The Greek Ramp Hybrid
Most of the historical ramps I research are generally of a pretty temporary nature: pyramid construction ramps, siege ramps, etc. They’re built for a single purpose and then abandoned or destroyed. They’re machines, and they don’t have a long-term purpose.
I have found a few ramps that are different, though, and one of my favorites is the Diolkos.
The Diolkos, built by the ancient Greeks, was half ramp, half causeway. It was used to transport ships across the Ithmus of Corinth, saving them a dangerous sea voyage. The ancient Greeks actually dragged the ships overland on it. (You’d think a canal would be easier to use, but canals are a lot harder to build and maintain.) Huge teams of men and oxen would have pulled the boats and cargo across it in about three hours per trip.
No one is quite sure when the thing was built, but at best estimate it was in use from 600 BC to 100 AD, which is a pretty good lifespan for a project like that. It was mostly used for shipping but also served a pretty vital role for navies during war.
There isn’t nearly as much information on the Diolkos as I would like out there. The ancient Greeks mostly wrote about their gods and heroes and wars and such, which is disappointing but not unexpected. Most people want entertainment; they’re not looking to find out how the world works.
Today the site has been destroyed in parts by the Corinth Canal, and much of the excavated portions are falling apart due to lack of maintenance and boat traffic on the Canal. It’s not exactly the Parthenon, but it represents a vital look at how the day-to-day functioning of an ancient society actually worked.
Hmm. Maybe I can convince Maggie that we should go to Greece next vacation.
Friction in the Ramp Department
If you’ve ever gone over simple machines in school, chances are—depending on when you took the course—there wasn’t a lot of math involved in the explanation. And if there was, it was pretty basic. It probably involved an absolute minimum of variables: when talking about pulleys, for instance, the teacher almost certainly didn’t include factors like friction, tension, sway, or sweaty hands. (That last one is hard to calculate mathematically, but definitely matters a good bit.)
With ramps, friction is the biggest variable left out; it’s a real pain to calculate. Often, teachers will just do the math with an idealized, frictionless ramp. Makes it really easy for students to figure out but gets a little ridiculous if you try to think about actually trying to use the thing—pure slapstick, really, and slapstick is one kind of humor you don’t want in the workplace.
Now, I’m not a great teacher, but I like to think I do an okay job at it. I helped the kids out with their math in school (I still do help one of the boys with some of his math from work, not naming any names), and I spent years using slide rules before converting to a calculator. I know my math, and I know how to show people how to do it. (No way I could put in the kind of dedication a real teacher does, though.)
So when one of the young guys at work came to me for some help with some math, I was happy to help. The kid thought he’d figured out a way to improve efficiency when loading and unloading. Given how much trouble he is at work, I really hoped this meant he was starting to actually care about his job. Didn’t think anything would come of his ideas, but at least he was trying, right?
Well, come the day he was to test out the idea, it turns out I’d taught him with the idealized frictionless ramp model. That should have resulted in a mess on its own but, luckily for me, his big mistake had nothing to do with my assistance.
The dumb kid hadn’t read the instructions on the ramp he was using. Should have lost his job, but kept it for the same reason he got it. Sometimes it’s about who you know. At least he got transferred to his dad’s department, so I don’t have to deal with him anymore.
Ramps in Higher Gravity
Ramps get more useful in higher gravity.
You’re probably wondering what kind of nonsense I’m going on about now, aren’t you? “McCoy,” you’re saying, “that diet your wife has you on has driven you straight around the bend, hasn’t it?”
Well, it hasn’t. At least not mostly. Hardly any, really.
Anyhow, ramps at different gravity levels: generally speaking, they’re much more useful at the higher ones. If you’re in zero g, just floating around, a ramp is going to be pretty pointless. As gravity gets higher, though, more and more solutions for bridging vertical distances (or, as I prefer to call it, going up and down) become infeasible.
Elevators, for instance, become useless really fast. Materials technology just isn’t able yet to create a material that can maintain the tensile strength necessary for lifts, elevators, etc. Same thing for pulleys and lifts. Building a high gravity ramp, though, doesn’t require expensive, crazy space materials—it requires dirt. Just dirt. Good old fashioned, boring dirt. Just start piling it up, and there you go.
As far as I know, there’s only one book where a ramp saves the day, and that’s Mission of Gravity, by Hal Clement. It takes place on this weird planet with enormous gravity that actually changes between the poles and the equator. It’s weird, but the math works out. Anyhow, these little centipede aliens who live there are hired to retrieve a human probe near one pole, where the gravity is highest, and they end up using a ramp to retrieve the probe’s computer at the end. My oldest son found it for me, back in the kids’ rocket-ship-loving days. Not much of a reader, but I liked that book well enough.
“McCoy,” you ask, “that’s all fine and dandy, but it doesn’t actually answer my question. Are you thinking about heavy gravity because the diet’s working and you’ve lost weight? Or have you been cheating on the diet and actually gaining weight?”
Well, let’s just say Maggie wasn’t happy when she found me taking apart our scale to try and gimmick it to read my weight lower than it is.
On Runaway Truck Ramps
If you’ve ever taken I-70 through the Rockies, you’ve probably seen those steep gravel turnoffs leading up from the road, then abruptly dead-ending, as well as all the signs advertising them.
Those are runaway truck ramps, and they’re for semis whose brakes have blown.
The idea is pretty simple: an out-of-control truck can’t stop, so the driver keeps his foot off the gas, waits for a truck ramp, then expends all the truck’s momentum going up it.
In practice, though, these ramps are pretty complicated.
First off, you’ve got to make sure the truck won’t roll back down. One way to do that is to have a long flat stretch after an initial rise (though this obviously doesn’t work in the Rockies).
Another version uses sand to absorb all the momentum: semi tires are big, but not big enough to take a semi through sand. The problem with sand ramps is that the semis have a tendency to flip on them.
Finally, there are the ones made of loose, ungraded gravel. They work great but rip up tires and undercarriages.
Steep gravel ramps—like the ones on I-70 are the most common. Moderate damage is better than overturning or rolling back onto the road. It’s not an overly complicated issue, but the sheer force of a fast-moving semi complicates the solution, especially since they’re nowhere near as durable as they are in movies.
All of that said: never, ever drive a non-semi vehicle up there. It will not survive.