Member Types & Implementation

Aluminum Members

General aluminum properties and notes can be found on this Arm page.

Tubes

Aluminum tubes, as seen from some other successful URC teams, are most commonly assembled together/connected through welding. Fasteners however are also commonly utilized in some places, for example in attaching the linkages to the wheel hub in Monash's rover.

Examples:

- Monash University Nova Team
  - (2019 Extreme Retrieval Mission Score: 70)
  - Straight aluminum tubes
  - Welded together at top of 'W'
  - Slide onto wheel-adjacent aluminum base at bottom of 'W' where components are then fastened together
- PCz Rover Team
  - (2019 Extreme Retrieval Mission Score: 80)
  - Curved aluminum tubes
  - Tubes welded onto wheel-adjacent aluminum base
  - Rocker welded to pivot component
- OSURC
  - Straight aluminum tubes
  - Tubes welded together perpendicularly (printed covers are thus used to close off open ends)

Box-Tubes

Aluminum box-tubes, as seen in use by some other URC teams below, commonly use gussets and fasteners for assembling linkages together. Welding is less common although does make appearances.

- Stanford Student Robotics
  - (2019 Extreme Retrieval Mission Score: 64)
  - Straight box tubes connected using aluminum gussets and fasteners
- Rudra
  - (2019 Extreme Retrieval Mission Score: 40)
  - Two smaller box tubes used for each linkage, space apart and parallel, connected by even smaller welded box tubes
  - Gussets and fasteners used at ends for connecting to wheels & chassis/differential
- Team Anveshak
  - (2019 Extreme Retrieval Mission Score: 50)
  - Straight box tubes connected with gussets and fasteners
- Mars Rover Manipal (2021)
  - Straight box tubes connected with welded gussets
    - Personally don't think it's very aesthetically appealing, but might just be a poor welding job

Custom Linkages

Examples:

- Cornell
  - (2019 Extreme Retrieval Mission Score: 70)
  - Each linkage is made of one thick custom plate, which is connected to using gussets and fasteners
- Legendary
  - (2019 Extreme Retrieval Mission Score: 72)
  - Two thin custom plates make up each linkage from chassis to wheel

Carbon Fiber Members

General carbon fiber properties and notes can be found on this Arm page and this CF Research page.

Tubes

Round CF tubes used by other URC teams tend to be assembled using an array of options, including being directly fastened with holes, clamped into hubs, or assembled with aluminum tube fittings.

Examples:

- Ryerson Rams Robotics
  - (2019 Extreme Retrieval Mission Score: 90)
  - Straight CF tubes connect to wheel hubs with fasteners
  - Bogie middle connection using gussets and fasteners
  - Rocker middle connection using a hub (looks like plastic maybe?) secured with fasteners, unclear if CF tubes are secured using the fasteners or are just clamped within the hub
- Missouri S&T
  - (2019 Extreme Retrieval Mission Score: 48)
  - Straight CF tubes connected to each other using various aluminum tube fittings

Box-Tubes

CF box tubes when used by other URC teams seem to primarily make use of aluminum gussets and fasteners, in addition to aluminum tube fittings in some places.

Examples:

- Michigan Mars Rover Team
  - (2019 Extreme Retrieval Mission Score: 32)
  - CF box tubes connected primarily by fasteners and aluminum gussets fitted to the outside of the tubes,
  - 2020:
  - CF box tubes once again assembled with gussets and fasteners, however this time in addition to aluminum tube fittings
- Team Anveshak (2020)
  - CF box tubes connected using gussets and fasteners

Comparisons

Member Style Comparison

Style	Pros	Cons
Round	Higher strength to weight ratio compared to square tubes More resistant to flexing and torsional twisting	More difficult to mount to compared to square tubes More complex mounting solutions might result in more weight & space
Square	Easier to mount to compared to round tubes less complex mounting results in less weight and less wasted space Better for bending	Lower strength to weight ratio compared to round tubes Less resistant to twisting and flexing
Custom	Save on weight by only reinforcing in required spots	More difficult / requires more effort to make custom carbon fiber parts

Member Material Comparison

Material	Pros	Cons
Aluminum	Easier to make custom parts Easier for mounting Less expensive	Weighs more than CF Not as strong as CF
Carbon Fiber	Weighs less than aluminum Stronger and stiffer than aluminum lower thermal expansion (not really relevant to us though)	Machining holes weakens CF More complex mounting solutions can potentially create more weight and take up more space Fails more suddenly compared to aluminum Anisotropic properties make analysis more difficult More expensive