Working on the foam Plug

I know that I could do my velomobile design work on a 3D program, and cut out templates for each 2″ slice of my design, but I want to do it “old school” – glue a bunch of pieces of foam together, and then sculpt the design from a huge foam block!

So I cut out blocks in the size that I wanted; I found I could get 5 and 3/4 layers from one sheet of foam. Used the Super 77 spray glue to put glue on both surfaces, let them air dry a short time, and then put them together in a block. I drilled a 1″ hole through each foam piece, for the center spindle.

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Getting ready to glue two of the sub-assemblies together.

I’ve had this spray gun grip for years, and it was nice to give my finger a break on that spray nozzle.

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All put together now. This will become the bottom of the plug.

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Checked for size next to the WAW. My design will drop about 15 inches off the front.

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At this point, the plug design will be a continuance of the hood line with no manhole opening or hood, so this will be enough foam. I’ll design and build a full hood at a later stage. My thinking on why I’m building it this way will become more clear as the project progresses.

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I took a mountain bike tire and leaned it up against the tail of the WAW, at the same location as the rear wheel (which is the same size as this tire). I have to add some more foam for the tail.

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I started off by sanding the bottom of the plug to make it level, and make sure it wasn’t a twisted plane. It was a combination of using a two-sided cut off saw, Perma-Grit sanding blocks, and a belt sander. Sanding this foam makes very small green granules or dust, and they are statically charged, so stick to everything. Easy enough to blow off with an air gun though.

And I spent some time working on a hot wire foam cutter. At first I made a simple C shape out of some scrap plywood, added a handle and some bolts that could be turned to keep tension on the wire. I tried it out with guitar strings that I ordered online. They fell apart very quickly, so definitely NOT the wire to use.

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My first attempt at a foam wire cutter on the right, and the successful one on the left.

And the wire tensioning was going to be a pain, I could already tell. Looking around the shop and trying to come up with a better solution, I think I actually found one 😉

I took an Irwin Quick Clamp, with about 24″ of clamp reach, removed a roll pin from one end of the clamp, took the handle off. Reversed the handle and put it back on the bar, and re-installed the roll pin. Then I drilled holes in each of the clamp arms and put a screw eye through. The clamp arms are made of some reinforced polymer and aren’t conductive.

Now when squeeze and release the handle grip, it moves the handle further from the clamp end, and tightens the wire. I’m using a variable amperage battery charger for my power supply.

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Someone mentioned that I should use Nichrome wire. So I ordered a small spool of .32mm wire (very thin). That worked OK, but the wire continued to stretch, until it broke after about 2 minutes of use.

So then I cut three lengths of the nichrome wire, and braided it together. Strung that onto the wire cutter, that lasted about 4 minutes.

So, I then cut 3 double long lengths of nichrome; folded them in half and then braided together, so it was 6 wires strong. That lasted a bit longer, before the wires started breaking one at a time.

I made a supply run to HF; picked up two air sanding tools, sanding discs and paper, etc. I also grabbed a spool of stainless steel wire, typically used to wire nuts or bolts to prevent vibrating loose.

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This wire is about 3x thicker than the nichrome wire. I twisted on a single strand, and it’s been working great since then. I’m also learning how to use the wire cutter; don’t try to keep it too tight, and loosen it when you turn off the voltage.

Along the sides I have to go in small strips, since I don’t have a wide enough wire cutter. But it is working well. I always have my workshop exhaust fan running when I’m cutting, and I found out that my battery charger has an over-temperature limit switch built in, so I also lean a desk top fan against the battery charger to help cool it down, although the charger feels cool to the touch.

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Beginning to show the curves of a velomobile!~

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And it’s time to add my 80/20 creation! I thought this up to help me keep things symmetrical and all. I stopped at this point to install the 80/20, so that I could make sure my centerline was accurate (which it wasn’t, I had it at least an inch off to the side.)

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The 2 horizontal pieces of 80/20 were set to the same height as the spindle through the center of the plug. I measured and set all 4 verticals to the exact distance from the spindle. As I move from one area to the other, I move the horizontals up or down to where needed, and occasionally I go back and re-measure to that center spindle.

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