How to make a round thing without a lathe (plus model making tips)

Step 5 Mix up some filler and start spreading it round with the profile

It's magic, you shape starts to appear immediately. try to make the shape as clear as possible, but you don't need to do all the shape at once. In fact this is almost impossible so don't try it. You are going to be building your shape up over a few goes. ( I have pictures of each step). Given the resin only takes about 10 minutes to go off, this process won't take that long, even if you have to do 6 layers!

Between each layer trim off any wayward prongs or bulges that impede the easy rotation of your profile, i.e. stick up in the way of the profile, If you are using car filler resin (see below) then the best time to do this is when the resin is in the gelling phase as it is going off. Be quick, the gelling phase is only about 30 seconds to 1 minute long. This type of resin is called a "snap cure" and once the setting reaction gets going it is a driven by what is called an avalanche effect at the molecular level. Once it is set the only real way to remove lumps and bumps is by rasping, filing or sanding. (note always wear a mask when doing this to avoid inhaling the dust). In the gelling phase the resin is hard enough to keep it's shape but cuts like rubber, so quick gross modeling is possible then. However, be careful, before it is set it is not stuck that well so you can also dislodge what you have just made, if you cut to aggressively.

As for the filler I used... My favourite is two part auto body repair filler (resin car bodywork filler). You mix it up from a big pot of resin and a tiny bit of hardener.

Model makers like two part fillers because they set very hard very quickly and can be sanded very smooth and take paint well.

Model Maker's Tip #3 Use two part car filler to make nice fillets round you models, and even cast the odd detail (if you have a suitable mould pattern).

TIPS...
Don't put the mixed up resin covered spatula back in the pot to get more, the hardener on the tip will set off a reaction that hardens the whole tin.

Be ready with your profile before you mix up, once mixed up, the resin is going off and will become very hard so you don't have much time to get things right

If you want it to go off quicker mix a tiny bit more hardener, but be careful too much and it will set as you are mixing it.

CAUTION
It sticks to anything and once hard is impossible to remove, either wipe it off straight away when it is semi liquid or wait till it is in the gelling pahse and chip off quickly (very quickly) before it is stuck.
It gives off fumes so open a window when using resin filler

Comments

[RaisedByRobots]

I'm impressed by your ability to make such a uniformly smooth object out of this stuff. After an hour of sanding, mine went from looking like a stone birthday cake to a crude pitted wheel made by some prehistoric tribe. I guess I need Sanding 101 or Bondo 101 class. It would be interesting to see a video of how you did the bondo step. You made it look easy, but I'm finding it isn't.

[KaptinScarlet]

OK, you need to start off with coarse grit paper, and I mean coarse 40 or 60 I think. then when you use the form to sweep round you do it lots of times and sand a bit between each time. To start with the shape looks rubbish but each time you do the sweeping round with new filler, the form makes sure that all the old gaps and cracks are filled by the filler. Don't try and put too much on to start with. when a layer has set, sand off coarsely until you can easily turn the form round without it snagging. Then mix up some more stuff and smear it on again. When you are putting stuff on that is smoothly going in the scratches of the previous snadpaper it's time to switch to finer grade sandpaper. It might seem tricky, but it's just a step wise process. However, the filler is tricky to handle when it has just been mixed up and it can be to fluid and then once it starts curing it goes off very quickly (it is called snap cure), so some practice is needed. Don't get too disheartened, I had to chuck my first one away, because I used wood filler and it wasn't smooth enough, nor easy enough to sweep round. BTW, this is one of the standard ways in which model makers make flowing curves on their models. AND yes, those styrene vapours over the years have probably killed off many brain cells and totally wasted my sense of smell, but it is an odour that reminds me of all my model making, so it is a happy smell for me. Good Luck, do get back to me and tell me how it's going, and send pictures in if you have them.

[RaisedByRobots]

Here is a video of the thing in action. Like all magical devices, it is frequently reluctant to work until the energies are right. :)

[RaisedByRobots]

Well, I finally did it. I could not resist trying to make it "work" (fingers making quoting gesture). So, here it is. I had to enlarge the pattern to allow for the workings inside (composed mostly of a pc fan and a meter needle from an old analog meter). I could not achieve the beautiful perfection of your finished piece. I struggled quite a bit with that. Maybe I could come up with some sort of old beat up tarnished look for it to make the blemishes just look like wear and tear. To your instructions I would add that the detergent bottle plastic for the profile is more of a necessity than nicety. I didn't get a clean edge as you mentioned until I used that. I also used a mask while sanding the bondo, which is good because I found that my entire work room is coated with a fine particulate dust of the stuff everywhere! So, if I were to do it again, I'd try to cover everything up with some cloth or something first. When I get a little more time and motivation, I am going to redo the faceplate and figure out how to make the crown glass part come out right. I just need to purchase some ink jet transparancies I think.

[KaptinScarlet]

That's amazing. The forming thing has worked really well. I know what you mean about the plastic forme. I would be even better if you were to make a profile from a thin sheet of acrylic, but I am fixated by making things from junk... mostly. However I'll look at the instructions and modify them. I love the video and the motor inside is a real bonus and innovation and very brave. How do you power it? BTW... I am redesigning dadcando at the moment and within about a month there will be a facility to upload pictures of your projects and each week I will be giving away prizes for the best. So keep an eye on dadcando, as this project looks as if it would definitely win!

[RaisedByRobots]

Yes, making things from junk is a great idea. The thick plastic of the detergent bottle worked great and was flexible and soft. Acrylic is too hard to cut I think, for me it shatters. The computer fan inside the contraption is powered by a little 9 volt rectangular battery. Turns out I only need one moving hand for it to work "correctly", so I might revamp it to work the way it's supposed to. I was at a loss as to how to solve the problem of the opening in the back/bottom for putting the parts in and changing the batteries. So I just put a thin wooden sheet in the back that I could lift in and out, but it doesn't look so nice as yours does. Ooh a contest, love those. Thanks, I'll keep an eye out on your site.