Airbrakes Engineering Notebook
10/8/2023 Getting Started
Requirements of a solution:
- Brake
- Not add weight
- Simple
- Easy to deploy
- Easy to integrate
Ideas
Design | Pros | Cons |
Compact, Easier to integrateSimpleLess mass than hinge deploy | Potentially less surface area than hinged deploys | |
More potential surface area than slide deploys | Would require significant force to open against the airflowComplex mechanismPotentially more mass than slide deploysWould require significant structural alteration to the outside of the rocket | |
Compact, easy to integrateSimpleLess mass than hinge deploy | Potentially less SA than hinge deploys | |
Not fighting drag, drag assists deploymentIncreased surface area compared to slide deploys | Could accidentally deploy, depending on implementationComplex mechanismPotentially more mass than slide deploysLots of alteration to outside of rocket |
Calculations:
Speed of the rocket: 1300 ft/s
Force on 14 in2 of air brakes: 866 N
10/15/2023
Goals
- Sketch multiple mechanism designs
- Try to maximize and then calculate how much area each can produce for drag
- Try to calculate how much torque is needed to actuate the system → do we need servo or motor? Does a servo/motor of reasonable size exist that can produce your needed torque (find where we could purchase said servo/motor)?
Servo motor SG90 Datasheet: http://www.ee.ic.ac.uk/pcheung/teaching/DE1_EE/stores/sg90_datasheet.pdf
Torque of servo: 2.170 lb in
10/22/23
Drawings and CAD
Slight change in design of current model to expand surface area
Now 2 levels of brakes that leave the rocket in 4 total leaves
Cad drawings started on the leafs, the connector and the base plate
Plan to complete CAD drawings and 3D print before next meeting
11/5/2023
Larger holes on connectors (3/32) - amber
Countersink under the leaves (3/16) - nicole
Change the leaf shape and add area (.625”), remove space between the inner part of the leaf and servo mount - pari
Decrease shaft cross section size (tolerance) - alex
Locknuts
Remove gap between leaves and the servo mount on the side, remove lip on servo mount - enrique
11/16/2023
5.49 in^2 (each leaf)
- 2.95 in width
- 1.86 in length
7.44 in^2 (each leaf)
- 4 in width
- Same length
11/19
Adding a top base plate (which are the rails)
Add something plastic for the leaves to sit on to reduce friction
Make leaves longer/arms shorter
Change the shaft to an octagon/hexagon
Edit base plate to accommodate one set of leaves instead of 2
1.75 in^3 →volume of leaf
11/30
Changing entire design basically
- Metal hex shaft (buying)
- New servo (1500 oz-in)
- Need 1100 oz-in
- Change connector width
- ¼ in thick
- Also add spacers between connectors
- Hexagonal hole
- Add plastic tray (x2)
- Screwed into base (threaded screws) w countersinks
- Add holder
- Make walls thinner (⅛ in)
- Servo Bulkhead
- ~ ⅜ in thick
- Have cutouts so it’s not as heavy
- Servo goes on top
- Leaves
- ⅛ in off the top lip
CAD all parts from scratch
- Due by sunday :)
PUT EVERYTHING IN “NEW AIRBRAKES” FOLDER
- Servo Bulkhead (Pari)
- Cylinder (Alex)
- Part beneath bulkhead
- Tray (Olivia)
- Frame (Juan)
- Leaves (Olivia)
- 3.5x2.5x.125
- Arms (width) (Nicole)
- 1/8 in width
- + Change middle connector to a hex shape
- New shaft (Nicole)
- Find shaft
- 2.77 in
12/03
Final area of leaves: 3.5 in x 1.57 in
5.49 in^2 each leaf
21.9 in^2 total
Spacers + tray that leaves slide in
PLA (3d print)
Servo
HS-1005SGT Servo
Frame, leaves, servo mount, everything else
Aluminum (machine)
6061
Cost breakdown:
- Servo
- $479.99 (servocity)
- Servo horn (servocity)
- Sonic hub (servocity)
https://www.mcmaster.com/products/hex-shafts/material~aluminum-2/
- Shaft (⅜ in 6061 Hex Bar)
- Density of aluminum
- .0975 lbs/in^3
Dimensions:
- Middle Connector (x4): 1.2in x 0.2in x 0.13in
- Servo Mount: 0.25in x 6in
- Hex Connector (x2): 2.3in x 0.67in x 0.13in
- Frame (x2): 6in x 1.25in
- Leaves (x4): 3in x 3.5in x 0.25in
Materials:
- Servo Mount + 2 Frames = 2.75in x 6in
- Aluminum Cylinder = 3in(height) x 6in(diameter) ($143.10)
- 4 Middle Connectors + 2 Hex Connectors = .51in^3
- Aluminum Sheet = 3in x 3in x 0.125in = 1.125in^3 ($40.79)
- Tight tolerance
- 4 Leaves = 10.5in^3
- Aluminum Sheet = 8in x 8in x 0.25in = 16in^3 ($27.17)
- Oversized thickness
1/8/2024
KERF List
Servo Mount: make screw holes larger - done
Aluminum Spacer: make screw holes larger - Done - 🦑
Leaves: make leaves vertically thinner (extruded part does not have to be vertically thinner) - Done, all screw-holes (larger) - Done, reduce width of leaf and extruded part - Done, bearing hole (larger) - Done - 🦑
Cylinder - Outside Casing: make screw holes larger - Done - 🦑
Frame: all screw-holes (larger), bearing hole (larger) - done
Hex Connector Middle: make hex bigger
Tray: reduce the wall thickness, reduce the width, reduce the height, bearing hole (larger) - done
The servo doesn't need to be as strong for the sustainer
Make a second airbrake with a new servo mount