Workbench Creations

Every so often I look out the back window of my kitchen to see the sad, sad sight of the trampoline safety net hanging down because one of the straps has broken. Sort of like this:

That, my friends, hanging down from the cross bar above where the net hangs, is duct tape on the strap. That broke. Duct tape did not fix this.

The look on the face of my little friend speaks of the frustration I feel at this moment!

I don't know if my kids and their friends beat the daylights out of the safety net or if other people have this same occurrence on their trampolines from normal wear and tear.

I mean, could there be WWF-type showdowns going on out there unbeknownst to me? Could they be bouncing each other off the net left and right and standing up on top to do a Jimmy "Superfly" Snuka dive on top of each other? Well....I mean...sure I guess they could be doing that. But if not, and if there are other parents out there like me who have rigged up the net straps one too many times to count, I think I have finally found a viable solution.

At first, I would try to repair the black elastic straps that were original to the safety net. My repair job would hold up a couple of weeks when sewn and patched together. We also tried knotting the elastic, and, yes, we tried duct tape. You can't try to pull a MacGyver and NOT at least attempt the duct tape.

When knotting, sewing and duct taping the elastic didn't hold, I tried denim. I used the bottom hems of jeans that I had used for other craft projects, sewing a couple together and attaching them to the clips. The denim didn't hold. Finally when I found my kids and friends using the open side of the broken down net to practice diving off the trampoline and rolling on the grass, I knew I needed a better solution to this seemingly never-ending issue.

I organized a search team and gingerly made my way into the abyss known as my "craft room", which currently appears ready for filming an episode of hoarders. [hangs head in shame].

I found some scraps of canvas and some grosgrain ribbon.

I then called out a warning to the kids, mounted the step stool to get onto the trampoline, dodged a flying cannonball and retrieved the clips from the net.

First I cut the strips of canvas and sewed them end to end. After I stitched a strip, I turned it over and stitched on the other side to reinforce the seam.

I folded the sides in to meet each other to make one long tube and placed the ribbon on top where the sides of the canvas met each other, and then stitched down each side of the ribbon.

Once it was all stitched it was a really strong strap! I tested the strength by having another adult hold onto the other end, each of us pulling with all of the weight we had. Since we had roughly 150-200 pounds on either side of the strap and it didn't show any signs of coming apart, I don't expect this strap to ever break or wear out!!

I threaded the straps onto the clips, and then sewed the end of the strap to itself to secure it. Here I am holding the last 2 straps I repaired. The sewing is sloppy and the sizes are different from each other because this is the 48th time I have repaired straps. Going into our 4th summer with this trampoline I am hoping the canvas is the answer to my trampoline prayers!!

Just take a gander at the mess that is the amputated mangled old black strap...this poor old net. Trying to protect my kids and getting the tar beaten out of it in the process. But this pretty pink strap dresses it up a little and even better, it is a (hopefully) permanent solution to this problem!

It has now been almost one year since these repairs were completed and I am happy to report that all of the canvas with pink ribbon straps are still fully functioning and need no further repairs. This was a very simple and inexpensive DIY fix that could be completed in less than thirty minutes or so, depending on your experience level.

With the upcoming and awesome holiday Halloween, some people would like to know how to make their own mask or just to learn how it is done.

To make a prosthetic piece with great edges you need a two-piece mold. The better the edges are the better it will blend into the skin. To maintain what you sculpted, accurate plasters are used. You don't want ones that expand too much or the ones too brittle like "Plaster of Paris". The plasters used here are White Hydrocal and Ultracal 30 Gypsum plasters.

The bust has been sealed with gloss paint. The gloss paint is more resistant to damage and as it is applied it fills in the imperfections to achieve the gloss finish. This will provide a sealed surface.

Water based clay is applied around the head. The clay is approximately 1/2" thick. I just sprayed PAM cooking spray onto a counter top. I then slammed a mound of clay on to the table until the thickness was achieved. The ends and edges of the clay were cut with a straight edge; then this is applied to the plaster bust where you want the final casing to end. The clay is CAREFULLY pressed onto the bust, trying to keep the edge flat and perpendicular to the surface. The area is then sprayed, lightly, with PAM and using a dry brush, the PAM is evenly distributed over the area.

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The next procedure uses alginate. Alginate is mixed and applied over the area to a thickness of ¼ to ½". The thickness is kept to a slightly runny consistency. The happy medium needs to be not too thick to trap air, and not to runny where it is being scooped up and reapplied. As the alginate is starting to set, cotton balls are pressed into the alginate for 3-4 minutes. Once the alginate has set, the cotton is carefully pulled leaving some of the fibers imbedded in the alginate. These will the keep the alginate in the mother mold. The mother mold is made with plaster bandage from an art supply store. The ones I used are 4" wide and 2 layers think. The entire head is covered with 4 layers and the outside edge has 6 layers. The edge needs to be a little thinker to take the abuse of removal.

Here is a shot of the inside of the alginate mold after is has been pulled off the bust.

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Hydrocal plaster is added to the mold. The first coat is applied very thin with a brush. I blow hard to make sure the plaster is in every nook and cranny to make sure there is no trapped air. More layers are added carefully until the layer is at least ½". This needs to set for 1 hour.

After it sets, remove the plaster bandage and alginate. The new casting needs to have the imperfections taken care of. Sanding works best when using drywall sanding cloth or a rasp. There are plaster knifes out there that also help.

Once the casting is clean, it needs to be sealed. Again using gloss spray paint, apply even coats over the plaster casting. Once it is sealed I added a few inches of clay to the bottom to allow for the overflow. A coat of PAM is sprayed and spread evenly with a dry brush. Alginate is applied again as before and backed up with plaster bandage.

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This time Ultracal 30 is applied into the mold. A thin layer is added with a brush to the thickness of 1/8". Any deep areas are filled in, i.e. nose and lips. Once the plaster starts to set, it will become warm to the touch and firm. The second layer is then applied with burlap dipped into plaster until four even layers have been added. I also used 2 smaller strips to secure the handle into place. A third batch of plaster is mixed and applied over the burlap layer. This layer is known as the finishing coat. As this coat sets up a spare piece of burlap can be used to buff out imperfections before it fully sets up. It will take a full hour before the plaster is set. This piece should be left in the mold for as long as possible. The longer left in, the harder the surface will become. I prefer to leave it overnight.

This positive is pulled out and is all ready for the sculpture. A thin layer of petroleum jelly is applied to the cast to help the clay stay in place. Now it's time to sculpt. I use Roma clay because it is oil based and never dries. Once the sculpture is complete it is covered in a layer of cap material: thinned down plastic used to make bald caps. Kryolan crystal clear spray can also be used.

From here, the sculpture is molded in Ultracal 30 plaster and is done the same way as before. A thin layer is applied to get all of the detail. That is allowed to set up. Then a second layer with soaked burlap is applied over the entire sculpture. Finally, the last coat is applied to keep the outside smooth so it is easier to handle. This is allowed to setup overnight. The two half's are separated and cleaned. I use acetone to help dissolve to plastic remnants.

You now have a two-piece mold that needs to be filled. Depending on the product you choose, find out what sealer to use, if any, and what to use as a release agent.

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Here is an example of two different test pulls from the mold using different materials before painting. This is a general idea of how it's done; just testing the waters. If there is a high interest in this, I can get into more detail on further DIY's..

Suppliers:

Alcone - http://www.alconeco.com/

PolyTec - http://www.polytek.com/

I'm always looking for easy ways to cross things off my daily to-do list. With the gazillion (yeah, I said it…gazillion) things we do daily, it's nice when we can automate something.

Fortunately watering your plants is now an automated option. A self-watering plant system (cool video), powered by an Arduino, is the set it and forget it time saver.

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^{The difference water can make…Image Credit: ehow and mamypap.com}

The instructions on building these self-watering systems are available on Instructables. It requires quite a bit of parts, and some mechanical/electrical knowledge (nothing you guys can't handle). Instructables offers step-by-step instructions and beautiful images to help you out. The hardest part would be programming the Arduino, but the website also gives you the exact code so you don't have to figure out the algorithm.

How it Works

The systems works with a set of sensors that detect when the soil is dry; based on a signal the system will water the plant accordingly. Depending on the type of plant and the conditions of the environment, the program can be adjusted to ensure the plant is getting the right amount of water.

^{Self-watering system. Image Credit: Instructables}

The Catch

Unfortunately you do have to remember something, and that is to refill the water reservoir as needed. Even this task can be diminished by scaling this project to an aquaponics system. Aquaponics is the combination of aquaculture and hydroponics, aka you grow fish and plants together in one integrated, soilless system. I've seen a couple of aquaponics systems first hand and I think the concept is pretty brilliant. The plants grow above a tank of fish. The waste produced by the fish provides a food source for the plants and the plants filter the water for the fish. Because the system is relatively self-sustaining, quality crops can be grown on a year-round basis, anywhere in the world.

^{Basics of Aquaponics. Image Credit: Nourishtheplant.com}

The self-watering device could be combined with this setup in order to design your own back-yard aquaponics system. Large scale, this could be a year-round garden. Small scale, you have a nice kitchen herb garden.

As a last note, for those who are not so programming savvy or just need a quick fix when going on vacation, I found instructions on how to make a self-watering system with a water bottle and a tray.

Resources

Arduino-powered plant can water itself, thank you very much

Grow Fish and Veggies Year 'Round

There's not a huge engineering content here but there's some use of adhesives, heat bending of wood and general design feel for balance, strength and heck it was just fun.
I hope it shows the need for an intimate understanding of the material and subject matter to make it look truly 'right'. It took some jigging and lots of adjustments to get the hand positions correct in relation to the bow at the 'low hands' position.
Here's the original sketch, you can see I'm trying to capture the movement and feel of drawing a bow.

The material is offcuts of Yew from my bowmaking, and using offcuts also lets you be influenced by the pysical size and shape of the material to hand.
It was in thin slats which had a slightly triangular cross section which is reflected in the design of the head.
I started on the wooden model trying for a sort of 3D cavepainting feel, but soon realised I needed a cardboard model to help work out how I was going to do it.

Then another working sketch...

I made the leg/trunk part first, then the shoulder/arm piece, once I knew how they fitted together I shaped the head. The bow and upper right forearm were taped in position while I worked on the other bits. Then it was fitting it all together and adjusting it to look right.
It's too fiddly to give it a really fine finish, I quit after going to 240 grit wet & dry paper, then gave it a coat of Danish oil.
The finished work is mounted on a slice of Oak which looks a bit like a rocky outcrop.

I added two tiny fillets of Yew under the heels for added strength of mounting, these were fixed with epoxy.
It's odd that superglue worked very well for some parts like attaching the bow but not for others like mounting him to the base. The reason being, I think, that some parts were too porous and didn't exclude the air to let the glue cure. I used high viscosity superglue for some parts and low viscosity for others. the very tight bends of ankles and elbows caused some fracturing of the wood, appliying low viscosity superglue fills the cracks and strengthens it very effectively. A couple of areas (right elbow of low arm position) were reinforced with sawdust loaded epoxy too.
I'm going to enter the work into a prestigeous exhibition next year, hopefully it will be unusual enough to get accepted.
Del

Should I build it? An oxygen concentrator for welding use.

Lately I have been very busy working on home remodeling projects and will be for a number of months. I haven't had time to do any more unusual projects, but that doesn't stop me from thinking about and researching projects I want to do when the time comes.

One thing I do on occasion is welding, and in that welding I sometimes use oxy acetylene. I can't say I use it a lot, but the one thing I hate is having to refill the tanks when the time comes. The place that fills them does not have convenient hours and is not conveniently located. I know when my grandmother was in the hospital she had a machine that provided her with oxygen.

The machine concentrates oxygen from the air to around 95%

Doing some research I found that many glass blowers buy refurbished machines so they don't need to buy oxygen.

For my use I know I would still need acetylene, but I tend not to use it as fast as the oxygen. I am also considering using propane or mapp gas for some things that don't need quite as much heat.

Used oxygen concentrators for medical use can go for as little as $200 but provide only about 5L/min of oxygen or less which may not be enough for welding.

Now that I am done with the preamble as to why, let me get to the meat of the project.

Oxygen concentrators work by using a molecular sieve that lets molecules of a certain size pass. You can read more about it here if you want (wiki link ). The sieve material is called zeolite and they have specific ones for different molecular sizes. It took me a while to find the correct sieve material and then find places that sell it at a reasonable cost. The cost of the sieve material is also a big consideration as it is most of the cost.

I came across a paper here that explains how to make an oxygen concentrator for hospital use and a cost analysis. For my project I don't need anything to be medical grade and I would use my shop compressor instead of a dedicated one for the machine.

The idea is to make an oxygen concentrator that can provide somewhere between 10 to 20 L/min of 95 to 99% oxygen and keep the price in the $200 to $300 range.

The key to all this is the zeolite material. Two different kinds of zeolite material is used for oxygen concentration and they both have positives and negatives. One type is called X13 and the other is called A5 and they typically use pellets for these machines. The paper linked above has a detailed explanation of the positives and negatives of each but concludes its best to use some of each as you can reach 99% oxygen instead of the usual 95%. These zeolites are contained in two canisters and air is switched back and forth between them. Since this is for welding I would just use PVC pipe or a large metal pipe to make the canister.

I found a company that sells the x13 material by the pound for about $4 a pound, and I would need about 20 pounds. The 5A material is harder to find and looks to be more expensive but I would need less of it, around 10 pounds. I could also skip the 5A material altogether and have 95% oxygen instead of 99%.

The rest of the design just includes some solenoid valves and a circuit to switch the valves at certain timings, I am hoping to use relays and a 555 timer for this, but I could use a microcontroller if I find it necessary.

The benefits of brewing your own instead of buying a used medical one include, fresh zeolite media that will last a lifetime for welding, and I can make the output double or triple of what a medical unit would supply. The other possible benefit of building my own machine is that I could also design the machine to supply nitrogen gas and possibly some argon.

So what do you think, is this a project worth doing?

Laser light shows can be pretty impressive. I was curious about how these shows are done, so I thought I would try to create one of my own. Below are the steps I took to design my own mini light show. I think laser light shows are neat, not that I have seen a lot of them, but when I have they are impressive. I started thinking about how these shows are done and decided to try something simple.

I took two dead hard drives and cut out the section that controls the drive heads, replacing it with mirrors. I then connected these voice coils to my computer speakers and aimed a laser on it. Playing audio did create some patterns but nothing that cool. So I found some software that generates audio in order to create random patterns for this type of laser setup. While the concept was cool and it was fun to play with, I wanted more and this was only a proof of concept.

I spent some time researching and looking at project designs, software and how laser shows are done. I learned that the devices I need are galvanometer laser scanners, which are basically voice coils with low inertia and a position feedback mechanism. I found designs on how to make them and the results I would get, but decided it was best to buy them for this purpose. For those that don't know different scanners have different speeds given in kilo points per second or kpps and start around 10k and go up to 50k or more. I found some 20Kpps laser scanners with the electronics to drive them for a decent price and ordered them.

The next thing I considered is how to connect these scanners to a computer. You need a DAC to send analog signals to the mirrors and the lasers. As it turns out the DAC's for laser projects aren't that cheap and go from about $200 up to thousands. I settled on a more DIY design which uses a USB sound card and a circuit to adjust the offset and peak voltages to get a 0 to 5 volt output. This design gives you an output that is compatible with the ILDA (International Laser Display Association) which is what the scanners use as an input.

And of course, you need the lasers and the circuit to drive them. I did some more searching and opted for simple diode lasers. I also found a design for an analog driver for them. In this case analog is better than digital or TTL as it allows you a larger color pallet.

After I got all these parts, I put them in a box and they sat for a while until my inspiration came back.

I started building what I call the light engine. This is the part where the three lasers, red green and blue (in my case violet due to price), are mounted so that they combine into one beam using dichroic filters to pass and reflect the lasers. This single beam, which looks white, has to hit the first mirror of the galvanometer scanner and then bounce off the second one and go out. I made an aluminum frame that would hold the lasers and also act as a mount and heat sink for the laser driver. It took a while to get everything mounted and aligned but it worked and I got a white beam.

The hard part after this was getting it all in a box, and because I wanted it to fit in a box I had it was not easy and took some time to figure out where everything was going to go. I also wanted the sound card DAC in the same box (although most laser shows don't have that built in.) I put a connector for an external DAC as well if ever I want to use one.

When I was done I tested it and it worked, not that I didn't have any issues, such as burning out the violet laser due to over driving it, but that is the benefit of building it yourself, you know how to fix it.

Once the actual device was made, I figured out the software. You can start out with free software and go up to software costing thousands of dollars. So far I have only been using free software. The one I have found the most useful is called LFI Player, which has a lot of hidden features. I have also gotten it to work with some software called HE laserscan. I have some other software to try but I am considering buying some lower priced software depending on what I can do with what I have.

It has been a fun project with some cool results, although for the most part no practical use other than its coolness factor.

The CR4 picture above is an actual picture of the output from my projector. You can check out more pictures here and see a video of my projector in action here.