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Copy file name to clipboardexpand all lines: mechanical/wheel_assembly/README.md
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The wheel assembly attaches the wheels to the motors and mounts the motors to the rest of the rocker-bogie suspension system that makes up the robot chassis. These are relatively simple to assemble.
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<imgsrc="images/wheels.png"width=900/>
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## Features
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## [DollarHobbyz Traxxas Wheels only] Drilling the wheels
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* The flexible wheels allow for high traction as they deform around objects, improving climbing performance
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* Drive motors chosen to handle the high torque that the system sees, achieving both speed and climbing performance
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If you bought the DollarHobbyz Wheels, you will need to drill some holes through the plastic to allow attaching them to the hubs that fit onto the motor axes. If you have the smaller or bigger Wasteland Wheels from GoBilda, you can skip this step.
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### Mechanical Interface/Attachments to Rover
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The wheel is normally meant to be mounted using one bolt through the middle of the rim. This will not work well in our case as the rover sees very high torque at the wheel and the one-bolt system would be difficult to attach to any part of our system without the wheel slipping. To attach more firmly, we will drill two holes on either side of the original hole where we will mount the motor hub clamp
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* The 4 corner assemblies connect directly to the servo blocks on the rocker-bogies.
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* The 2 middle drive wheels attach directly to the rocker bogie
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Drill at least 2 holes in the wheels such that they can be mounted to the [Hyper Hub](https://www.gobilda.com/1310-series-hyper-hub-8mm-rex-bore/) that attaches to the motor shaft. You'll want to make sure the holes you drill are centered, otherwise the wheel will wobble while driving. Once you've found where to drill the holes, consider using a center punch or small drill bit first before drilling to ensure your drill bit doesn't start 'wandering' before it locks into position. The distance from each hole center to the center of the wheel is
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$$\sqrt(8^2 + 8^2) \approx 11.3mm$$
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## Machining/Fabrication
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**NOTE:** While the following approach is valid for v2, it is not ideal as it requires drilling. There may be better ways to attach to these wheels (or other wheels) without drilling. The only requirement is that the middle of the corner wheels aligns with the axis of rotation of the servo output shaft.
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**NOTE**: These instructions are a work in progress. Please ask for assistance on Slack.
| hand drill or drill press | D3 || <imgsrc="../../images/components/tools/D3.png"height="100"> |
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| center punch or starter drill bit | D7 || <imgsrc="../../images/components/tools/D7.png"height="100"> |
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> The wheel is normally meant to be mounted using one bolt through the middle of the rim. This will not work well in our case as the rover sees very high torque at the wheel and the one-bolt system would be difficult to attach to any part of our system without the wheel slipping. To attach more firmly, we will drill two holes on either side of the original hole where we will mount the motor hub clamp as shown in Figure 1
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Drill at least 2 holes in the wheels such that they can be mounted to the [Sonic Hub](https://www.gobilda.com/1309-series-sonic-hub-8mm-rex-bore/) that attaches to the motor shaft.
Note that the sides of the rover are mirrored and so you'll be building 2 pairs of similar but not exactly the same subassemblies, as shown in the right image above.
***3 X** Roboclaw 2x7A Motor Controller [Basic Micro](https://www.basicmicro.com/Roboclaw-2x7A-Motor-Controller_p_55.html)
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***1 X** Power Measurement Unit INA260: Sold out on DigiKey, possible replacements are on [Adafruit](https://www.adafruit.com/product/4226?gclid=CjwKCAjw5dqgBhBNEiwA7PryaLOm_zC9GhlzRH1NwN4bSRwDg84sIhSh3LEqTOrIvQ3j_kRBscTAYhoCBOQQAvD_BwE)
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***1 X** PCA9685 corner motor driver [Mouser](https://www.mouser.com/ProductDetail/Adafruit/815?qs=GURawfaeGuCGKbWyy9179Q%3D%3D)
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* DC power meter: [Amazon](https://www.amazon.com/gp/product/B017FSED9I/). This LCD display reads out current, voltage, power, and energy, and can be put on the back where the rectangular hole is in the laser cut cover.
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* DC power meter: [Amazon](https://www.amazon.com/gp/product/B017FSED9I/). This LCD display reads out current, voltage, power, and energy, and can be put on the back where the rectangular hole is in the laser cut cover.
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* batteries: many options available here. We recommend getting LiPo batteries. You'll need a battery that can provide over 14V(*), so a 4s battery works well. You can get batteries with various mAh ratings (how many milliAmperes the battery can output for 1 hour). We recommend any option over 4000mAh. Higher capacity comes at a higher cost. You can also get more than one battery and swap them out. The rover can carry them as well.
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* Zeee sells many options [on Amazon](https://www.amazon.com/stores/page/25B7018D-26CC-4E43-BC6D-EFAF737D8F5E?ingress=2&visitId=1b4115fa-2240-424d-a0e6-a466830819ce&ref_=ast_bln)
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* Zeee sells many options [on Amazon](https://www.amazon.com/stores/page/25B7018D-26CC-4E43-BC6D-EFAF737D8F5E?ingress=2&visitId=1b4115fa-2240-424d-a0e6-a466830819ce&ref_=ast_bln)
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* You'll also need a charger for the battery. Make sure it can support the battery you bought. For the Zeee options, [this model from Amazon](https://www.amazon.com/Hobby-Fans-Professional-Balance-Discharger/dp/B09XC91BWJ/ref=sr_1_6?keywords=LiPo+charger&qid=1690484744&sr=8-6) will work.
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* Consider getting a fireproof battery bag. LiPo batteries are extremely flammable/explosive and a fire caused by a battery is extremely difficult to put out.
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* You'll also need a way to connect your battery to the PCB via a XT30 connector (MH-FC) which depends on the battery you get. Often these come with the charger for the battery
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## Different wheels
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* The wheels we previously included as the default from [DollarHobbyz](https://www.dollarhobbyz.com/collections/all/products/traxxas-2-talon-tires-gemini-black-chrome-wheels-5374x) are $34.95 per pair of two for a total of $104.85 (excl. shipping), saving ~$135 compared to the default Wasteland wheels. They are a perfectly fine choice but require some drilling to fit to the motor hubs.
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* Gobilda also sells a larger version of the [Wasteland Wheel at 192mm diameter](https://www.gobilda.com/wasteland-wheel-192mm-diameter-72mm-width/). This adds $90 total compared to the default Wasteland wheels. No drilling is required.
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* Gobilda also sells a larger version of the [Wasteland Wheel at 192mm diameter](https://www.gobilda.com/wasteland-wheel-192mm-diameter-72mm-width/). This adds $90 total compared to the default Wasteland wheels. No drilling is required. Those wheels are bigger and wider and look like this:
Values between parentheses are the additional screws that would need to be ordered if all 'either' types with same length are used in that type. In general, socket screws are preferred because of their resistance to stripping and use of a larger hex key.
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The parts list also includes 1 [25-pack of M4 washers](https://www.gobilda.com/2801-series-zinc-plated-steel-washer-4mm-id-x-8mm-od-25-pack/), 1 [25-pack of M4 hex nuts](https://www.gobilda.com/2811-series-zinc-plated-steel-hex-nut-m4-x-0-7mm-7mm-hex-25-pack/), and 1 [25-pack of M4 locking hex nuts](https://www.gobilda.com/2812-series-zinc-plated-steel-nylon-insert-locknut-m4-x-0-7mm-7mm-hex-25-pack/).
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The parts list also includes 1 [25-pack of M4 washers](https://www.gobilda.com/2801-series-zinc-plated-steel-washer-4mm-id-x-8mm-od-25-pack/), 1 [25-pack of M4 hex nuts](https://www.gobilda.com/2811-series-zinc-plated-steel-hex-nut-m4-x-0-7mm-7mm-hex-25-pack/), and 1 [25-pack of M4 locking hex nuts](https://www.gobilda.com/2812-series-zinc-plated-steel-nylon-insert-locknut-m4-x-0-7mm-7mm-hex-25-pack/).
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