Why are block brakes needed?

Yes, I know - it's so more than one train won't be in a certain section of track at the same time.  But why is this necessary? 

Take, for example, PKI's Vortex.  There is a set of brakes in the station, as well as a set outside the station and a third set before that, before the final curve.  That's enough room to stop and hold three trains.  So if anything should happen, those sets of brakes could be used to prevent a collision, right?

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You can't spell "dishonorable" without "honorable."

The block brakes are just mainly a back-up stopping point to be used only when needed. They are there for anytime you may experience stack-up of trains. Sometimes there are mechanical problems where a train may get stuck on a certain set of brakes and the train behind it may need to stop on the block brakes. They are mainly just a extra pre-caution to be used only when needed.

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PKI Flight of Fear Crew 01' & 02'

well, Den, imagine a train is "stuck" on those brakes right before the final curve...you'd hate for a train to enter the last block, so the mid-course brakes would be necessary to prevent a collision...
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PoTP acolyte - remove fear to reply
Son of Drop Zone - PKI CoasterCamp I Champions!!!

Train A cannot leave the top of the lift, until train B has passed the block brakes.

If those brakes are at the end of the ride then train B cannot be dispatched as quickly, because the crew has to make sure that it won't get to the top of the lift before train A hits the brakes.

With the block brakes in the middle of the ride, train A can be dispatched a lot sooner (hopefully as soon as it's ready) as train B will have passed the mid-course block brakes by the time A gets to the top of the lift.

Wait until Dave replies, he'll do a far better job of explaining this.

Cam.

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Cameron Silver

Isn't this where Dave Althoff, Jr. goes off into one of his manifestos about block brakes? ;)
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Ride the New England Bush!

To answer what I think your question is. If two trains are allowed into the same block, and the first train stops for any reason including mechanical failure, valleying, or even the brakes at the end of the block, then the next train will crash into the back of it.  If the speed is slow there will be injuries.  If the speed is at all fast there will be deaths.

These sites can provide answers to all of your questions on blocking:

http://capital2.capital.edu/admin-staff/dalthoff/
http://www.coasterquest.com/

*** This post was edited by Jim Fisher on 1/30/2002. ***

Nemesis doesn't have block brakes...

There are a lot of rides that have blocks that aren't used because they can't run the ride efficiently. A perfect example would be Batman at SFWoA. On that ride, the next train is usually in the final brake run long before the next train crests the lift.

Why bleed off speed at a mid-course block? Well, as has been described before, it's a matter of spacing out the trains to hit interval in most cases.

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Jeff - Webmaster/Admin - CoasterBuzz.com, Sillynonsense.com
"As far as I can tell it doesn't matter who you are. If you can believe, there's something worth fighting for..." - Garbage, "Parade"

Finally, Jeff gets to the heart of the matter.

Going back to the original message, regarding the Vortex: It has been noted that there are brakes in the station, on the transfer table, and immediately uptrack of the transfer table, behind the Troika. With three trains on the ride, that's three brakes, and the lift makes a fourth block, so provided that the trains can move through the blocks in less time than it takes to crest the lift, there should be no need for a mid-course block brake. As a matter of fact, that's exactly how Magnum XL-200 operates. But on Magnum, there is a long, slow bit of track between the two block brakes, and the lift is extremely long...it takes a minute to get to the top. In fact, that's why it works so well: From the time the train is dispatched until it gets to the top of the lift is about a minute, from the top of the lift to the block brake at the end of the ride is another minute, from the block brake to the transfer table is about 25 seconds, and it takes another 20 seconds to park the train in the station. That way, a train is dispatched from the station, and within 75 seconds, the lift is clear to allow another train to go. While that second train is on the lift, the first train completes the course and rolls through the block brake, so by the time the second train reaches the top of the lift, the first train has passed the block brake and is well on its way to a brief stop on the transfer table. Once the second train clears the lift, the third train can be dispatched from the station, the first train rolls into the station, and the second train cruises through the high-speed portion of the ride.

That's Magnum. Vortex is a little different because the lift is significantly shorter than the lift on Magnum. Overall, the ride is about the same length, but because so much less of the ride time is spent on the lift, leaving out the mid-course block brake would leave the ride with a short lift block and a very long ride block. So once the first train crested the lift, the next train couldn't be allowed to leave the lift until the first train was nearly finished with the ride. So you have a fully-loaded train waiting in the station, a train on the lift, and a third train sitting on the transfer table. Finally, the first train approaches the Boomerang, and the second train can be dispatched to the lift. The third train then enters the station just as the second train is approaching the transfer table for a very long wait. Putting the mid-course brake in before the Corkscrew means that in the time it takes to get a train up the lift, another train can clear the block between the top of the lift and the mid-course brake. That way, as soon as the first train clears the lift, the second train can be dispatched...by the time the second train gets to the top of the lift, the first train will be past the mid-course brake. The third train can be dispatched as soon as the second clears the lift, as by the time it gets to the top, the second train will be past the mid-course brake and the first train will be back to the station. With fast crews, this configuration means NOBODY should have to wait on the transfer table. In practice it takes a little longer to load the trains, but even at that, waiting time is minimized and the capacity is maximized.

--Dave Althoff, Jr.

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FoF said:
"Block brakes are used to create an additional block, therefore being able to run an additional train.

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That's true as far as it goes, but as Den pointed out, Vortex has enough blocks to run three trains even without a mid-course brake! In that case, as I outlined in my other message while you were posting your comment, the extra block doesn't allow for an additional train, but it fixes the block spacing to allow for more efficient operation.

--Dave Althoff, Jr.

Um, the idea of a midcourse brake is so you can have 2 trains on the ride course at the same time, increasing capacity greatly.  If you had 3 trains and no block brake, you wouldn't be able to dispatch the one in the station until the previous train had hit the brakerun (which would be just like 2 train operation pretty much).  If for some reason the first brake in the brakerun doesn't open up and there's already a train in the ride course with no block brake, you have a collision.  If there is a block brake and the first brake in the brakerun doesn't open up, the block brake will stop it.  It really isn't as complicated as some people make it.
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Is it the roar of Kumba or the kumba of Roar?  Discuss!

*** This post was edited by Spacecase8310 on 1/30/2002. ***

what Dave said  :)

 

(Why did I know there's be a thesis on applied blocking theory in this thread the instant I read the title?? :)  )

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Scott W. Short
mailto:scott@midwestcoastercentral.com
http://www.midwestcoastercentral.com

If block brakes are meant to allow for multiple trains on the course at the same time, than why don't we ever see that?  For instance, Raptor has a mid-course block brake, but the way they run the ride, the train on the lift never crests the lift until the train on the course hits the brakes at the end of the ride.  Theoretically, the block brakes aren't even needed because if there was a rollback on the course, the chain lift would stop since the train on the course would not reach the end of the ride.  This goes with just about every coaster I can think of (except Mean Streak).  The intervals are designed so that the train stays on the lift hill until the train on the course has completed it, therefore making the block brakes on the course pointless.  Just an observation.
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"I'm just trying to find a decent melody...A song that I can sing in my own company."
- U2 - "Stuck in a Moment You Can't Get Out Of"

Mr Hippo: Rides like Nemesis and Batman:TR need no midcourse brakes due to the fact that the ride duration is pretty darn short. The ride time on B:TR is 34 seconds (or very near that) and I'm not sure about the lift hill time, but it couldn't be very long either. Even with a quick crew, it is a rare event that a dispatch on B:TR to have to wait for the block to clear. Nemesis has an even shorter track length, so I suppose the same blocking rules apply.

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Nothing... NOTHING... can prepare you for... the Fourth Dimension!

I think another reason we see so many sets of brakes is because in addition to having onely one train per block, it is desireable to have an empty block separating each train.

The Mindbender at SFOG has 5 blocks.  There is a station block, the transfer block, lift block, main brake block (from top of lift to end of main brakes), and a 'ready brake' block between the main (reduction) brakes and the station.

What's important here are the main brakes and the ready brakes.  They obviously work independent of each other.  Considering this, the Mindbender could technically run three trains with no problem (it did have three trains but never ran them all at once).  However, the ready brake is only used to stop trains in emergencies... such as if the main brakes failed or didn't fully stop the train.

If Bender was running three trains, think about this situation:

One train is in the station being loaded.  One is sitting behind it in the ready brakes, and one is out running the course.  That train enters the main brakes which don't work for some reason.  It them slams into the train staying in the ready brakes.  That's why even though many coasters have enough blocks to run more trains than they do, tehy don't. ;)

I should add:  many coasters will automatically slow or stop trains on the lift if the train in front of it hasn't entered the next block.  Just another safety feature

MooreOn: Raptor, generally speaking, with a good crew, does have a train cresting the lift just prior to the one ahead hitting the final brake run. While that's late in the second half, it still couldn't do that without the block. When said crew is "on" you'll roll right into the station without stopping. I saw it happen quite a bit in August... they were really pushing them through. It's fun to watch!

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Jeff - Webmaster/Admin - CoasterBuzz.com, Sillynonsense.com
"As far as I can tell it doesn't matter who you are. If you can believe, there's something worth fighting for..." - Garbage, "Parade"

Mr Hippo & Soggy:

You are Correct, Soggy. Also, the ride only operates with TWO train top capacity, eliminating the need for a mid-course braking system. The station platform contains TWO blocks. The loading area, and the station re-entry (which on B:TR is a VERY long enclosed brake run, sometimes shrouded with a really cool mist effect :) )

Just for the record, IMO, B:TR gathers up plenty of speed that it should NEVER stop on an element by natural means.

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My other car is a Giovanola!

I should comment on something that MisterX said that I didn't...

(well, I guess I can't copy it since every time I click on the top of the page to select the text the browser jumps to the bottom. Strange!)

Anyway, he said something about it being desirable to keep an empty block between trains. This is a procedure which is by no means consistent across the industry. Some parks are rigid almost to the point of paranoia about keeping empty blocks between trains, and at other parks you will sometimes see trains running literally only a few feet apart. The absolute rule is that there must be a reliable stopping point between the trains at all times. Prudent practice usually means two block-brake calipers. Technically, it's OK to have trains in adjacent blocks, but not OK to have more than one train in the same block. Cedar Point are masters at running trains really close..there are times when I have watched two trains pull into the Gemini station before the other two trains have cleared the downtrack wall, such that there were parts of four different trains in the station all at once. And it was safe because the brakes were closed and while the exiting trains hadn't yet cleared the station, they had cleared the last brake caliper. That's technically OK, but you'll never see that at a Paramount park (unless something goes wrong), because Paramount's operational standard requires an additional brake between trains beyond the active block. As an example, that's why Adventure Express has two brake calipers on the track between the station and the first tunnel...brake calipers which should NEVER be used to stop a train.

--Dave Althoff, Jr.

Thanks, Dave.  You are a cornucopia of knowledge.
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You can't spell "dishonorable" without "honorable."