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Hydraulic Drive


duztee

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Hi Duztee.

 

This is another of those perennial topics, looks very attractive doesn't it having an engine located somewhere (anywhere) in the boat, connected to all manner of machines by a couple of pipes, there can't be many 'boffin types' who haven't considered the convenience and originality of such a system.

 

The problems are numerous, a modern £5,000 marine diesel with all it's associated bits hanging off it, is a very cheap deal when you work it out.. Hydraulic systems can be very expensive indeed when you come to making a list of all the components you need.

 

Efficiency, a conventional boat setup with virtually a straight through drive to a propeller is probably as good as you can get with very little in the way of mechanical losses.. It is said in design engineering that every time you change from one medium to another you loose at least 25%.. An engine driving a pump, that squirts oil through a pipe and a few valves that turns a motor 40 odd feet away.. Losses can be enormous, not that silky smooth transmission of a stacker truck either, you will be plagued with noisy rattley pipes which transmit to the hull if mounted rigidly and little better if flexibly mounted.

 

But don't let me discourage you, there is little enough innovation on the canals, 'Go for it'.

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Have done quite a few with that setup and to be honest I would stay away from hydraulics without the boats design dictates it to be the only viable option.

 

What starts off in theory being reasonably cheap and simple rapidly becomes very expensive and complicated with some major drawbacks that aren't mentioned by the suppliers.

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and................ the engine would run at a constant speed, so when you went past other boats and the engine note does not change you will get shouted at to slow down. :lol:

 

 

Oops!! wrong thread but you will get shouted at anyway.

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The new super-duper BW pusher work tugs have hydraulic drive, apparently.

 

Just a shame several can be spotted canal-side with notices like "hydraulics drained - do not attempt to move", attached to them.

 

A.

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I think diesel-electric drive has more to offer but the only websites I have found seem to make it enormously complicated. Any views on a simple system incorporating the boat electrics and a bow thruster, using a 'silent' package genny?

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Thanks Guys,

Yes, I am still at the theory and planning stage, but now is the time to ask for advice, so I don't make a regretable decision (hopefully!)

I was aware that I could be looking at loosing as much as 30/40% in power loss.

I didn't realise there was a noise factor to consider, and had not as yet priced the various bits required, so perhaps this idea is moving to the back burner for now.

Since I will be a single handed boater with no one to swing on a pole for me, I liked the idea fo having a bow thruster, but electric operation seems to be woefully short of usable time before the batteries are exhausted.

Thanks again.

Duztee.

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... but electric operation seems to be woefully short of usable time before the batteries are exhausted.

The electric solution isn't normally limited by battery capacity. The batteries provide some buffer capacity, and may be heavily loaded at full throttle, so you wouldn't want to rely on it for a tidal passage or in fast river flows, but normally the power needed to drive a boat at 4mph along a canal is only a few HP which may be within the capacity of a small package diesel genny (say 6 to 10 KW).

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Sorry Chris,

I was only referring to electically powered bow thrusters having a limited amount of time, since i gather the usual set up is to have a couple of batteries at the front to power thruster, which then need time to recharge.

As for electric propulsion, I think it would certainly need much more than 12/24 volt, a 240 motor and supply is a possiblity, Toyota use 360 volts for their petrol/electic hybrid cars, a worrying amount of volts!

Duztee

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I was only referring to electically powered bow thrusters having a limited amount of time, since i gather the usual set up is to have a couple of batteries at the front to power thruster, which then need time to recharge.

 

The battery life of our bow thruster is actually pretty good! Which is fortunate because I can't find where to fit new batteries to the ash pole....

 

Richard

 

I predict that you will only have a problem with bow thruster battery capacity when you first start using the boat. After a while you will find that your skills in manouvering improve and you will use the bowthruster less.

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Hi Duztee,

I visited the Hercules Hydrulics stand at the IWA exhibition at Wolverhampton yesterday. They claim that a conventional drive has loses of 10% from the flywheel to prop and that their hydraulic drive has an additional 8% on top, making an 18% loss.

Their costs seem on a parr with conventional drive as a gearbox and flexible couplings are not required. The time and engineering expertise reqired to install a conventional drive is much greater (they claim) and there are savings to be made there.

Their web address is

www.herculeshydraulics.co.uk

 

They seem keen to offer full support to boaters.

With regards to your idea of using an hydraulic generator, I would suggest that you investigate the tax implications, because you would want all the fuel used for electrical generation to be taxed at red diesel rate.

 

Regards

East

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Hi Duztee,

I visited the Hercules Hydrulics stand at the IWA exhibition at Wolverhampton yesterday. They claim that a conventional drive has loses of 10% from the flywheel to prop and that their hydraulic drive has an additional 8% on top, making an 18% loss.

Their costs seem on a parr with conventional drive as a gearbox and flexible couplings are not required. The time and engineering expertise reqired to install a conventional drive is much greater (they claim) and there are savings to be made there.

Their web address is

www.herculeshydraulics.co.uk

 

They seem keen to offer full support to boaters.

With regards to your idea of using an hydraulic generator, I would suggest that you investigate the tax implications, because you would want all the fuel used for electrical generation to be taxed at red diesel rate.

 

Regards

East

 

Did they tell you who make the hydraulic drive system used on the new BW work boats? :lol:

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Yes Eastern, I visited them today, the quoted 18% loss is for the piston type pump which is the more expensive option over the vane type which has a bigger power loss.

The stand which did interest me equally was the Beta Hybrid.

They are using a 10kW motor mounted directly behind the engine driving onto the same prop shaft, giving electric propulsion when required, the motor then operates as a 5kW generator when the diesel engine is running, a dog clutch means it is possible to have the genorator running without the prop turning.

The big advantage of this system to single handed boaters is that it will be operatable by remote control, so it should be possible to stand on the lock side and command the boat to come hither or go thither.

As always with new produces to the market.....time will tell if it is a winner or not!

Anyway it was a good festival, enjoyed it totally and came away a little wiser on many subjects

Duztee.

P.S. Chris is right that this operates at 48 volts.

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the quoted 18% loss is for the piston type pump which is the more expensive option over the vane type which has a bigger power loss.

 

Quite correct Gary, but to be fair the piston pump type including a Beta 50hp engine was £3700.00 and the vane motor was £3550.00. Not a big difference, I'm sure you will agree!

 

The BW workboats are rare sight on the system, broken down or otherwise. I wouldn't have thought that hydraulic systems were inherently unreliable, as I see plenty of JCBs etc working away at digging holes and such like. I'm afraid I'm old enough to remember when the earth moving machine all worked on steel cables being wound on and off a drum! But don't lets go there :lol:

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...electrically powered bow thrusters having a limited amount of time...

The limitation is usually the motor, not the battery! Our 4HP Aquafax/Noble BT user guide recommends typical usage should be 5 second burst with 10 second pauses, and a maximum burst of 25 seconds. There is a panel above the motor control with "overheat" lights which, if they come, on you should stop using the BT.

 

If you assume the motor takes 600amps then even a 25 second burst is only nominally 4Ah, although the Peukert effect would make the battery discharge effectively much higher.

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