Ideas to inspire...
Pulling the cover on and off the spa pool was going to cause significant wear and tear and reduce the life of the cover significantly. So I initially looked around for something that would do the job. However, not only were the commercial models very expensive, they were also going to be unsuitable in my situation. My requirements were:
I searched the internet high and low for a design but couldn't find anything suitable. As a result, there was only one option; that was to design this thing myself. I started by looking at some of the commercial models. The principle appeared to me to be reasonably simple - something that flips over taking the cover with it. Even better would be something that rolls rather than requiring lifting. After some thinking (a few iterations), I came up with a design that I thought would work.
Initially, I started looking at fabricating the design with stainless steel or aluminium. However, at approximately $30 - $50/metre for these types of material, this was going to become quite expensive. Further, the more I thought about using metal, the more it occurred to me that the level of complexity in building it was increasing, eg, soldering or welding would be required. I wanted to keep things very simple using material easily sourced and able to be put together without significant technical knowledge and capability. In addition, the material used would be exposed to water and weather so it needed to be something that was not going to rust and would require no maintenance. I also wanted to make sure that the cover was rubbing up against soft materials, not hard materials.
As luck would have it, I had to make a trip to the local plumbing supplier and it occurred to me that it may be possible to build my contraption using PVC plumbing pipe and elbows. PVC will handle exposure to water and weather easily and will require no maintenance. Needless to say, working with this material gave rise to other challenges and my initial attempts were not that successful. The idea seemed sound but the practice proved to be more difficult. However, in the end, I was successful in working out a solution.
This is how I eventually put my cover opener together.
I chose 20mm PVC pipe because this size fits very snugly in the fold along the middle of the cover. In addition, it just looks and feels right. If the pipe is bigger or smaller, it just doesn't look right and I have the feeling that its operation will not be as effective. Also, as noted earlier, many of the commercial models appear to be quite bulky which tends to make them look like an addon rather than something that is part of the pool. Putting it all together is reasonably straightforward - well, it was eventually.
The pipe that sits on the fold of the cover created the greatest challenge. The 2m PVC pipe on its own has too much flex at its centre so it will not carry the weight of the cover easily. You have to make this pipe as rigid as possible. Initially, I thought that dropping a wooden dowel down the centre of this pipe would be sufficient. However, I can definitely tell you that it is not, even though there is some improvement. I tried out various other options but they lacked simplicity (one of my self imposed constraints) and the more elaborate the thought, the more expensive it appeared to get and or messy. Eventually I came up with the following.
I cut 2 stoppers from the 19mm dowel and inserted one of the stoppers at one end of the pipe. Next, slide the three 10mm aluminium pipes into the PVC pipe. I was able to obtain these pipes for the same price as a length of dowel This creates both circles and triangles inside the pipe which are strong structures. However, although this reduces the flex in the pipe, it is not enough. Pour sand into the pipe and put the other stopper in place. Now the pipe will be strong enough to hold the weight of the cover.
Finally, place a 90 degree elbow on either end of the pipe but do not glue it in place just yet.
With these other pipes, they do not require significant reinforcement as the weight of the cover either impacts on them end on (as is the case for the pipes on the sides) or the pipe is fully supported by the ground/deck/paving (as is the case for the other 2m length).
With each of these pipes, I simply inserted a length of 18mm dowel. This will provide all the support that is needed for these pipes and give them a feel of solidity.
Next, working your way around from one side attach the 1.12m length to the 90 degree elbow, followed by the 45 degree, then the 190mm pipe, another 90 degree elbow, and so on. Refer to the pictures below and you will get the idea. At this stage, fit it together but do not glue it. Make sure that everything sits in place properly and is capable of lifting clear from the pool. Warning - if you try to test it by opening your cover, it will more than likely fall apart.
Once you are satisfied that it all sits properly around your pool, start gluing the elbows into place one by one. You can get the appropriate PVC glue from your local plumbing supplier.
I felt that it is not enough to rely on the glue to hold the joints together. For additional support, I've drilled right through the joint where the pipe and elbow overlap and set in place a nut and bolt. This provides reinforcement right across the joint. You can use rubber grommets over the ends of the nuts and bolts if you wish. However, this last reinforcing step is an optional one as the glue tends to fuse the parts together so should theoretically be very strong.
The final thing I had to do was work out a way to secure the cover opener to the ground, otherwise it will just slip away. If I had a timber deck, then it would have been simple. I could have used PVC saddles (the next size up from the pipe) for the pivot and the lower pipe would simply rotated inside the saddles. However, my pool sits on concrete pavers and I did not want to secure anything to these pavers as they could crack. I also did not want to attach anything to the pool itself (consistent with my original constraint).
My initial attempts focused on using the PVC saddles in some way. However, they generally turned out to be either impractical, did not work, was ugly or some combination. One of my ideas was to use a length of skirting board and mounting the saddles on this. Because of the bevel, the board slips partly under the pool. This works for opening the cover but slips out from under the pool when you go to close the cover. It also looks ugly - idea terminated.
As I was wandering through the hardware store, I noticed screw hooks. It occurred to me that the hook could provide an ideal pivot. I tried this out. Generally, it works fine but has two shortcomings. First, because the bottom bar sits inside the hook, it raises this bar off the ground. As a consequence, the bar requires a lot more support. You can add bits of timber under the bar to give it more support but that just makes it look shoddy. The ideal support is the ground itself - it doesn't get much more solid. The second issue I had with this was that I had to screw the hooks to the support timber of the pool. This violated one of my self imposed constraints and I was not happy with that. The following two pictures demonstrate this.
After playing around with a few other ideas, I came up with the following (which did involve using saddles).
First, take a 32mm saddle and divide in 2.
From a length a metal that is approximately 25mm wide, cut a piece that is 120mm long. Mark 30mm from one end and drill a hole at centre. Mark 20mm from the other end and bend using pliers or a vice as above. This creates a hook at one end that is capable of slipping in under the lip of the pool.
Place the half saddle as shown and rivet from the top down. If you rivet from the bottom up, you may end up splitting the saddle. This little "snail" piece slips in under the lip of the pool and the pipe drops inside the loop of the half saddle. The "snail" needs a tail otherwise when you come to close the cover, the rotational force will cause it to slip out from under the lip (in the same way as for the skirting board mentioned earlier). By placing your half saddle 30mm in from the end, the rotational force is more centred and prevents the end of the piece from rising. You will need two of these to support the bar.
This little "snail" idea works very well, is small and unobtrusive, allows the bar to be fully supported and does not attach to anything.
In my case, the pool enclosure supports the cover when it is open as you can see in the pictures. As such, the cover is not going to drop backward. If your pool is located in more open space, a simple chain with a small dog clip can be used to prevent the cover from falling backwards when open.
Also, because the cover sits partly below the top of the pool when it is open and because there is vertical pressure at the 45 degree elbow (ie. the shortest pipe is leaning backwards when everything else is upright), there is no need to secure it to prevent it from falling forward onto the pool. You actually have to roll it forward in order to make that happen.
When standing in the pool, it simply rolls open and rolls back to close. It is the 45 degree angles that give this rolling effect. You can build this with straight sides without the 45 degree elbows but you will notice the difference - instead of a roll, you will have more lifting. When standing at the side of the pool, you push and lift gently and it just rolls over.
Finally, the PVC (and the snail pieces) can be painted any colour you like (another significant plus) although I've decided to go with plain white.
For spa pools that are larger than 2m square, this design will have limitations. It will work when opening or closing the cover while standing in the pool because you will be lifting from the centre. However, larger spans will cause more flex at the centre. It will also become more difficult to open the cover when standing at the side of the pool due to the torque. When you lift one side, the other side will not easily follow due to the larger span and weight.
For pool sizes up to 2m span, it works really well, is water proof, requires no maintenance and best of all, it is really simple both in the use of materials and in design.
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