**E178 DX3 Basic Assembly Instructions TLDR** |[home](index.md.html)|[syllabus](syllabus.md.html)|[assignments](assignments.md.html)|[labs](labs.md.html)|[final project](finalproject.md.html)|[flight data](FlightData.md.html)|[getting certified](RocketryCertification.md.html)| # Notes: Things used so far: Calipers, gloves, tape measure, kitchen scale, dremel, epoxy, JB Weld, toothpicks, newspaper, epoxy cups, craft sticks, 100 grade sandpaper, ¾” wooden dowel, masking tape, drill, #52 (or 51) drill bit, 2-56 tap, 3 x 2-56 screws, small screwdriver to screw in screws, X-Acto Knife. Things I needed (i.e. not in the box): calipers, tape measure, kitchen scale, dremel, ¾” dowel, drill, drill bit and tap, small screwdriver, angle iron. I thought it needed a diagram for which part is which in the beginning as I was confused so I made one to make sure that I was using the right piece: Here is the diagram. ![Figure [DPL]: The parts that come in the kit](Images/DX3_rocket_parts.png) # Notes on the assembly steps ## Step 4 – First steps: Sanded the entire motor mount. When it came, it was shiny. After sanding, it is much whiter and matte. Sanded the inside of the coupler tube for the base plate (I then marked which end I had sanded with a small arrow pointing that direction on the outside of the tube). Sanded the other side of the coupler up to a little less than halfway as it will be epoxied to the inside of the payload tube. I also roughed up the inside and outside of the centering rings. I also sanded the outside of the base plate. Things I sanded in list form: Motor mount, coupler tube (inside one end and outside of the other), centering rings (inside and out) and base plate. ## Step 5 – Motor mount assembly: Placed lines on the motor mount. I found that when I had the motor retainer top and bottom screwed in and inside the body of the rocket, it was easier to turn the motor mount inside the body rather than turning the body of the rocket. Before I began gluing I (was reminded by my mother to) put down newspaper to protect the table. I also opened the window next to where I was working to allow for ventilation. Before I began gluing I also dry-fitted the centering rings. They fit totally fine on the motor mount, but were slightly too big to fit inside the main body, so I sanded it down until it fit easily, but snuggly. _Gluing aft ring_ – Mixed about a tsp of each the resin and the hardener (this turned out to be too much and there was much left over). I mixed with a popsicle stick in the mixing cup, this was a bit awkward with the size of the stick. I tried applying the epoxy to the motor mount using a popsicle stick and found that this was a little too imprecise a tool to get it between the lines and also left large clumps in areas and very thin lines in others that I had to smooth out. Then put the aft ring on, slowly twisting it to get the epoxy more evenly in the joint. I then took a toothpick and very carefully smoothed the fillet. After I took a small piece of paper towel folded so that there was a straight edge and wiped the epoxy that had gone beyond the lines on either side. I let this sit for 10 min before starting on the fore ring. _Gluing fore ring_ – This time around I mixed less resin and hardener. I mixed approximately 1tsp total if not slightly less. This gave me just enough to epoxy the fore centering ring. This time to mix and spread I took two toothpicks and cut them so they were flat (cut off the points) and mixed and spread using this. It was easier to work with as it allowed for more precise spreading and wasn’t as bulky to mix with. I recommend using the toothpicks and will be using them again. _Gluing the motor retainer to the motor mount_ – I had heard that JB Weld was incredibly hard to work with, but I had no problems. I mixed about a tablespoon of the hardener with about a tablespoon of the resin. The hardener was white and the resin was black meaning that when I had mixed thoroughly, the color was a nice even dark grey (with no streaks). I again used cut toothpicks to mix and spread. I again needed less epoxy than I had thought and ended up using maybe a third of what I mixed. As I put it on, I made sure to twist the motor retainer. After it was on, I twisted another half turn, creating fillets of the epoxy at the base of the retainer. I then wiped the (very small amount) of epoxy off the inside of the tube. I then set that off to the side where it wouldn’t be bumped and let sit, standing on the motor retainer. I kept the cup of leftover JB Weld with a toothpick in it as an indicator of when it was set. As the back of the JB Weld packaging cautioned against breathing in the fumes, I put a fan in the window to add some circulation. As the epoxy was setting I went on to the Forward Assembly before adding the shock cord. ![Figure [DMM]: The Motor Retainer Curing on the Motor Mount](Images/DX3_Alt_Motor_Mount.jpg) _Epoxying the chord to the motor mount_ _note: I did this step after most of the forward section was completed allowing the motor retainer to set before handling it._ The instructions call for tying the kevlar and nylon ropes together using a double fisherman’s knot. Before tying the knot, I would recommend melting the nylon rope to stop it from fraying and taking a small piece of masking tape and taping the kevlar rope together to stop it from fraying. I would recommend the REI climbing YouTube video for this: https://youtu.be/YHUv-oOMwRA ![Figure [DK]: Double Fisherman's Knot in Shock Cords](Images/DX3_Knot.jpg) Then I mixed up a batch of epoxy and using a popsicle stick, spread it in a fillet right below the fore ring. The end of my kevlar rope was a bit frayed, so I made sure to overlap the rope at the end before bringing it up through the hole in the ring. I made sure to also glue the rope to the hole. I would recommend doing the gluing step wearing gloves. I thought I could get away with wearing just the finger portion on my pointer finger in order to smooth down the rope, however, I still managed to get epoxy all over my hands and fingers (I recommend washing your hands thoroughly with soap and then again with hand sanitizer as between the soap and the rubbing alcohol, most of it was off my hands). I would also recommend pushing the rope into the hole using a popsicle stick as to not use your finger nails. ## Step 6 – Forward Section _Bulkhead Assembly_ – I dry fitted the bulkhead into the coupler tube and found that it did not fit, so I sanded down the outside a bit and checked the fit again. The initial bit of getting it into the tube required a small amount of force and then it slid perfectly. I fitted the bolt through the hole, added the washer, mixed a small amount of epoxy and added the nut. Then I epoxied a small amount of epoxy on the top of the nut creating a fillet with the bolt. Then I marked the approximate ⅛” with a sharpie, clamped the eyebolt to a table outside and dremeled the bolt off slightly above the mark. Having just dremeled through it, I went to pick up the excess and found it to be incredibly hot (and now I have a couple nice lines on my fingers from being burnt by threads — whoops). _Gluing the bulkhead into the coupler_ – The instructions say to mark a line ⅛” into the coupler. I struggled with this until I realized that the bulkhead itself was about ⅛”. So I inserted the bulkhead assembly and made the bulkhead flush with the top of the coupler and through the open end, traced a line around it. Then I mixed up some epoxy and spread it on the inside of the coupler. I pushed the assembly into the coupler (while turning of course). I had a hard time making it level. I had to keep pushing one corner further in or pulling another a little out so that it would set perpendicular to the coupler and behind the line. After this had set for approx 10 min, I mixed another batch of epoxy and made a fillet on the top of the bulkhead with the side of the coupler. I cut a finger off of a latex glove and smoothed the epoxy into the right shape with my gloved finger. I had to wipe the top of the coupler and the eyebolt free of epoxy. _Gluing the coupler to the forward section_ – I marked a line 2” from the edge of the open end of the coupler. I made 3 small lines equidistant from each other (so depending on which side was up after I had turned it into place, I still wouldn’t over shoot. I also did the same at the 1” point so I would know where to epoxy to. I then pre-folded a few paper towel pieces to have flat edges and then mixed up some epoxy and spread it evenly around the coupler with a popsicle stick. The directions call for a very thin amount of epoxy and I still put a little too much on. As I pushed and turned the coupler into the forward body, a few drops of epoxy fell off and onto the newspaper. I also had to quickly wipe away the excess from the coupler tube and joint where the forward body and the coupler tube met. _Cutting the nose cone_ – The instructions call for 1 9/16in from the shoulder of the nose cone. This is approximately just below the three lines. I measured this out with calipers and marked it with a silver sharpie. Then, using an X-Acto knife, I traced a light cut around the nose cone. This turned out to be harder than I thought to keep it level. I then pushed the blade through and cut along the line I traced. Then, using the 100 grit sandpaper, I sanded it down to the line I had made earlier. I recommend cutting a little far from the line and sanding to it. It is easier to take off material than to add it back. I then took the X-Acto knife and cut off the bit of cone that had accumulated from the sanding, leaving a nice square edge to the cone. _Holes payload and altimeter_ – I used a #52 drill bit to drill the six holes. To get the right placement of the holes, I used the method described in the instructions. I marked the forward body at ¾” from the top (the nose cone to the shoulder was 1.5”). Then using the paper I had marked with the three equidistant points, I market a vertical and a horizontal. Then I did the same at an inch from the bottom. Next, I made a small mark using a silver sharpie, vertically, across the nose cone and the forward body just in case it moved slightly after I drilled the holes. Next, I used a drill to drill the holes. I didn’t have a drill press or a vice, so I very carefully and slowly drilled it as vertically as I possibly could using my hand to hold it in place on the table. It worked better than expected. When drilling the holes through the forward body into the nose cone, it was a bit harder and required a (very) small amount of force. When it finally broke through, there were slivers of black plastic that came through. Next, using a 2-56 tap, I tapped the top three holes — 2 turns forward, ½ turn back (as per the youtube video I watched, which otherwise was completely unhelpful). After each hole I screwed in a screw into the newly tapped hole. ## Step 7 – Final Assembly _Inserting the motor mount assembly_ – First I dry fit the motor mount assembly into the body tube. It was a little hard to move in and out as there was a bit of epoxy on the fore centering ring from gluing the shock cord. I sanded the bit off and it went much more smoothly. This gluing process was far easier than I was expecting. I measured on the motor mount assembly from the motor retainer to the fore centering ring. For me this was about 7.5 in. I then marked this on my dowel and taped a 2x3/4in piece of sandpaper to the end of the dowel and sanded the inside of the tube to where the line was. I sanded probably an inch on either side of the 7.5 line as I figured that sanding a larger area was better than not sanding enough area. Then I taped three popsicle sticks together using the masking tape and marked on the sticks where approximately 7.5 in was. I screwed on the motor retainer and pulled the shock cord through the tube. Then I mixed up a batch of epoxy and spread it a little short of my line on the craft sticks (so the centering ring could push the epoxy into place). Then, moving quickly (great advisory, thank you). I pushed the motor retainer in halfway (ish) and spread another line of epoxy along the bottom of the body tube before slowly pushing and twisting the motor mount assembly into the body tube. I left a small amount of room between the bottom of the body tube and the top of the motor retainer as I wanted it to be able to screw and unscrew the motor retainer (maybe 1mm of room if not less). _Marking for launch lugs_ – As I didn’t have a length of angle iron, I used the piece of paper I had used earlier to make the marks for the screws and lined it up so that there was a mark exactly in the middle of the holes for the fins. Then, using a carpenter’s square, I drew a line quickly up the middle of the rocket (having my roommate hold the square in place and square with the bottom of the tube). This worked well, and the line is straight and almost perfectly in the center between the fins. _Gluing fins_ – I started out by dry fitting the fins and they in no way fit. I sanded each slot with a small piece of 100 grade sandpaper and then tried again. I had to do this a few times before I was reasonably certain I would be able to get the fin in without bending or breaking the cardboard in the process. I found the best method for sticking the fin in was to start at the back of the fin and rotate it into the slots. As I didn’t want to get the shock chord accidentally glued, I pulled it through the rocket body and tied it to the forward part of the body tube. Then I mixed up a batch of epoxy and applied a good amount of epoxy to the bottom of the fins (the root end of the fin tang) and inserted them into the slots. Working quickly, with a piece of paper towel, I cleaned up the little bit of epoxy that had spilled out and slid the fin jigs into place (one on each side of the fins and one by the front of the rocket. I then let this sit overnight. _Fin Fillets_ – The best way I found to do all of these steps was to put the nose cone and all three fin jigs on the rocket (see picture below). This allowed for room around the fins and the rocket didn’t tip back as easily as the weight of the nose cone acted as a counter weight. To draw the lines on the rocket, the best method I found was to shade an inch by inch square on a piece of newspaper with a non-mechanical pencil and then rub the edge of the spoon on that. I found that shading a bit with a dark colored pencil also helped for clarity of the line. I followed the instructions to draw the lines in. In the beginning I was a bit confused about which direction the spoon went to both draw the lines and fillet. Later in the instructions, it says to “pull along the fillet . . . with excess epoxy being gathered up by the spoon,” which I assumed meant that the concave portion of the spoon was facing the motor retainer. Note: I wore a mask for these steps as I didn’t want to inhale the microballoons. I measured out 5mL of microballoons into a mixing cup. Then in a separate mixing cup I mixed up 5mL of epoxy and added the microballoons to the mixture. This was very similar to adding flour to wet ingredients while baking. The first time, I added all of the microballoons at the same time and when I went to mix it in, a little puff of them escaped. For the next two mixes, I mixed them in a small amount at a time (approx 3 small amounts). The total 10mL of epoxy and microballoons was a good amount as it allowed for coverage of the fillets with a little bit left over. I found it incredibly satisfying to pull off the blue tape. ![Figure [DF]: The Almost-Finished Rocket in the Fin Jigs](Images/DX3_Almost_Complete.jpeg) _Launch lugs_ – Making sure to sand down the launch lugs and the rocket, I glued the launch lugs into place. Note: probably best to move the fin jig to the back of the fins if you want to keep it on, because I left it between the launch lugs and had to cut it off. Tying the shock cord: Follow the directions. This part was pretty easy. Attaching the chute: Is there instructions for this? ----