Modeling updates

Over the past few weeks I’ve been mainly working on 3D modeling my trumpet valve design using Autodesk Inventor. I absolutely love using CAD (computer aided design) software. You start with a notebook full of sketches and you come out with a model that looks exactly like what you are going to create in real life.

I started out using very primitive CAD software a few years ago, called OpenSCAD. It is based on scripting, so you are basically using a programming language to create your 3D object. I’m very familiar with programming so this was the perfect first CAD program for me and it was good enough for the simple things I was making.

Once I started working with more complicated things, I needed a way of making 2D drawings to illustrate my ideas. I came across QCAD, which is a super simple and powerful 2D-only CAD program. This worked well for a lot of things, but now that I’m working on my trumpet and some other projects, I need a lot more features and the ability to do 3D modeling.

Now I am learning how to use Autodesk Inventor, which is probably the most feature filled CAD program currently available. This comes at an astronomical price, but luckily Autodesk gives it away to students for free, presumably to get them used to it so that they use it in their professional career. Inventor is extremely complicated, but by watching other people use it, I’ve learned how to use most of the important features. I’ve put off learning a complex 3D CAD program for a long time, but now I’m finally ready to use it, and I can tell you it is a joy to have this new ability.

Inventor has the features that I need to be able to design and build my trumpet. Many of the curves and shapes that the tubes have are very complex and I need to be able to adjust them very easily and accurately so that I can make the trumpet sound better. The part of the trumpet that I’ve been modeling the most recently is the valve block. This is a very complex piece of aluminum and it forms the center of the trumpet design. Inventor lets me make changes to the design and make it absolutely perfect before I spend a lot of time milling it out of aluminum.

So far I’ve designed about half of the valves. CAD is also great because it shows you the possible problems you’ll encounter before you spend time and money building it. I’ve come across a design problem that I’m not quite sure how to fix yet.

This is essentially the valve cut in half so you can see the inner workings of it.

base aligned closeup base aligned base not aligned closeup base not aligned

As you can see, the darker part rotates inside of the main part. This is what actuates the valve. When the valve is in the top version, it lets air flow right through the valve, and when the valve is in the lower version it redirects it out through a carbon fiber tube extension and back into the trumpet. You can see that in the top images, the channels all line up perfectly and air will flow through without any resistance. The problem is that when it rotates 90 degrees, the channels don’t line up the way they’re supposed to and the air will encounter significant resistance that will change the sound of the horn. I’m fairly certain there’s a way of designing it so that they line up perfectly in both orientations, but I’m not sure what this design is. So this means I just need to try a bunch of different designs and figure out what the pattern is that creates the perfect alignment and then I can punch in the numbers and it will create the correct alignment. That’s the hope anyways. I’m pretty sure I setup the design so that I can just modify one 2D drawing and it will affect every part involved. That should make it very easy to fix this problem.

Wax molding technique update

I found this patent describing a method of manufacturing fairly similar to my idea of using a wax core. This method is essentially resin infusion, without the vacuum, but with high pressure resin. I think this patent is notable because it confirms that it is possible to use wax as a core that you can melt out later.

http://www.patentbuddy.com/Patent/5132069

I received 1lb of carnauba wax from McMaster today along with some new vacuum oil. Hopefully replacing the oil will mean my vacuum pump can get down to a super low pressure. Right now it is only able to get to 26.5″Hg, but I’d like to get down to 29 or 30″Hg.

I also got started on a sealing mechanism so that I can seal the vacuum bag while it is in the chamber under vacuum. Once I get this all figured out, I’ll post more about it. This method is looking extremely promising and simple compared to other methods I’ve tried.