The Big Think

May 23, 2016

R2 Aluminum Pile

Filed under: The R2 Project — jasony @ 9:29 am

That’s a great big old pile of aluminum:

IMG 2199

What you’re seeing here are all the aluminum parts I’ve milled, water jetted, lathed, and otherwise mashed up since last September (really since about February). 

Starting from the left are the leg boxes, horseshoes, ankles (bottom left), battery boxes, and ankle bracelets. Then on the right hand side are the feet (all spread out on the table).

I opted to let Big Blue Saw cut the water jet files for the feet since it wasn’t that much of a premium and since they would replace any pieces that were messed up. Overall I think this was the wiser course even if it wasn’t immediately cheaper. It was cheaper in the case of the water jet making a mistake (something that happens about 10% of the time at TechShop). Even so, there are 90+ pieces of the feet (center foot and two outer feet) that have to be welded.

And oh, the welding. Most of the above pieces except for the horseshoe at the upper left still need to be TIG welded. There are 174 remaining pieces that will need to be cleaned, aligned, clamped, and TIG welded. I’m not sure of the total length of welds but it’s a lot and I’m sure I’ll be at it for months. Fortunately, except for two pieces, all of the machining and cutting is pretty much done for this year. Once the feet are welded I have to cut some pipe to size and then lathe, cut, and mill out a weird piece. Then once all of what you see here is done I’ll begin designing and cutting/welding the foot motor mounts. I think I’m going to do those custom but I’m still thinking about it. That’s for later.

My goal is to finish all of this by September but I still don’t have a good handle on how long the welding will take. I’m going to put in a few more 4 hour sessions practicing before I try and tackle an expensive-to-replace part. I’m going to hopefully get a one-on-one lesson with Keith at TechShop this weekend. He’s the good welder from my previous posts (one of the best in Austin). Then I’ll go through the pile of parts and start welding up assemblies from easiest to hardest, thereby gaining experience as I go. I suspect the battery boxes are going to be the hardest so they’ll be last.

I’m thinking that I’ll end up missing my September deadline as things progress since I haven’t even included time to correct the leg boxes on the mill (long story for a future post), drill and tap holes for mounting the horseshoes, drill out the ankles and install bushings (no idea how to do that), and probably spend two or three long sessions making the funky curved parts for the outer feet. Oh, and I also need to research how to remove anodization with a lye bath. Got some industrial strength lye (and a pile ‘o protective gear) to remove that but I’ll need to do a practice session on some scrap to make sure I have the procedure down correctly. 

Then it’s on to the foot motor assemblies, which I’m kind of looking forward to. I’ll need to commit to the motors (I’m thinking a pair of NPC2112 motors — they’re pricey but they represent “real” robotics motors instead of hacked up scooter motors). I’ll get those soon and then start designing the motor mounts. The feet need to be welded up first, though, so that I can make sure that I have enough clearance inside the shells.

Going to TechShop this morning for a 4 hour TIG practice session. I’m running out of scrap and will probably drop by Metals4U and get some .125” pieces (hopefully from their scrap pile) to continue practicing.

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