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Author Topic: Emma Maersk  (Read 7533 times)

Bunkerbarge

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Re: A really BIG Engine
« Reply #25 on: October 08, 2009, 09:21:45 am »

Just a couple of interesting little bits that you perhaps don't see in the statistics:

1) The crankshaft is fabricated and the pieces are held together by no more than a heat generated shrink fit.  Imagine all that power being transmnitted through nothing more than the grip of a shrink fit?  At the joints there are little witness marks so you can determine if the seperate components of the crankshaft have slipped.  If this should ever happen, as a result of say the propeller ever being knocked, you would have to retime the part of the engine after the slip.

2)  All the fasteners on engines such as this are hydraulic and it is remarkably easy to remove the various components.  The fastener, such as a stud, are 'stretched' hydraulically to a point whereby the 'nut' can be removed by hand.  The hydraulic pressure is then released.  Items such as cylinder heads can then be fitted and removed as a single operation as all the studs are stretched together.

3) You check the transfer ports by standing on the top of the piston and turning the engine on the turning gear.  You then go down into the cylinder as though you are in a lift!

4) Did you notice the ladder fitted into the crankcase?  This is necessary to gain access to the lower piston seal and you have to go down one ladder into the bottom of the crankcase, then up another that goes all the way to the top.

5) When these engines are running you can stand at one end of it and align a particular item, such as an injector or air start valve, on the cylinder head by eye. You can then 'see' the engine 'flowing' as each cylinder stretches slightly when it fires.

6) To accomodate this effect each cylinder is built as a completely seperate item, which sits on top of the crankcase, and are all bolted together.

7) You need a crane to transport the injectors around!

8) The crosshead arrangement is exactly as Peter suggests, to transmit all the sideways forces generated from the crankshaft into the crosshead guides, thereby removing them from the piston.  This allows the piston to be of a comparatively lighter construction and removes any unwanted sideways thrust on the cylinder wall and the piston rod seal.  It also enables the two stroke configuration to be used with the transfer ports in the base of the cylinder wall and the space below the piston to be used to 'pump' the charge air into the scavenge space, known as 'Under Piston Scavenging'.
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Damien

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Re: A really BIG Engine
« Reply #26 on: October 08, 2009, 09:55:33 am »

Some of the text attached to each picture were lost in the file conversion what i remember are p5 a shot of the piston with lots of holes bored into the underside pic6 shows the connecting rods with a myriad of fingers which are tube that feed oil into the piston to dissipate the heat of combustion.
Damien.
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farrow

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Re: A really BIG Engine
« Reply #27 on: October 15, 2009, 02:30:24 pm »

Thanks Bunkerbarge, your post was very interesting.
David
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gondolier88

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Re: A really BIG Engine
« Reply #28 on: October 17, 2009, 06:00:18 pm »

Hi,

A couple of questions for someone in the know- the pic of the three guys craning the main bearings into place-

1- They don't look overly big- I would have imagined 5-6inch deep with the amount of pressure on them?
2- If they are so thin then what are they made out of- they look like a plastic to me!

Greg
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Martin [Admin]

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Re: Emma Maersk
« Reply #29 on: October 25, 2009, 04:16:51 pm »

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Dreadstar

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Re: Emma Maersk
« Reply #30 on: October 25, 2009, 06:19:07 pm »

Not exactly a small piston rod was it!! :o
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riggers24

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Re: A really BIG Engine
« Reply #31 on: October 25, 2009, 10:23:13 pm »

Just a couple of interesting little bits that you perhaps don't see in the statistics:

2)  All the fasteners on engines such as this are hydraulic and it is remarkably easy to remove the various components.  The fastener, such as a stud, are 'stretched' hydraulically to a point whereby the 'nut' can be removed by hand.  The hydraulic pressure is then released.  Items such as cylinder heads can then be fitted and removed as a single operation as all the studs are stretched together.


Bunkerbarge,

Here is a pictorial view I have of bolt tensioning using hydraulic jacks. If anyone has seen large diameter nuts with blind holes drilled in the spanner flats, this is what they are used for.

Riggers
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