MIT students build a roller coaster in one week

[msandford]

Did anybody else laugh at the idea of using 2 grade 5 1" bolts per 2x4? I know wood is strong and all, but it's not that strong! They could have held it all together quite successfully with some 3" deck screws or 3/8" lag bolts.

By using such big bolts they actually made the structure less safe because they had to drill very large holes; those holes made the wood weaker than it otherwise would have been. I don't know who at MIT insisted that they use 1" bolts but that person had no business sticking their nose in.

[moeamaya]

Ben mentions his frustrations in his blog: Despite my personal opinion that these changes were unnecessary and frankly absurd (in addition to costly: 1" bolts cost around $10 apiece), we didn't really have any choice but to make the changes. After all, for the Cambridge and MIT to let us build this thing and have people ride it, we absolutely needed our plans to be signed off by a professional engineer.

The Roller Coaster used to be an annual tradition but was put on hold the past few years because of EHS regulations and safety concerns. I know they really wanted to build it this year, so they obliged with the request.

[rtkwe]

There are some benefits to through bolts over deck screws or lag bolts. It's easier to inspect a proper bolt to make sure it tightened and fix it if it is too loose. A screw could strip out with the vibration and stresses of the ride and it'd be really hard to check and fix.

[jleader]

I'm not a structural engineer, but would there be any advantage to the larger bolt spreading the shear load over a larger area of the wood? Imagine a needle-thin (but incredibly strong) bolt; it might just tear through the wood fibers under load.

I've seen rings (like http://www.portlandbolt.com/products/others/splitrings.html) used to spread the load over a larger area of the wood, with a bolt keeping the wood members pressed against the ring.

[bpowah]

Yield strength for steel is about 5x that of wood's UTS, and the cross-section of a 2x4 is about 5x that of a 1-in bolt, so yeah wood is 'that' strong. Screws are typically used in a way that they are not carrying a static load -- basically just holding the structural wood in place. The static load in a structure is usually transferred wood-to-wood. When you do see steel carrying a load in a wooden building, it is generally surprisingly beefy-looking.

[dugmartin]

Deck screws don't have much resistance to sheering. When any kind of force is involved other than gravity deck screws do well holding things down but not up or on. If you look at a well built deck all horizontal attachments are bolts or nails.

[Animats]

The support structure may be overdesigned, but that's OK. What bothers me is how the cart attaches to the track. Here's a view of that:

http://formlabs.com/en/company/blog/2014/08/27/from-3d-print...

The retention wheels are just riding on the underside of the plywood sheets. If they had a jam at a track joint, those might tear through the plywood or break off, allowing the car to derail and fall off the track. Unsupported plywood edges are weak and not good working surfaces.

Here's a standard roller coaster wheel assembly, with six wheels.

http://www.themeparkreview.com/forum/files/dsc_0207_3.jpg

Any 3 wheels can fail without serious trouble.

[Someone]

Any 3? If the top two fail, the assembly drops from the rail, doesn't it? If the bottom two break off, the thing could derail in a negative g track part.

I would think that is only true if we consider that cars have more than one of these.

[hollyfeld]

Oh hey, and look at the 18" long cracks in the plywood you can see in that picture.

But at least they used 1" carriage bolts to hold it all together.

[iammaxus]

We are proud to say that Ben Katz, one of the leaders and designers of the project interned at Formlabs over the summer and used our printers to make a beautiful detailed model of the roller coaster.

http://formlabs.com/en/company/blog/2014/08/15/formlabs-engi...

[thejerz]

There's something about "roller coaster" and "built in one week" that doesn't sit well.

[baldfat]

You kidding me I am seriously thinking this is a "doable" project for the annual friends picnic in June.

[fit2rule]

Come on, really? Plenty of great houses have been built in a week, lots of other workable structures in less time ..

[eru]

Most fairground attractions are assembled in a few hours. Including roller coasters.

[ada1981]

I would have liked to see a loop combined with a gyroscopic chair, so no person is actually upside-down. It also seems like these are the sorts of things you are supposed to just build without university approval ala Real Genius.

[fortawesome]

MIT used to ignore this sort of thing and let it happen. After some students died roof and tunnel hacking, the attitude slowly changed, sadly. You can't do it without approval anymore.

[ackalker]

"EHS said No Upside-Down People. Period."

Well, they didn't say anything about cows, did they?

Hey guys, you're MIT hackers. Involve a cow, will you? Upside-down, if at all possible...

[pokpokpok]

I welcome any hack that involves consenting parties

[brianpgordon]

It would be easier to calculate the forces involved as well, since, as everyone knows, cows are approximately spherical.

[willvarfar]

Did they point out to all passengers that there was no stop block at the top of that final incline do you think? Get the mind racing that would ;)

[wolfgke]

I think the end is as least as high as the beginning, so by energy conversation there should be no danger.

Additionally there is probably so much friction in the system that it should not be necessary.

[afarrell]

This is attempted every year, the rush chairs were just on-point with project management this year.

[fortawesome]

Yep. Been a big rush event for a while now. IIRC, Mark Feldmeier was a big part of the first incarnation. Such an awesome dorm. Always making stuff.

It was (is?) a big center of roof and tunnel hacking. One guy from my floor went out every night for a couple of years trying to collect all of Sophicles' sign-ins. And don't forget the Oddball Olympics. I remember the Master Lock picking event usually being won in less than 10 seconds.

[leephillips]

Aren't they a little young to be building roller coasters?

[ykl]

"Why yes. Yes [they] are."

[jpmattia]

Excuse the inside baseball, but old 5W EC dude from '86 raises his glass (of coffee at this hour) in your guys' general direction.

[losvedir]

5W '07 checking in. I think the first roller coaster for EC rush was around my junior year. I'm glad to see the tradition is still going strong!

[TylerE]

This is pretty much the gold standard, built by ONE guy...

https://www.youtube.com/watch?v=5gcoV3MkmY8

Took a lot longer than a week, I'm sure, but it's an actual proper coaster. He later went on to work for one of the coaster companies for awhile IIRC.

[kdavis]

Next time start it off the top of the Green Building!

[ordinathorreur]

As a skateboarder I could see this being a lot of fun. It would be great if the project could be donated to a local skatepark once taken down.

[andrewbarba]

Believe it or not, we have zero skateparks in Boston. There are plans to build a pretty extensive one however I haven't seen any real progress being made.

[lnanek2]

Kind of lame they weren't allowed to put a loop in. You are just as well off sledding down a hill at what they ended up with.

[papad]

Ha totally agree. The loops and vicious turns are central to a roller coaster (and being tied to the track). Without those, sledding is way better cause you can get some serious airtime on the right hills and have some control over your direction too.

Overall a neat project for a large college team to work together on but the end product doesn't appear that functional/fun.

[canjobear]

While this is awesome work, I find it sad that those involved seem to have cheerfully acquiesced to the diktats of a safety- and image-obsessed administration.

Or perhaps their true attitude just wasn't appropriate for this blog post.

[cdnsteve]

Get rid of the end vertical and make it launch you into a foam pit. I can see some "midnight" modifications for a 1.1 release.

[brador]

How do they get it back to the starting position? It's not shown in the vid.

[asportking]

They had people manually pushing it back up the last two humps, and then they had a rope they hooked to the cart to pull it up the last hump.

Source: was one of the people pushing it back over the humps. Surprisingly a sketchy job - you have to really go for it to get it over the middle hump, and if you don't make it then you have to bail really quickly.

[justfane]

It doesn't have enough momentum to fully go up the last 'slope' so it rolls back down with the momentum to get back to the starting position... I believe that's what i gathered from the end of the page.

[sangwen]

Look up to these east campus kids!!