Power for barge

[Mako2]

Not sure if this is the correct form for the following question, I did post it on one other site and have had some good feed back looking for any thoughts here. I attached a few photos if that helps. Thanks, Mark

We have a 30? x 12? x 3.5? steel barge all .25? plate which weighs approximately 17,000 lbs. It is used for dredging around our dock area; when working it has a 20,000 lb excavator on deck along with a 5 yard container for spoils. The total weight is approximately 45,000 lbs loaded. It is currently powered by a single 150 hp outboard engine which even at half throttle supplies plenty of power for our use. We would like to replace the engine with either hydraulic drives or submersible electric drives because the outboard cooling system has trouble operating in the silt filled shallow water.

Hydraulic Marine Systems, Inc., Harbormaster, and Thrustmaster all make really nice commercial systems but they are all out of my price range.

Our primary use would be for movement in and around the dock and boat house. Most travel would be limited to about two hundred feet from the shore and is on a lake so current is not a concern. This is all personal use and limited to about 80 hours a year.

We are exploring one of two systems:

1: Using twin electric submersible motors (similar to trolling motors but much larger) powered by battery packs.

2: Using single or twin electric motor(s) mounted inside the barge with a hydraulic pump mounted directly to it (them) which would drive the two hydraulic motors mounted in an outboard configuration. This would also be powered by battery packs.

The weight of the batteries is not a major concern; we would probably use AGM batteries because they would be below deck. The batteries would be kept on maintenance charge while not in use from shore power while tied to the dock. Considerable thought was given to using a small diesel to power the hydraulic pump but with the limited use we are leaning to battery power.

Obviously with a barge speed is not a concern even empty it would only travel about 5 MPH, we are only looking for pushing power. We think a pair of 18 to 20 inch diameter propellers with a shallow pitch; slow turning would give us the thrust required.

Considering we only use the current outboard at half throttle or less (it starts to cavitate above ? throttle, most likely because of the small diameter high pitch prop) and still have more than enough performance; it would seem we could design the system for a total of around 30 to 40 HP and still have good results.

Thank you again for reading, any thoughts or suggestions would be welcomed.

Mark

 

[4JawChuck]

Re: Power for barge

I have remanufactured many "drive leg" barge drive systems in my province, they are used to keep our river mouths clear where they enter the lakes and keep the channels from narrowing along its length. All of these barges were powered by either four or two leg drive legs mechanically driven and 360 degree rotatable with integral augers and pumping systems and driven by twin 350HP diesels, one for the auger...one for the drives.

I think electric is ideal for your setup considering the small size, however I would consider an on board powerplant to prevent power failure from the battery banks from causing an "adrift" situation. There may even be requirements from the coast guard for onboard backup, something to look into.

To be honest none of these alternatives are going to be as cheap as a small outboard on the back, as a matter of fact I would think 5-10 times the cost as an average to perform such an upgrade for your situation. That being said have you considered going to a bigfoot style outboard with larger props and lower drive speeds, I think a dual system with two small 40 HP Bigfoots a better setup for your barge. You need torque not HP and that comes with a big prop and low rpm. You could easily modify the outboards for remote water pickups to avoid the mud collection problem with strainers and sumps.

As for electric there is nothing on the market except consumer level "outboards" with plastic cases like the Torqueedo that is likely way out of its league doing barge duty and nowhere near heavy duty enough.

Some of the things to consider in your upgrade are if you need power for "station keeping" to allow the loader to work in position, you may find pods near the stern but inset into the hull better for manouverability, of course this would require hull modfication to accomplish. Twins mounted at the extreme ends of the stern might be sufficient for this task, having separate controls for each outboard will allow a lot more control in these situations.

The last alternative to consider is jet propulsion as it is powerful and works well in shallow water, they make them as small as 25HP in four stroke and two of these might be ideal if the wear on the pump components would be acceptable in the muddy environment you intend to run them in. Of course there are a lot of power losses with jet drives and their reverse power is less than an equivalent prop motor and you still have the cooling system fouling problem as with an outboard conventional drive.

As always there is no perfect solution and much depends on your budget, here is a link to a lower cost drive leg hydraulic unit configurable to your setup. You may have already investigated this company and in my experience hydraulic is the only real alternative at this HP level besides outboards.

http://www.hydraulicmarinesystems.com/page/page/4692398.htm

 

[Mako2]

Re: Power for barge

4JawChuck,

Thank you for your well thought out answer. I am at this time leaning towards using two 48 volt 12 HP electric motors each of which will power a hydraulic pump. I would like to keep the voltage at 48 because of safety even though the 96 & 144 volts systems are more efficient. The batteries, motors, and pumps will be mounted below deck with disconnect hydraulic fittings mounted to the transom of the barge.

On the outside I will most likely use twin outboard style pods system which would house the hydraulic motor, similar to the link you provided. I had spoken with the owner of Hydraulic Marine Systems, but their systems are to large for my application.

Our thought on using electric motors instead of a small diesel for the power plant came from the very limited usage it will receive, at most an hour or two at a time then idle periods of several months. While using the barge it would be no more than 200 feet from our dock. The only time it would be in open water is going to the marina (about 4 miles, an hour ride at the barge's breakneck speed) and then it would accompanied by our regular boat to tow it if the batteries went dead.

Another interesting thought you brought up was the use of remote water pick up. I'm not quite sure how that is accomplished. I was going to use the flush connector but the dealer said it was not for constant running as the impeller does not get enough water for proper cooling.

I agree with you the small twin engines are a much better set up especially for control The barge was build for twins, but I already had the 150 and used it for one week our project took. Going forward we want to set it up properly thats why we are looking to change to the twins. The high thrust props will hopefully give me a better bite in the water then high pitch I have now especially in reverse. It is going to be our winter project so that it is ready to go by March.

Again thank you for your time and good advice.
Mark

 

[4JawChuck]

Re: Power for barge

My pleasure Mako, not to often my experience on these barges comes in handy. They haven't used those dredges since the early 90's but with increased yearly flooding it looks like they will have to start them up again.

I certainly like the electric idea as it is simple and easy to maintain and you have 100% torque at all RPM's. Are you going to do Dc or Ac with frequency drives? Most of my expereince is with the low cost older Dc drive systems but I have heard a lot of newer installations going with Ac frequency drives for their efficiency. Since you will be so close to dock it will likely not provide any advantage to you to go Ac. Dc is a natural with a direct battery connection however you might want to consider a Ac powerplant on board and forget the batteries with Ac drives. It may cost the same or only a little more.

As for the remote water pickups, they require modification of the lower unit but is easily accomplished. This technique for cooling water is used most commonly for high performance racing OB's that run surfacing props but it can certainly be used to great effect for what your needs will be. Typically the pickup is mounted on the transom and the power head replumbed for this remote. Here is a webpage with some of the more common types available;

http://www.cpperformance.com/products/Cooling_System/water-pickups.htm

Plumbing the remote pickups is a simple matter or blocking the existing nose cone pickups and threading a NPT angle fitting into the side of the lower for the remote, blocking the nose cone pickups is a simple as epoxying them up with a blocking plate. I haven't seen one exactly the same as your situation would require but some ingenuity and careful backyard engineering could create something workable. A sump open at the bottom of the hull with a slotted pickup is an idea that comes to mind as an easily workable solution although requiring some welding and hull modification to accomplish...might be overkill though as the amount of mud intrusion danger would dictate the pickup location.

Good luck with your project, I am interested in how it works out.

 

[Mako2]

Re: Power for barge

I found these instructions on http://www.bobsmachine.com/Products/transom_cooling.cfm
they sell kits for remote pick up. I will let you know how it works out. Hopefully all done by March.

Thanks, Mark



Transom Mounted Water Pick-up

Installation Instructions It is best to remove the lower unit from the engine to locate the water accumulation chamber which will either be in front or behind the water pump housing, depending on your motor.

Drill a 23/32 inch hole and tap a ? inch pipe into the side of the lower unit that is coming into the chamber.

You will need to acquire a hose of appropriate length, (long enough to reach from the tapped hole, over the mounting bracket of the engine, and down to the pick up tube), Approximately 50-70 inches long with a #12 female fitting on one end and a ? inch male pipe on the other.

Note: You must also close off the original factory installed water pick-up.

Mount the pick-up to the left-hand side of the pad or transom when using a right-hand rotating prop and vice versa for a left-hand rotating prop.

Mount the pick-up bracket as close to the bottom of the transom as possible. This will allow area for up and down adjustment of the pick-up tube, if required.

Note: The same instructions apply to both models of BMS International?s transom mounted water pick-up tubes.