Old #38 -- The FreeCAD variation


#1

I'm committed to building one of these and have started acquiring some of the parts. I'm going to be self-sourcing as much as I can because I have a laser cutter.

I also wanted to re-implement the design in FreeCAD so that those without Autocad Inventor would have some options. Each of the parts is a separate, fully constrained sketch. That means that critical dimensions can be adjusted fairly easily. FreeCAD doesn't have an assembly tool yet but it's coming.

So far, I've modeled the frame parts outside the tube. I've created a github fork if anyone is interested. I'm also blogging about my progress.


#2

One variation in my design has to do with the shell. FreeCAD can't model a bent part yet and that stock shell is too large to cut on my laser cutter. My variation splits the shell into three parts that will glue together.


#3

This is great! I meant to also export the inventor CAD files to STEP and IGES, but it looks like you're already pretty far beyond that point. It would take me a bit of time to convert the whole assembly (there are a lot of parts now, and I think I'd have to convert each of them individually) but let me know if that would make a big difference for you. Also, I understand the dilemma with the folded shell requiring both a large cutting space and a special strip heater. The sides may be somewhat susceptible to breaking off if they're just glued edge-on (especially since laser cutters usually put a bit of a taper on edges) so I think for your approach, you'll also need some piece of reinforcing plastic that can flex. Perhaps some polycarbonate angle bracket would do the trick. Polycarbonate welds to acrylic so it could be attached with the same glue as everything else.

Anyway, keep up the good work. Hooray for open software!

Eric


#4

One thing that would be helpful would be some pictures of the tube internal assembly. I'm figuring it out by trial and error and by studying the pictures on the site, but the glare on the tube makes it difficult. That and the fact that the backside of the assembly is hidden.

I also noticed that the BOM calls for a Hitech servo. I can see where it mounts in the tube, but I don't see what it does. I also don't see it included with the kickstarter kit. My conclusion is that it's for an incomplete mechanism to rotate the tube internal assembly up and down. Can you verify?


#5

Sure thing!

Here are two photos I just took of the internal structure which I call the "Electronics Chassis"



You are right about the servo- it's used to rotate the Electroncis Chassis up and down inside the clear tube. The current design accepts an HS-65, but I'm thinking I may change that to a servo that is less expensive (some sort of generic servo) and one that does not stick out so much. The "+" shaped servo horn of the servo engages with the "+" shaped hole cut into the circle shown in the laser cut pattern. That circle is mounted onto one of the end caps which stays static.

Make sense?

Eric


#6

Yeah, that helps a lot. Thanks!. I can't quite see, but I assume the piece that holds the web cam slides into the two long U shaped pieces. Are those just glued face flush to the disks?


#7

Yeah, you've got that precisely right. I wanted people to be able to adjust the height of that face in case they used a different webcam (with a different depth). I kind of want to change to a different webcam in the future anyway, so that whole bit is definitely opt to change. The current HD-5000 requires that the rubber base be dremeled off in order to fit, and I don't really like the big Microsoft logo as the face of the ROV. I was kind of thinking of this one. What do you think??

E


#8

Looks great. Except I just bought a HD-5000 on sale at Fry's last week.

Crap. :-)


#9

Lol- sorry about that! ...Actually, the camera itself works really well, and I've been very happy with its performance. All of our development has been done with it (Bran and I both have one). The biggest issue is just the hassle of dremeling off the rubber stand. Let me know if you need help with how to do that.

E


#10

Thanks. I'm a couple weeks from that step.

I plan on keeping a photo record on my blog and also something of a buildlog here if that's o.k.

Hopefully the pictures will help document it for others too. And if (when) I screw it up, I can go with the wide angle version. ;-)

I see you guys have an IRC channel at #openrov. You should note that on the site too. I just stumbled on it.


#11

Good call- I'm ashamed to admit that I didn't even know about it until a few weeks ago. Someone else started it. lol!

Eric


#12

That did the trick. Thanks again Eric. Next step will be the endcap assembly. No hurry, but if you could post some pics of how that goes together it would really help.



#13

Starting to cut plastic. Details on my blog