Top Thrill Dragster gets stuck on the tophat once again!

Nope. It's quite level.

Besides, if a person (or 2/3) can give it a push to get it moving when it is balanced at the top, I'd venture to say you can find a motor with enough hp and torque to do the job.

Yeah, I don't see how a set of kickers would not be able to push it over. When the train is at equilibrium like that, it will take much less force to get it moving in a direction versus pushing that same train on flat track. A little weight shift or push could get it rolling, unlike if it were on the ground.

But I don't think they mind going up there to push it when need be. I don't think the occurrence rate is high enough to justify them spending the $$ to "fix" it.

So I have a question...why hasn't KK stopped at the top yet? I can't remember from my rides on it if the brake fin is at a point that will not impede the passing of a train, or if they are located in a position that would be "under" a train if it was to balance on the top hat?

If so, wouldn't that increase the likelihood of KK having a "stop"?

It was theorized on PointBuzz that they over-launch by a couple miles per hour, with the down-side brakes in place to slow it down a bit. I can't imagine that would be good for humans, but I don't know. The other theory is that the peak is more pointed, so as to reduce the likelihood that the train could balance up there, but I've never really compared photos.

Touchdown said:
Im pretty sure that the transfer track is at an angle so that the train rolls down it from its storage track.

Of course the kicker wheels can move the trains around. What happens when the trains move from the unload to the load on Dragster or Millennium Force?

They look pretty similar to me.
[Dragster] [Ka]

It also looks like the static fin on Ka is downtrack from where it would balance, but that's just an eyeball approximation as well.

Edit: I never realized the trains were that different. Maybe that's why it hasn't happened on Ka?

Edit 2: That Dragster pic looks to be from testing, hence the shorter train. Still, Ka holds 4 in its first car rather than just 2 and vice versa for the back cars of each.

Also on a flat break run after a complete stop how does the train start moving on its own? I am not sure it is true they can't over come stopped friction a guy was able to push it by hand

Top Thrill Dragster is not the only coaster to do this. Here is Stealth that has no elevator. http://www.youtube.com/watch?v=chkej8kLLkM

I hope I posted the link properly if not I am sorry guys.

They should've just launched another train into it's butt. ;)

Do they just have a crane chilling out?

My understanding is that Jeff is right. The brakes are past the point of no return (otherwise they'd cause more rollbacks) but they do allow the launch to be a little stronger than "normal" to make sure the train clears.

I know there's a whole lot of other factors, but an off the cuff calcuation (ratio of square of speed to height) tells me that if 120 MPH can clear 420' then 128 MPH should be able to clear 477'

Touchdown said:
Im pretty sure that the transfer track is at an angle so that the train rolls down it from its storage track.

Let's assume this is true, how does the train get *on* the storage track? Wouldn't it have to be pushed uphill? I'm pretty sure they use kicker wheels to move the train on/off the storage track.

I wonder what the distance is between just getting stuck going up and just getting stuck going down. I assume it's pretty small: on the order of inches, even. It would depend on the friction between the wheels and the axle which would theoretically vary throughout the day. If the axles are lubed in the morning, getting stuck could be more likely at night.

Also, even if some transfer track is slanted down (there are many like this), almost every station is completely level, and kicker wheels are used often to accelerate the train out. Look at the Texas Tornado.

http://rcdb.com/ig492.htm?picture=3

It uses liberally spaced wheels to bring the train up the lift. I'm sure they could even put the kicker wheel(s) on a motorized unit so they drop down under the point of contact during normal operation and just pop up when needed. Can't be that hard.

It's probably not too hard, but is it worth the effort and cost to install at 420' when it's needed once a year and only saves 20 minutes?

So in a sense what we are theorizing is that KK is launched at a speed higher than normal to clear that tophat, and the brake installation is to help offset the additional speed. Comparing it to TTD, it would be like continually launching it at 125, compared to the "norm" of approximately 121.

I also remember thinking the shape of the top hat on KK seemed like a slightly smaller radius, thus decreasing the potential of a stop. It seems a kicker wheel would be a simple solution, however placement could be tricky. Although I agree the chance of a train balancing is probably reduced to a few inches, the location of that could vary, based on the distribution of weight in the train. I doubt anyone has compared this, but the location of the train when it was stuck with only 4 people on it is probably different than when a trainload was stopped. I am guessing more than one kicker wheel would need to be in place. Honestly, I don't think it would be worth the investment and engineering though, based on the mathematical chance of it happening. On Stealth though, without an elevator, it might be worthwhile (thanks for the link Armsdown as I was wondering what the simple fix was for XLR8R in that case).

Regardless of where it would stop, I think it's more than a safe bet that the some part of the train would be over the apex every time. One wheel would do. It would need to be one of those retractable types, I assume, and you couldn't put it at the apex due to the support junction.

An electric motor with one or two kicker wheels wouldn't be that bad. You could just add a simple switch on the control panel to control it. The biggest cost would be the 1000' of extension cord...

Um, kicker wheels are used to start movement typically on flat track where once the brakes are released, there is no way for the train to start coasting on its own. So what about the kicker wheels on flat track which move the train from a static position out of virtually every Intamin and B&M coaster station? Regardless you're seriously arguing that a mechanically-driven tire can't do the job, but a humanoid maintenance man can? I don't buy it. It shouldn't take much force at all to unbalance the train from that point, as suggested by the fact that a single maintenance man just has to give the train a push.

Jeff, the only reason one wheel might not work is if that one wheel is positioned perfectly between two cars. There would have to be a ridiculous offset of weigh distribution (as the human mass pales in comparison to the train's mass) in either direction for this to happen, though.

I just kept help but wonder if this conversation occurred in the Intamin Engineering office:

Person 1 - "I am just finishing up the drawings on the XLR8R ride concept. You don't think we need to have a contingency plan for a train stopping on the crest of the hill do you?"

Person 2 - "Ahhhh....are you crazy? That's not going to happen. Not possible...the chances are too small"

Person 1 - "You're right. Let's go have something to drink."

OK...maybe not quite that way...but you get my drift. :)