Despite the fact that in the Make Lab we build and test every how-to project in MAKE magazine, we’re always on the lookout for exciting projects to try. The Power Racing Series event served up the perfect challenge. Their site describes it thus, “an annual racing series in which small teams from all over the country strip down and build up kids’ power wheels cars and race them on a specially designed track for hundreds of cheering fans.” To make it more interesting, there’s a $500 limit (not including safety gear) to what can be raced on the track. Clearly, this is a race about constraints.
Among those constraints, each car must be composed of 70% of the original exterior. We weren’t sure exactly how much that meant, except that we’d need a fairly intact body to start with. Since it didn’t need to be in good (or even decent) shape, we began searching the internet. The batteries in powered plastic cars aren’t meant to go forever, and we’d guessed that few parents would bother replacing them once they were shot. But despite our best hopes, most of the cars we found were toddler-class and too small for most adults to even stand up in. We finally found a bright pink Barbie Jeep in Rohnert Park for $100. Considering they go for $300 new, that wasn’t so bad.
Naturally, the first thing we did once we got it back was wire up a spare battery and drive it around the office. What would you do?
Note: for those of you trying it out at your place of business, plastic toy cars don’t corner very well indoors.
First step in making a race car is removing as much of the original as possible. These are big, molded plastic parts, and there’s a point when there’s nothing left to remove. There’s no tool really made for this, but a Japanese handsaw works fairly well. Except for the 36 inches of wobbly plastic waving around and the effort to keep it in place, it went somewhat smoothly.
Once we had the car emptied of all nonessential material, we could start sizing it up and figuring out part positions and such. We knew it would be a tight fit from the start, but the tininess of the thing was becoming tangible. And uncomfortable.
And then we had a stroke of luck.
Sometimes things work out in your favor, even when they work out two weeks later than you’d prefer.
On a trip to the local recycling center spurred by another project entirely (a turntable for the Flame Tornado in MAKE Volume 35), Paloma happened to see, out of the corner of her eye, a dirty, paint-covered Power Wheels Jeep Hurricane.
This car would fit an adult as well as any plastic kid’s car could. This is the biggest car we could get – it’s what the maximum size limit was based off of. And it was only $10.
We also found out that we got a bonus from our junkyard find, ants!
The car spent some quality time sitting outside, doused in WD-40, until it was nearly insect free.
Once again, we took it upon ourselves to ride it around the office. You know, for handling. And stuff.
Brian riding around on what was later revealed to be only one motor. [Edit: Apparently our Hurricane video went missing. To make up for it, here's Brian trying to corner the Barbie car between desks.]
The motor is (shockingly) one of the most critical and expensive parts of any electric car (at least, as long as you want it to move). With only a $500 budget, you have to plan carefully. Or you can luck out and get a tip that a local EV company is moving shop, unloading surplus stock, and willing to let you in the door the day before their garage sale. Wisely, we decided to luck out. We ended up with a beefy ME909 motor from our friends at ThunderStruck Motors. Thank you, ThunderStruck!
On the right, one of the two original Power Wheels motors. On the left, our replacement.
The speed controller is another critical component. These things can easily go for more than the motor, and they’re no less important. Sadly, we failed to find plans for one we could construct. Someone should work on that.
So we returned to our strategy of dumb luck. Our engineer Brian Melani had an old Taylor Dunn speed controller laying around in his garage. As always, free is good, and that gave us room in the budget for other important parts, like tires.
Our first set of wheels were designed for hand trucks and came from Ubiquitous Discount Hardware Store. A week after we got them, they smelled just as much like rubber as they did seven days earlier. They may have been new, but they would have been terrifying to ride on.
The local tractor repair shop, Sebastopol Tractor Co., was kind enough to give us a set of four. Two small in the front and large in the back went perfectly with the Rat Fink aesthetic we had in mind. And the ones in the back almost matched!
Our fabricator, Dan Spangler, did most of the heavy-lifting on the car. Yes, literally and figuratively. One day, the body disappeared from the lab and left a junkyard plastic-shaped hole behind it. Several days and an absurd amount of CAD work later, we got back a rolling chassis. The steering was complete a few days later, a frame for the seat a few days after that. And with the motor sitting in its future position, it was starting to look like we knew what we were doing.
ThunderStruck has a very helpful gear ratio calculator on their site to help you figure out the top speed of your vehicle. Once we got the motor and drive sprocket in place, Brian used the app to figure out the likelihood of one of us failing to survive the race. The numbers were entered, and the app spat out 47mph. In a shell with an advertised top speed of 5 mph, we would go nearly 10 times that. That’s when we realized we were possibly building our own death trap.
Yet the death trap still had plenty of work left to do. The frame for the seat was welded together, and we’d tested out the position with a couple plywood boards. It felt like sitting on a couple plywood boards, balanced on a rock. We’d need something better if we were going to last through the endurance race. Some of us wanted to just tear apart an office chair and be done with it. Lab Engineer Paloma Fautley insisted otherwise. She was determined to build a seat that was more comfortable and better looking than anything we would get on an office chair. We told her that we only had a few days, and if she couldn’t do it in that time, then it just wouldn’t happen. She said she could do it. We reminded her she’d never done any upholstery or built a piece of furniture in her life. She said she’d do it.
And then she did it and it was awesome.
The seat was looking sweet, and there was some murmuring about what the final appearance of the car would be. Most people loved the junkyard aesthetic that came free with the body. But from early on we had imagined a “Rat Fink” design to go with the Lab Rat theme. So flames were a must. And ‘cmon, we had a magazine to represent. So we handed the body to our Shed Intern (now Graphic Designer) Uyen, who happens to have an interest in spray art. She grabbed a few cans, went to town and two days later, we had this.
No one missed the junkyard look at that point. It was beautiful.
It also still didn’t run.
And we soon found ourselves with a beautiful car, filled with sweat, mental anguish, and luck, that still hadn’t ran once.
With Maker Faire three days away.
To be continued…