Houston - OFS Mount

Task Description

OFS stands for Optical Flow Sensor. The goal of this task is to design a mount for the OFS to attach it to Houston. Link to the OFS: Optical Flow (OFS) - SysInt - WARG (atlassian.net)

Open

In Pegasus 1, the OFS was mounted on the Monster Mount. A grey and thick double sided sticker was used to join the OFS onto the Monster Mount, and the OFS was lightly clamped with a TPU bar. Feel free to use different mounting mechanism as long as it satisfies the constraints. Dimensions can be found here: https://docs.cubepilot.org/user-guides/flow-senor/here-flow

Constraints

Relevant Contacts

Assignees

Task Progression/Updates

Author: @Agapa Goombs updating Date: 2024/02/09

Initial Ideas:

The initial idea was to create a rectangular plate with zip ties connection on each side to secure the OFS in place using the friction between the zip tie and the sensor.

Design #1: 2024/02/9 - Author: @Agapa Goombs

Open

Figure 1: Design #1 of OFS Mount for Houston

Upon further consideration, the decision was made for the Design 1 to have walls to enclose the small delicate sensor in the event of a crash so it does not move around and escape the mount as seen in Figure 1. Aside from this, the zip ties could pose a concern for the board as it is not protected in this proposal. The front wall of the OFS mount is removed to allow for the wires to remain connected.

The design also includes two M3 screw holes for mounting to ensure the sensor remains in the correct orientation during flight.

Construction

This part would be 3D printed and mounted using M3 screws. Double sided tape could be used on the base of the mount to ensure the sensor stays in place.

Design Review 1: @Smile Khatri 2024/02/9

• I like the wall idea

• When you bolt the mount onto the metal plate, won’t the head of the bolt obstruct the OFS?

• I can’t open PDM atm but could you make sure the holes are 28 mm apart? There’s already holes on the plate so we will use them

• We could attach the OFS to the mount using a thick double sided sticker

Design #2: 2024/02/9 - Author: @Agapa Goombs

Implementing the feedback from @Smile Khatri resulted in the following design:

As seen in Figure 2, In this design, to address the concern of the top of the screws getting in the way of the senor, thickness of the base was increased and the holes with a diameter 0.1 mm greater than the diameter of a M3 screw were sunk into it to a depth equal to their thickness. The idea is to still have the flat surface for the sensor to rest on while still using the two screw mounting approach.

Zip ties were decided to be the easier approach in attaching the sensor to the mount alongside double sided tape due to their ease of use and minimal risk to the sensor. As a result, a bottom groove were added and the height of the side wall was also decreased to allow for the zip tie to rest over the sensor and secure it in place.

Finally, to ensure there was space for the holes to be placed 28 mm apart according to the mounting constraint on Houston, the entire mount was lengthened to 40 mm.

Design #3 - 2024/02/9 - Author: @Agapa Goombs

Based on another in person design review before the 3D printing, a few more design decisions implemented.

After meeting with @Smile Khatri before 3D printing the part, a few small changes were made. These include increasing the base thickness by 2.5 mm to increase material at the bottom of the counterbore to 2.85 mm. The distance between the holes was also decreased from 28 mm to 24.5 mm to bring it in line with the mounting frame on Houston. Both of these changes ensured the part was compatible with the M3 screws used in mounting.

Design #4 - 2024/02/13 - Author: @Agapa Goombs

Based on feedback from @Smile Khatri after 3D printing the part, a few small changes to the 3D model were made. These include revising the bottom cut of the mount for weight saving. The mass of design #3 was 3.09 grams while design #4’s weight was decreased to 2.36 grams due to the revision.