Reference / Paper · 2015
Peak of Flight #406: Gluing In Engine Mounts
Apogee Components' Peak of Flight newsletter, issue 406 (2015-12-15).
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- apogee-components
- model-rocketry
Reference / Paper · 2015
Apogee Components' Peak of Flight newsletter, issue 406 (2015-12-15).
Apogee Components' Peak of Flight newsletter, issue 406 (2015-12-15).
ISSUE 406 DEC 15 2015 IN THIS ISSUE Engine Mount Installation https://www.apogeerockets.com/Rocket_Kits/Skill_Level_2_Kits/Quest_Courier_Egg-Lofting_Rocket Engine Mount Installation By Tim Van Milligan 2.25” Since I’ve been around (12.7mm). To get this position, 1/2” a long time in model rocketI cut the slot for the front tang ry, I’ve seen a lot of poorly of the hook at 2-1/4” (57.2mm) constructed rockets. Typifrom the rear of the tube. cally it is the fins that aren’t Figure 1 shows the example glued on properly, but I’ve dimensions for the engine tube 1/2” seen a fair number of examthat I use when I design a new ples where the engine mount rocket. wasn’t glued into the tube Once the engine mount is correctly. That is what I want assembled and all the glue has to cover in this article. dried, it is ready to go into the 1/4” The engine mount is a main body tube of the rocket. collection of parts that center Figure 1: Engine tube dimensions example Step 1: I like the engine the rocket engine within the tube to stick out the back end of the rocket a little tube of the model, and hold that engine in place bit. The reason is that I want to make sure there so that it can’t shift either forward or backward. is enough room for the engine hook to be bent It typically consists of an engine mount tube, backwards and it doesn’t interfere with the end two centering rings, and some sort of engine of the body tube. I like to have a minimum of 1/4” retention device. For small model rockets, that (6.4mm) of the engine mount tube sticking out of engine retention device is an engine hook along the rear of the main rocket body tube. The furwith an engine block that is glued in front of the ther it sticks out, the easier it is to bend back the rocket motor. engine hook with your thumb. But too far out, and This article assumes that the engine mount it just increases the drag on the model. Mark the is built, but is not installed in the rocket tube “stick-out” length on the engine tube as shown in itself. The only thing that I would mention here Figure 2. is that before you build the engine mount, Step 2: Lay the engine mount next to the make sure that you position the aft centering main body tube. Position it so that the marked ring far enough from the back end of the enline (for the gine mount tube so that you can easily bend stick-out length) the engine hook upward. I’ve seen a lot of kids is at the aft end build rockets where they put that aft ring on the of the body tube back of the engine mount tube flush with the of the rocket. edge. Since it holds the engine hook in place, What we want to it doesn’t really have enough room to allow the visualize here is hook to be bent upward to allow the rocket mowhere the positor to slide into the tube. tion of the rings I typically put that aft ring no more than will be inside of 1/2” (12.7mm) from the end of the tube. I also the body tube. position the engine hook so that the back end This is where the of the hook will hang out the rear end by 1/2” glue needs to go when the rocket is assembled. Figure 2: Mark the “stick-out” length About this Newsletter You can subscribe to receive this e-zine FREE at the Apogee Components website www.ApogeeComponents.com, or by clicking the link here Newsletter Sign-Up Page 2 Newsletter Staff Continued on page 3 Writer: Tim Van Milligan Layout/CoverArtist: Chris Duran Proofreader: Michelle Mason Issue 406 I December 15th 2015 Engine Mount Installation Continued from page 2 I like to put the line a little bit on the short side, because I want to make sure that the forward ring on the engine mount will slide through the glue line. Step 3: Get a wood dowel to help you spread glue deep inside the rocket. I like to premark the dowel with a pen to show how deep the dowel needs to be inserted into the rocket to place the line of glue (see Figure 3). Figure 3: Pre-marked dowel Step 4: Squeeze some glue on the tip of the wood dowel. I like to spin the dowel in my fingers to keep the glue from sagging and dropping onto the table. An alternative to using a dowel is to use a Q-tip. My good friend Chris Michielssen of Odd’l Rockets likes to use a Q-tip, probably because it acts like a sponge and can hold more glue than what you can get on a wood dowel. For me, I’d probably use them if I had more of them lying near my work table (see Figure 4). With the glue on the tip of the dowel, carefully make a line of glue around the inside perimeter of the tube. Use the mark on the dowel to know how far to insert it into the tube. If you slide the engine mount at this point into the glue, you won’t have any glue on the back ring. A lot of younger modelers will put glue on the back ring of the engine mount assembly, and simply slide the whole thing into the tube. But what happens is that the edge of the tube simply wipes off the glue as it goes into the tube, and there is no fillet in front of the ring to give it strength. At this point, only the front ring would be grabbing and holding the engine mount in place. You need glue on both rings for a strong glue joint. Step 5: Once the ring of glue is around the inside of the tube, slide the engine mount partially into the tube. But not too far that the front ring gets into the glue you put deep in the tube (See Figure 4). If you do, you’ll often end up with a stuck engine mount tube because the glue “grabbed” too quickly. And then you have to wiggle it back and forth to get it unstuck. If you didn’t allow the glue to dry on the rings attached to the engine mount tube, you might have a worse situation where they come off the tube Figure 4: Slowly inserting engine mount Continued on page 4 https://www.apogeerockets.com/Christmas_at_Apogee Page 3 Issue 406 I December 15th 2015 Engine Mount Installation Continued from page 3 and get stuck inside the rocket. This nightmare situation has happened to me plenty of times when I was in a hurry to get the rocket built. So ideally, you want to stop sliding the engine mount tube before it gets to the ring of glue inside the rocket. This is why it is also important to make sure to be neat when you apply the glue ring in the first place. If there were any drips inside the tube while you created the ring of glue, you could hang up on them too. Step 6: Tilt the engine mount to one side. The purpose of tilting it to one side is so that you can use a small dowel to apply a second line of glue inside the body tube of the rocket. This can be seen in Figure 5. For small diameter rocket, like 24mm diameter (BT-50 size) and smaller, you’ll need a smaller diameter dowel. This step is kind of tricky, as you have to keep tilting the engine mount in different directions until you can make a complete ring of glue just inside the tube. You do have to work fairly fast, because the previous line of Figure 5: Applying second line of glue with a glue is starting to evaporate and smaller dowel the moisture in the glue is being wicked into the fibers of the paper body tube. What this means is that the first glue ring is getting thick the longer you have it sitting there. If it gets too thick, it will grab and freeze the part in place too soon as you begin sliding the engine mount into the tube. I like to make that forward ring a little heavier Figure 6: Spreading the second ring of glue with glue because of this. I want to keep it fairly runny so that it lubricates the inside of the tube as you slide the engine mount forward. Figure 6 shows what the second ring of glue should look like when you get it done. Step 7: Slide the engine mount forward so that both rings are in the middle of the glue lines. While you won’t see this because your tube is not see-through, Figure 7 shows what the glue joints should look like. Notice that there is a built-up line of glue in front of both of the centering rings. This is what you want, as it means that Figure 7: Once the engine mount is the parts will be completely inserted Continued on page 6 www.ApogeeRockets.com/Rocket_Kits/Scale_Rockets Page 4 Issue 406 I December 15th 2015 Page 5 Issue 406 I December 15th 2015 Engine Mount Installation From that, I got this idea of changing the front ring on the the strongest. engine mount tube. I thought To be honest, applying the glue that if it was made with some like this does take some practice. teeth in it, you could slide the It can be fairly messy as the glue whole assembly in straight withdrips off of the wood dowel as you out having to tilt it over to one are trying to install it. The process side (see Figure 8). is worse on smaller diameter tubes What happens when you too, because you can’t tilt the have a toothed front ring is tube far enough over to use a big that it doesn’t push all the glue glue-laden dowel into the tube. If from the aft line of glue. It kind you have to use a small dowel, you of glides through it and leaves just can’t apply much glue at any enough in place for the aft ring Figure 9: Plenty of glue slips past for the one time. to be glued in place. You can next ring Simplifying the Process see this in Figure 9. As I was writing this article, I was trying to In Figure 10, where both rings are in the corthink of a way to simply the process. Especially rect position in the tube, you can see that there for younger modelers that don’t have their fine is glue pushed up in front of both the forward and motor skills developed yet. It is hard to manipaft rings. This in ulate a dowel when you have too many thumbs an indication of a - if you know what I mean. good glue joint. The modeler can’t make both rings of glue Using this inside the tube before sliding the engine mount toothed ring is no in because the front ring would just push all the different from a glue forward. And then the normal ring. It is back ring wouldn’t have applied the same enough glue on it to hold it way to the enin place. gine mount tube as a solid ring. But that gave me an The big advanidea. What if you could aptage, as menply both rings of glue inside tioned previously, the tube before you put the Figure 10: A good glue joint has glue in Figure 8: Toothed front ring engine mount in? Wouldn’t is that you can front of both the forward and aft rings design make both lines that be simpler? Continued on page 7 Continued from page 4 Rocket Jewelry • The Perfect Launch-Range Accessory • Subtle, Tasteful, Fashionable & Distinctive • Makes A Great Gift for Family and Friends • Display Your Passion for Rocketry https://www.apogeerockets.com/Wearables Page 6 Issue 406 I December 15th 2015 Engine Mount Installation Continued from page 6 of glue inside the perimeter of the tube at the same time. This speeds things up, and minimizes the mess inside the tube. If you would like to try out these new toothed centering rings on your own models, we are now selling them at Apogee Components at: https://www.apogeerockets.com/Building-Supplies/Centering-Rings/For-24mm-Body-Tubes/ Forward-Grooved-Centering-Ring-18-24. As mentioned, these would be good rings to use if you are working with younger modelers and you want to speed up the assembly process. It should be noted that the back ring still has to be a solid ring, and not toothed like the front one. The reason is that because of the gaps in the front ring, some of the pressure from the ejection charge will want to go through the tooth channels and try to get out the back of the tube instead of pushing off the nose cone. The back ring has to be solid so that it can seal off the tube end and keep all the ejection pressure going out the front end. If your rocket has any opening in the rear centering ring, then the front ring must be solid. An example of this is the EggStorminator rocket https://www.apogeerockets.com/Rocket-Kits/ Skill-Level-4-Model-Rocket-Kits/EggStorminator kit with holes in the back ring (see Figure 11). In this situation, the engine mount is assembled differently. The back ring is not glued onto the engine mount tube until later in the sequence of construction. About the Author Tim Van Milligan (a.k.a. “Mr. Rocket”) is a real rocket scientist who likes helping out other rocketeers. Before he started writing articles and books about rocketry, he worked on the Delta II rocket that launched satellites into orbit. He has a B.S. in Aeronautical Engineering from Embry- Riddle Aeronautical University in Daytona Beach, Florida, and has worked toward a M.S. in Space Technology from the Florida Institute of Technology in Melbourne, Florida. Currently, he is the owner of Apogee Components (http:// www.apogeerockets.com) and the curator of the rocketry education web site: http://www.apogeerockets.com/educa- tion/. He is also the author of the books: “Model Rocket Design and Construction,” “69 Simple Science Fair Projects with Model Rockets: Aeronautics” and publisher of a FREE e-zine newsletter about model rockets. Figure 11: EggStorminator Aft End Think of the convenience of getting everything to professionally install your dual-deployment or other electronic payload into a e-bay of your rocket! Includes: nylon standoffs, screws & nuts, wire, push-switch, drill & tap, ejection charge cannisters, barrier strips, wire ties, and step-bystep DVD instructions. https://www.apogeerockets.com/Electronics_Payloads/Electronics_Accessories/Electronics_Mounting_Kit Page 7 www.ApogeeRockets.com Electronics Hardware Installation Kit Issue 406 I December 15th 2015