Prokura Innovations

structure design of a fuselage| size of the fuselage

drone design
Figure 1: Fuselage Structure and Assembly of Wing in Fuselage

While building a fuselage structure, first of all, space requirements and load requirements are to be fulfilled. The size of the fuselage structure also mainly depends upon the size of the payload, size of the battery, CG balance, etc. Fuselage and wings are easily assembled and disassembled using a quick-release axle.

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Figure 2: Quick Release Axle on the fuselage
drone design
Figure 3: Stress Distribution in fuselage due to internal loads

Stress Analysis due to impact on the tail

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Figure 4: Stress Analysis due to impact on Tail

The analysis result shows that there would be maximum stress on Quick Release Axle joining Fuselage and Wing.

Drone Interior Plan

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Figure 5: Drone Interior Plan

Some of the interior plans like the assembly of wing and fuselage, dimension of payload box, and dimension of fuselage according to payload box, the position of the battery, and electronics components have almost been set.  Figure 5 shows an updated plan of the drone.

Two Quick Release Axles support the leading edge part of the wing with fuselage. The trailing part of the wing gets attached to the fuselage from a sliding motion. So the procedure to install wing on fuselage would be to put a wing on a fuselage, then slide it horizontally forward that locks the trailing part of the wing with the fuselage, then put a battery cover that includes electronics components as shown in figure 5, then insert the Quick Release Axle, tighten a Quick Release Axle and the wing is fixed with fuselage structure.

Considering the size of blood packet to be of 110mm * 110 mm, the thickness of ice pack to be 10mm which is for maintenance of blood temperature and thickness of bubble wrap to be 20mm which is for insulation and reduction of impact, the size of payload box is estimated to be 175mm * 175mm which also includes the thickness of the payload box. The height of the payload box depends upon the thickness of the blood packet and the number of blood packets that drone can carry. The height of the payload box is yet to be defined. Then on fuselage structure, 195mm of space is separated as a width of fuselage excluding wall thickness, and 243mm of space is separated as a length for payload that includes 175mm of payload box, 50mm of the locking mechanism and 18mm of door opening mechanism.

The Quick Release Axle can be defined into three modes i.e. tight mode, loose mode, and dissemble mode. For a normal time, the Quick Release Axle remains in a tight mode which binds the wing, fuselage, and battery cap with electronics components strongly. To remove or insert a battery in a drone, the Quick Release Axle remains in the loose mode so that the battery cap can be easily rotated as shown in figure 6.

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Figure 6: Rotation of Battery Cap

The dissemble mode of Quick Release Axle facilitates the disassembly of the wing and battery cap from the fuselage. 

Shifting from Payload Box Locking System to Door Locking System

drone design
Figure 7: Illustration Of door locking mechanism

Previously, we used to lock a payload and there won’t remain any pressure from the payload on the door. The payload box was also used to be made from plywood as a payload box locking mechanism requires a rigidity of box. But the box was somehow expensive and time consuming to manufacture. So the decision was made to manufacture a payload box from cheap cardboard which would also be easy to manufacture. But that payload box made from cardboard would not be rigid. The previously designed Locking mechanism would not work on this payload box made from cardboard. A new and similar mechanism was designed as shown in figure 7. The working effectiveness of the mechanism is yet to be discovered.

 

Questions

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It has been proposed to build a Quick Release Axle from 3D printing so that it could easily bear stress during the normal flight but has to break during a crash so that the minimum damage occurs in the fuselage structure. The proposal was also made due to its simplicity, easiness, and accuracy of manufacturing from 3D printing. So the question lies on, should we make the joints (that involve the Quick Release Axle) very strong using metals or should we make our joints that could not hold the crash which may prevent other parts like the wing and fuselage?

Note:-The impact analysis on the tail shows that there would be maximum stress on the quick release axle. Our doubt is that if we build a Quick Release Axle from metal, the metal would bear that stress but instead, it would transfer stress to the wall of the fuselage which would risk the destruction of the fuselage.

drone design

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Description of Author

  • Rupesh Bade Shrestha is a Mechanical Design Engineer for Drones at Prokura Innovations, who loves working with Machines, Mechanisms, and Manufacturing. He received his Bachelor's in Industrial Engineering from IOE Thapathali Campus in 2019. Shrestha is proficient with several engineering tools such as Ansys, Matlab, Catia, and Solidworks. He is also enthusiastic about and excellent in conducting research and problem-solving. In his free time, he loves learning something new, singing, playing the guitar, and enjoying with his friends and family. #Drones #MechanicalDesign #Innovations #Research

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