Good Idea /Bad Idea?

Hi all,

I have been thing about a concept regarding low power operations on twin diesel engines. The topic may seem more suited to the technical section but, I would like to get a better understanding of how it would be received and if it would be of use to many or few??

Here is my idea and it is a concept only at this time although I have been researching materials and components to build a proof of concept. The background for this is my concerns about operating two high power diesels at very low power setting while cruising in canals and other low speed areas. The idea that the engines would be running at low speed for hours had me think about options. You could perhaps shut down one engine and tool along on one engine but you have a bit of drag from the dead prop and rudder bias to deal with. That brought me to the idea that one engine at moderate power could easily drive both props. I don't know if this has been done before and what the out come was but I would be very interested in your take on the idea.

The basics are developed from a theoretical boat say 50 ton with two 1000 HP engines. An express cruiser or sport fisher is a good example. The boat has two speeds fast and slow, the slow speeds put the engines well below their power curve and while the fuel savings from running on one engine is not an advantage in most cases the engine wear and idle time could add up. The idea also adds a redundancy feature to the drive system. If an engine fails you still have symmetrical thrust to both props on one engine. The weight would be under a 1000 pounds for engines up to 1200HP not much more for bigger engines and the maintenance would be minimal, lube checks and tension adjustments.

Would this be worth the effort and is it a viable idea for the market. I understand that most folks that have these type of boats don't mind burring lots of fuel but this could add life to the engines and therefore reduce the bottom line cost in operating the boat.

Steve

Hi Lars,

I have not seen anything to run two shafts from one engine other than DE or hyd aux drives. This is more of a way to use one main engine to drive both prop shafts, kind of like a trolling feature but from zero speed to the torque limit of the engine on line. This would tie both shafts to one engines throttle and transmission control. The idea is instead of having both motors running at low power use one engine to drive both props without aux gear in the transmissions. It is a simple design that could be very light weight and transmit the power with almost no loss.

Steve

Hi Lars,

This would work just like two engines both props would be be at the same speed so you couldn't do any fancy throttle work but both would respond to forward and reverse off of the active control. It would be interlocked so that when it was in use the other controls would be locked. You could start the other engine and un-clutch the system and be on two engines in no time. The shafts would both turn in the right direction from either engine in both forward and reverse.

Steve

Lars,

I am talking about a boat that has two 1000 HP engines not a hardware store full

Steve

Hi Loren,

I was thinking of this for use on cruisers on inland canals and rivers like the Great Loop, New England Loop and maybe sport fishers. This would be less costly and deliver symmetrical thrust while cruising.

The purpose of this would be to keep a single engine in a load condition that was desirable for efficiency and engine life. Where droning along at low power levels for days on end with two engines is used now. It would not reduce fuel flow by much but it would reduce engine time and keep the running engine at a better BSFC. This is something that would work on almost any boat with the gear they have now.

Reducing direct operating cost is the reason behind this, it is a simple way to manage power assets with out replacement equipment.

Steve

I am either not adequately describing the purpose or reasons for the idea. Yes you can install feathering props, add two or three different size engines, or use transmissions that accept power from more than one source.

The idea I am thinking of is for a boat that has two engines and two fixed pitch props. The boat for conversation sake has two Cat C32's that are E rated at 1550 HP. Instead of running both engines while cruising at low speed where each engine is developing low power and running at low load factors, use one engine to drive both props. The drive system would be far less costly to install than feathering props and you would not have asymmetrical thrust. Both shafts would be developing thrust not drag, even the feathered prop creates drag and, both rudders will have good authority with equal thrust.

All diesel engines are more efficient at higher load factors, the BSFC is not much different but it is better where one engine is loaded to a higher level. The low power boats are running their engines at or near optimum speed most of the time, a high powered boat is not using most of it's potential power. If it takes 2800HP to move the boat at 30 knots it will take a fraction of that, 300-500 HP to move the boat at 10-12 knots. To operate a 1550HP engine at 150-250HP is not good for the engine or the owner. While it is low power the clock still ticks on oil and service items and it is not burning fuel as efficiently as it would at higher power settings. Running one engine at 500HP and splitting that power between two props is more efficient than running both at half that power setting. The numbers get better where the engine is at its sweet spot for BSFC. The amount of fuel saved per hour is a gallon or three but over time it adds up and the wear on engines can be halved.

A few pulleys a couple of belts and a transmission wouldn't weight more than 4-500 pounds and with mounts belt covers and all you'd be hard pressed to have a thousand pounds in system. It would fit on existing transmission and shafts and be able to engage and disengage at the flip of a switch.

Steve