Save the date: Dollywood, Saturday, May 19, 2012

What is there to know? Did it affect the speed of the ride? Probably a little bit at the bottom of the first drop (maybe an MPH or two if that). By the end of the ride, I'd be surprised if anything but an incredibly finely tuned instrument could detect the difference in speed.

Okay, so I was bored an crunched the numbers:
If the train had 0 initial velocity and no friction, it would be traveling 94.7 MPH at the bottom of a 300' drop.
10 MPH initial velocity, it would travel 95.25 MPH at the bottom.
20 MPH initial velocity, it would travel 96.8 MPH.

Over a track which normally takes about a minute, that's a difference of a half second and a second respectively without friction. Friction would tend to push the ride times together since some component of friction is proportional to speed.

I seriously doubt you could actually tell the difference just on pure speed. You could probably tell a difference in the amount of airtime on the first drop, though, because the centripetal force is proportional to the square of the velocity and at the top of the drop, that would be a big difference.

The weather and contition of the wheels and lubrication are probably the biggest factors with regards to having different rides from day to day.

Calculations based on a point mass are theoretical and erroneous - especially when you are looking at something as mathematically complex as a roller coaster train loaded with riders. In reality, you have to take into account the weight distribution of the riders on the coaster train, the stuff Jason mentioned above, etc., etc.

When we used to test the Blue Streak on a cold morning after the wheels were packed with grease - all the bigger kids had to sit in the front of the train and the smaller in back (it was usually the manager reminding us "girls in the back, guys in the front." Of course, there were always a few amazon girls that sat near the front. Either way, we still had roll backs, but the weight distribution helped.

There are a few coasters that load front to back, only - no riding in the back if the train isn't full, to prevent a potential roll back. The Tornado at Adventureland in Iowa, Gemini at Cedar Point and the former (still sad about that) Laser from Dorney Park come to mind.

It seems to me that they rope off the middle rows of gemini when the lines are short. Am I wrong? They definitely do it on Magnum.

^It definitely used to be the back car roped off on Gemini, then the back two if it was that dead. But that was also years ago when 3 trains always ran, and there were no seat belts.

CoasterDemon said:
But that was also years ago when 3 trains always ran, and there were no seat belts.

Heh.

SFoGswim said:
ISo, using these numbers, 99.19% of the car's energy at the bottom of the hill is from the drop itself and just 0.81% is from the chain speed.

Thanks... this is what I was after. I wish I remembered more of high school physics, but I knew the science could back up what I was saying.

I won't totally discount people who think they can tell the difference in speed on some coasters, but not Millennium Force in typical weather conditions. A loaded train on an average day tends to deliver a pretty consistent ride time. Now Magnum, that's a different story.

CoasterDemon said:

When we used to test the Blue Streak on a cold morning after the wheels were packed with grease - all the bigger kids had to sit in the front of the train and the smaller in back (it was usually the manager reminding us "girls in the back, guys in the front." Of course, there were always a few amazon girls that sat near the front. Either way, we still had roll backs, but the weight distribution helped.

There are a few coasters that load front to back, only - no riding in the back if the train isn't full, to prevent a potential roll back. The Tornado at Adventureland in Iowa, Gemini at Cedar Point and the former (still sad about that) Laser from Dorney Park come to mind.

Point mass is a good enough approximation to show that you really can't tell the difference in speed of the train, though. Sure, there's a ton of other things going on, but you can't deny that a 20 MPH difference in initial velocity results in a 2 MPH difference in final velocity.

Why would that help prevent a rollback? If anything, you'd want the most mass at the back of the train (center of mass is highest when the chain releases -> most potential energy, center of mass is lowest when the train crests hills -> least energy needed to avoid rollback).

Well Andy, go do it in real life, and tell me how it works for you :) That's all I can say; I can't prove it with words.

It worked when I was there, to have the heaviest people in front. It didn't work well the other way, that's why they did it. I'm simply passing on my experience and my educational background in Mechanical Engineering.

A point mass is a rough theoretical approximation for a condensed solid mass, as it is - let alone a coaster train.

I'm not saying it didn't, I'm just curious why, because my physics intuition (which is obviously completely theoretical) seems to indicate the opposite. (editted from obvious)

But in terms of simple mechanics of a falling object, it's a good enough approximation. A ball thrown off the top of the MF lift hill will behave more or less the same way as the train going down the first drop, at least for those few seconds.

I can understand your point :)

But I have a feeling I shant throw a ball from the Millennium Force! Could you imagine a super ball thrown from there!

I'm sure it's terminal velocity would make for a less than spectacular performance. :-) Just like when Mythbusters busted the myth of a penny being thrown from a skyscraper.

Here's a video showing testing of the newly reworked Georgia Cyclone, showing the dummies in the front half of the train.

^Of course they're dummies in the front half, the back is where the action is! ;)

:)

P.S. The hill looked to be performing pretty well...

Did I miss something? What did that have to do with anything being discussed here?

Responding the question of whether a front loaded or back loaded train is more likely to valley.

Just something to be aware of in the coming weeks (and likely months) for anyone using I-75 to get to Dollywood:

http://news.tn.gov/node/8534

Having spent more than two hours slowly crawling into Tennessee on Friday evening we can attest to just how much this has impacted southbound traffic on I-75. Anyone traveling at high-volume times like Friday afternoons/evenings would be wise to plan for extra drive time and/or a good detour.

Ugh. Thanks for that.

I had no idea there were issues and plans to head down via 75 on the Firday before the event.

That KY/TN border on 75 has been miserable every time I've driven though there, although usually thanks to very poor weather conditions, not road work.