Considerations:
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| Consideration/Topic | Entirely 3D Printed Wheels | beach tires with 3D printed treads | Solid Tread, flat free wheels |
|---|
| general/description | - self explanatory, design entire wheel
| - design various attachable 3D printed tread patterns to the beach tires
| - most basic option
- used as is
|
Timeline/prototyping | - may take many weeks to create from designing, sourcing filament, printing, prototyping to final product
| - can reliably test far faster - begin testing with just the beach tires and can add treads later
| - would need to alter hub to accommodate motor
|
| Educational aspect | - improve design skills
- opportunity to analyze various tread styles for the terrain
- analyze possible spoke styles/internal support for weight of rover as well deformability
- create/implement custom hubs
| - opportunity to analyze various tread styles for the terrain
- figure out a way to firmly attach treads to wheel
- Stanford - zip ties (prototyping)
- Cornell (2020)-adhesives -cyanoacrylates, epoxy?
| |
Accuracy to what can be used on an actual Mars mission | - airless tires would be more accurate to what is possible on Mars missions
| n/a | |
| Size options | entirely customizable (between 10" -15") | Wheeleez: - diameter: 9.4" width:
- diameter: 11.8" width: 7.3"
- diameter: 16.5" width:
McMaster Carr - 8"
- diameter 10" width: 1 5/8"
| |
| Weight | unsure, but would likely be heavier as it is made of solid material | WheelEEZ: 11.8" : 1.3 kg (2.9 lbs)
McMaster-Carr 10": couldn't find | n/a |
| Price point | n/a | 11.8": $89.00
10": $85.58 | $75-160 13": $124.43 |
Customizability/design uniqueness | - entirely custom allowing for custom wheel hubs and any spoke/tread design we may want
- would have the ability to expand on this for future years
| - tire is OTS but treads would/could be custom made and this would also allow us to prepare for a more advanced wheel design for a future rover
- possibility of a custom hub (hub that comes with wheels is completely removable
| |
| maintenance | - cannot be fully sure until prototyped
- design could be less resistant to catching sand, wearing down etc.
| - unlikely, but sand could enter hubs/bearings - should choose a reliable design (Wheeleez has multiple parts such that the entire hub can be easily taken apart and cleaned/repaired/replaced)
- cuts can be repaired using a soldering iron
- possibility for 3D printing different interchangeable attachable treads to have better treads prepared for competition/less worn down/new treads
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|
Coefficient of friction | 0.38 (for hole wheel design)* 0.45 (for spike wheel design)* | WheelEEZ: 0.2-0.25 (website did not have specific values, against steel) McMaster-Carr: n/a | n/a |
Maximum load | n/a | WheelEEZ: 55kg McMaster-Carr: 1.2kg | 0.3kg |
Other teams | | | n/a |
| OTS Options/purchase options | filament here Thermoplastic Polyurethane TPU (AGH Space Systems, ITU) Polyethylene terephthalate glycol PETG (ITU) black SemiFlex clear generic TPE90A white NinjaFlex (very soft, therefore harder to print)
| | McMaster-Carr https://www.mcmaster.com/22245T33/ https://www.mcmaster.com/rubber-tread-wheels/ |
| Example photos | Monash: 
ITU: 
| WheelEEZ wheel: 
Cornell: 
hub: 
Custom hub (cornell): 
| |
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Tread Adhesives (for prototyping/removable)
| Adhesive name | Description | Cost | Image |
|---|
| Silicone Sealant/glue | - can be used for glass, metals, plastics
- water resistant, flexible
- can be removed with exacto knife and acetone (for excess remaining)
- any cuts made by exacto knife on wheel can be fixed with soldering iron
- equipment: caulking gun
| ~$20 for 11oz container |  Image Modified
 Image Modified
|
| APAO Based hot melts | - non crystalline adhesives that stay flexible and tacky
- good adhesion
- long open times
- can be used for woodworking, automotive assembly
- remove with rubbing alcohol, hot gun, scraper
- equipment: hot melt gun (glorified glue gun)
| |  Image Modified
|
| rubber cement | - can be removed with heat and force: heat gun and scraping
- good long term option, used for outdoors (bike tire repairs)
- acetone can be used to remove any excess remaining
- note: acetone supposedly beads up on/does not affect polyurethane
- equipment: brush for application
- does suggest scuffing up the area first for better adhesion
| ~$9 for 8oz container
mcmaster carr: plastic cement https://www.mcmaster.com/adhesives/for-use-on~polyurethane-rubber/cement-for-plastic/ |  Image Modified
|
| other testing option | - stanford used zip ties to attach the treads to their wheels
- would only use for prototyping
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Tread Styles
| Style Name | Photo | Notes |
|---|
| | - thick groove patterns, wear down evenly over time
|
| Asymmetric | | - move in a single direction, most common type of tire tread
|
| Directional (also called unidirectional) | | - highest level of traction, control
- designed to roll in only one direction
|
| | - highest SAR Score
- scored well in 2019 competition
- greatest diameter along center of wheel
- angled ridges/small paddles
|
| PCz - zig zag pattern | | - 4th place for SAR
- video shows strong traction on snow
- contact about material type?
|
| | - additional rubber (??) strips added, horizontal lines
- 10th place SAR
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| Anveshak | | - 8th place SAR
- horizontal ridges
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| ATV sand tires | | - paddle like ridging to dig into sand
- generally smoother than traditional (car) tires
- printing time may be very long
- bc they stick out more, they could be harder to attach/could fall off
|
| | - reduced weight
- maintains turning ability
- printing time may be very long
- bc they stick out more, they could be harder to attach/could fall off
|
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-teams that just used balloon tires as they are: Manipal, Rudra
Tread Styles to use:
Current treads:
Image Added
notes: possibly have treads stick out slightly less/more paddle like (triangular profile vs square)
Image Added
Image Added
Rough sketch of hub design
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