Project P.L.A.I.D. Update #1: No Bad CAD

When starting a large and possibly costly project like this I always like to try to get all of the ideas bouncing around in my head out and into CAD before I start purchasing components. Projects like this where the majority of the parts will be designed and made in house are awesome because it lets me get the entire project in CAD before I start building. This comes with some big advantages namely allowing me to find issues early and fix them before they cost me anything while also letting me to know exactly what supplies I need to complete the build. Make sure to put as many parts into the model as possible even if you need to add a place holder. For example, the motor for this build does not need to be exact in the model but it should have similar overall dimensions. This will let you see if the part will hit anything or be in the way. A quick and easy hack to make the CAD process go a lot faster is to see if any the parts you are using are already available somewhere else. Grabcad & McMastercarr are two of my favorite places to go looking for these and it’s where I found the sk3 model in my CAD.

Deck Design

The deck is the backbone of this whole project. It’ll determine the turn radius, the ride height, and overall feel of the board. If I get the board design wrong it could ruin the whole feel and maneuverability of the project. For the build technique, I’m going to use Homeateadenomics technique of laminating thin sheets of plywood together over a mold. He made this look really easy so hopefully, it will be just as easy when I try. For the board length I decided to go with around 27 inches of deck space, around 33 inches total length, and a 9-inch width. With how long and heavy this board will be I’m going to need as much turn as I can get. So to minimize turn radius I’m going to make the ends 45 degrees, anything past this would just result in a larger turn radius. The deck dimensions come from looking at other board dimensions and what I want my stance to be. Finally, the top will be covered with grip tape to help keep the rider on the board with the help of the straps.

Overall Truck Design

Having never built skateboard trucks I’m going to try and keep these as simple as possible. The majority of mountain board trucks look like this and are what’s called a channel truck.

The hanger or the part the wheels attach to rotates inside a piece of C-channel that is then secured to the board. Springs are added between the hanger and the channel to force the truck to return to center when unloaded.

Homesteadenomics drastically simplifies this design but you can still see the resemblance. My Design will closely follow his except most of the parts will be waterjet plus I’m going to try and minimize the number of bolts I use by welding wherever I can. The threaded rod seems a bit heavy to me so I’m going to see if I can’t get away with a single bolt at each end. The harbor freight wheels he mentioned are a pretty sweet deal at $3 each but that gaudy white will have to go, hows matte black sound? (yes this is rhetorical but hey you could always comment below (who am I kidding no one reads these ))

Transmission Design

The powered rear trucks will follow a similar design to the front trucks using the same C-channel and wheels but the hanger will need to be redesigned to allow for a live axle through the center. For the axle, I’ll be using steel 1/2″ hex shaft from my local machine shop (I’m pretty familiar with this from my time in FRC). To support the shaft I’ll add some steel plates to the end of the trucks to support a pair of 1/2″ hex bearings. Finally I’ll weld a motor mount to one side and brake caliper mount to the other.

From what I learned from the other projects the sprocket will have it be a little complex. I’m confident some of the issues I had with the Mostly Printed Electric Bike came from the motor being directly connected to the drivetrain. On the moped I didn’t have any motor issues and I think that’s because there is a one-way ratcheting sprocket on the rear wheel that allows the wheel to spin independently of the motor. The plan for accomplishing this same system with PLAID is through the use of a one-way sprag clutch bearing. These bearings are super cool because there is minimal backlash with the added bonus of being ultra silent. Youtuber AVE has a pretty cool video of how these work (he actually released it right after mine came in the mail, Fate?). Disclaimer: he’s a potty mouth.

The keyways on the bearing are super important because otherwise it would just spin on the shaft/sprocket and not transmit any power. My only concern will be if it can hold up to the load of a person riding it…

Finally the last part of the transmission, the wheels. The rear will use the same ones as the front but the bearings will need to be removed and a hex adaptor put on. It looks like the bearing blocks should just unbolt and then I can sandwich a hex adaptor on both sides of the hub with the existing bolts. On most axles like this C clips would be used to hold it all together but often the assembly can end up being a little loose. This drivetrain will have spacers between all the components allowing for a bolt and washer on both sides of the axle to sandwich the whole assembly together making for a super tight fit.

The Electrics

The electronics are coming straight of the moped (it’s been relegated to storage until I can figure out how to make it street legal). If you want to learn more about that system check out the Electric Moped Update #5: The Rebirth where I go into detail of how the whole system is set up. But to summarise, I’m using a Hobbyking sk3 motor paired with a cheaper than hell chinesium speed controller, with all that sweet sweet power coming from a 16,000 mAh 12s or 800 watt-hour battery. The moped had some umph to it with a top speed of 35 MPH and the ability to get up any hill in Pullman without breaking a sweat. With project PLAID geared down 25 MPH this should be an absolute hoot to ride around! I may not be a psychic but I see some awesome powerslides in its future!

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