Making an Inclined Plane Thin Enough for a Book.

One Week Left

There's one week left to read all my best dad jokes on the Kickstarter campaign for Simple Machines Made Simple. Please do me a favor and forward them a link to all the friends and relatives you know that are super passionate about Inclined Planes. Thank you!

Up until now with, Computer Engineering for Babies, when things have gone wrong, I've largely been able to just update the code and keep rolling. Yeah, "updating the code" on a batch of 5,000 books is terrible, but I've done it, and as long as I keep up with orders it doesn't have to happen all at once. But with this new book, Simple Machines Made Simple, stakes are high. Once these books are made, I can't just open it up to update the code before I ship them out. 

How the Ramp Works

I have so much to complain say about the design journey for the inclined plane. But for now, I just want to share about my latest win.
A few days before I launched the book on Kickstarter, I found that I needed to redo the molds for the Inclined Plane. I want the weight to fall down the ramp when you let go of it, but it was kind of sticking if you let go of the weight near the top of the ramp.

Works pretty well here, but you let go at the top of the inclined plane, then it wanted to stick.

So here's the behind-the-scenes of how the ramp works:

Basically to simulate gravity, I have this giant arm connected to a spring that puts a force on the weight downward (in the -y direction). I thought this was pretty clever because gravity is a constant force; it pulls on you just as hard when you're at the bottom of the stairs as when you're at the top of the stairs or the top of a mountain. But a spring's force increases the farther you get from it's relaxed state; it may be easy to stretch a spring when you're stretching from its relaxed state, but really difficult to stretch it even more when it's already been largely stretched:

And then we're also working with a lever. So as we move up our "ramp", and extend the spring, the farther we get up the ramp, the more leverage we are getting from our lever. So even though the spring is getting harder and harder to stretch, the lever arm is making it easier and easier. Those two forces largely cancel out and the force that you feel as you move the weight up and down the ramp feels very constant (like gravity).

So that's the idea of how this is supposed to work. But for some reason, in the prototype books, the weight was getting stuck at the top of the lever arm. So I had to rip everything apart to figure it out.

The reason why the weight wasn't always falling down the ramp is that the axle of the weight is being pinched by the ramp and the lever arm. There were these opposing rotational friction forces. It's like when you hold a small pumpkin with two fingers:

I needed the axle of the weight to slip to prevent this pinching action. So I added a bearing and we're good to go. The only problem is that adding a bearing requires all the plastic pieces to be a slightly different size, so everything needs to be remade.

And now to my good news! I thought this meant that I would have to get a new mold made, and they would have to start completely over requiring another 40 days to make the mold. But apparently, somehow, they are able to modify the old mold and get it done in half the time. So for the first time in forever, I'm ahead of schedule on this book. I'm sure 100 other things will go wrong over the next couple of months, so just celebrate this one with me.

Thanks for letting me share!

Cheers,
Chase