distributed hydraulic systems on boats? why not?

Discussion in 'Boat Design' started by ijason, Jan 25, 2009.

  1. ijason
    Joined: Jan 2009
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    Location: florida, usa

    ijason Junior Member

    @rick. i mentioned more options to where you mount the main engine, because you would not need a linear connection between it and the drive shaft for the propeller. this is certainly an advantage offered by using a generator/electric drive too... i'm 6'6" and have had more than my share of trouble trying to get into tight spaces to service an engine, so it seems being able to give yourself room to work would be a HUGE advantage over a direct mechanical drive. of course, just being a little more generous with shaft length can give you that. i guess i've seen too many pictures of cramped engine bays :)

    i think i may agree with teddy, it sounds like you've had more than your share of bad experiences with hydraulics. in the 6 years that i ran my loader, the only time i would need to change the hydraulic oil was when i needed to change the filter, and the only time i had a leak big enough to require topping off the reservoir was when i had a failing hose or coupling. that's not to say that the bay wasn't spattered with blow-off oil and dirt... but certainly not the constant and endless leaking that you seem to experience.

    i think we may just have had diametric experiences with electrical and air/hydraulic systems. IMO most people who have power tools will have electric or battery operated, because they're cheaper to buy and reasonably reliable and most people won't put them to their duty-cycle limit. most shops will have as many of their tools air-powered as they can, because the individual air-tools are cheaper than their electric counterparts (once you've made the investment for the compressor), and because they give longer life, and have no duty-cycle limits.

    i would be interested to see how you calculated that 15% efficiency rate... calculated the wattage to keep a 50 gallon tank at pressure during continue use of an air-wrench vs the wattage used to run a corded equivalent? i'm not doubting you've done it, i'm just curious to see how the heck you'd compare such things :) i think that life of the device should be considered when figuring efficiencies, too. it doesn't matter if my electric drill is three times more power-efficient than the air-powered one, if i'm also going to have to buy 5 of them to do the same drilling that one air-powered drill would provide.

    i've always considered electric hand-tools to be more dangerous than air-tools. you're almost always going to have a hose failure before anything in the tool itself goes, and i would much rather have a plastic hose blow than a power cord short out while it and i are in the same puddle.

    i think that electrics will usually win when it's a question of pure efficiency and cleanliness. but it's been my - very different than your own - experience that electrics are substantially more fragile than hydraulic/air counter-parts. and i would also contend that hydraulic/air are a winner in questions of cost; they have a higher initial price with a compressor or hydraulic pump, but you can then buy cheaper end-drivers (such as the actual air-drill, etc) than electric counterparts.

    i'm fairly convinced that a hydraulic motor would not be the best choice for the main propulsion on a ship, and distributed hydraulic systems to run other devices is already accepted practice. but how much more expensive would a diesel/electric system be than a slightly larger motor to drive a large enough hydraulic pump to run a main-driver? i wonder if equipment cost might be greater than efficiency issues?
     
  2. amolitor
    Joined: Jan 2005
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    Location: San Francisco

    amolitor Junior Member

    I'm pretty sure that the leaks Rick's talking about are not leaks out of the system -- the system remains closed, but oil leaks past the rams, eating efficiency. That oil's staying in the system, but it's still leaking. It's just leaking from one part of the system to another.
     
  3. Guest625101138

    Guest625101138 Previous Member

    In this case I was meaning external leaks. Those that contribute to mess; slip hazard, fire risk and area pollution. I have hundreds of photos like the attached. This is not bad. In fact it is cleaner than most I look at. The only leak free hydraulic installation is one that has not been used.

    I would never want to encourage use of hydraulics. If you can find an alternative then take that route.

    Rick W
     

    Attached Files:

  4. ijason
    Joined: Jan 2009
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    Location: florida, usa

    ijason Junior Member

    @rick, bah! those look perfectly clean! :D i usually only noticed a leak when i started leaving trails on the ground i was leveling. the never-reassuring : "oh crap, did i hit a water line? no? great. what color is it?"

    i'm curious though, it looks like that's stationary equipment, which would be the least prone to leakage. my hydraulics get bounced around inside a tractor all day long and apparently suffer from less chronic leakage than your equipment? that seems to go against common sense. or perhaps construction equipment is built to different standards than other stuff?
     
  5. Guest625101138

    Guest625101138 Previous Member

    Yes- most people who live with hydraulics do not see the mess and other risks associated. I get paid to identify such things.

    Rick W
     
  6. ijason
    Joined: Jan 2009
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    Location: florida, usa

    ijason Junior Member

    slip hazard? c'mon, safety is over-rated!
    [​IMG]
     
  7. Poida
    Joined: Apr 2006
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    Location: Australia

    Poida Senior Member

    ijason buddy,

    You won't see a hydraulic ceiling fan? I've seen one.

    A ceiling fan for a shower cubicle. The water from the tap first goes through a turbine attached to a ceiling fan before coming out of the shower rose. The fan then automatically starts when you turn the tap on.

    As I said previously I do a bit of design work, but some of the people posting on this thread would be very bad designers if they used only one method of drive just because they like it without taking other alternatives into consideration.

    Power Steering versus Alternator
    You would probably have to replace your power steering quite a few times if your steering wheel went around as fast and as many times as your alternator.

    Environment.

    I would not like to see a heap of hydraulic oil being pumped into the ocean because a seal blew.

    Blown a seal? No it's icecream.
     
  8. TeddyDiver
    Joined: Dec 2007
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    Location: Finland/Norway

    TeddyDiver Gollywobbler

    I have to agree.. it's not bad.. But where's the leak:confused: I couldn't find it :(
    Ok anyways when in the same space (speaking boats again) you have allready a diesel engine, fuel filters and stuffing boxes so I don't see any major drawbacks having a hydraulic pump too :)
    The most messy thinghie I have is a scuba compressor. Filter and cylinder drain contain some oily water with pressurized air..

    Broken Tools:
    electric:
    three circular saws
    chainsaw
    two cordless drills
    bandsaw

    air:
    panel nailer
     
  9. Guest625101138

    Guest625101138 Previous Member

    The leaks are visible by way of the washed areas with no settled dust as you can see on the electrical plugs. Slight leaks are visible by the darker look of the dust. The real problem is in the sump or on the floor, which is not shown in the photo.

    I have seen sumps with hundreds of litres of dirty oil. I can recall one operation where the highest single cost in an area of the operation was hydraulic oil. The offending power packs and motors have long since been replaced with variable frequency AC drives. A much more reliable and controllable system having a fraction of the operating cost of the hydraulics.

    Your list of broken electric tools suggest you continue to buy same and put them to heavy use. If you have such dislike for electric tools why do you persist with buying them. You could replace same with air powered units.

    Rick W
     
  10. TeddyDiver
    Joined: Dec 2007
    Posts: 2,589
    Likes: 125, Points: 73, Legacy Rep: 1650
    Location: Finland/Norway

    TeddyDiver Gollywobbler

    Have no dislike, it's just reality that those things have a limited life span. Like my favourite tool, Festool PSB 300 EQ , it's life time is about 100 working hours..
     
  11. Guest625101138

    Guest625101138 Previous Member

    My best balanced hand drill cost AUD39. Made in China of course. It has really nice speed control, will hammer for masonary, reverses and keyless chuck. Absolute delight to use. It is now 2 years old and my only concern is that I will not be able to find an equivalent when the brushes wear out.

    These are treated as disposable but offer great utility.

    Builders here buy these tools by the dozen, absolutely flog them, leave them sitting around on sites begging to be stolen and still reckon they offer excellent value.

    By the way all households in Australia are required to have sensitive earth leakage protection systems since the early 90s and these have also been a mandated requirement on building sites for about 10 years. These trip before you feel any sensation - typically 10ma. Most of the electric power tools these days are double insulated as well. Electrical systems can be very well protected these days from careless use.

    By comparison:
    http://www.cdc.gov/niosh/FACE/stateface/tx/99tx468.html

    Rick W
     
  12. ijason
    Joined: Jan 2009
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    Location: florida, usa

    ijason Junior Member

    @rick, is the "earth leak system" you're referring to also called a GFCI or AFCI? i think that's what we call the same animal here in the states, it will cut the circuit off if either a ground-fault is detected, or an arc-fault.
     
  13. Guest625101138

    Guest625101138 Previous Member

    Same as GFCI. Also termed Residual Current Device (RCD) here. The AFCI is something different and we do not have an equivalent in use here.

    Our higher voltage and lower current reduce the tendency for arc faults to cause fires although they do occur in older houses where insulation has been eaten by rodents or damaged through careless renovations. Some of the light fittings we get from China are not well designed for heat dissipation either and these have been known to cause fires. As we move away from incandescent globes the heat production is being reduced so lower risk of fire from lighting.

    Rick W
     
  14. Frosty

    Frosty Previous Member

    You can buy cheaper cheap tools here and they are just not worth it.
    Elect drill with hammer--about 15 Aus dollar I have plugged then in in the store and had then smelling and smoking just with my hand, Ive done this on more than on occasion.

    The jigs saws are absalute crap too.

    Bosch bosch bosch you cant kill them and you will throw away 1 dozen cheapos to one bosch.

    If you try to cut steel with a cheapo 4 inch grinder --ille give you 10 minutes.
     

  15. Guest625101138

    Guest625101138 Previous Member

    That is why I pay the extra $30 and get a good one. If you are paying more than AUD50 for a 10mm hand drill you are likely to be getting taken for a ride. I doubt many are made outside of Asia these days:
    http://www.made-in-china.com/trade-offers/offerviewODxQrlnvqmwf/Sell-Hammer-Drill-Bosch-Model-.html

    Don't kid yourself about the brand name and think it comes from a particular country. This is typical:
    http://www.contractortalk.com/f40/where-your-tools-made-14593/

    You have to assess it on its merit. If you are buying by reputation you are just like the label junkie kid who will not wear anything other than Nike or Reebok. Unable to discriminate something that is well made or poorly made but just buy because it has a known brand name.

    When I was young and got Japanese made toys I learnt how to repair them because the broke easily. By the time I was working in industry, Japanese equipment was the most sought after. I still remember the annual visits of the Hitachi motor designer to our operation to get feedback on the performance of his motors. Around this time I bought my first Korean made stuff and swore I would never buy from there again. Now the LCD TV I have is from Korea and regarded as the best value and, on picture quality, the best there is. The majority of clothes I wear are made in China and I expect most of the western world are the same. Mark up on this stuff with a Reebok or Nike label is maybe tenfold but all made in the same factories as the unlabelled stuff.

    The only brand I look out for is Canon. This company produces cameras prone to failure and yet they have managed to stay in business. I would never recommend a Canon product and whenever possible discourage people from buying their products:
    http://en.wikipedia.org/wiki/E18_error

    Rick W
     
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