Tube magazine fed bolt action rifle—Cal .30-30 Winchester



Design of Tube Magazine Fed Bolt Action Rifle—Caliber .30-30 WinchesterET 493: Senior Design IAdvisor: Dr. Junkun MaInstructor: Dr. Chris Koutsougeras Student: Dallas Clayton DaigleTable of Contents. Abstract………………………………………………………..…2Background……………………………………………………....3Objectives…………………….....………………....………….....6Mechanism Description……………………………………….…8Breakdown of Designed Components and Methods…………......9Deliverables………………………………………………….......28Timeline……………………………………………………….....28[Tentative] Goals for Next Semester……….……………………30Conclusions……………………………………………………...30Abstract. The focus of this project is to design and model an action and components for a firearm chambered in .30-30 Winchester that is fed from a tubular magazine running under the barrel of the firearm, much like the popular Marlin 336. However, unlike the Marlin, this design utilizes a bolt action, rather than a lever action. This objective of this design is to eliminate the problems with the Marlin’s lever action design, namely the fact that it has an exposed hammer that needs to be manually depressed to decock it, which is a large safety concern. Using a bolt action instead of the lever action will allow the exposed hammer to be removed, and put in its place a safety mechanism that completely disengages the firing pin, creating an action that is much safer for shooters. The final design will consist of an internal mechanism designed around a bolt action that will reliably and safely move a round from the magazine to the headspace of the barrel while preventing another from leaving the magazine, fire this round, and extract and eject the spent round; repeating this cycle until the magazine is empty. Background. The Marlin 336 is a classic firearm that is beloved by many. However, it was designed in 1948, and it is based on a design from 1893, and is not without flaws. It is the one of the highest selling American firearms of all time, surpassed only by the Winchester Model 1894, which is also made for the .30-30 Winchester. This shows that there have been little to no significant design developments surrounding the heralded .30-30 Winchester cartridge in many years. The following design, when complete hopes to change that by eliminating some of the issues that the Marlin has. Fig 1. Marlin 336 diagram. Figure 1 shows the working parts of a Marlin 336. The mechanism’s lever action design utilizes an exposed hammer to strike the firing pin and discharge the round. This is fine, unless the user decides that they do not wish to fire upon their target. In which case, they must pull trigger, and with their thumb on the hammer, control it as it moves down into the safe position. This can be extremely dangerous for inexperienced shooters, as they may accidentally release the hammer, and cause a negligent discharge that could lead to property damage, or worse. It is also worth noting that figure 1 shows many moving parts, which in the event of a complete disassembly or repair, can prove problematic. Figure 2. A simple/standard bolt action. Figure 2 shows a diagram of a standard bolt action. Notice how the exposed hammer is removed and that the firing mechanism is contained within the bolt by having the firing pin under spring pressure. In this way, when the trigger is pulled, it releases the tension on the firing pin, which moves forward and strikes the primer on the round. This design allows for a safety mechanism that can totally disengage the trigger from the bolt, which is much safer than having to manually depress the hammer. The bolt action also allows for fewer moving parts inside the action’s housing/receiver, which leads to increased simplicity and reliability. Problems with bolt actions arise when rounds like the .30-30 Winchester are considered. As figure 3 shows, it is a rimmed cartridge, which often causes feed problems from the box or internal magazines commonly seen in bolt actions because the rim frequently catches on carriers on feed ramps. This is why tubular magazines are the commonplace for this round. Figure 3. Dimensions of the .30-30 Winchester. Objectives. The principal objective of this project is to design and develop a mechanical feeding/firing mechanism that can reliably and safely complete the firing ejecting feeding reloading cycle. The final mechanism needs to repeatedly perform this action under the many stresses applied by the different individual movements of metal parts within the action. The chamber/barrel/headspace needs to be designed to handle a working pressure of 42,000psi (290Mpa). It must also be able to handle variable or dynamic working pressures from rounds with a weight range of 125-180 grains, where 1 grain=1/7000th of 1lb. The magazine assembly will need to hold 5-7 rounds and be able to load them into the action singularly. The whole system should also be light and compact, with internals that are simple and reliable. It needs to be easily disassembled for cleaning, and need little maintenance to run smoothly. For this, the 493 semester, the main objective was to come up with an early prototype design and build a 3D model of it such that the design may be tested and simulated without having to build physical models. This is highly advantageous because it is unlikely for early prototype designs to work at all, let alone work well. The methods to which the model was constructed will be covered in section(s) 5 and onward. Initial research, discussion, and conceptualizing led to a design utilizing a round carrier sitting atop multiple leaf springs that would be compressed by the force of the magazine spring pushing the round onto the carrier. The carrier and round would then be pushed up by the leaf spring force, where the round could be picked up by the bolt and loaded into the headspace. In short—there is no way this design would work. It would be too complicated and rely too heavily on the magazine spring for it to be feasible. Through more discussion, researching, and conceptualizing, the following mechanism shown in figure 4 was decided to be the most suitable to meet the needs described previously. Figure 4 was created by modeling each individual part in the CAD software SolidWorks, then using the mate command in the assembly mode of SolidWorks to form the complete prototype model of the mechanism. Figure 4. A 3D model that was constructed in SolidWorks showing the outer assembly with visible hidden lines giving a view of the inner mechanism(s). Firgure 5. A 3D exploded assembly diagram showing the individual parts of the mechanism. 4. Mechanism Description. The mechanism shown is centered around the carrier, which is shown in figure 6. The carrier is the most important part of the entire system and has been designed to not only transport the cartridge from the magazine to a position where it can be picked up by the bolt, but also to act as the magazine retention device when the bolt is in its open most position, and to engage the secondary magazine retention when the bolt is fully closed. It is held in place by a pin that allows it to pivot upward and downward, as shown in figure 5. The mechanism functions as follows: When the bolt handle is rotated upward and the bolt is pulled back, a leaf spring applies an upward force on the carrier causing it to travel upward in an arc. This allows the magazine retention device to be disengaged into a rest position, and for a round to move backward onto the carrier. As the bolt continues to move backward, the carrier continues to move upward on its arc into its resting position, placing the new round in position to be picked up by the bolt when it travels forward. While the bolt is fully opened and the carrier is in its resting position, the feature on the bottom front of the carrier acts as a magazine retention device, effectively keeping other rounds from exiting the magazine during the charging cycle. As the bolt starts to travel forward, the round is moved forward into the headspace or into battery. As this forward motion happens, the bolt face runs along the ridge of the carrier, pushing it down into position where it re-engages the magazine retention device to prevent the magazine from emptying itself. 5. Breakdown of Designed Components and Methods. The following sub-sections will break down and discuss the design, function, dimensions, and placement within the mechanism of each individual component. All parts were built in the Computer Aided Design software SolidWorks. The construction of each part will be discussed in their respective sections. Before any model could be created however, the needed geometry had to be established. For many cases, it was an assumption based on the dimensions of the round, which are shown in figure 3. Since this is a new design, most of the dimensions were left to my discretion. Because of my being new to SolidWorks, I attempted to dimension all of the parts by hand before modeling. This proved to be a huge waste of valuable time and energy because as I discovered, the dimensions are almost constantly changing due to different changes in part geometry and understanding. It would have been a far better investment of time to just go into SolidWorks and dimension as I went. 5.1. The Carrier. As mentioned previously, the carrier is the most important part of the entire mechanism. Its leaf spring assisted pivoting allows it to act as transport for the round from the magazine to the headspace, act as the secondary magazine retention device when the bolt is open, and to engage the primary magazine retention device when the bolt is closed. The unique geometry of the carrier was specifically designed to meet those demands. Referencing figure 6, it can be observed that the carrier has several geometric features that allows it to be a multi-functional component of the mechanism. By designing the carrier in such a way, the entire mechanism can be simplistic, which aids in both reliability and disassembly. However, the uniqueness of the carrier could cause it to be difficult to manufacture initially, but that issue is inherent in most any design component that is newly designed or custom. Figure 6. 3D SolidWorks model of the round carrier. Note the geometric features that allow the carrier to serve multiple purposes, such as the ridge that allows the carrier to be forced downward by the forward motion of the bolt, and the lip on the bottom front that acts as the secondary magazine retention when the bolt is open. Before the carrier could be modeled, its travel arc needed to be calculated to establish the path that the carrier takes when pivoting. To do this, I needed to acquire the arc length of travel using the formula(s): S= θr. Or S=2r*π*θ360° Where S is Arc Length, θ is the travel angle in degrees, and r is the arc radius. Doing a quick trig calculation using a predetermined y travel of .645” and the following formula gives us our angle, which is then plugged into the formula above with the known radius of 3.5” to give our arc length. This arc helps establish the dimensions for the secondary magazine retention device. tan-1.645"3.5"= θ=10.44° S=2(3.5") * π * 10.44°360°= .6377” To build the carrier, a .66” by 1” square was drawn on a plane in the sketch mode of SolidWorks, then extruded 3.5” using the boss extrude command. This created a .66” by 1” by 3.5” block that represents what one might start with in a machine shop. The ability to create blocks of material and use the extrude cut command to cut out geometric features is highly advantageous because it allows the drafter or designer to create his or her models with the end fabricator in mind. Figure 7. The .66” by 1” by 3.5” block that was created in SolidWorks and used as the starting point for creating the carrier geometry. After creating the starting block, a new sketching plane was created on front face, and on it, a rectangle was drawn. This rectangle was .35” from the bottom, .508” wide, and it went through the top. The extrude cut command was then used to cut out this channel 2.65” inches deep into the block to create the channel for the round to ride in once it leaves the magazine. The carrier has a hole bored through the side, 2.85” from the front. This hole is where the retention pin will go to hold the carrier in place. This pin is also the support that allows the carrier to rotate around the center point of the pin, while preventing the carrier from moving in the X or Y direction. This is known as a pinned support in Strengths of Materials. Figure 8. The process used to create the channel for the round to be transported. Also note the pin hole. To create the ridge that moves the carrier down, a similar process was used. In this case, a sketch plane was created on the side of the carrier, and on it, the outline of the ridge was created, as shown in figure 9. Then, the extrude cut command was used to remove the material necessary to leave the finished geometry. Because having two ridges would prevent the carrier from moving up into the bolt path, one of them needed to be leveled off. To do this, another sketch plane was created, this time on the rear. A rectangle that contained all the material I wanted to remove was created, which in this case was the rightmost ridge when observing from the rear. Then, the extrude cut command was used to level off the right side of the carrier, leaving just the one ridge to control the location of the carrier relative to the bolt. Figure 9. The sketch plane showing the outline of the geometry used for the creation of the carrier ridges in SolidWorks. The same methodology was used to create the rest of the geometry: Create a plane, draw a sketch of the geometry, then boss extrude or cut extrude to add or remove material to create the needed geometry. The creation of the magazine retention lip can be observed in figure 10. Figure 10. Creation of the magazine retention lip or secondary magazine retention device in progress. Since the processes for creation of the geometry on subsequent parts were fundamentally the same, they will be touched on more briefly than in this section, unless they need to be expounded upon. 5.2. The Barrel. Initially, the intention was to completely design a new barrel. One that had the ideal amount of rifling, was the ideal thickness to remain safe under the round’s pressure, and was harmonically stable to achieve maximum accuracy. However, after doing the calculations for the needed barrel thickness and ideal rifling ratio, I discovered that the standard barrels available are already very close to the ideal case, so a custom job was no longer necessary. For redundancy purposes, I went ahead with my calculations, but only used the ones for the headspace pictured in figure 12, and not the entire barrel. That data is as follows. To find the minimum safe thickness of the barrel/headspace, I needed to use the thin-walled pressure vessel model. The maximum chamber pressure for the .30-30Win is 42ksi. This will be used as our internal pressure. The diameter of the .30-30Win is .308”. This will be used as the inner diameter. I chose a barrel length of 20in. Consulting the Statics and Strengths of Materials Textbook by Robert Mott, I decided that based on the load conditions, a design factor of 2 should be used. Understanding that stress equals force per unit area, I came to the conclusion that the stress (In this particular case, thin-wall Hoop Stress) will be its maximum at the headspace, and its minimum at the muzzle, so the headspace should be considered first. Through one of SELU’s faculty, Mrs. Amanda Brown, I was put in contact with a former metallurgist from Remington who informed me that the standard material for firearms purposes is ANSI 4140, so that was chosen as the material for this project. ANSI 4140 OQT900 has a yield stress of 173ksi, and with the chosen design factor of 2, this gives us the design stress: σd= 173ksi2=86.5ksi. Now that all the necessary data has been compiled, the necessary wall thickness and outer diameter can be found using the “gunsmithing version” of the thin-walled hoop stress equation, which is as follows: σ=(P)(Di)2(t) Where P is the pressure, Di is the inner diameter, and t is the wall thickness, which is the unknown in this case. After re-arranging, and inputting all data, the needed wall thickness can be found: t=(12.936 (ksi*in)86.5ksi* 12= .07477" = Wall Thickness. Now that we have the necessary wall thickness, we can find the outer diameter, or Do by doing the following calculation(s): Do= Di+2t=.308") + 2(.07477"= .45755" = Do To find the diameters and wall thickness at the muzzle, the same calculations must be done, but with the addition of Boyle’s Law (P1V1= P2V2) to find the equivalent pressure at the muzzle. After calculating the volumes and re-arranging, we get the pressure at the muzzle and can solve for the wall thickness and diamter at the muzzle. P2= P1V1V2= 42klbin2(.121in3)1.49in3=3.407ksi t= 1.05ksi*in86.5ksi= .012"= Wall thickness. Do= Di+2t= .308" + 2(.012") = .332" = Do The above calculations were perfomed for an ideal case where no friction exists, and the rifling lands and grooves are not present. The real values for the muzzle end would be much thicker. In fact, the outer diameter would be almost the same at any cross-section throughout the length of the barrel. Using another formula, the ideal rifling twist rate could be found. That formula is: Twist Rate= 3.5*V0.5*D2L Where V is the velocity, D is the round diameter, and L is the length of the round. When inputting the necessary parameters, the result is that the ideal twist rate is 1:12” or 1 full rotation every 12 inches, which is the standard for this round. This discovery, combined with the above calculations, led to the decision to use a standard barrel if this design were to ever go into production. Creating the 3D model of the headspace was relatively simple. After sketching half of the geometry around a center line, the revolve extrude command was used to extrude the sketch around the center line to build the model shown in figure 12. Figure 11. 2D representation of the headspace resulting from calculations and created in SolidWorks. Figure 12. 3D model of the headspace sectioned to show the inner geometry. Created in SolidWorks. 5.3. Magazine Retention Device. The magazine retention device is extremely important because it regulates the cartridges leaving the magazine. In this case it makes sure that only one cartridge leaves the magazine per loading cycle. It basically functions as a simple lever. When the round carrier comes down, the lip on the bottom from pushes down on one end of the device, which pushes the other end up as it rotates on its pin, blocking the exit of the magazine and preventing more rounds from leaving and causing feeding problems. To create its model, all that I needed to do was draw its outline on a sketch plane, and boss extrude it to create the main geometry. Then, after creating another sketch plane on the top, two rectangles were drawn on this plane and cut extruded to make the device fit in the groove in the magazine tube. Figure 13. 3D model of the magazine retention device.5.4. Tubular Magazine. After some online research, it was discovered that a standard tubular magazine for the .30-30Win had an outer diameter of .650” and an inner diameter of .560”. This made modeling the magazine a relatively easy task. A circle with the above dimensions was created and boss extruded to create the main body, and then a rectangle was drawn on the front plane and extrude cut was used to create the geometry for the magazine retention device. Noting figure 14, it can be observed that there is no clearly defined method to which it will be mounted in the final assembly. This is true for several of the parts in this design because it is not certain how they will be mounted when the design/assembly is finalized next semester. For the magazine itself, it will most likely be threaded into the receiver, but I will need to be establish what kind of geometry these threads will have, and I must learn how to construct them in SolidWorks. Figure 14. 3D model of the current magazine in SolidWorks. Once I created the tubular magazine and its functional components (Follower and End-Cap) I mated them into a mechanical assembly using the assembly mode of SolidWorks. This assembly is shown in figure 15. Also, once I started construction of the final assembly, this mechanical assembly was incorporated into that assembly as a sub-assembly. Figure 15. Magazine assembly completed in SolidWorks assembly mode with hidden lines showing the internals. 5.5. The Bolt. For this project, it is my intention to use a standard bolt because designing an operational bolt from scratch is a project that would take more than a year by itself. Because of cost and availability, I decided to design around the Mosin-Nagant bolt, which is pictured in figure 16. This bolt was chosen because I currently have two on hand, and acquiring a firing pin that can be made inert for legality/display purposes would be an easy and inexpensive task. However, this choice has its downsides. The design for this bolt is old, with its current iteration being produced since 1891. Because of this, no solid dimensions can be found anywhere (which is a problem that will come up again in section 5.6) for me to create a model of this bolt to use in the SolidWorks assembly. To get around this, I created a pseudo-model using the outer diameter of the bolt (which I was able to find) to use in the 3D model, which is shown in figure 17. This model would in no way be functional in the final design. This issue must be taken into account from here forward through the next stages of the project. Figure 16. The Mosin-Nagant bolt considered for the design. Figure 17. The inert pseudo-model of the bolt modeled for visual purposes in the assembly. 5.6. Receiver/Housing. In section 5.5 the choice to use the Nagant bolt was discussed. Since I decided to use that bolt, I initially wanted to use the standard receiver that went with it. Throughout a large portion of this semester, I was designing with that receiver in mind. However, when it became time to model everything, I ran into the same problem from section 5.5. The age of this design made it to where there were no accurate or legible dimensions to use to model the receiver. Because of that, I have been forced to design a new receiver/housing, which has been admittedly difficult considering the short time frame. After deciding what needs had to be met by the receiver, I designed a separate receiver for the bolt and housing for the mechanism, which were mated together in an early assembly model. This made me notice the glaring flaw that was present in this design from the beginning: The dimensions of the parts in the mechanism did not match the bolt/bolt receiver dimensions. This means that because the mechanism is wider than the clearance for the bolt in its receiver, this mechanism would not function. I am currently in the process of scaling everything in the mechanism down to meet the dimensions required by the bolt. I have also re-designed the receiver/housing to be a singular unit for ease of design and manufacturing. The improved design is shown in figure 18. Figure 18. SolidWorks 3D model of the one piece receiver/housing unit. 5.7. Other Hardware/Parts. It can be noted in almost all of the figures in this document that none of the springs needed to operate this design (Magazine Spring, Carrier Spring, Magazine Retention Spring, etc.) are present. This is because it is not yet certain what springs will be used because the parameters for them are not yet available. Before they can be discussed at length, their needed data must be established and the type of spring, as well whether they will need to be custom manufactured or not, must be established. That cannot be done until the design parameters are established. Another important aspect of this design that is not yet present is the method to which a system with this design would be loaded. While it will almost certainly be a loading gate of some kind, not unlike that of a shotgun, the full function of the loading mechanism must be established before the loading can be considered in a way that is beyond conceptual. I am also currently researching the possibility of putting a removable plate on the bottom of the receiver/housing that would aid the disassembly and cleaning process, but that cannot be done until the receiver/housing design is completely finalized. 6. Deliverables. 1. Conceptualize and complete rifle/mechanism design. (Complete) 2. Compile all necessary data. (Complete) 3. Complete all necessary calculations. (Complete) 4. Choose best material(s) based on calculations. (Complete) 5. Build assembly model prototype in SolidWorks. (Complete) 6. Complete analysis of all parts in COMSOL. (In Progress—Tentative) 7. Total build cost estimation. (In Progress—Tentative) 7. Timeline. Start Conceptualizing Idea/Potential Designs……………..January 20th-27th 2015Begin Learning SolidWorks……………………………….March 2nd 2015Complete Initial Design Concept/Drawing……………..…March 17th 2015Complete Proposal and Presentation………………………March 27th 2015Final Design and Calculations……………………...……...April 13th 2015Complete Part Drawings and Assembly Model……………May 5th 2015Complete Analysis on all Necessary Parts…...…………….May 5th 2015Final Report and Presentation.……………………………...May 8th 2015 All of my deliverables were completed in line with my timeline and proposed list of deliverables, with the exception of two, which are currently ongoing. The reason for deliverable number 6 being delayed/tentative is because I had initially wanted to do a COMSOL multi-physics analysis on all designed parts in this design. However, as I was designing I realized that because of Newton’s laws, most of the energy remaining from the ignition of the propellant in the round would be transferred through to the end user as recoil, creating very little stress within the parts in the internal mechanism. Most of the force the propellant ignition would be taken by the barrel and headspace. The rest would send the system pushing into the shoulder of the end user after the round leaves the barrel. But, since the barrel/headspace dimensions were calculated based on the acquired stresses, the COMSOL analysis ended up not being completely necessary at this stage of development. I will likely continue with the analysis next semester to back my hand calculations and theoretical conjectures. At this point, the total cost estimation was established to be nearly impossible to calculate. We know that cost of manufacture would be much higher for the first prototypes than for streamlined production because this is a new product/design, but it is impossible to tell by how much. For this semester, there was no cost because everything has been theoretical design and modeling. Depending on what kind of build is created next semester, the cost can be compiled for it, but I am not sure if any production cost can be established in the immediate future. However, the end goal for commercial cost would be <$600.00 to put the unit in the range of its competitors prices. 8. [Tentative] Goals for Next Semester.Finalize Fully Functional Design (Summer—Early Semester).Identify and Complete Hardware (Screws, Springs, etc.).Tolerance and Function Testing in SolidWorks.In-Depth Materials Science (Surface Hardness, Frictional Stresses, FEA, etc.).Further Calculation as Needed. COMSOL Analysis.[Tentative] Cost Analysis/Estimation.3D Printed Display Assembly Model. 9. Conclusions. Over the summer, I intend to research and learn more about the subjects used in this project such that they may be applied further as time progresses. I hope be working on my design more over the summer to update, troubleshoot, and repair with the goal of having a design that functions perfectly or near perfectly for the beginning of next semester. Once next semester starts, it is my intention to move more into the “micro” level of the design, whereas this semester I focused more on the “macro” aspects of the mechanism. More specifically, this semester has focused on designing a first attempt or early integration if my design. It has also focused on learning to use the tools needed for this sort of design. Next semester, however, I intend to look more at specifics instead of just the design as a whole. Understanding of how these parts work in conjunction with one another and the effects this has at their respective interfaces is key. Specifically, looking into things like frictional behavior at part interfaces and what that means for the material heat treatment or surface hardness. FEA is something that will be used/considered. I also intend to optimize the tolerances and dimensions to give everything a tight fit for maximum reliability and functionality. This will be done in part when trying to perfect the design over the summer, however. Next semester is also when the various hardware needed for assembly and functionality of this system will be analyzed and established. This refers to the various screws and bolts required for assembly, but also the coil and leaf springs needed for the mechanism to function. The end goal for next semester is to have the individual parts manufactured through additive manufacturing (3D Printing), then assemble them together and test and troubleshoot the entire mechanism. I would like to thank my advisor, Dr. Junkun Ma, for his counsel and encouragement over the course of this semester. I would also like to thank Mrs. Amanda Brown for her ongoing support, and for helping me in gathering materials data for this project. ................
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