Thinking of what next if opportunity to build again?

Discussion in 'Diesel Engines' started by masalai, Jul 9, 2012.

  1. masalai
    Joined: Oct 2007
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    masalai masalai

    CNO is proving to be a very worthy design - - but - - I have a couple of changes on my wish list...

    Remove the "back verandah' on the aft of the bridgedeck by re-locating the "window-seat back to where the rudder posts are... That will make a LARGER space for the engine room, and facilitate larger doors to the saloon P & S...

    Why all this in an engine forum? well part of the dream is a "why has it not been done before" quest...

    In my naivety on matters engineering I thought 'Why not a straight six with slightly larger capacity than present and being a straight 6 possibly smoother running, comparatively lighter also because things are smaller and less loaded...

    My kubota based 3 cylinder engines are 722cc and develop 21hp at 3600rpm.
    - Why not something running at say 1500rpm and LONG stroke for better torque and less than 1.2 litres total swept area... - Less than 200cc (12.2 cu in) per cylinder ...

    Some of the "from-scratch-home-built-models-diesel-engines" look very interesting but not a small straight six in sight... http://www.youtube.com/watch?v=E4-fOw6vr34

    According to the performance information on my Kubota nanni sail-drive engines I make about 10hp each at 3000rpm and a pair push my boat at 10knots and the engines weigh in at 80kg and with the saildrive leg at 144kg... Would it be possible to not exceed that weight with a straight-6 of displacement less than 1.2 litres - even down to 900cc?

    Here is the build thread for may boat "CNO" - http://www.boatdesign.net/forums/boat-building/my-little-piece-peace-25962.html - and presently she does 10knots at 3000rpm and burns less than 3 litres of diesel per hour for each engine giving better than 1.6 n miles per litre of diesel fuel... images of the finished.launched boat begin about here http://www.boatdesign.net/forums/boat-building/my-little-piece-peace-25962-64.html#post461096
     
  2. WestVanHan
    Joined: Aug 2009
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    WestVanHan Not a Senior Member

    What is wrong with what you have? :confused:

    If you want that hp at 1500 rpm you'd need something a lot larger and heavier and fork out another $$$$$.

    If you want cheap diesels,import some from China. Good luck with them.
     
  3. WestVanHan
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    WestVanHan Not a Senior Member

    Well I'm stuck in town an extra day waiting for a gf to get her act together before going out on the boat.

    Anyways,what would be good-except for weight- would be the 40 hp non turbo VW 1.9 marine engine. I think they'd put out 15 hp or so at maybe 1500 rpm or so.Plus give you some "runaway/getaway" speed which I like having.

    A six cylinder would be too expensive to build as opposed to a 4 or 3 cylinder of 1l displacement.Or you could couple two 3 cylinders but that seems silly.
     
  4. groper
    Joined: Jun 2011
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    groper Senior Member

    I dont think anyone can say much, until you tell us WHY you would want to do such a thing?

    Do you want to go faster?
    Do you want less noise?
    Why?
     
  5. masalai
    Joined: Oct 2007
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    masalai masalai

    Hi westie,
    When I have bought an item, I tend to accept that as a fair consequence of production line manufacturing... - - That is, except when there is evidence of some previously unidentified defect/deficiency - then one justifiably gets pissed off with the poor quality of the work/design of the manufacturer... - - Or one is left to accept that the commercial build was constrained by production moulds etc - only allowing little "tweaks" around the edges as a refinement...

    My response seems to be a regular - owner-builder related thing. - - Now that I have built that one, although it performs in many aspects, better than I anticipated, but one starts to think "well If I had done this and then that advantage would be realised", and so on...

    In the objective I had been looking at hobbyist models and they all seemed to be those MINUTE V8 engines that would fit nicely in the palm of ones hand, and the one I linked a straight 4 with a bore of 1 &1/16 inch and a stroke about 1.5 inches ... I was think just a little bigger - small enough to pick up with BOTH hands, light (alloy), but with steel sleeves and such-like but weighing in at less than 80kg (hopefully considerably less than 80kg (50?)

    Slightly bigger swept volume so that continuous rating could be around 20 to 30hp still at slower rpm, at 1500 rpm ?

    I suppose the BIG question is - - - - could it be made as a 6 cylinder for smoothness & balance, and could it be significantly lighter? - more fuel efficient so that the engine more closely matches its purpose - - LONG distance and LONG range cruising under power...

    I tried to get info on the Mercedes Smart diesel - as used in trikes (Ramphos) - ultralight aircraft) and other Euro engines like the 5 cylinder diesels - all I got was a blank wall of - - "shut-up and go away" - - .... :eek: :D
     
  6. masalai
    Joined: Oct 2007
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    masalai masalai

    My mental doodle was because I could find some very nice "toy" diesel engines 4 cylinder, V8 and V12, and even a radial and all were working "TOY - models" that would sit easily on your hand...

    So why not something a bit larger - sort of half way between an UNBELIEVABLE working toy - - to - - an ordinary small commercial diesel engine...

    The commercials are too heavy and the toy models are too small in the hp department - - so how about something like a straight six, that would run very smoothly yet still offer the hp I have now with LESS weight and lower rpm yet still produce 20 odd hp?

    722cc (44 cubic inches) 3 cylinder now produces 21hp at 3600rpm - - - so why not a 980cc or 60 cubic inch 6 cyl engine producing the same hp and weigh less with light construction of aluminium alloys? and LOTS more torque....
     
  7. groper
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    groper Senior Member

    And spend how much time and money...? for what gain? save 10 or 20kgs on a circa 6000kg max displacement vessel? Sounds well past the point of diminishing returns...

    Are your current engines not running smoothly?
    are they too noisy? - i suspect the latter... my last 4cyl turbo diesel navara was quite annoying for its in cab engine noise, and not surprisingly had a poorly rated NVH - (noise, vibration, harshness) - as most small diesels do....
     
  8. FAST FRED
    Joined: Oct 2002
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    FAST FRED Senior Member

    Most diesels will put out the same HP per cubic inch.

    Sure some car turbo diesels are rated very high , but that output would not be for long on a boat.


    So to compare engines the volume times RPM is simplest.

    700CC times 3000 rpm=

    Take the number found and divide by the rpm desired.

    In this case a 1500cc engine should do what you want .

    FF
     
  9. Fanie
    Joined: Oct 2007
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    Fanie Fanie

    The problem is that if you add more cylinders you add more overheads too keepint the motor running. It has compromizes, same as boats, what you win here you lose elsewhere.

    We all dream of the motor that runs extremely economic that has huge amounts of power if you kick the gates open.... except that it doesn't exist yet.

    Certain size motors jusy work out better than others with all the compromizes, so you end up with something that offers a bit of everything and lacking a bit of it all too.
     
  10. masalai
    Joined: Oct 2007
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    masalai masalai

    Hi Fast Fred & Fanie,
    Oh bugger, Thanks Fred, that shattered the daydream, sort of but conversely, if I retained the 3000 rpm then a 722 cc 6 cylinder engine would still give me the 12hp delivered and if the stroke was the same then the bore for each piston would be less and the compressive loading lighter? and because it is a straight-6 the vibration & noise could be less? is there any advantage in more cylinders yet retaining same swept volume? - - - like more torque and a potentially lighter engine?

    Sorry to sound like an ill-educated pain in the ***, but this engine theory is bordering on witchcraft... Being modestly dexterous, repairing and rebuilding is relatively easy with a manual and torque wrench at hand, and having rebuilt the 149 ci straight six engine in my old Holden ute with occasional oversight be a friendly mechanic, - - but number crunching performance theory is the sort of magic I am best served at leaving to others expert knowledge...

    How about something like this http://www.dair.co.uk/ the revs are OK at 2500 so existing gearbox-sail-drive leg but I only need less than a third the horsepower... and it is light, has a dry sump . . . . . redirect the exhaust up? but not critical as there is plenty of "sump space" delivers 60 hp at 2200 rpm and burns 10 litres/hour if my conversions are reasonable...

    NUMBER OF CYLINDERS - - - - - 2
    NUMBER OF PISTONS - - - - - - - - 4
    NUMBER OF INJECTORS - - - - - - 4
    BORE - - - - - - - - - - - - - - - - - - - - - 80mm
    STROKE - - - - - - - - - - - - - - - - - - - 90mm
    DISPLACEMENT - - - - - - - - - - - - 1810cc
    COMPRESSION RATIO - - - - - - - 18 : 1
    DRY SUMP CAPACITY - - - - - - - 5 Litres
    FUEL GRADE - - - - - - - - - - - - - - AVTUR / DIESEL
    ENGINE MOUNTS - - - - - - - - - - - 4 POINT
    DRY WEIGHT - - - - - - - - - - - - - - - 92.7 Kg - - - - - - - - - - - Bugger, too heavy :eek:
    INJECTION SYSTEM - - - - - - - - - DIRECT
    CONTRO- - - - - - - - - - - - - - - - - - SINGLE LEVER
    RATED RPM (Propeller) - - - - - - 2500
    POWER- - - - - - - - - - - - - - - - - - - 100 HP
    ALTERNATOR - - - - - - - - - - - - 12V / 20a (Optional 12V / 60a)
    STARTER - - - - - - - - - - - -- - - - - 12 volt
    PROPELLER FLANGE - - - - - - - SAE 1 / ARP

    Oh well still nice to dream, and one day I may find the ideal powerplant?.....
     

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  11. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    My dream power plant is a steam turbine driven by a nuclear that weights200 lb and makes 1000 HP. Instead I have 3000 lb diesels that make 275 HP. But at least I don't have to worry about used fuel rods.
     
  12. masalai
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    masalai masalai

    HE,He,he, only when you need to refill the diesel fuel tanks after burning --?-- gallons/hour to get --??-- n. Miles? :D :D :D :D :eek: :p - It is a bloody viscous circle. . . . . . . .
     
  13. masalai
    Joined: Oct 2007
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    masalai masalai

    I found an image of the back of CNO http://www.boatdesign.net/forums/boat-building/my-little-piece-peace-25962-68.html#post464791 and you can see on the starboard hull a hatch that is access to the engine

    - - the forward end of the hatch is the forward end of the engine bay - BLOODY tight fit, as the aft end is under the bow of the "rubber-duckie"...

    This thread was to address that issue by moving the back walls of the bridge-deck saloon (where the boats name and home port are written), to the bulkhead on which the rudder post is mounted (aft end of present space for the engine bay)... That would add some 500 mm to the space available for the engine / sail-drive after allowing some 300 mm for the repositioned double bulkhead and removing the aluminium rails aft... That would give me a reasonable amount of space and almost able to call it an "engine room but with squatting space vertically... This would make a rather complex and expensive rebuild - - - - or serve as good guidelines to rebuild - when and if fortune smiles... :D :D With this thread I seek to be as prepared and well researched as possible...
     

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  14. masalai
    Joined: Oct 2007
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    masalai masalai

    Back on the self built RO watermaker project,

    I am not pricing the high pressure pump as most hardware stores have those and the user needs to be satisfied that it is "salt-water-tolerant as is also applies for the "feed / boost pump" a sea water strainer is available from most chandler suppliers...

    What I will price is the 20 and 5 micron filter pair and low pressure T valve to facilitate fresh water flush after each daily use (which also serves as the cleaning/storage pickling intake... (no separate fresh water flush as in diagram unless you specifically require that option)

    Next the High pressure pump capable of delivering 800 psi and 10 to 15 litres/minute of filtered 40 psi seawater (low pressure gauge is optional)...

    The mambrane pressure vessels - 40 inch seem to be the better option and for those seeking to extract more potable water a pair set up with the high pressure sea water feeding one and then the other in series to ensure a good salt water flow to keep the system well flushed to remove algae, salt and other contaminants efficiently and flush back to the sea...

    Next is the product flow meter (a calibrated glass cone with a ball inside) and a T valve to redirect flow from the purge / taste test and then turn to fill the fresh water tanks with 'product'...

    The waste from the membrane vessels is still high pressure and has a high pressure gauge of the style filled with glycerine so the gauge can be read without the pulses from the high pressure pump and a high pressure control valve so the working pressure may be built up to the optimum 800 psi and the flow rate of product is appropriate...

    The only things left is the high pressure hoses and fittings and the seawater inlet fittings and suction lines/fittings to the boost pump and beyond (ordinary high pressure domestic lines and fittings to the high pressure pump)...

    I am thinking of mounting the pressure vessels, valves and flow indicaters etc to a plywood panel and connectors from the "seawater deck wash pump" to the RO system via a high pressure pump (that may end up attached to the plywood assembly board), - and from the system to taste/waste and product to potable water tanks and another for the waste reject water...
     

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  15. masalai
    Joined: Oct 2007
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    Location: cruising, Australia

    masalai masalai

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