Excavator engine in a boat?

Hi there,

I'm looking to get a hydraulic drive propulsion system in my 60ftx4m steel boat. It's flat bottomed and not seaworthy. The straight drive takes up a huge amount of space in the stern, so I want to install some sort of hydraulic system and place the engine under the wheelhouse (where there is also lots of wasted space).

A) I could use the original 130 hp engine and try get an engineer to work out what kind of pumps etc will be needed. Then try and hook them up so nothing moves under high pressures - very expensive and complicated

or

B) get an engine from an excavator/ JCB with the pumps already in place.
All i need then is the appropriate prop. I was thinking the 90 hp engine from a hitachi ex120 delivers 5000 psi of pressure. Else an EX 60

My question is : Has anyone heard of anyone doing this before. I've searched forums and havent found any information yet it seems fairly logical

 

Mccaffrey,

I don't know much about hydraulic propulsion for boats, but I do know a lot about hydraulics, and hydraulic excavators. Here are a few things to ponder:

1. Running under continuous load, you will need a large hydraulic reservoir, and high capacity hydraulic oil cooler.

2. The pump from the excavator (which is typically two piston type rotating groups inside one housing) has some specific requirements, such as signal pressure to control pump output, which is resolved at the control valve. The most logical answer to this would be to also use the main control valve and pilot system from the donor machine.

3. Drive motor for the prop?

4. You state that the hitachi ex120 delivers 5000 psi of pressure. What kind of flow do you need? This is more important than pressure, as it will directly effect prop speed depending on drive motor displacement.

5. The concept is easy, but I think that the reality would probably not be cost effective.
Just my 2 cents.

 

I repowered with an 84hp J444 Mermaid Marine engine from the UK.
Its the same engine they use in JCBs.

http://www.mermaid-marine.co.uk/HTML/MermaidSummary.htm

 

Thanks a million H180,

Thats really helpful information. Like you suggested in point 2, I was hoping to use the pilot system from the donor machine. I was hoping that i could use the hydraulic reservoir and oil cooler from the host also. From your expertise on hydraulics do you think that a standard reservoir might not be large enough if the hoses are a little longer to the drive back in the stern?


4. You state that the hitachi ex120 delivers 5000 psi of pressure. What kind of flow do you need? This is more important than pressure, as it will directly effect prop speed depending on drive motor displacement.

Thanks for advising me. I do need to do more research on this. At the moment the 90 hp engine with 30% loss in energy for hydraulics should still have some power to push a barge slowly up a canal. If the flow was low perhaps I could go for a bigger prop to make up for the difference?


Many thanks

Ian

 

McCaffrey,

First, looking at Kaluvic's reply, it appears that he has the engine coupled to a gearbox that is driving the prop shaft. You are wanting to do hydraulic drive, with the engine mounted remotely from the prop. right?

 

Thats correct. There was a large engine sitting right in the centre of the boat with a direct drive shaft to the prop. This is the most efficient way of propulsion i'll admit. But space is at a premium for the function I have in mind for the boat. Not so much the travelling around. I would be prepared to handle a few losses if I could get a hydraulic system to work. I'd have to make sure there was ventilation, fireproofing and cooling.

I'm a bit nervous to go about it . That's why I'm trying to do as much research as possible!

 

I've seen skid pack hydraulic drive systems driving giant outboard motor type devices advertised in Boats and Harbors. The pictures look like they weld the skid pack to the deck of crude steel barges that are then self propelled.

 

Why Hydraulics and NOT Electrics? A 100 Hp Induction Motor is a lot smaller than a 100 Kw Diesel Genset that would easily power it, with plenty of power left over for other uses while underway. Engine Control is easy using a FreqDrive . You can buy completely Marinized Diesel Gensets, the Motor, and FreqDrive, off the shelf in ANY Marine Electrical Supply House in the world. The Genset could be mounted anywhere, aboard, and you don't have to worry about any pollution if the Hose Breaks, cause Electrons don't pollute. Just say'en...

 

You are right..my engine is connected to a Velvet drive trans...then shaft.
My response was just to show that you can get a marinized JCB engine.

 

McCaffrey,

This set up will be quite an undertaking. Just so we're on the same page, I want you to know that I know little to nothing about about boat rigging/scantling. I don't know the laws and/or standards of retrofitting this system to a boat. What I can offer you is ideas and suggestions to make the system work together. Have you thought about what you would use for a prop shaft drive motor? You said that you would use the pilot system from the excavator. I assume you will also be using the main control valve, oil cooler, and hydro reservoir? One thought I had is that most excavators use a 2 speed travel motor to drive each track, and, obviously, those motors are bi-directional. I am intrigued by your plan.

 

With good-quality piston pumps, you shouldn't be seeing 30% losses in the hydraulics- closer to 5-10% at each end should be achievable, plus friction in the hoses, so maybe 15-20% loss due to the hydraulics.

I'm assuming you're planning on a load sensing, variable displacement pump? There's not much point in going hydraulic without going variable displacement. As has been pointed out, flow rate is at least as important as pressure- and it's worth noting that even if your pump can do 5000 psi, going down to 2000-3000 might be easier on your equipment as well as allowing a greater selection of relatively inexpensive hydraulic accessories.

I'm not a hydraulics expert, so don't take the above as gospel.

It sounds, though, like this is a boat with a large house load and low propulsion loads. In such a scenario, an electric primary system often makes sense. The downside, of course, is the capital cost of a DC generator, motor and controller, and an inverter bank for the house loads. AC generation for diesel-electric really only makes sense if you have multiple gensets that can be automatically brought online as demand increases; otherwise, the one engine will be grossly underloaded most of the time.

 

Thanks guys,

Theres a lot of great information there. Enough for a couple of days research!

here was the general idea


The guy I bought it from wanted it for fising in Holland so he unsucessfully tried to have 2 large 130 hp engines connected to z-drives in the aft. They were not fully connected and there was no steering when I bought it. The engines take up a large amount of room also. The original shaft is in the boat and it works perfectly - However the original engine also sat in the middle of the boat. There is so much unused room under the wheelhouse it would be perfect

HP180. Thats correct - I would need a prop drive motor joined to the existing shaft in the middle of the boat. I think that would be fairly easy to come by. I really need to work out what flow would be needed. I'm cery interested in what you said about using the track motor for this purpose aas the bi-directionality would be ideal. I'd of course have to get a hydraulics expert to rig it up. I'm wondering what would happen to the rest of the valves in the box as I would only need i presume 2 pipes running to the track motor connected to the drive? Could they just be blocked off? Apologies for not being an expert. I'm just trying to figure out if it would be possible.

Marshmat - Its good to hear about the losses not being so much but You know the rule - always expect the worst? Just overestimating it as the system might be a few years old. I think 5000psi was the maximum pressure of an ex120. Hopefully like an excavator I would not use it at full throttle. Else get the system from a smaller machine. There are loads about after this property crash!Therefore the system from a 120 and ex60 would not be that much difference in price believe it or not.

Last and not least is the diesel electric system. I have thought about this before and it has everything going for it but alas - not price! However after reading your post I costed 100hp motor and Drive unit from a company in the UK. It was more expensive but only by 2500 EURO. However you mentioned a DC Generator and invertor bank. I'm going to do a quick cost on those. Its looking like it will be very expensive. Just emailed the guy in the uk again

Also would it be dangerous? Would it be an electrician along with a mechanic that would be required to install it or would an specialist in installing diesel electrics be required?

I think the hydraulics system although more work, might be the most affordable..

once again , many thanks for all the great posts

ian

 

I think that you are going to spend a lot of money for very little gain and a lot of power loss

Why don't you try to fit a long shaft, or two in line with universal joint?

 

Hydro drive

I spent time on a boat with a 55hp hydraulic bow thruster. The fluid was run through an in line heat exchanger (I don't know the exact size but fairly large) and had an approx 30 gallon tank. The fluid would start to overheat after around 5 minutes constant use. I don't know if something was wrong with our installation but we had tried to size everything correctly according to manufacture's specs. I think a full time installation would have required a "keel cooler" style external heat exchanger. B

 

BruceB - it sounds like that setup may have had an undersized heat exchanger. The other possibility, of course, is that it used a hydraulic fluid designed to have the correct viscosity for that pump/motor at a higher than normal temperature. In any hydraulic system, the fluid grade and the cooling system have to be matched so that, under normal operating conditions, the fluid's viscosity is within the specified ranges of all the motors, pumps, etc. in the system. For a system typically used only a minute at a time, this could mean correct viscosity at a very low (near ambient) temperature, ie. viscosity too low at high temperature unless extremely large coolers are used.

Re. diesel electric: Yes, anything over 48 volts is going to involve an electrician, preferably a licensed one familiar with high-voltage marine systems.

Ian, if the sketch you posted is at all accurate, Marco1's suggestion of a shaft with universal joints is going to be simpler, cheaper and more reliable than any hydraulic or electric system. Just take the engine of your choice- an excavator diesel if you like- and bolt on a suitably rated F/N/R gearbox with a reduction ratio appropriate for your engine and propeller. Universal joints from rear-drive trucks/lorries should work just fine. There will be a bit of custom lathe work to produce suitable couplings, and a securely mounted thrust bearing on the prop shaft itself- overall, a pretty straightforward, simple solution.