Marine Engineering - Practical Tips & Tricks

A place to exchanges questions and ideas of a technical / procedural nature. Go ahead, try to stomp us !
User avatar
Merlyn
Fleet Engineer
Posts: 784
Joined: Wed Dec 25, 2013 7:19 am
Currently located: South Coast UK

Re: Tips & Tricks

Postby Merlyn » Tue Jun 30, 2015 7:10 am

Well, here's one for folk with, how can I say, more hours / experience on the hour meter of life and who ever at some point in their career came across magnetos, in outboards/ motorbikes and marine engines. One cyl up to six and beyond, the lesson to be learnt was don't be the last one in the line when testing. New boy at work, a senior apprentice would say, we need to bench test this mag we have just removed from this tripping boat. We need to subject it to a load and the bench test is we get about four apprentices to stand in line and as the mag is in a steel vice the end person should touch that vice about fifteen feet away from the mag. All on a steel bench and all holding hands. You don't have to worry, we have done it lots of times over the years with petrol and TVO engines. As there are five of us in total the load will be shared and you will hardly feel anything. Wrong, no one receives a belt/ electric shock save the character who earths it out on the second vice. Should this be an impulse mag, ( it's got a coil spring which winds up and then let's go a terrific spark ) believe you and me you will never, ever in your career go back for a second helping. Should you spot an air wrench with a socket on it which fits the sprocket nut on the mag then you are in for an even bigger shock all round. Just a thought in case you ever get set up. Anyone out there know this ?
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

User avatar
JollyJack
Fleet Engineer
Posts: 1128
Joined: Wed Mar 24, 2010 3:57 am
Currently located: Eastern Canada

Re: Tips & Tricks

Postby JollyJack » Tue Jun 30, 2015 8:41 am

As apprentices, we'd charge up a condenser from a coil ignition system by flashing wires from battery terminals across it and toss it to the guy on the next bench.

There were many expressions of pain, war dances and dire threats......
Discourage incest, ban country "music".

User avatar
Merlyn
Fleet Engineer
Posts: 784
Joined: Wed Dec 25, 2013 7:19 am
Currently located: South Coast UK

Re: Marine Engineering - Practical Tips & Tricks

Postby Merlyn » Wed Jul 01, 2015 8:05 am

Hah, forgot about that one. Reminds me of the apprentice who used to do that a lot and further reminds me of his other party piece trick. Some of our work overhalls used to have in the right hand leg a rule sleeve sewed in, part of the overhalls. To save loosing rules in the top pocket over the side when you leant over to look at something this idea was meant to stop all that. However I always had a six inch rule but if you had a two foot rule which was hinged in the middle these pockets were a godsend. When you were talking to someone, perhaps explaining something in passing he would drop a red hot nut into this rule pocket. When he had passed your overhalls would be smoking badly and about to catch fire. If you could not get them off quick enough then you would be in for a burnt leg at the very least. Of course no one ever knew anything about it, as normal. So the tip here is should you ever be working with a crew like ours used to be don't buy any rule pocketed overhalls. Just one example of all the apprentice shenanigans that used to go on an almost daily basis at work back then.
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

User avatar
JollyJack
Fleet Engineer
Posts: 1128
Joined: Wed Mar 24, 2010 3:57 am
Currently located: Eastern Canada

Re: Marine Engineering - Practical Tips & Tricks

Postby JollyJack » Thu Jul 02, 2015 7:59 pm

Remember the brown paper bag filled with acetylene thrown under a welder's cutting table?
Discourage incest, ban country "music".

User avatar
JK
Enduring Contributor
Posts: 2696
Joined: Tue Sep 04, 2007 2:29 am
Currently located: East Coast, Canada

Re: Marine Engineering - Practical Tips & Tricks

Postby JK » Fri Jul 03, 2015 1:48 am

Last time someone did something like that to me, I picked up a can of layout dye and threw it at his retreating head as hard as I could. He turned at the last instant, saw it and ducked. The can went through the window behind him. The lead instructor was unhappy, I had to fix the window with a sheet of tin which was probably still there when the building was pulled down. Funny, that was the end of tricksys. There was a clampdown from the instructors.

User avatar
Merlyn
Fleet Engineer
Posts: 784
Joined: Wed Dec 25, 2013 7:19 am
Currently located: South Coast UK

Re: Marine Engineering - Practical Tips & Tricks

Postby Merlyn » Fri Jul 03, 2015 4:57 am

Yes, I well remember the acetylene tricks, we had an old oxy/acet profile cutter, big old beast it was. You had to make up a template of the plate you were flame cutting with a sheet of 22 gauge mild steel, this would be drilled and bolted to the top of the profile cutter and a spring loaded roller would follow it exactly as you had cut it. The cutting torch above the job bolted down onto a huge faceplate would then cut exactly following your template. I could never set it up without numerous blow backs and leaving huge burrs on the job to be ground off when finished. Doing this job was a target for acet filled balloons thrown when you were peering closely at the flame on the cutter. Another favourite one was to fill a Durex contraceptive with acet and when the years went by and you had your first car ( having been thro' the motorcycle phase ) and they knew you had a girlfriend that they knew you were keen to impress on a Friday afternoon someone would place the inflated acet. contraceptive in your car boot. They made it their business to find out your weekend plans and subsequently knew that on Sunday you would be going around to her house to meet the parents and take her for a picnic which she had ( hopefully ) prepared. The ultimate outcome would be that having met the parents and done your best to impress them that they would all carry the BBQ and all the food to the rear of the car whereby the boot would be opened and the acet powered Condom would rise from the boot depths. Should you be puffing a Woodbine fag at the time would merely increase the em assessment factor to ten.
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

User avatar
Merlyn
Fleet Engineer
Posts: 784
Joined: Wed Dec 25, 2013 7:19 am
Currently located: South Coast UK

Re: Marine Engineering - Practical Tips & Tricks

Postby Merlyn » Fri Jul 03, 2015 5:26 am

Talking of tappet / rocker adjustment just reminded me of the old feeler gauge trick. You would be boasting of this new warranted for life set of feeler gauges that perhaps mum had bought you. Everyone would admire this new set of gauges going from two thousands to maybe fifty. One day some wag had rebuild a head and innocently wondered if there was any chance of doing the job " properly " and borrowing your feeler gauges. Wanting to impress the senior apprentices and to be "in with them " you eagerly lent them your brand spanking new set. Now as you were on another job and unbeknown to you the tappets were all adjusted ( cold ) and the apprentice concerned then set about his new party piece of showing off how to adjust tappets with the engine running. Whilst this may well have been ok for a quick confirmation check no set of feeler gauges would withstand the treatment that was about to follow. The long and the short of it was the gauges were given back to you and into your box they went. Some time later, maybe weeks away you had a set of tappets to reset. Out came your super duper feeler gauges and you discovered to your horror that a fifteen thou feeler was ten in one part and seven in another. Shock and horror, apprentices would gather round and remarks like " looks like a warranty job to me M " would be bandied about. " Woolworth set " was a favourite remark throught the apprenticeship years addressed to cheap no good Sunday only use age tools. Trying to convince the tool supplier that "of course I don't abuse my tools " was no straightforward matter and of course as usuall no one knew anything about it.
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

User avatar
The Dieselduck
Administrator
Posts: 2743
Joined: Sun Jul 22, 2007 1:41 pm
Currently located: Nanaimo, British Columbia, Canada (West Coast of Canada)

Re: Marine Engineering - Practical Tips & Tricks

Postby The Dieselduck » Sun Jul 05, 2015 3:36 am

the "em assessment factor", too funny.
Martin Leduc
Certified Marine Engineer and Webmaster
Martin's Marine Engineering Page
http://www.dieselduck.net

User avatar
Big Pete
Engineering Mentor
Posts: 814
Joined: Fri Apr 24, 2009 11:18 pm
Currently located: Solihull, England

Re: Marine Engineering - Practical Tips & Tricks

Postby Big Pete » Mon Jul 06, 2015 2:02 am

Something to avoid rather than to do:
Cleaning plates from a plate heat exchanger should not be done with a wire brush, the ends of the wires can become friction welded to the surface of the plates and create tiny Galvanic corrosion cells which will perforate the plate. I read the theory of this in the MER many years ago, and on one ship I saw the result, LT cooler plates that looked as if they had been the target of a shotgun. I have also seen the instruction manuals for plate coolers specifying that they should only be cleaned with a maker's supply wire brush, made of the correct grade of steel to avoid this problem.
Better to clean them Ultrasonically or in an Acid bath.
BP
It is always better to ask a stupid question than to do a stupid thing.

User avatar
Merlyn
Fleet Engineer
Posts: 784
Joined: Wed Dec 25, 2013 7:19 am
Currently located: South Coast UK

Re: Marine Engineering - Practical Tips & Tricks

Postby Merlyn » Tue Jul 07, 2015 4:23 am

Something slightly different, the old sixty five is on the horizon and that retirement pension fund you have spent all your life building up is bursting at the seams. Not wishing to completely turn your back on the old briny you elect to buy a 60 powerboat and shove off round the Mediterranean with the wife for a few years and live on the boat. Collecting it from the UK you go down through the bay of Biscay and into the Med to Majorca. Although your cruising speed is a respective 18 knots the boat will max out at 26 knots and this you try on the way down, no problems. You use the boat around the Med and apon trying full throttle one day to beat the weather you find that you can only achieve 23 knots max. You check all the stern gear, slip the vessel, check throttle settings etc etc and as the vessel is under warranty call in the makers. It's obviously common rail and FCR 's and all diagnosis reveal no problems. You are stuck with this problem. You note that the top RPM s are slightly down at full throttle and a reprogram of the ECU does nothing to help the matter. Next season you decide to go through the straits of Gibraltar and into the Atlantic to Portugal. A spot speed test reveals the problem has cleared itself and 26 knots and top RPM is attained. The three months spent in Portugal reveal no loss of top speed. How can this be? What's the problem?
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

User avatar
D Winsor
Superintendent
Posts: 331
Joined: Thu Nov 22, 2007 8:23 am
Currently located: Dartmouth

Re: Marine Engineering - Practical Tips & Tricks

Postby D Winsor » Tue Jul 07, 2015 5:38 am

I expect propeller efficiency and hull hydrodynamics were affected by the difference in water temperature and density in Med and the Atlantic Ocean and the effect known as propeller squat.
This effect is very common in the fresh water of the Great Lakes
Last edited by D Winsor on Tue Jul 07, 2015 5:46 am, edited 1 time in total.
Troubleshooting 101 "Don't over think it - K.I.S.S. it"

User avatar
Big Pete
Engineering Mentor
Posts: 814
Joined: Fri Apr 24, 2009 11:18 pm
Currently located: Solihull, England

Re: Marine Engineering - Practical Tips & Tricks

Postby Big Pete » Tue Jul 07, 2015 5:44 am

Air temperature and humidity?

Speed record runs are always done at Dawn to benefit from the lowest ambient air temperature and thus highest air density, enabling engines to produce maximum power.
I think High Humidity will also reduce the power output, although it might reduce your NOX!

I think if the power being absorbed by the prop was reduced by cavitation due to high water temperatures, low density then the prop/ engine revs would have increased rather than decreased.

It sounds as if the engine is producing less power.

However, if the reduced speed occurred in shallow water, it could be caused by "Squat", the gap between the bottom of the hull and the Sea bed acting as a venturi, creating a partial vacuum in the water forced between them, sucking the stern of the boat down and generating a large stern wave, which will absorb a lot of extra power.
BP
Last edited by Big Pete on Tue Jul 07, 2015 10:53 pm, edited 1 time in total.
It is always better to ask a stupid question than to do a stupid thing.

User avatar
Merlyn
Fleet Engineer
Posts: 784
Joined: Wed Dec 25, 2013 7:19 am
Currently located: South Coast UK

Re: Marine Engineering - Practical Tips & Tricks

Postby Merlyn » Tue Jul 07, 2015 7:05 am

Bah, that one did not last long. It's the S. G. of the water actually. In order to correct the situation you ideally have to prop up or down. The thing is I have to be truthful here, I can't remember which way round it is? Any ideas? The Med appears to be more salty than the Atlantic. So when you buy your boat and head that way don't forget to carry a spare pair of props in your back pocket. Or if you fancy doing pitch changing take your grinderette along together with that pitch changing scriber block thingy.
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.

User avatar
JollyJack
Fleet Engineer
Posts: 1128
Joined: Wed Mar 24, 2010 3:57 am
Currently located: Eastern Canada

Re: Marine Engineering - Practical Tips & Tricks

Postby JollyJack » Tue Jul 07, 2015 11:37 am

The Baltic and the Med are both "enclosed waters" with one small outlet. The Baltic has been subjected to more industrial pollution over the years than the Med, silt carried by riverwater is suspended, the water is brackish, but denser than the Med. The Med, of course, is denser than the Atlantic.
Discourage incest, ban country "music".

User avatar
Big Pete
Engineering Mentor
Posts: 814
Joined: Fri Apr 24, 2009 11:18 pm
Currently located: Solihull, England

Re: Marine Engineering - Practical Tips & Tricks

Postby Big Pete » Tue Jul 07, 2015 10:48 pm

I remember from reading a lot of Naval History, that there is a hot, Fresher, less dense surface current out of the Mediterranean, and Black Seas, and a denser colder Saltier current flowing in, underneath.
British Submarines going into the Black Sea and Sea of Azov during the First World War didn't have sufficient endurance to make the passage through the Dardanelles under water (Theoretically), so used the differing currents to help them through more quickly, in both directions. Google "E11" her Captain( Nasmith? )won a VC for his repeated raids through the Dardanelles. The "E"class "Boats" were the first decent British Submarine design, and several of them operated in Turkey's inland Sea during WWI.
The Boundary between the two layers acts like a Physical Barrier to A.S.D.I.C. ( Allied Submarine Detection Indication Committee)/ Sonar and bounces the sound waves back, (Thermocline) helping to conceal submarines in the lower current.
All Submarines used the same trick going into and out of the Med in WWII.
I expect going into the Baltic would have been the same in Summer, but not sure in the Winter when the Baltic Sea Freezes and is much colder than the North Sea. I have read relatively few books about British Submarine operations in the Baltic, compared to the Med and Black Sea.
BP
It is always better to ask a stupid question than to do a stupid thing.


Return to “The Workshop”

Who is online

Users browsing this forum: No registered users and 1 guest