Saturday, May 13, 2017

Booster Covers


The next part I am going to talk about is the booster cover. The is the blue part in the middle of the leg. I decided to make this out of wood and made it in three main pieces, the top block and the two arms that come off the bottom of the block. I will start with the top block.


I started by gluing up some pieces of pine to form a block bigger then needed, I then cut the piece down on the table saw to the correct final dimensions.


The next step was to form the curve at the top of the block. This is a little tricky since the curve slopes down to the front of the block. I started by printing a full size template for the curve. I then cut this into two pieces, the larger piece defines the edge of the curve on the front of the block and adding he smaller piece defines the curve on the back. 


I used the template to mark the block on the front and back and also marked which side was which.


I started the cut using the band saw to remove some of the material. This is the front of the block so the cut isn’t close to the line, but it is much closer on the back.


To finish the cut, I made a wedge that is the same angle as the slope of the curve. I then used that wedge along with the largest drum on the drum sander to remove the material down to the line on the front. The wedge will  assure that it comes out correctly on both the front and back.


Here is what the piece looks like after that operation. I believe I had to do more more to form that angles on the edges but it’s been a while and I can’t remember how I did this, probably on a belt sander.


The next step was to form the cove along the bottom edge. I did this with a cove bit on the router table. I clamped a guide block to keep the block against the fence and a used a feather board to keep it tight to the table.


Once cove was cut I marked up the block for the location of the slots in the block.


I started cutting the clots using the drill press. I clamped a block along the back to hold the piece in the right position front to back.


Here is the piece after the drilling operation.


I cleaned up the slots with a chisel. Here is the piece after some cleanup and a coat of primer. Still needs a little work.


Sunday, April 16, 2017

Dome Top Section

To make the stop section of the dome I first needed to create two more discs. Since the top of the head slopes in I needed to cut the discs with edges beveled to that angle. To do this I used the same fixture I used in my last post to create the two next discs.
I cut these discs out of 1/2 plywood. I added a stop block to the fixture to set the finished diameter of the disc. The angle of the fixture will control the angle of the bevel on the edge of the disc. I used this technique to cut both the bottom and top discs.
Next I drew the layout lines on the disc. I first divided the disk into 10 equal segments. The sides and back of of R5’s head have pockets in them so you can see the wider layout lines in those positions. The remaining segments have layout lines for plywood pieces that will form the frame of the head.
With the layout complete I could cut out the inside of the disc to form a ring. Since this edge will not be seen it could be cut free hand or on the router table.
The support ribs are cut out of 3/4” plywood with the ends cut at the same angle as the angle cut on the edge of the disc. I rounded the outside edge of the ribs slightly so that the styrene skin will go on smoothly. To do this I just put the edge on a belt sander and gently rocked it back and forth to knock the edges off.
Here is the top ring that was made the same way as the bottom ring.

Saturday, April 15, 2017

Head pockets


On either side and back of the head are these pockets.


These are the pieces for each pocket. The sides go the full height of the head and the small blocks are used to form the top and bottom edge of the pocket. These pieces are rounded slightly on one side to match the curve of the head. I also slightly rounded the edge of the side pieces, again to match the head curve. Finally there is a piece of 1/4” luan that forms the back.


Here are the assembled sides and back. Ignore the yellow, it was just a piece of wood I had laying around that was already painted.


Before installing the finished pockets in the head I painted them with some white spray primer.


Sunday, December 18, 2016

Dome Rings

I chose to build an R5-D4 because I wanted a dome that I felt I could build from scratch, but this doesn’t mean that R5’s wasn’t without challenges. The first part of the dome I worked on was the two angled rings that form the neck. I did see a build log for an R5 where the builder created wooden ribs the shape of the head and then used curved strips of styrene for the surface of the angled piece.
I decided to take a different approach, I made the slopped pieces as rings of MDF with the slopes cut into them on a router table. To do this I created another jig, here is what the finished product looks like:
I started with a sloped table with a nail that the part will rotate on. I screwed on the angle pieces so that I could change because the top and bottom rings have a different angle. At the bottom middle of the table is a small slot to provide clearance for the router bit. Next I clamped two strips of wood to the router table to allow the sloped table to slide straight in and out of the bit. Finally I added a stop block so I knew when I was at the finished depth. This technically wasn’t needed since the design of the jig would allow the bit to pass under the part at the end of the bevel.
To use the jig I first cut a disc of MDF using the router table circle jig I have used for other parts. Here you can see the disc mounted to the jig.
Here you can see a close up of how the bit makes the cut.
To make the cut I started with the bit lower then the final depth since a lot of material needs to be removed along the outside edge. Since I was cutting MDF I also took some time to setup some good dust collection. I slowly slid the piece into the bit, rotated the disc all he way around, moved it in a little further and repeated the process. Next I raised the bit to it’s final height and repeated the process to get the finished angle. Here is one of the finished rings. To complete it I hand sanded the angle to get it smooth and then  I cut the center out using a jig saw since it doesn’t need to be precise.

Sunday, August 7, 2016

Shoulder Hubs Part 3


The next step in making the shoulders hubs is to drill the holes needed to mount the hub to the leg. This required a bunch of different size drilling operations that all need to line up perfectly when they are done. To do this I started by drilling a small hole in the inner leg layer that will be right in the middle of where the hub will go. On the back of the leg piece I used a compass to mark a circle for where the holes will go and then marked the position of six holes even spaced around the circle. Next I used a nail to get the hub aligned with the leg, and then screwed both sections of the hub to the leg. With everything screwed together drilled small holes all the way through all three layers to mark the position of each bolt.


The first drilling operation was to drill shallow holes using a forstner on the back of the leg to accommodate the flange of the t-nuts.


Next I drilled the holes for the body of the t-nuts. The body of the t-nuts is a little larger then the bolt so be sure to measure them to get the right size drill.


The next holes were the large holes on the inside layer of the hub. I made these large enough to accommodate a socket wrench to tighten the bolts. Next I drilled the bolt holes in each larger whole and through both layers of the hub.


The bolts I am using to hold the flange on are not totally flush with the surface of the flange so I drilled some very shallow holes on the other side of the flange to accommodate this and allow the to sections to come together tightly.


I did some reading to see how others mounted the flange to the hub and I found that a lot of people used a metal plate on the back instead of washers. I am not sure what the advantage to this is, but I decided to still do it that way.

For the metal plate I used what most people seem to use, a cover plate for an electrical box. I started by marking the positions of the holes on the plate and drilling the holes. As always I put marks on the plate so it ended up back on the same hub and in the same position.


The plate needs to fit within a hole in the leg so I needed to trim the plate a bit. Since the plate already had rounded corners I only needed to do a little bit of trimming. I did the trimming with a hand held jigsaw with a metal cutting blade.


To hold the hubs to the leg I installed T-Nuts in the holes in the leg layer. The t-nuts have prongs that hold them into the wood, but since these will eventually be inside the leg and in-accessible, I took the extra precaution of securing them with epoxy.

There will eventually be some more assembly work on the hubs but I won’t do that until I am closer to doing the final assembly.

Sunday, June 12, 2016

Shoulder Hubs Part 2


The shoulder hub are a little tricky to build. They require quite a few drilling operations and some of them have to be done in a specific order.

The first step in building the hubs is to cut the disks. These are made from 3/4 plywood and two are needed for each leg. I cut them using my router table and circle jig just like I did with the frame disks.


Once the disks are cut the next thing to do is mark them so you know which ones go on each leg and which is the inside layer (nearest the body) and which is the outside layer (nearest the leg). As I have mentioned before, if you are really accurate with your drill holes, which one goes with which leg isn’t important, but since these operations sometimes aren’t as accurate as we want it’s better to keep things matched up.

Next I worked on mounting the flange to one of the disks. I didn’t want to measure to the outside of the flange since it isn’t machined and is a little inconsistent.  Since the threads in the center are machined it was a more accurate place to make measurements. I put a nail in the hole in the disk and used calipers to measure around the nail to be sure it is centered. Once it was centered I marked the position of the holes. I also put a mark on the flange and disc so they could be put back together in the right orientation.


With the holes marked I drilled them with a drill press.


On the other layer I needed to cut out a 3/16” deep area to accommodate the bottom part of the flange. To do this I used a fly cutter in my drill press to make a template. This cut out doesn’t need to be perfect so I made the template slight larger then the diameter of the flange to be sure it would fit properly. I marked the position of the flange on the disc and then screwed the template on. Finally I used a router with a guide collar to cut out the area within the template.


With that cut-out complete I used a 1 5/8” forstner bit to drill a hole through the center of the disc to accommodate the smaller portion of the flange. The area where smaller part of the flange meets the larger part is slightly rounded so you may need to file the inside edge of the hole so it will all fit together properly. There was also some raised lettering on the flange which I had to grind down a bit to make everything fit. Here is the flange sandwiched between the two discs. If done properly the disc should fit tightly together.


Sunday, May 29, 2016

Shoulder Hubs


The next thing I want to show is how I built the shoulder hubs. There seems to be two parts on a droid that are referred to as shoulder hubs. The first is show here, that silver part within the shoulder horse shoes:

R2_Shoulder - Copy

The part I will be talking about in the next couple posts is this one, the hub that attaches the legs to the body.


After doings some research I found that attaching the legs to the body was one of the trickier parts of building a droid. The legs need to be able to rotate so that the droid can be switched from two leg position to three leg and when in two leg position all the weight of the droid in on this connection point. One of the most popular ways of doing this is what is called the “gas pipe method”. To do this, two different size steel gas pipes are used, one screwed into a flange on each leg and then slipped inside each other. The hard part turns out to be finding pipes that will slide into each other but not be to loose. You will find that these pipes often have a ridge down the inside of the pipe that prevent them from filling together.

I eventually found pipes that will work at Home Depot, but did a slight variation of this method. Instead of using two different size pipes on the legs, I used the same size, and then used a third large pipe to connect them together. Here is what the finished product will look like.


Here is a diagram of the hubs I built. It starts with a metal pipe flange that the pipes will eventually screw into. The flange is sandwiched between two plywood discs and bolted to the one that is closest to the leg. The entire assembly is then bolted to the leg with t-nuts installed on the leg. In my next post I will start to describe how I made the hubs.