Sunday, December 18, 2016
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
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
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
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:
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.
Thursday, May 19, 2016
Early on in my build I decided to try my hand at some styrene work just to see how easily I could produce some of the body details. I decided to start with the front vents, and particularly the vent housings.
The wall of the housing is a little over 1/8” thick. I initially thought it might be possible to bend some styrene that thickness but the curves were to tight. I also tried heating and bending a piece of styrene but that didn’t work either. Bending the 1/8” is probably possible if done right, but I decided on a different approach, building up the thickness with multiple pieces of thinner styrene.
I started by building a form. I cut three pieces of 3/4” thick pine to the rough dimension of the vent and then glued them together to make a 2 1/4” high block. Next I attached a template for the interior size of the vent housing cut from one of the scale plans.
With the template attached I cut the block to the exact size of the template and also cut most of the material on the corners. Finally I used a drum sander to round the corners down to the template and the screwed it to a piece of scrap plywood.
The upper vent is 1.938” deep at it’s largest point so I cut a strip of .03 styrene 2” wide (although in hindsight I would have gone a little wider to leave some room for error) and long enough to go all the way around the form with some room to spare. To hold the first layer together I beveled the opposing edges of the strip so that they overlap and cleanly as possible:
To do this I beveled one edge with a file, wrapped the piece tightly around the form holding it in place with clamps and then marked it for length leaving about a 3/16” overlap. I then removed it from the form and filed the other end. With the piece prepared I re-attached it to the form, holding it in place with some squeeze clamps and finally joined the edges with some liquid styrene glue and then clamping over the seam to hold it together until the glue dried.
When the first piece dried I remove the clamps and left the piece on the form. Next I cut another piece of styrene the same width as the first one. I did not try to cut the exact length on each layer since each one will need to be a little longer then the previous so I just started with a piece that was long enough with a little to spare. To start the second layer I glued one end to the side of the first layer opposite where the other one started so that the seams will alternate from one side to the other. When applying each layer try to keep the piece tight down to the plywood base. The edges won’t come out perfect but this can easily be cleaned up later. Once the first edge has dried I started working my way around the piece, gluing and clamping a small section at a time. Once I got 3/4 of the way around I bent the piece the rest of the way without glue, marked the length and then removed the piece from the form to make the length cut. Finally I put the piece back on the form and glued the end.
I repeated this process until I had built up the proper thickness for the housing . You can see that the final seam didn’t come out perfect but I can probably clean this up with some filler and sanding. You may want to apply your layers so that the seam ends up at the bottom of the housing so it will be less noticeable
To finish the part I sanded the back end of the housing on a belt sander to get it level. Not that the back of the lower housing has a small angle to it, but the upper is square. With one edge cleaned up I sanded the other end to being the housing down to it’s final height. If you left a lot of extra you could start by cutting some off on a band saw. The front edges of the houses is slightly curved. I handled this by marking lines along the side at the final height and the formed the curves on the belt sander.
Here is what the final part looks like.