Airframe Design
- Alison Thompson
- Evan Janakievski
- Smile Khatri
- Thushanth Parameswaran
Big Project | Project | Project Manager |
|---|---|---|
Fixed Wing | Frame | S24: @Alison Thompson F24: @Evan Janakievski |
Task Description
The goal of this task is to design the base frame of the new fixed-wing aircraft, essentially this is the structure which will support all of the main components and allow for different fuselage and wing options to be mounted to it.
We don’t already have a set idea or particular direction for this task, but rather would like to have several people help brainstorm ideas and discuss what makes the most sense for us to move forward with.
Discussions to be had on particular direction for this at mech meetings
Please read:
And attend Fixed Wing Syncs: https://discord.com/events/776618956638388305/1252954173868216404
Constraints
Constraints | Written By | Append Date |
|---|---|---|
Must have the ability to change out fuselage, tail, and wings | @Alison Thompson | Jun 23, 2024 |
Permanent mounting location for:
I suggest a standard 30.5mm x 30.5mm M3 mounting pattern on the frame so we can account for any location of these components. Some will have specific requirements and their own mounting pattern, ie the Pixhawk but generally we will have cases made for things to comply with the pattern. Specs and requirements on the components are here: Fixed Wing 2025 | Electronics System Diagram The focus here is on having the space to mount the components, others will make the cases to allow for this. | @Alison Thompson | Jun 23, 2024 |
Full airframe needs to be under 5kg, so frame should be <1.5kg with no electronics | @Alison Thompson | Jun 23, 2024 |
Assignees
Assignee | Asana Task | Date |
|---|---|---|
@Evan Janakievski | link to asana task assigned | Date assigned |
@Thushanth Parameswaran |
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@Divit Gawri |
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Task Progression/Updates
Author: @Alison Thompson Date: Jun 23, 2024
Initial Ideas
16th wall alumunium frame with some sort of panel in the middle for electronics?
Author: @Alison Thompson Date: Jul 2, 2024
Concept Sketch
Author: @Thushanth Parameswaran Date: Jul 3, 2024
Source: https://www.boldmethod.com/learn-to-fly/performance/what-effect-does-center-of-gravity-have-on-your-airplane-performance/ , From The Ground up book
Important note:- The distance between CL and CG is exaggerated in drawing below. In real distance be around 3 cm.
When creating a frame, it is important to ensure that the center of Mass is in front of the Center of lift (CL) because we have a net zero moment using the downforce from the horizontal stabilizer. As seen in the Picture below. This means all electronic component needs to be mounted left of the CL. Having the Center Mass close to CL will allow us to have a short tail because Moment = Force x Distance, the moment created by the weight will be less since the distance is small from CL. Remember that CL is not a fixed point, unlike CG. The amount of lift created control is the Angle of Attack (AoA). As AoA increases ( as the aircraft Pitches up) the CL moves forward and moves back as you pitch down the aircraft. At a certain AoA, Max Lift force will be achieved as seen in Image 2 below. it is important to ensure CG is always forward of CL even at Critical Angle of Attack (which is the AoA just right before Stall and AoA where max lift is produced).
This is my Concept based on initial research.
Author: @Evan Janakievski Date: Jul 28, 2024
Notes from meeting July 25, 2024
Adjust how wingspar mounts to frame, use a “crush bar”
Use channel as material for wingspar to reduce weight
Add motor mount with camera built in attached to it
Think about how fuselage will mount to the frame
Decrease size of the plate for minimum required to fit all electrical components
Extend battery shelf so they are not hanging off
Author: @Alison Thompson Date: Aug 17, 2024
CAD review notes:
Looking good! Some suggestions:
Look at aluminum circular shaft for the stand offs in the corners of the wing mounting plate instead of the big blocks. You can tap these (think like the PEEK standoffs on Peggy and similar to what you have holding up the batteries)
Aluminum > Peek here bc Peek is brittle and shears (saw this w/ peggy peek standoffs that were shattered)
I would extend top gusset to the same width of bottom plate (extend farther along wingspar) , and make bottom plate a similar shape (wider to accommodate bolts for stand offs) to cut out some material
Author: @Evan Janakievski Date: Sep 8, 2024
Following deflection calculations for 1/2” box tube aluminum for 25 N (half of current lift force needed for cruising) and 68 N (calculated for just under half of lift force on take off), decided to update size of box tube to 3/4”
Deflection was up to 2 cm
Repeating tests (changed 68 N to 80 N for greater safety margin) with 3/4” box tube, deflection decreased to 2 mm
Files for sims on PDM in Fixed Wing → Wings
Author: @Evan Janakievski Date: Sep 20, 2024
Removed electronics (excluding batteries as they are part of the COG calculations) from frame model and will add to main
Materials needing to order from EMS
14 x 6 in. - 8 GA (0.1285 in) Aluminum Plate → main plate
11 x 6 in. - 8 GA Aluminum Plate → battery plate
2.125 in x .375 Round Aluminum - X 9 → standoffs
27 in. 3/4 Box Tube Aluminum - X 2 → wing spar
26 in 3/4 Box Tube Aluminum → tail boom
6 x 2 in. - 8GA Aluminum Palte → gussets
Author: @Evan Janakievski Date: Nov 3, 2024
Adjusted standoffs to be 5/16 in. instead of 3/8 in.
Shortened motor mount plates to reduce weight
Need to check what max gauge could be bent in student shop
Author: @Evan Janakievski Date: Nov 7, 2024
Materials needing to order from EMS
14 x 6 in. - 8 GA (0.1285 in) Aluminum Plate → main plate
11 x 3.25 in. - 8 GA Aluminum Plate → battery plate
2.125 in x 5/16 Round Aluminum - X 9 → standoffs
27 in. 3/4 Box Tube Aluminum - X 2 → wing spar
26 in 3/4 Box Tube Aluminum → tail boom
6 x 2 in. - 8GA Aluminum Plate → gussets
3 x 2.25 14 GA Aluminum Plate X 2 → motor mounts