please share...

 

Have you ever installed oars and sails on a tugboat? But you might agree that it is a mad idea?

Do some calculations and you will find, that the single engine combined with a CPP solves the problem of a very flexible propulsion, much better and cheaper. And it is proven in hundreds of thousands of vessels.

Regards
Richard

 

Dick Carr owns Superior Gearbox Company of Stockton Missouri and he had a running prototype in a Mainship Pilot 34. The twin prop single engine boat was more efficient from 15 to 26 knots. There was a full feature article on the "geared up" prototype in PMM February 05. They definitely didn't consider it a mad idea. Read the article instead of talking about oars on a tug boat.

Easy Rider

 

It is nice to hear Mr. Carr has a good running business, thanks.

Instead of attacking those who build boats in noticeable numbers, i.e. me, you should ask yourself why the commercial world and the Navies have given up on that concept.

You may find after some studies, that the gearboxes did not live long. And so the much simpler and cheaper CPP was the replacement in the successors of such craft.

But one has to know the market to be aware of that. PMM is not the only source of information, and sure not the best either.

Regards
Richard

 

To be sure you're correct and GM had all kinds of combinations of DDs and multiple shafts and engines that did'nt match. AND the "Geared Up" drive system WAS a proto type AND I haven't heard anything about them since.
I was going on memory saying it was an over the counter item. I was wrong and sorry I mentioned it however it seems as though they DID show that from a standpoint of efficiency the system works.

Easy Rider

 

When you study CODAD systems (which is the right term for these applictions) you soon will find more issues than advantages.

Sure, a installation providing more flexibility than the common ones has some benefit in efficiency, thats natural. But when it gets complex, the advantage quite often is gone. We see the same effect in hybrid applications.

Regards
Richard

 

I checked the volvopenta web site, if an outboard motor could have the duoprop forward arangement, then install the motor on a quick raisable / lowerable plateform, all that into a well vented enclosure amidship of a cat pontoon... AND diesel. Fuel economy, torque, low fumes, etc. This would also allow the possibility for water pressure from a water pillow squished slowly by the weight of the engine at mooring. Hence, have a watermaker run at night with no electrcity. Needs more explaining perhaps.
As for the hit something problem, having relatively small diam. props allows for a 18 inches water dip with directional like jet tubings. It could be called the "outboardpodtubine" . I guess i'll have to do with a std 4 strokes until ... could be an electric pod. "e-outboardpodtubine" wireless runned with an "Ipad" ...
Food for thoughts , sounds crazy, but trying to make heavy stuff on a boat work for something else from their original purpose makes sence to me, especially on a cat.