Hi, this is Wayne again with a topic “Making Makey Part 2: Building the Prototype”.
Welcome back here’s part, two of building the makey robot mascot costume um, we’re gon na be starting with, is mostly gon na be mdf. It’S medium density fiberboard, like you, pick up from your local lumber yard and a lot of pieces that are going to be shaped. Using really basic carpentry skills, these pieces, don’t really matter all that much as far as what they’re made out of they just need to be kind of the right shape. I’M going to cheat a little bit for the head.
It turns out, since we’re looking to make essentially just a section of a sphere, i’m going to start with an acrylic sphere that can be purchased online they’re used for lighting fixtures that have big dome lights. This is just going to be a simple plastic shape that i’m going to be able to pull a mold off of and replicate in fiberglass. The reason not to use the acrylic sphere is because it’s going to be prone to splitting or cracking or shattering on the off chance. If somebody unfortunately drops it somewhere along the way. I’D rather have this thing bounce instead of having to make another one in a hurry, so the main body is kind of going to set the tone for the rest of the build.
For most of these parts, we’ve got sharp corners. We’Ve got, you know fairly tight radiuses we’re going to end up being able to do just using a router table for the main body based on the scale. This radius here is going to be about three inches. Where that you know edge is covered over.
So, in order to get that proportion correct we’re actually going to end up using just some basic auto body techniques, we’re going to back it up with some foam and then skin over it with bondo and use a contour gauge. In order to set the surface to the right shape that we want so we’re using an x30 expanding foam – okay x for expending 30 for 30 times its original volume according to the way they’ve pitched it. So it’s one to one by volume. Temperature is going to adjust the way things go as far as curing time and expansion and here’s another five.
It’S important to make sure you scrape the sides of the bucket, which is why i’m doing the up and down motion with the mixing head. You can already see it’s getting bigger, which is neat now. If we just set this down, it would gladly pour out all over the place, cover the table and make a huge mess. We’Re going to go all the way around this guy. Of course, you’ll notice.
The dollops that i’m leaving behind are bigger as i’m going along because the foam has expanded as it’s doing its thing now, i’m gon na scrape some off the edges and continue to blob it on the top. In hopes that we minimize the amount of time we’ll spend reshaping the blob when it finishes blobbing, so we just do kind of a rough shape with the saw, because you know if you had to sit and sand through all of that first, it would take forever. Second, you’d have dust all over the place, it’d be a horrible mess, and this stuff gets all staticky and clings to everything.
So got a couple options. This is your automotive body, rasp also called a sure form or cheese grater. So this one does a pretty good job of eating through the foam in a hurry. It’Ll give us a smooth er curve and again we’re going to take the foam back a little bit more than we need in order for that curve to fit, because we are going to skin over this later with some body filler.
In order to make it the right shape so right, there we’re pretty close, but we’re still going to make it smaller. Okay, so we already went ahead and we made the main box. We got the corners kind of filled in with foam and then once the foam was on, we roughed it out using a hand, saw some different body shop type tools. So we have a shure form and rough sandpaper on a long board.
Things like that and then once the shape was roughed in, we still need to make it nice and glossy and smooth when it’s done so the end result is. We have to go back and skin over it with automotive body filler called bondo his most popular brand name. So in order to get this nice and smooth and fair we’re going to end up building up a bit of a skin, you sand it fill it sand. It fill it repeat at length until eventually it becomes the exact right shape and then we can make it all shiny paint it and wax it and prep it for molding.
So for mixing a bondo we’ll go ahead and start on the next piece here. Making a huge mess next piece in the lineup that hasn’t been touched is actually going to be the forearm, which is massive, because this thing is got this whole gorilla crab, robot thing going on. So, in order to put a skin on the forearm, we’re going to mix up another rather large batch of bondo.
Now when you’re mixing bondo, you want to make sure that you’re scooping out of your bucket using something other than your mixing tools. This little guy is really handy reason you don’t want to use your mixing tool is because you don’t want to get any of the mixed bondo back into the bucket and contaminate it with hardener, which might end up causing it to catalyze, and you end up with Hard lumps in the bucket all of a sudden. Normally i wouldn’t mix up a batch this large because it’ll end up going hard before. I can actually use it all, but in this case, since we’re just going to be slathering it over a fairly large area, we’re going to make a really big batch. All in one shot start off with our big blob of the first part, and then we put the cream hardener on there. Now, when you’re mixing, you want to make sure that you only end up getting the material on one side of your mixing tool. That’S just a regular putty knife, so you scoop it up off your mixing surface and then just blend it back in until it all becomes one color.
So we end up with the just right shade of reddish tannish brown, whatever you want to call it, but if there’s still streaks of color in there or streaks of gray, you still have more mixing to do. Of course, while this is going on, you also have to bear in mind that you’ve got a big pile of unmixed material loading up on the blade itself. So, while you’re mixing from time to time, you want to scrape that off of the edge and then mix it back in and fold it into everything else and then eventually, as time goes by, you get the one color. Now you end up with a couple of different tools that you want to use to spread this stuff out. You use a rigid metal, putty knife like the one that i’m using here. It’S got a little bit of spring to it, and then you also use flexible plastic spatulas, and i like to buy the one.
That’S on the shelf right next to the same body, filler that i’m using because it happens, it’s the just right color. This means that when the material is mixed properly, they should be the same color. If it’s a little more rich red color, it means i’ve got too much catalyst and will go off too fast and it’ll be brittle when it cures and if it’s a little too gray, it may not cure at all and again we’re just gooping it all over. The part, so we can make ourselves a temporary hard shell on top of the foam.
Now we’re also going to end up forcing this into the open cells that are on the surface of the foam where it was sanded, that’s going to make. It adhere a little bit better, give us a mechanical bond out of the whole thing. So this is the point in the video where about a million different people who work in the automotive body industry are going absolutely crazy. I’M going to point out in the comments a million ways: i’ve done this wrong.
You want to be using this stuff at about a normal room temperature right now, it’s a balmy, oh 70ish degrees, fahrenheit. Here in the workshop for all you metric folks, that’s about 20 degrees, canadian, so there’s that hotter will cause the material to actually cure faster and colder again could keep it from curing ever at all. You can make up for that by adding a little more catalyst on a cold day or a little less catalyst on a hot day. If you want to alter your cure time, something else. I’D like to point out you’ll notice, we carved out a groove along the edge here and the reason for that is so that we don’t have a nice thin skin of bondo right up to the hard corner where it’s going to end up flexing and it’ll start To split right along that edge by building up a bit of a wedge behind it, now it’s going to end up having a transition before it becomes a thin spot. So you won’t have that stress point on the corner so, as time goes by, each successive layer is going to be a smaller batch covering a smaller area and then the sanding is going to remove.
You know less high points if that makes sense. So if you look at the first pass here, you’ve got all these big ridges that have been built up. Just you know the tool marks from spreading everything on there.
So once you’ve got all these high parts, the next thing is you’re going to go through and knock them down with either a sure form. So for this edge, we’ve already gone a few rounds. This is going to be the third or fourth pass with the bondo.
I’Ve still got a couple of high marks from the last pass, but i’m just going to use long board. This is just a big clamp with handles. It’S got some 36 grit sandpaper, which is one step smoother than gravel driveways, and i’m just going to go through and grind off. All these high points, real quick. So with all the really high parts knocked off we’re going to switch to something a little less aggressive got some 80 grit sandpaper on a hand, sanding block. So, as you can see, there’s still quite a lot of work left to do the shoulder’s still pretty rough. The forearm’s still pretty rough, the hand’s a little bit smoother main body smoother still and the dome, because i’m cheating and using somebody else’s piece of work is as smooth as it needs to be. I still need to make the legs turns out. A lot of these parts are going to be exactly the same as the parts that go on the other side, so i only have to make one prototype for the entire arm, because the other arm will be the same same thing with the leg parts so it’ll.
Actually come together, pretty quick at this point. So after we do a little bit more sanding and filling and sanding and filling and sanding and filling, then i can prime it find out where all the flaws are that are still there and then we’ll go ahead and fill those and sand them down and find New ones and fill them and sand them, and then once that’s done, we can prime it again and if that works out to be smooth enough, we go back in and paint the whole thing. Some nice shiny color and then we can start molding so tune in next time and we’ll have everything standing by all shiny and ready to start making molds you .