Hot tub Cover 4 post lift
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  1. #1
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    Default Hot tub Cover 4 post lift

    I live in Minnesota, we have had three hot tubs in the last 30 years and many more hot tub covers. The covers typically are flat with crappy vinyl that the sun destroys after about 3 years. I was sitting in the hot tub this morning thinking about an automatic cover. Turns out the same idea i had is already being manufactured, see link. About $5,000 bucks.

    Covana automated hot tub enclosure, gazebo, cover in action in the snow - YouTube

    I am looking for ideas on a similar design. My idea is to use four 1/2 inch -10 ACME screws with a sprocket attached to each one and use a single drive motor and sprocket to spin the screws. The sprockets would be at ground level. I would use thrust bearings at the bottom of each screw.

    The top that the 4 posts would lift would be designed using aluminum angle and double wall acrylic panels with a pitch that would allow the snow to slide off all in one direction. I have a 3000 sq foot greenhouse that sheds snow as it builds up and works very well. The heat loss from the hot tub cover in use would slightly heat the bottom of the panels that allows the snow to melt just a tiny bit creating a slippery slope as all the snow will just slide off.

    Comments on design options, size of screws, linear track on each post etc welcome.

    I am wondering about the chain size needed for 32 feet as it would be going around the entire base.





    The Hot tub cover would use the same design as the greenhouse roof.

  2. #2
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    Wouldn't a double clam shell design be simpler? Also, consider the costs, and the stability of the four screws. The four posts will need to be tall enough to get in under when the roof is raised.
    You could use a couple of air cylinders for the clam shells, and combine the air system with the next big idea...

    If you have the hot tub anywhere near a basement, then you could put a big tank in the basement, with a pipe to the hot tub. An air compressor, and a couple of valves...
    If the pipe were sloped properly, you could Zero heat loss in the winter, all the hot water would be in the basement, and well insulated. Pressurize the top of the tank, and have the tub filled outside in seconds..
    Dump the pressure in the basement tank, and the whole contents could drain back into the basement just as fast.

  3. #3
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    First thing that comes to my mind is that there's going to be a lot of cold condensed water dripping off the bottom of that flat cover onto your head and shoulders, taking all the pleasure out of sitting in the tub. Needs to be tilted to make the water run off to one side at least.

    How about low precision ballscrews?

  4. #4
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    How about some multi stage air cylinders? 2" bore would give you 800 lbs of lift @ 100 PSI.

    Just thinkin out loud.

    Just checked the cylinder chart, its 278 lbs of force @ 100 PSI per unit x 4 = 1112 lbs of lift .. how much does snow weigh?

    You would need needle valves at each cylinder to provide adjustment for rate of extention, a valve or solenoid to actuate, and of course a supply of compressed air. I would think everything would run fine on 3/8" plastic tubing, your not launching anything off of it, slow and steady wins the race.

    Also: Single stage flange nose mounts go all the way to 50" of extention, after that its multi stage only.

    Guessing this thread might get locked soon, good luck with the project!

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    So the majority of the screw would be recessed in the ground when the cover was down? Or will there be four "columns" that are always 6' tall whether the roof is up or down?

    Chip... who would just do a removable "winter greenhouse" for the tub.

  6. #6
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    Also: Single stage flange nose mounts go all the way to 50" of extention, after that its multi stage only.
    Where is a good place to buy those?

    General automation is allowed here so i don't know why it would be locked.

    I like the clam shell Idea as well, perhaps just incorporate the existing foam cover in the design, that way the whole thing comes off from a push button in the house, run out and jump in, press button to let it back down when you get back in the house. At 20 below it gets a bit cold getting out and then putting a cover back on!

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    We use Bimba cylinders for general motion work.

    Online part number configurator here ----> http://bimba.technicon.com/CC_host/p...tsf=&cc_tvl=()

    Also uploaded a Xcell cylinder sizer for you, sorry bout the ads, but PM doesnt allow XL uploads. -----> http://www.mediafire.com/?3netxnh55j4v065

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    The major problem with air cylinders is keeping them in sync.

    Even hyrdaulic cylinders can be a problem unless a flow-divider is used...but, it seems I had read somewhere that these are available to sync 4 at a time....would need to do some research.

    Chain drive may be the simplest; obviously you'll have to take into account that the "posts" will have to be supported above the sprocket.
    Perhaps telescoping square tubing that envelopes the sprocket with entrty/exit openings for the chain in the sides would work.

    The chain would have to run in a trough between the posts to keep it from sagging. Half-circle wrap on the drive per your sketch should be sufficient.

    If going with the chain and screw idea, I'd suggest 3/4" (min) over 1/2" acme.

  9. #9
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    Uh...

    Why not just buy one of the ones that bolt to the side and let you flip it over the edge???

  10. #10
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    consider a alum cover? we had one once, lasted like 8 yrs instead of 3.... time for a new one here too,...

    something like this?

    Aluminum hot tub spa covers


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