Or: how I had no idea what I was doing and improvised with extreme prejudice.
I really wish that was a joke.
I loved the idea of making a foam dumbbell, but I had no idea how to start. I had given some thought to how things would fold out and which component parts I would need to make, but I was completely unsure of the order of operations. After thinking about these things a lot, I realized weeks had passed and I still hadn’t begun doing anything. So I changed tactics.
Since trying to plan ahead wasn’t getting me anywhere, I went the full improvisation route. I would just start cutting things that I thought I’d need and then see if I could use that to make progress. I’d count anything cut into or glued into an approximate shape as progress – I figured some progress would be better than no progress.
The idea I had was to make the weights of the dumbbell (the large things at the end of the rod/bar) separately. I also wanted to have them be almost completely hollow. Rather than just stacking about ten large pieces of 1cm foam (which would have been costly) I wanted to use two 1cm pieces of foam on the sides and to then add only some minimal supporting structures inside of the “weights”.
I could have started with a number of things, but I chose to start with the circular outer edges of the weights of the dumbbell, which… was another problem I hadn’t tackled yet. I figured if I could start with something square, I could work my way down towards something rounder. So I began by cutting off four identical-ish square pieces of foam.
I then had to work out how to go from squares to circles. I did have a simple office compass for making circles on paper, but that only has a pencil lead in it, which I figured wouldn’t really show up on foam. Luckily, I was mistaken. It did end up making a bit of a hole in the center, but the line was… not very distinct, but still visible enough to cut around. I made the same circle on all four foam squares, then cut them out into the exact same circle.
Or at least, that’s the way I’d anticipated that going in my mind. In reality the compass slipped a few times, and all four circles were noticeably different. In hindsight, it would have helped a lot if I’d just made a paper circle once, then traced that circle four times. I wouldn’t have punctured the foam pieces with the compass (oops) and the results would have been more accurate. Oh well, live and learn…
To then make the four “circles” more similar, I called upon the aid of my sander. I grabbed all four circles at once and sanded them at the same time so that even if the results wouldn’t be perfectly circular, at least they’d all be similar enough that you probably, hopefully, wouldn’t notice. It’s a good thing I always have a stack of dust masks on hand, because this sanding foam is NASTY. You wouldn’t want to breathe this in.
At last, after making some circles in the dumbest way possible, and then spending forever sanding things back into shape, I finally had something interesting enough that it was worth taking a picture of:
Okay, so the bar for “this is interesting” was pretty low at this point in the project. Sue me.
The next step was to figure out what the supporting structure should look like, and where it should go. I figured I’d probably need some rectangles of foam, even if I wasn’t entirely sure yet where exactly that should go. Again, rather than worry too much about it and make no progress, I decided to just cut off some pieces of foam, continuing under the mantra that some progress is better than no progress.
While cutting off this piece of foam I remembered that, at some point, I would need some kind of bar to connect the two weights. At first I wondered if I couldn’t simply glue something in the middle in between the two “weights”, but I realized that if I was going to do that, the connection between the weights and the bar would be pretty terrible. I did want something that you could swing around at a high pace (as shown in the video in the first post) and not have the “weights” come flying off, possibly hurting someone or breaking something in the process. So the bar between the weights was going to have to go all the way through both of the weights.
This was an important thing for me to become aware of, as it helped me decide what kind of support I wanted for the inside of the weights. The outer edges of the weights I planned to supported with a layer of foam I’d wrap around the two circles and glue into place. The absolute middle of the circles would be glued into place at both circles / sides of the weights as well, and thus also be sufficiently supported. But this leaves the middle parts of the weights unsupported, and able to flex and bend more than you’d want for something that’s supposed to look super-rigid.
You can see this on the image below, where the black indicates foam, and the green and reds indicate places that are well-supported and not supported, respectively:
My solution was to take my rectangular piece of foam and cut it into four pieces per weight that could go into that unsupported area to help keep the weights rigid without making entire thing out of a massive block of foam:
Cutting the foam into pieces was easy enough:
But as I thought about placing these and putting the two circles together, I realized I couldn’t move ahead without causing a major issue down the road. As I’ve explained above, the rod can’t just go in between the two weights, it needs to fully go into both weights, and be glued to the inside of the far edges of the them. I couldn’t do that if that rod didn’t have something to be pushed into on the inside of the weights, which at this point, they didn’t. So I had to do that, first.
To make something that the rod can grab onto inside the weights, one needs to know the size of the rod. And at the time, I still had nothing I could use for a rod. I definitely didn’t want to use just foam. That stuff is super flexible, and I wanted and needed rigidity. So I went online and started looking around for things I could use. I needed to buy a bunch of other things, and while I was shopping with my dad at a local Action store, I ran intothis super-light ribbed-plastic-wrapped thin metal universal broom-and-more stick for 70 cents that was so perfect that I just took this home instead:
I first got rid of the plastic caps. Then I used my 1-meter ruler to measure out 40cm, drew a line there, and cut off that 40cm piece of the rod using a cutting saw for metal and a simple miter box to get a nice 90-degree cut. I then stripped off the ribbed plastic wrapping from the edges and used a caliper to measure the diameter of the rod.
Once I knew this, I could cut out a bunch of foam shapes in which I could make a hole that was roughly the right diameter, but I made it a little bit smaller on purpose to ensure a really tight, snug fit. You may notice these aren’t uniformly shaped, and there’s a good reason for that as well: I used some of the leftover foam from cutting these circles out of their original squares to minimize waste.
You may also notice that I added some small holes in the middle of my circles. There’s a reason for that as well. Since I wanted to glue the rod into the foam, I needed somewhere to put in the glue. The order of operations I had in mind would have meant that both of the “weights” would be completely sealed at that point, which would make it impossible to put in the glue. So I added the hole so I could put in the glue from the outside. I figured I could hide my crime later by covering up the holes with something else.
With all of that worked out, I was finally able to start gluing things together. I glued in the inside center pieces to hold the rod using contact cement. I wasn’t able to do that for the four structural spacers that surround the center pieces, because they weren’t shaped perfectly rectangular. To work around that, I put two spacers on either circle, used hot glue to make up the differences:
That almost looks like I made a miniature foam table by accident! I then combined both circle-pieces by flipping one over and rotating it 90 degrees, and liberally applied hot glue around all of the structural spacer pieces to fill up any remaining crevices:
Ta-daaa! At this point, the basic shapes for both of the weights were finished, and by keeping my process loose I was able to do it in a way that made it incredibly light-weight (it is, after all, mostly empty).
Naturally, the entire thing was far from finished. I still needed the wrap-around foam to hang over the edges of the circles to really give it that “this is a weight” look, I still needed to get the bar in to connect the two weights, and that’s not counting all of the priming, painting, and detail work — let alone everything that was going to go wrong with this project later on.
But if you want to know more about those things, you’ll have to tune in another time. 🙂
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