# TTD rollback question

Thursday, September 25, 2003 2:27 PM
I'm sorry. I know it's been awhile with no Dragster topics. I just have one question. Sometimes when people talk about they say 'they had to launch it at ______m.ph. to make it over the hill'. My question is do the ride ops control the exact speed of Dragster or is it automatically done with weight? Thanks.

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-Sean Newman

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Thursday, September 25, 2003 8:39 PM
It's neither. The launch speed (power) is controlled by the speed of the previous train over the top. The differences in weight between each train load is miniscule compared to the overall 5-ton weight of the train. In theory, if the train that just went over was going too fast, the next launch will be slightly less powerful and vice versa. Keep in mind we're talking a 2 or 3 mph window between a rollback, and unsafe negative G's.

-seth

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Friday, September 26, 2003 1:56 AM
How are negative G's on TTD unsafe?
I guess you're OUT OF YOUR SEAT on this ride for some time anyway... especially on the way down.
Isn't that why they staple you into those cars?
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Friday, September 26, 2003 3:11 AM
Last friday most of the launches were being clocked at 120-123 MPH. They were having many rollbacks and eventually they loaded the trains to only half full. Later on they filled the trains up with the exception of the last 2 or 3 rows. I have seen them do this several times.

Maybe they should of limited each train to two cars max in the first place? There is obviously a weight issue here, especially after they removed the tires and spoilers off of each train.

-Tina

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Gimme speed, height, airtime and plenty of LAUNCH!!!

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Friday, September 26, 2003 3:56 AM
Seth, That doesn't make much sense to just launch a train according to what the previous train did. I would link that there can be a wide range of passenger weight from train to train. If you have a train load of, say, large adults, 250lbs. X 18 passengers = 4,500 lbs. Now say the next train is mostly kids, 100lbs. X 18 passengers = 1,800lbs. That's almost 1 1/2 tons difference in total passenger weight. I know that these are extreme, but would have to be planned for. I would think that the speed of the launch has to be controlled by some sort of a mechanical governor, either on the hydraulic motors or on the spool that draws in the launch cable, that controls the main valve supplying the hydraulic oil to the motors.

Superman, even though you are stapled, you still get some good air. If you go too fast over the top, the negative Gs could become dangerous, causing too much blood flow to the head, bruising your legs or even breaking them.

I saw them testing one time where all of the breaks on the launch track came up before the train reach the end of the launch. I don't know if this was an overspeed test or just something went wrong, but I am sure that there is some sort of backup that kicks in if the train is launched too fast.

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2003 Parks: Cedar Point, SFWOA, Kennywood, PKI, MIA, SFGAM, SFKK and HW.
Still deciding where to go in 2004.
*** This post was edited by CP ismyhome 9/26/2003 8:07:08 AM ***

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Friday, September 26, 2003 5:01 AM

coasterqueenTRN said:

There is obviously a weight issue here, especially after they removed the tires and spoilers off of each train.

I've felt since they made that change that this is the reason they have so many (comparative) rollbacks now. I know there isn't *that* much they can do about it, but when they're launching empty trains, they have to know that its going to roll back, lacking that major weight source on the back to provide momentum over the top of the hill. I would think it would be a rather simple matter to just always have 4 water dummies filled and ready to go for post-breakdown testing, just to speed the process up. Other than that, I no longer have any complaints about CP's operation of this ride, I think they deserve much praise for the way they've turned things around with this ride.

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Brett
Resident Launch Whore

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Friday, September 26, 2003 5:12 AM
We've got a great thread on GTTP where no one has come up with a logical and scientifically sound reason to half-load trains.

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Jeff - Webmaster/Admin - CoasterBuzz.com - My Blog
Blogs, photo albums - CampusFish
What time does the water show start?

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Friday, September 26, 2003 5:19 AM
Weighing of trains? The trains aren't weighed... what are you talking about?

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Jeff - Webmaster/Admin - CoasterBuzz.com - My Blog
Blogs, photo albums - CampusFish
What time does the water show start?

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Friday, September 26, 2003 11:26 AM
According to Monty Jasper at the Coastermania Q&A session (2nd session) the speed of the launch is determined, basically, by the computer taking the average speed of previous trains as they passed over the top of the tophat and adjusting the launch speed accordingly.

He went on to explain that this is one reason that rollbacks are more likely to occur when trains haven't cycled for a while- the computer resets to a default speed and will adjust from there.

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- John
Homepark: CP Home-away-from-homepark: PKI
My Campusfish Blog

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Friday, September 26, 2003 12:20 PM
That bit of information sheds a lot of light on things for that GTTP thread. It would make sense to me then, to start a couple mph higher and adjust down then during the test launches.

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Jeff - Webmaster/Admin - CoasterBuzz.com - My Blog
Blogs, photo albums - CampusFish
What time does the water show start?

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Friday, September 26, 2003 1:41 PM
Is there a non-obvious consequense of rolling back? Just curious if something wears only on rollbacks or if something isn't designed to rollback too often.

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Be polite and ignore the idiots. - rollergator
"It's not a Toomer" - Arnold Schwartzenkoph
"Those who know don't talk and those who talk don't know." -Jeff

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Friday, September 26, 2003 1:46 PM
Also, just to bring a point that was on GTTP here, I don't think front loading the train will help it when it crests. Presumably the amount of energy imparted on the train in launch will get the CoM up to a certian height. It will hit this height on the way up rather than the way down, regardless of whether you frontload or backload the train. If this height is > 415' (wherever the CoM is when the train is equally loaded and perfectly balanced on the top) you won't rollback. If it's less than that, it will.

I think.....

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Be polite and ignore the idiots. - rollergator
"It's not a Toomer" - Arnold Schwartzenkoph
"Those who know don't talk and those who talk don't know." -Jeff

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Friday, September 26, 2003 4:00 PM
I definitely think that Dragster will get a lot of care this off-season. Hopefully, they will find something to help this problem. Really, I believe that they have most of the kinks sorted out, it is just the rollback problem. Hopefully their smarts will find something to solve this, it does cause much longer queue times!

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Enjoy your ride on Millennium Force and your day at America's #1 Roller Coast!

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Friday, September 26, 2003 4:10 PM
Could they put really lower power lim's at the top to make sure the coaster make's it over?
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Friday, September 26, 2003 4:23 PM
No. I mean technically they could, but it would require all new control systems, debugging lims that were 400' off the ground, a new power source, some way to get the power up 400', new fins on the trains, and some way to keep fins on a train that's curving down straight in the LIM's. (I suppose they could be on the tower, but I don't really know how much straight track there is).

This ain't RCT, folks.

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Be polite and ignore the idiots. - rollergator
"It's not a Toomer" - Arnold Schwartzenkoph
"Those who know don't talk and those who talk don't know." -Jeff

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Friday, September 26, 2003 4:43 PM
Michael, you said the same thing I had already said. I guess I didn't mention Monty Jasper said it, so I lost credibility. OH well.

-seth

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Friday, September 26, 2003 7:42 PM
Sorry, Seth. I guess that's just how it goes, eh? ;)

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- John
Homepark: CP Home-away-from-homepark: PKI
My Campusfish Blog

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Friday, September 26, 2003 11:27 PM
Yeah...people tend to read the first post, and then skip ahead...such is life on an internet messageboard. No hard feelings. ;-P

-seth

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Saturday, September 27, 2003 7:48 PM
Doesn't HyperSonic XLC weigh the trains to determine how much air pressure to use? Why couldn't a similar mechanism work on TTD?
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I'm a loser.
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Saturday, September 27, 2003 8:59 PM
I think they do on Hypersonic XLC as far as i know, but that kind of mechanism costs more and will slow the load time becuase it has to get the wait and then calculate how much oil and nitrogen it needs. In addition it could be becuase XLC's air launch is more sensitive to weight
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