Optimized Riflescope Mount

The goal of this project is to create a lightweight riflescope mount that comparable in strength and production cost to an existing model made by Nightforce. To do this, a twofold approach was taken: First, a simulated model of the mount and forces acting on it were created to identify high stress regions during firing, and how they can be mitigated. Second, prototypes of three different material mount concepts (Magnesium AZ61A, Al 2024, and Al 7068) were fabricated, and tested to client standards as a deliverable by the end of the spring semester.F

Problem Definition
=Background= Nightforce desires an in-depth analysis of the economic and material optimality of their Ultramount riflescope. They requested the development of a lightweight model that would meet or exceed current Ultramount specifications, in addition to maintaining current production costs. The client specified their current model’s alloy used for production, in addition to strength, spatial, mass, and durability requirements at the first team/client meeting. Military-specifications, previous live-fire testing, etc. were also discussed. Required files were given to the team to begin work on the simulation of the mount.

=Deliverables= •	Create a force testing math model, that would accurately summarize the rapid impulse effects on the dynamics of the mount.

•	Implement math model into mount design, and use for geometric optimization. Ideally, this will be used for not only the Ultramount, but for other products in the future

•	Deliver final prototypes with specs including: Improvements in stress distribution via displacement testing on the original, and comparing to the same force applied on prototypes, weight reduction values, and designated material necessary for said prototype

=Specifications= The new prototype mount was qualified upon the following specs •	Corrosion resistance in saltwater environments •	Capable of surviving within a temperature range between –40 – 225 °F •	Capable of surviving recoil of 10,000 rounds on a corresponding rifle •	Must look visually appealing •	Will maintain position after a standard 5-foot drop test. •	Must be lighter than 104.6 grams •	Cost effective compared to current model

=Design Considerations=

Material Selection
A materials candidacy study was conducted based upon the above specs. Metal alloys, polymers, and composites were all considered. Polymers, while lightweight and strong in some cases, would fail in terms of cost effectivity and optimal temperature range. This eliminated all but carbon fiber reinforced polymers. Other composites considered were glass fiber reinforced polymers. Over 50 Al-alloys were examined for comparable properties, but only a handful possessed the strength and low density to continue in the selection process. Magnesium and Titanium alloys were also considered. After checking the corrosion resistance, and temperature range, each material was indexed according to its Young’s modulus (E), yield strength, cost per unit volume, and density. The results and most attractive candidates based upon the indexes were shared with the client and team, allowing for further steps to be taken in acquiring quotes for the various materials and taking note of the bulk price for each material.

Over the course of the winter, over 15 companies were quoted for material prices, which provide the range of values given below.

The large range for magnesium alloys is due to national and international trade. Lower prices can be obtained internationally for AZ61A, but due to increased border cautions due to spreading illness, it was not purchased. All pricing given above has shipping,handling, and import cost accounted for.

Finally, a validation study for corrosion and hard coating of materials was performed. Al-7068 would hard coat quite similarly to that of 7075, 2024 would have issues hard coating due to its high copper content (3-4 wt%), and Mg-AZ61A has hard coating capability, but would result in a thinner coat overall, and would be less effective. Salt spray testing to MIL-A 8625 specifications would need to be performed on hard coated Mg-alloy prototypes in order to validate this for future use. Hard coating any of these alloys in bulk (4000+ parts) would fall in the ball park of $500/batch.

Data Analysis and Prototype Development
After 80 live fire recordings, accumulating 1.6-1.92 million points of acceleration and force data on the front and rear of the rifle scope mount and rail, peak forces were taken from each shot, and applied into modeling software to predict where high stress regions may occur in the mount. Based on this, a worst possible scenario simulation was ran, enacting the highest stresses upon the mount. From there, mount geometry could be optimized.

Below is the finite element analysis used to apply force in the simulated scope (assuming clamping points as fixed positions).

The following prototypes were developed via different approaches. They are shown in the table below. =Project Learning=

Proof of Concept
In order to prove our assumption of a simple F=m*a relationship enacting on the mount, a proof of concept (PoC) was needed to be designed. This took several iterations, all trying to show that a short, sharp force enacting on a simple geometry would be able to relate a math model to the mount as a whole. Originally, a stool and a hammer were attached and dropped from a set height to get repeatability in results, but to get a more accurate angular velocity, and striking angle in general, a secondary box PoC was developed. Both of which are shown below.

Simulation Stress Outputs
While acquiring a realistic math model, simulation with the understanding currently known by the team was performed, changing independent parameters, with the intent of getting realistic peak strain values in the mount (≤ yield strength of the material). Despite manipulating force application regions, material properties, =Final Design=

=Validation= Research is validated through in depth literature research given in the references below, and the prototype is validated via a standard 5-foot drop test, in which it must survive without flaw. =Team Members=

=Additional Documentation=

Project Schedule



Meeting Minutes































Presentations



Client Interview