Self Leveling Bed

Discussion in 'Boat Design' started by Bahama, Jul 2, 2010.

  1. mark775

    mark775 Guest

    With the precession timed right, it might serve as an alarm clock!
    "One of my ships had the whole of the officer's wardroom gimballed." - havn't seen that but have the interior "floating" so as not to transmit vibrations. I guess that wud be the next step!
    I've slept in some horrendous accomodations, including on a pocket shrimper with a communal galley/bunkroom/engine room with running 6V53. The worst sleeps have all had something to do with condensation or leaking portlights but not motion. I've slept multiple off-watches (6 hours) with one arm locked at the elbow against the above bunk, one leg knee-up wedging a sick kid into his bunk so he doesn't land on me. If it's time to is just time to sleep.
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    BATAAN Senior Member

    mark775 is obviously an experienced seaman who walks the walk and has paid his dues. This is reality. I love the boat shows with their wine bottles and flower vases so carefully arranged on the polished teak table and the girl says "look at the cute little kitchen". I want to say imagine yourself sitting on the settee, soaking wet and cold, very scared, puking uncontrollably into a bucket between your knees as the monogrammed pillows and expensive wine bottles swirl about in the rising bilge water. Ahhh, sailing.
  3. jg451
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    jg451 Junior Member

    I suspect the gimbel, on the roll axis would work. Caviats...ONE person, berth axis through body axis, dampener against incomplete motion, no finger guillotines, overhead hand hold to get in and out or a quick lock feature. I cannot see any reason where with the right bearings a 6-7Deg. incline could not be done. Head aft please, at or near longitudinal C.G. I can't imagine a crossways berth...either on your head, or on your feet. or worse back and forth! GAG!

  4. Bahama
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    Bahama Junior Member

    I thought of another possible way to make a gimballed bed that is interesting if it will actually work.

    It's essentially a dual gimball system both working only on the athwartship heeling movements. The first gimball is used to stabilized the bed as a person or couple move about on the bed or get out of bed--it's job is simply to keep the bed level based upon major weight shifts on the bed.

    That gimballed system is then placed into a second gimball that is closer to what we are all familiar with, it keeps the entire system level regardless of the waves and boat.

    It's easy to gimball a bed simply by hanging the entire bed by the ceiling, but this causes large movement athward... as we lower the fulcrum or pivot point, the lateral athwardship movements reduce, but at the cost of stability in the bed as the people shift their weight around.

    What if, SMALL (millimeters) downward or upward movements in the bed caused by weight shift, were instantly translated into LARGE (inches) shifts in the pivot point for the bed. So if a 280 Lb. guy climbs into bed with his 90 Lb. wife, the pivot point rapidly moves way over to his side of the bed to keep it mainly level... it tilts down about half an inch, but is basically level. As he rolls around, the pivot point keeps shifting automatically so that her 90 Lbs. are given far greater leverage than his 280 Lbs... in fact, the pivot point is probably almost directly below him, but slightly skewed to the center.

    Here is how I think that could work:

    1. The bed must be prevented from shifting athward (laterally left or right)--so it has to be in some kind of a frame, or at least the frame below it will not allow it to move about laterally... this is required because when the pivot points are pressured to move, they will not move if the bed is allowed to shift about freely (laterally).

    2. The system uses hydralics (or pnumatics); a pivot plate is placed under the bed and is allowed to glide left and right--the bed will tilt on this pivot plate like a tee-ter-totter. This plate presses down (or pulls up) on a very WIDE and FLAT hydraulic cylinder. There's one on the left side, and one on the right. A very small movement on this plate will cause large movements of hydralic fluid to move.

    3. The large hydraulic cylinder (describe above) on the left side will be connect directly to a NARROW LONG hydraulic cylinder located on the right side. This cylinder is attached to the pivot plate and will move the plate toward the left side as the left side begins to lower. And as you'd expect, the large cylinder on the right side will connect to the narrow cylinder on the left.

    You get the bed leveled out originally, and then at that point, any minor downward pressure on either side will cause the pivot plate to rapidly move over to that side. The ratio between the large and narrow cylinder diameters will determine how quickly the plate will move--and that is related to how wide the bed is.

    The formulas to calculate the large cylinder diameter, here would be the formula to get pretty close:

    W=width of bed (inches or metric... but stay consistent); I'll use 60" for a queen size bed.

    C=W / 2 (center distance of bed); this equals 30" for me.

    L = distance from center of the pivot point on the plate to the center of the large cylinder; I'm going with 6".

    M = Max downward (or upward) distance allowed on the far edge of the bed; I don't want my bed going down or up any more than 2".

    X = M / ( (W-L) / L) This calculates the max distance that the large cylinder will travel downward; this assumes that the plate has moved all the way to one side, and so a very small downward movement at that point will cause huge movement upward on the other side. For all of my numbers give, this will be 0.222222"

    Y = C - L The maximum travel distance of the pivot plate from the center of the bed. with my numbers given, this is 24" for me.

    S = The Diameter of the small cylinder; I'm going with 1".

    D = The Diameter of the Large Cylinder, which is calculated with this formula:

    D = SQRT(Y / X * PI() * (S / 2)^2 / PI() ) * 2 and in my case this equals 5.196152423"

    So, a large cylinder with a 10.39230485" diameter will move the pivot plate 24" from center all the way over to the edge of the bed (the center of the pivot plate would then be 6" from the edge and the plate and large cylinder centerpoint is touching the edge) and at this point the bed would be allowed to move 0.222222" downward, causing the other side to move upward a total of 2" (our limit)--this is because the pivot point is 6" from the edge orf the bed; 6" to 54" is a 9:1 leverage ratio at that point.

    So this entire device would then be mounted upon a standard gimball, which would keep the stablized bed level from the sea movments.

    A device like this would need a bypass valve on both hydralics so that you could position the bed level, and then close off the bypass valves to make the system work.l

    This would not be too hard to test out, and so when I get a chance I'll try it out.

    I'll attach a basic picture--it's not to scale, but does show that they large green cylinders will move downward, forcing fluid to move into the lateral smaller diameter (but longer shaft) cylinders. The entire pivot plate and hydralics will glide left and right.

    Here is why I think that this stands a chance of working. I'm allowing for movement to occur, but I'm limiting this movement to very small downward/upward movement.

    It's important to have the glide work very silently, so I would not recommend bearings. instead, I'd spread the weight out over a large smooth surface area and simply glide on that... this is the same principal that semi-trucks use when having their loads pivot on that large metal plate in back of the truck.

    Well, there it is, an idea that I litteraly had in a dream and then quick wrote it down when I woke up. Well see if it works... Even when one partner climbs out of bed, the pivot plate will immediately swap over to the otherside to shore up their weight so that they don't fall out of bed.

    Attached Files:

  5. rwatson
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    rwatson Senior Member

    I think you are on the right track with hydraulics - especially if you combine them with microprocessors.

    Many modern jet fighters cant fly without computer input, and I think that a "self levelling bed" would be a natural development from the world of "fly by wire", to "sleep by wire"

    One downside - many a skipper has suddenly woken bolt upright because the wave/wind/heel angle has changed to warn him of a dragging anchor/change in sea state etc.

    It probably wouldnt be viable on smaller boats - compensating for a 2 ft bow rise on a wave would probably push one end of the bed through the deck. :)
  6. latestarter
    Joined: Jul 2010
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    latestarter Senior Member

    You could install a platform on the lines of a flight simulator.

    They are designed to throw you about on dry land.

    With suitable sensors and programming it could compensate for the movement of the boat including vertical motion, which hammocks and gimbals do not.
  7. dskira

    dskira Previous Member

    Very true Richard
  8. Bahama
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    Bahama Junior Member

    Thanks for the laugh, I needed it today. I wanted to see if I could come up with something that did not require electricity for use so that it didn't drain the batteries. The only way that I could think to do this, was to allow for small movement--this allowed you to convert the small mechanical energy into something that could be used and still work... If I wanted next to zero movement, then that would require electricity. If done right, this design would not require any electronics, it would simply work... the bed would move, but only slightly--within the parameters that you build into it via the mathematics for the cylinders ratios in relationship to the leverage due to lengths in the bed.

    Although this concept was a bit hard to describe, it's actually a very simple design, which is why I like it. I'd originally been thinking of gears and wires to do the work (and figured out how to do it), but then it occured to me that hydraulics would greatly simplify the design.
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    BATAAN Senior Member

    The sea is a violent and cruel place that laughs at our pathetic attempts to turn it into the quiet land environment we are familiar with. Get a boat that has an easy motion if you want to sleep.
  10. SheetWise
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    SheetWise All Beach -- No Water.

    Hello Tom ... we weren't thinking about sleeping in them.

    Bahama --

    Have you ever played with the Wii? Solid state gyroscopes, and the response time is phenomenal. You can buy the chip off the shelf for about $25. It's not necessary to use a lot of weight.
  11. timothy22
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    timothy22 Junior Member

  12. Bahama
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    Bahama Junior Member

    Although very little electricity to recognize the movement needed, it would start to drain a battery a bit to actually keep the bed constantly level all night if the design relied upon power to keep it level. I was just trying for zero electricity, all natural movement. I actually like being rocked to sleep so I don't plan to install such a device, but I know that some people like something a bit more level... the idea came to me and so I threw it out there for folks to consider as they design their own versions. Although, I've gotten myself interested enough to actually try this out sometime... but down the road, right now I'm working on final design and the building my boat.
  13. MikeJohns
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    MikeJohns Senior Member

    I think you need to consider what causes motion sickness on a boat. Then look at the amplitude of those motions. You will not reduce motion sickness with this approach.

    It’s caused by vertical acceleration, no amount of self leveling will help I’m afraid. Also as someone noted already motion sickness is least when you are actually lying down.

    The only really effective way of reducing induced motion sickness in heavy weather is to get on the heaviest displacement boat around relative to its waterplane area.

    There’s probably a cheap concrete submarine in Columbia that would suit :)
  14. apex1

    apex1 Guest


    And I recommend the cheap Colombian sub. also. The police will most likely get rid of it.

  15. MikeJohns
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    MikeJohns Senior Member

    Wilfried has been very quiet lately, I hope he didn't try and test dive it !
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