Reflections on Motorized Longboard
Assessment of your machine’s performance. Consider the differences between your design calculations and the actual performance. How did your machine work (e.g. handle, accelerate, turn) in your head while you were designing it vs. how it performed in real life. Describe what real-life factors might have influenced the machine and how witnessing it gave you a better model by which to judge future designs.
When I was first designing my longboard, I really wanted the method of acceleration to be a foot pedal at the front of the board, or some sort of force sensor. However, I thought this more carefully and realized that I would be demo-ing a lot. People who can’t balance on the board would probably accidentally accelerate and having a foot pedal could end up being quite dangerous. I still do want to try out the pedal sometime, just not this semester. I estimated the longboard would go about 15 mph, and it turned out to be pretty exact.
In my calculations, I overcompensated for the weight of the rider (I used 150 lbs, though I can assure you I weigh a lot less), but underestimated the weight of the board (used 10 lbs even though it’s more like 15 or 20). The top speed of my vehicle depends a lot on who’s riding it. If I ride it on a full charge, it goes up to 20 mph though I rarely go that fast because it gets really dangerous and harder to balance. Someone who weighs about 150 or 160 lbs would go 15 mph on a full charge.
<link to video riding standing up>
I’ve also discovered that “supermanning” the longboard can be quite thrilling and entertaining :)
http://www.youtube.com/watch?v=Bx8tX6UEsZo&feature=youtu.be
I took a lot from reading up on the Z-board (http://www.zboardshop.com/) and asking Manyu about longboards. It also helped to see Jed’s skateboard and browse around Instructables (http://www.instructables.com/id/Electric-Longboard-Build-Clever-CIM-Motor-Drivet/).
If I were to build a new one, I’d probably make hub motors and have a truck in the back. Because there’s only one driven wheel in the back, it’s very difficult to turn because you get twice the turning radius. If it were solely for personal use, I’d use a foot pedal in front. However, being the showoff that I am, I’d want to have other people try it out-in which case I’d just stick to the hand-held radio throttle.
Comparison to other machines and designs. If there was another vehicle of your same general type (e.g. scooter, go-kart, etc.), what made your machine stand out? Was there another machine which had some design element which you found particularly well-executed? Promising but not very well-executed? (Exclude names, only describe the design element). What was the single best idea (of any machine) you witnessed this term?
No other vehicle of the same type. I liked the idea of using a hinge for opening/closing the battery pack. If I had to change my batteries, I’d have to unscrew all the screws that are holding the vacuum formed polycarbonate to the board. I also really liked Travis the motorized tricycle. In general, the electric scooters are pretty cool, but I wouldn’t want to have one for daily use.
Gauge your own learning. What was the biggest takeaway for you this semester from a learning perspective? How does seeing the design process and outcomes of your peers influence how you will design systems in the future? Compare and contrast how confident you are in the following areas before and after this term:
o Mechanical power transmission design using CAD software, analyzing mechanical systems for torque, speed, power, etc. with first-order math
I learned a lot about how to mate gears/pulleys, create a belt around them, and measure its length. Before, I was not confident at all in analyzing torque, speed, power, based on a motor’s specs, but now I’m pretty comfortable doing so. Other than that, my familiarity with SolidWorks has pretty much stayed the same.
o Understanding, designing, and fabricating low-voltage electrical systems
I’ve never really worked with low-voltage electrical systems before (electric violins don’t really count..), so I definitely improved in this area.
o Ability to read product specifications and gauge their usefulness to your design
Before this class, I had no idea what kt/kv was, or how knowing the current/power/voltage of motors, motor controllers, chargers, and batteries could help me design. Although I’ve made progress in this area, there’s definitely room for improvement.
o Correlating design calculations and specifications to existing parts in a catalog and making design compromises based on that.
I would say I’m pretty confident in this area, both before and after. I’ve had experience shopping on McMaster before, but now I can browse hobbyking, and sdp-si without fear.
MY ROBOT WORKS!!
Well, kinda. As long as it can drive to roughly the right place.
Some stuff still needs to be tweaked, like having the end curve up a bit so the robot doesn’t jump back as much. Also, the battery and controller weren’t secured. I’m going to fix those things and start working on the code so I can score points autonomously!
Portfolio (PDF)
Portfolio as of 4/18/2012:
Sketch Model for Football
Here are pictures of the football and the process we had to go through :)
Best quote of the night was from Jessica: “MY FINGERS ARE EXPANDING!” Yup, that’s her in the picture :P
The first picture of the diagram is a bit outdated. There’s actually 4 LEDs on each side (8 total) to make the football stripes even brighter! Also, we used two AA’s, and the LEDs are wired in parallel.
The football was made from 5 parts (2 stripes, 2 ends, 1 center) and used 3 different molds. The black parts are Flex Foam IT-III, made by a company called Reynolds. It’s pretty much like nerf foam. The blue stripes are actually translucent rubber pieces which have no color by themselves. The blue glow comes purely from the LED’s. We tried dying the rubber light blue to help with the color and hot spots, but found out the LED’s didn’t shine as well with the rubber tinted.
For our final prototype, we’re going to integrate the “spiral-sensor” (aka accelerometer) and make the football a bit smaller. Right now it’s rather heavy because of all the rubber (which we’re planning to reduce). Also, we changed the concept so that it changes between red, purple, and blue depending on how fast it’s spiraled :)
Yet another base. Also, shiny wheels! :D
Still fiddling around with the shape of that base..but look! Holes for two polulu ball casters have appeared :) if you look to the bottom right of the picture, you can see one of them.
I was lazy and press fit the servo wheels into .375″ acrylic. The acrylic might stay, depending on how screwed I am with time later on (I’ll probably add sandpaper so there’s more friction)
Confirmation that Robot Fits in Starting Box
Kind of close, but it’ll fit!
Robot with Base!
Base is still foam core, but getting closer! I’ll also be replacing the servo wheels with 4″ diameter wheels, and adding two ball casters to the back end.
Here is the robot next to the high striker lever. As you can see, the curves in front help guide the robot and align it so the hammer comes down at the right place.
Finished the base (I think)
As you can see, there are many slots and holes in the base. This is for aligning everything that’s supposed to go on it (including supports, continuous servo mounts, gearbox, and vs-11 mount. I prototyped it out of laser-cut foam core and tested the curves on the competition board. Seemed to work pretty well, need to make a few minor changes then send it off to be waterjetted!
Better Render
More people seemed to like the stripes going all the way around, so I made a better render of it:
I guess I should blog about 2.00b :P
What is 2.00b? Only the funnest class ever! The class is intended for freshmen (wasn’t offered my year, so I’m taking it as a sophomore) and is called Toy Product Design. Through brainstorming, ideating, refining, and iterating, each team of 5 will eventually fabricate a toy for “Playsentations”.
This year, teams were named according to animals. My team (Team Panda) decided on a light up football for out final toy idea. Instead of having a glow-in-the-dark football or one that is continuously lit, we wanted it to be dimly lit when you’re holding it, and glow brighter the faster it is spiraled. These are the SolidWorks models thus far. The blue indicates translucent, squishy SmoothOn EcoFlex material where a bright blue LED light will shine through yet be diffused. The black is nerf-like foam. (ignore the different renders, I was just playing around with SW Photoview :P)
