A Voyage question...

Monday, December 10, 2007 8:35 PM

J7G3 said:

needless quotation removed -J
Proves once again, you get what you pay for! Remember in the 80's and 90's when PTC were really all the rage and Morgans were the red headed step child. My how things change!That was before PTC began 'refitting' all the old coaster trains with those hideous new L lap bars... uck! The ones on the American Eagle are much better, don't hurt and they 'stay up'. It must be a Great America thing, b/c the hideous PTC L bars on Viper are specially fitted with tough shocks that prevent the bars from falling down. And that does a good job! *** Edited 12/11/2007 1:04:45 AM UTC by Jeff***

The L Bars on Viper (SFGAM) also eliminate the having to sit at a angle due to the bend in the bar of the standard PTC.

I had no problem with them.
Chuck

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Monday, December 10, 2007 10:05 PM
rollergator's avatar

RideMan said:PTCs trains will inflict damage on the track, in many cases apparently substituting track damage for rider damage.

Gerstlauers just go ahead and damage the riders...

Hehe, sorry Chuck. LOL...

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Tuesday, December 11, 2007 1:39 AM
^LOL!

To Dave (or anyone else who might know): What's the difference mechanically between PTC and Gerstlauer trains?

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Tuesday, December 11, 2007 2:54 AM
Gator: You know I was implying that... :)

Craig: Basically, nothing at all.

The original John Allen PTC trains are essentially a box with two or three (or four) seats with four wheel assemblies bolted to it. Not much to it, really, and on a ride like the Kings Island Racer or the Cedar Point Blue Streak, they work reasonably well.

At some point, somebody noticed that the new wood coasters being built were twisters, and one of the problems with a twister is the superelevation of the curves...the banking. If you take a ride on the Lakeside Cyclone and watch very carefully from one of the back cars, you can see the problem. There are places on that ride where the track banking changes, and even though it uses 2-bench cars, that banking change happens very, VERY slowly. I wish I had it on videotape, but the ride was just too violent for that. In order to keep the roll rate within the tolerances of what the Vettel/NAD trains could handle, the roll rate had to be kept at a minimum. The PTC boxcars are similar in that the maximum roll rate is actually determined by the distance between the upstop wheel and the bottom edge of the track, since that's what will jam up when you start to roll. Note also that if you try to roll a car with fixed wheel sets, unpredictable things can start to happen in terms of which wheels get lifted off the rail as the car rolls. You can really see this on the Stricker's Grove Tornado as the train comes out of the first curve and lifts the inside rear wheel on the lead car.

PTC addressed the problem by mounting the rear axle of the car on a longitudinally oriented pivot shaft. That is, the rear axle is attached to a pivot shaft running back to front down the center of the car. There isn't a lot of space for the axle to swing, about three degrees in either direction. But this is a dramatic increase from the older design. If you add that up...a 2-bench car has a wheelbase that is about four feet long. If the front wheels are fixed to the car, then the front of the car and the car body will follow whatever the track does ahead of the train. At the back of the car, four feet behind the front wheels, the rear axle can roll about three degrees in either direction relative to the front axle and the car body. This means that the train can roll three degrees in four feet, or 0.75 degrees per running foot. A 7-car train would be about 49 feet from the front axle on car #1 to the back axle on car #7, meaning that in a single train length the track can roll almost 37 degrees. The lead-in to a 90-degree banked curve has to be about 120 feet long at minimum. Three degrees isn't much, but it is enough to handle some pretty twisted track. It's hard to twist wood track much faster than that!

Well, this is all well and good, and would have been great if coaster designers would stick to fully banked curves. See, by superelevating the track, the actual motion the train has to go through to navigate the curve becomes not a yawing motion as is required for a flat turn, but rather a rolling and pitching motion. If you have ever ridden a bicycle or motorcycle, you already know this: when you lean over to one side or the other, you go 'round a curve, even as the front and rear wheels remain aligned perfectly straight, parallel to one another.

It's kind of clever, and it works reasonably well until you have a flat turn, or any kind of curve where the forces applied are not perpendicular to the rail. If the resolved force going around the curve is directed outward at all, it means that there is a yawing component to the curve motion, and the PTC train is completely incapable of steering around a flat curve. This is when the wheels start screeching unless there is a liberal coating of lubricant on the track and wheels.

So that's how the PTC articulated trains are built, and from the 1930's until the early 2000's, that was the state of the art in wood coaster cars. Morgan had experimented with trailered cars which actually track remarkably well, but ride very poorly, and had some problems with excessive forces breaking the hitch components. PTC experimented with trailering, but overlooked some problems with trying to build a *train* of trailered cars. So while the entire steel coaster industry adopted full articulation, trailering, or a combination of both, in wood coasters the general consensus was to stick with the boxcars with a single axis of articulation. Why? Because PTC's trailers didn't work well, Morgan's trailers didn't work well, and PTC's articulated cars seemed to work better than anything else.

The interesting upshot of all this is that when Gerstlauer got into the wood coaster train business, instead of adapting a Schwarzkopf chassis to operate on a wood coaster, what they did was to basically copy PTC's age-old design. They did make some changes through the use of modern sealed bearings instead of the open bearings on the PTCs, and the steel car bodies and molded seat pads make the car a bit more rigid, plus the molded seats removed the need for seat dividers, and a redundant latch on the lap bar eliminates the need for seat belts. I can understand Gerstlauer doing this as they built their cars for CCI, I understand that CCI participated in the design process, all other CCI coasters ran PTC trains, and they basically wanted a drop-in replacement for the PTCs. This was, of course, good for Holiday World when they opted to replace their Gerstlauer train with a pair of PTCs.

What I don't understand is why Premier Rides, in building a totally new wood coaster train (for Son of Beast), and having already built a high-performance steel coaster chassis, also chose to essentially duplicate PTC's design instead of building a new train from the track up.

--Dave Althoff, Jr.

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Tuesday, December 11, 2007 7:37 AM
Dave a perfect example of that Jam up effect is Racer after the turnaround where the track rises and twist to come back inline with the outbound run. Man I've never heard trains grind so much.

Chuck

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Tuesday, December 11, 2007 7:40 AM
So what would Morgan trains with PTC running gear run like?

IMHO PTC has simply bought out and threw out more technology that their trains ever had.

I don't hate PTC but IMHO the NAD's tracked better than even some of PTC's articulates (Might have been well greased but still)

Chuck

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