Hey guys, if you look at the trains on Vortex, as well as some other coasters, they have a bar/set of wheels that is drug behind each of the trains. My question is; what are these for? I was always curious, but could never quite figure out the purpose.

To balance it.......

Most coaster cars only have one set of wheels. For example, Diamondback has the nose because the cars only have back wheels. Vortex has the back cart because it only has front wheels on its cars. From what I have seen, only PTC trains have 2 sets of wheels.

See here:

Most coaster cars only have one set of wheels. For example, Diamondback has the nose because the cars only have back wheels. Vortex has the back cart because it only has front wheels on its cars. From what I have seen, only PTC trains have 2 sets of wheels.

See here:

Oh, now I understand. Thanks for the answer, I never really paid much attention to where the wheels were positioned. I always thought that each car of each train had two sets of wheels (one in the front, and one in the rear). I didn't realize they were spaced out in a way that there has to be an additional set of wheels on either the front or back.

Its not just PTC trains that are like that. The trains like Diamondback are called articulated. Essentially, two cars share the same wheel assembly (like in the Diamondback illustration). The wheel assembly acts as the front wheels for one car, while simultaneously serving as the back wheels for another car. This necessitates a lead "zero" car either in front of the train or the back of the train.

Flight of Fear and Backlot are not set up like this (neither is Adventure Express). There, each car has a front and back set of wheels. Millenium Flyers, Timberliners most Vekoma, B&M and Intamin creations all have the "zero" cars.

From what I have seen, only PTC trains have 2 sets of wheels.

Actually most wooden coaster trains have two sets of wheels. Millennium Flyers and the new Timberliners are the only ones that I can think of that don't.

PTC did experiment with trailering their cars, it didn't work to well.

As seen above RWB at GL had the trailer trains originally.

And I can think of at least one roller coaster whose zero car is supposedly heavily weighted, and is required in order for the train to make it through the course without valleying.

PTC did experiment with trailering their cars, it didn't work to well.

As seen above RWB at GL had the trailer trains originally.

I actually liked these trains on Raging Wolf Bobs. They were much more fun than the Gerstlaur trains they had in the end. In the old PTC trailer trains, if you rode in the backseat by yourself, you could literally be tossed into the floor on the first turn around. Now, THAT'S good times!

I never got to ride RWB in either set of trains, but since those have buzz bars, I'm sure that would be my preference.

They had buzz bars the entire time I believe. Later seat dividers were installed, in which my sister flew over once and ended up on the other side! The glory days before seat belts.

And I can think of at least one roller coaster whose zero car is supposedly heavily weighted, and is required in order for the train to make it through the course without valleying.

Actually, every lead axle is extremely heavy to make up for the weight that is not there. Without that weight, the axle could not effectively steer the train and would slip.  There are two axles in the 'zero car'. The front axle can roll while the rear axle I believe helps turn the train. The other cars on the train can roll, pitch, and yaw. Which is pretty much the ability to rotate along the Z-axis(longitudinal axis), X-axis(rotation on lateral axis),and  Y -axis(rotation on vertical axis) . 

May sound a little crazy... lol. 

All B&M coasters have the pilot coaches.. be it a zero car (Diamondback, Kumba, Mantis) or the first row (Montu, Kraken, Dominator, etc.)

Montu has the optional zero car that replaces the front row making one of the trains 7 rows during film shoots. They run a full train in tandem with the train with the camera mount zero car. For off ride footage, they film the full train. On ride footage is taken from the Zero car obviously.

Photo from Johnny Upsidedown - http://www.johnnyupsidedown.com/events/events10/bc25a.jpg

I am sure that is the original intent of the zero car on Alpie. You can see the holes where the camera mount hangs.