Some motor questions

I'm building a retractable canopy to provide some shade over our swimming pool in the summer. The canopy is about 24 feet wide by 40
feet long. When retracted, it will be wound up around a "spool" which is a 25-foot long, 5-inch diameter stainless-steel pipe. I intend to have a motor rotate the spool to unwind and wind up the canopy at one end, and a similar spool and motor at the other end to wind and unwind the cables attached to the edge of the canopy:
<--- Canopy --->| <-- Cables --> | | \|/ ________________________________ / \ / \ | | <-- Spool Spool --> | | \_/ \_/
This all sounds good in theory, but, being a novice at this sort of thing, I'm wrestling with some elementary details that have me stalled. The canopy needs to have 200 pounds or so of tension on it to keep it from sagging excessively, and what I haven't figured out is how to
A) maintain the proper tension when the canopy is extended B) as part of A, to lock the motors so the canopy doesn't move when they are turned off C) decide what kind, size, torque, horsepower motors to use D) whether to drive the spools directly via coupling, or use a chain with some gear ratio E) related to D, what RPM to use F) do all this with a modest budget (no $5000 control systems!)
Can anyone offer some suggestions (in simple terms for the neophyte) for how to make this work?
Thanks!
--
Nom dePlume, Ph.D




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This is a rather complex setup you are purposing. I believe ultimately you would be much happier if you hired the services of an engineer, or a technician experienced in these type of designs. At the least have a system designed for your needs, and secure at least occasional limited supervision while you install it.
That said there is a motor/system designed for greenhouse use that sounds as if it would fit your needs precisely! There is a cylinder shaped motor/gear reduction assembly (available in single, or three phase) that is designed to fit inside a take-up spool, or mount on the end, that has adjustable up/down limit switches. The use I observed it applied to was covering/uncovering the glass ceiling of a greenhouse. It was rather slow to operate, but very effective, and predictable. After installation there was a bit of time required to set the upper/lower limits, but after that it operated flawlessly. I believe the company making the system was from Germany. Check with various greenhouse suppliers to find a vendor where you live.
Louis
"Nom dePlume" <nomdeplume1000-at-yahoo.com> wrote in message

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Nom dePlume wrote:

Eliminate the cable spool. Run the cables through pulleys and back to the canopy spool. Wind the cables around the ends of the canopy spool in such a direction that winding the canopy unwinds the cables and vice versa. At the pulley ends, mount the pulleys on sliding tracks held by springs that can be adjusted to maintain the proper system tension.

Use worm drive gear reduction units. However, with the above cable pulley system, you won't need to 'lock' the spool since the torque imposed on it by the tensioned canopy will be opposed by the torque imposed by the tensioned cables.

C, D and E depend on how fast you want to deploy the canopy.

The structural (and related safety and liability) issues surrounding this might warrant having the design done or reviewed by a licensed P.E.

--
Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com
note to spammers: a Washington State resident
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"Nom dePlume" <nomdeplume1000-at-yahoo.com> wrote in message

Have you considered the electrical issue near the pool? Having 2 motors sounds like a dangerous/ complicated situation to me. I will not even swim in my pool when the light is on. Nor will I allow anyone in the water. My home my rules. Look into something like a garage door opener. Fair amount of torque and the stops are already prewired. You will have to attach cables or chain from one spool to the other so you get the pull and push that your looking for. Having 2 motors sounds more like a synchronization issue to me. One motor driving both spools sounds easier. The there is the matter of the track down each side. To keep the cover down and doing its job. might be easier to build a solid cover and use a screw or scissor mechanism to open and close it. Something like what they use for the retractable stadiums ceilings. It could run on a rail down both sides and stack up like seats in a gym.
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get some gfi sockets and you are safe

will
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tbone wrote:

GFI's are good - but there's a whole bunch of safety requirements pertaining to electrical wiring around the pool that they don't address.
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Like what, pray tell?
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Grounding, bonding, overhead wiring clearances, wiring methods, locations of receptacles, etc. It is all there in NEC article 680. Of particular relevance to this thread is 680.27.B "Electrically operated pool covers" which discusses location and protection of the motors.
Ben Miller
--
Benjamin D. Miller, PE
B. MILLER ENGINEERING
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Fortunately, no motors or wiring will be near the pool itself. The motor would be mounted on a second floor balcony, which already has an adjacent outdoor (GFI) socket.
Thanks
--
Nom dePlume, Ph.D

Why, yes, in fact, I am a rocket scientist.
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Yup
Get someone in to do it for you.
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