Project P.L.A.I.D. Update #2: Building PLAID

With the CAD out of the way, all the parts ordered in the mailbox, and haggling done with the metal shop it’s time to get to building. I tried to get as much of the build process on video to show how exactly I built everything and (hopefully) to make a youtube video on the whole project. So if you’re here from the YouTube channel: Welcome to my build blog! If I still haven’t gotten around to making that video: Hi ma!

Deck

As described in my last post I’m following Homeateadenomics tutorial to build the deck. After picking up some 1/8th inch ply from Pullman building supply (Katie or Tyler if you’re reading this I would love a sponsorship) I set to making the laminate mold and folding the plywood sheets over it.

Then I did my best to make it look like a pointy porcupine with clamps to hold it all together.

After letting the glue dry for a couple days I cut the board down to width with the bandsaw and then used a jigsaw to cut the ends into the shape I wanted. Not a lot of detail here because Homeateadenomics has a pretty great explanation.

Trucks

I started with the front trucks because it was the simplest. All the parts came together really easy with a little weld goop here and there. The only major issue I ran into was how I attached the axle bolts. I started by cutting out a square with a hole in it from 1/8th” steel, the plan was to have the bolt go through the hole and then weld the bolt head to the square, then weld the square flush with the end of the tube. Turns out the welds where to big and wouldn’t allow the bolt to sit flush inside the tube. So I got the good ol angle grinder out and ground off a little of the weld so it could fit inside. Aha it fits! Welded the square to the end of the tube and wala an axle… that was until I put weight on it and snapped the bolt head weld (gonna have to figure out a fix for this latter). But besides this issue, the front truck looks pretty dang good.

The whole assembly looks even better when put on the board. I’m starting to get really excited at this point.

The sprang clutch sprocket assembly came out super nice and it feels so precise. I did this part out of aluminum to minimize rotating mass. To design the sprocket I pulled a #22 sprocket CAD model from McMaster-Carr and then changed everything else but tooth profile to get it how I wanted. (if anyone knows of an easy way to produce sprocket CAD models with any tooth count let me know because I’m still looking for a good method)

The motor mount came out looking really nice and allows the motor to slide up and down to tension the chain and adjust the hall effect sensor. I added more slots to aid in cooling and add a little style.

With both front and rear trucks mounted this board looks mean!

The Issue With PLAID

Alright here arises the issue, after getting everything put together and running including a battery tray, throttle, handbrake, and springs for the trucks I took it out for a test drive. It has plenty of power and easily spins the rear wheels but turning feels really off for some reason. Like when trying to turn if I shift my weight all the way over to one edge the board barely turns but then once it does it doesn’t want to return to center. I’m pretty sure four things could be causing the issue. The deck is too low and gives little leverage when trying to turn, the board end angle is too steep and again doesn’t give enough leverage when turning, the springs are too weak or not set up properly (honestly they’re on the weak side), and finally the lack of differential is resisting and change in direction. I’m going to experiment with these issues but let me know if you have any suggestions! I’ll also try to get some video of the isue asap.

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!

Pullman Light-weight All-terrain and Inexpensive Driver

Or Simply Project P.L.A.I.D.

I’m not a huge fan of walking. It’s not so much the effort and workout of it as it is the inefficiency. Why would I walk to class in 15 minutes when I could bike there in 5, or even better ride something motorized and not be all sweaty and hot when I get there? Yes, of course there’s an argument to be made for physical health from walking and mental health from being outside but I’m already a college student so it would be a drop in the ocean. lucky for me I’ve got the electric moped and the $24 motorcycle and they are way too much fun to ride to campus. That is they are great when the roads look like this. Bone dry and uncomfortably hot.

“Girlfriend for warmth Scale”

And not like, two feet of snow and ice rinks where there used to be roads.

“Girlfriend for cold scale”

Point is, Pullman has some cold winters with a lot of this slippery white stuff. Two wheels can only get you so far in the winters and most of the time it’s just outright dangerous to try.

Design Criteria

The goal is to build a vehicle that has the stability of a car in the snow but the weight and portability of the electric moped. It also needs to comply with WAC 504-15-930 which defines what kind of personal transportation is allowed on campus. I’ve had some issues with the moped not complying so I want to do it right this time.

The best idea that came to mind that fulfilled the criteria was an electric mountainboard. Mountain boards are skateboards with much larger pneumatic wheels, a better suspension, straps to hold you to the board, and often a brake. The four points of contact would make it much more stable on loose surface, the straps would make it easy to manipulate, and best of all it would Comply with WAC 504-15-930.

(1) The riding and use of bicycles, skateboards, scooters, and roller skates is prohibited on all building plazas, all pedestrian overpasses, interior building spaces, parking structures, parking structure ramps, all stairways, steps, ledges, benches, planting areas, any other fixtures, and in any other posted area.
(2) Bicycles, skateboards, scooters, and roller skates may be ridden and used on sidewalks outside the prohibited areas when a bike path is not provided.

https://apps.leg.wa.gov/wac/default.aspx?cite=504-15-930


WAC 504-15-930 has no different definition for an electric skateboard so the electric mountain board should be able to go anywhere a skateboard is allowed to go.

Powering a Mountain Board

There are some retrofit kits out there to power a mountain board but they come in at around $500 for the cheapest and only use one motor and only power one wheel, there is also that I don’t own a mountain board. The ideal situation would be to use one of the motors and speed controllers I already have from the electric bike and electric moped project which should have plenty of power for plowing through snow, set it up to power two wheels off only one motor to avoid any of the countersteer and traction issues from only powering one wheel, and be able to easily ad a mechanical brake. Most e-boards use regenerative braking to slow down but the speed controllers that can do that safely are really expensive. All the ones I have are super cheap Chinese e-bike speed controllers with an e-brake setting that would probably get me killed. That’s why I used disc brakes on the moped to achieve progressive braking. After looking around and doing some research on designs I found this awesome youtube video by homesteadonomics where he makes a mountain board completely from scratch, including the trucks!

The best part about his style build is it would allow me to build the skateboard trucks myself. I wasn’t aware until I saw this video that skateboards turn by angling the trucks in such a way that when the deck is tilted it forces the wheels to turn into the direction the board is angling. On most skateboards, this angle is built into the design of the truck itself so the skateboard deck can be flat. Saber trucks have a good picture demonstrating how this is accomplished along with a awesome description on their website.

Image result for skateboard truck angle

Mountain boards accomplish this angling differently by building the angle into the skateboard deck itself. This makes the trucks a lot simpler to manufacture compared to ones with a built-in compound angle. Best of all this will allow me to design a live axle transmission into the rear truck. This means I can use a single motor to power both rear wheels and even attach a disc brake that would stop both. Finally with the general design concept out of the way I’m going to get started piecing it all together in CAD. Stay posted for the next update where I’ll show you how the CAD model turned out and the design choices I made.