BART. SEPTA. CTA. No taper.

http://onlinepubs.trb.org/Onlinepubs/tcrp/tcrp_rpt_71v5.pdf page A-15.

heck, MBTA even has cars with some solid axles and some independently rotating.

Thanks Robert - you saved me some considerable file diving. I've done my share of work on old mine equipment including man cars, most of which have a chilled iron wheel rotating on an axle with high squarish flange profiles and (after years of service) concave tread profiles. Probably the newer stuff uses steel wheels........

I've got somewhere a drawing showing trolley wheel profiles from Melbourne Tramways W class cars, and another showing profiles from other trolley systems. Dug it out way back about 1989 when adapting Melbourne hardware to Charlotte Trolley car 85 to run on existing freight track. Given that track, I did opt for 'AARizing" the treads and flanges - also, due to narrow tread width, writing tight track geometry specs as well.........but for use on street railway tracks installed to street railway standards used by MT, I'd have left it alone.

It seems a recurring theme in a lot of my posts on technical stuff lately - but removing one thing from the organic whole for seperate consideration rather than looking at the entire system and how all its components interact can lead to a lot of inappropriateness. Use the right profile for the right application.

Whether Chance design is a good system or not I'm too ignorant to decide. I'd bet there was more than one factor that compounded into the incident mentioned in the original posting, however. Wheel profile / track geometry may have been a part of it. We may never know.

dave

In my humble opinion, this accident was caused by excess speed, these trains have a high center of gravity, which is exacerbated by live bodies moving about to see and photograph the various animals. The train tipped over with minimal track and truck damage. An operator could run the train at the same speed for years, marginally exceeding the design speed without incident, but the one time a mother happens to lean over to pick up a diaper bag or what not at the exact moment the train enters the curve, adds to the moment arm and causes one car to tip which then cascades the whole train on its side. Loco 112 is right about the radius of the tread before the flange being critical to preventing flange wear, but this derailment was not caused by rail wheel interface issues or there would be a whole lot more damage to the track structure and surrounding earth. Combine a high center of gravity by design with a narrow support system underneath, and the only controls you have is the speed at which the train should operate at and the quality of the trackwork supporting it. The fact that there have not been more of these type incidents of tip over of high center of gravity trains is because one of the design parameters is low speed operation, it is the standard that must be adhered to in order to operate safely. If you exceed the design parameters, it does not matter whether it is a miniature or full scale, it is an accident waiting to happen.
Mike Tillger

http://onlinepubs.trb.org/Onlinepubs/tc ... t_71v5.pdf page A-15.

That is a great article.

If you guys had a visual image of the Chance tread/flange profile it would help us.

BART uses real flanges and their tread width is normal, everything I see there is within reason. The only uncommon part is the lack of taper and like Tillger said that is mitigated with speed restrictions. I think BART is right where it should be for low speed operation on the track conditions that they use, taper is for flange protection on curves, and at speed on tangents. BART probably hasen't needed the taper until now, they must want to increase their speeds, so they are moving to a tread/flange that is proven for a more all around use.

I'll dig out my Chance standards info and post it here tonight for us to look at, I think it has the flange and tread profile in it.

When people cite the speed of this train, how fast did it go in typical operation? 10mph? 30mph? The only train of this type I am familiar with is on the boardwalk in Pt. Pleasant, NJ. This layout is table-flat and runs at about 5mph, which is what I presume these trains are designed for. I am surprised that anyone would use these trains on a long run with lots of grades and curves.

Again, my armchair observation is that this train derailed first, then overturned - look at where the trucks are in the wreck pictures. So, I think it is very pertinent to look at items such as flange height and design and question if and when the wheels climbed over the rails.

Chris.

Fun as this speculation could be, is there anybody posting here that has actually been to the incident and inspected it firsthand? What I'm not seeing is real credible evidence based on expert firsthand observation. I'm not sure the view from Dallas or Pennsylvania is any clearer than mine from Charlotte, and the only thing I KNOW, not simply think might be possible, based on the coverage we've all seen, is that we don't know what happened. If anybody truly expert in railway mechanical forensics actually has made a fact based determination, I'd like to see the research and results - would make a fascinating case study.

dave

I don't see too many people defending park trains here at all. While I own a small 3' gauge Porter and have spent much of my free time over the years working on 3' gauge full sized equipment, I do also own a 24" gauge amusement park train which ran on the sand in Point Pleasant NJ for the better part of 50 years (The "remains" needed a home). I have also been around 15 inch gauge Cagneys (and similar equipment) and some live steamers over the years as well. I have also visited a couple of what some might call "estate railways" over the past year which were 24" gauge as well. And living near the beach, I have been around Chance based operations for just about forever.

So, just based on the above first hand observations and experiences, I'd like to make a few comments.

If you look at industrial 24" gauge equipment (Plymouths for example) and park train 24" gauge equipment (National Amusement Device for example), they really are not compatible at all track wise. The industrial stuff is too heavy for the park train tracks, and the park train stuff tends to work poorly over heavier industrial based trackage. The frogs in particular are a problem. This is a fact.

Why the difference in track and wheel profile and tracking capability? Its really a capacity issue. If you look at my National cars, they each hold about 8 people, say no more than 150 pounds each on average or about 1200 pounds max capacity. The car body with no trucks is about 300 pounds, each truck is about 100 pounds. So, fully loaded the National cars may be 1700 pounds max. The locomotive weighs in at about 4000 pounds and can haul upwards of 10 or 12 cars no problem. Granted Nationals are a bit cruder than Chance CPHs, but they do the same thing, and on the same light track with the narrow treads and sharp flanges. Flanges on my National cars (8 wheel cars) unbolt and are replaceable. Each season, the park welded new flanges on the locomotive wheels (8 wheels), keeping in mind it ran in the sand hauling more passengers per season than perhaps 50% of the tourist lines in the USA today. And it was inspected by the State of NJ each year. (Yes, I have brand new wheels for it)

If you take the 24" gauge Plymouth example I mentioned above, the locomotive may weigh in at 5 tons or much more and be sitting on 4 wheels, not 8. Each car may hold 5 tons or more (on 4 wheels perhaps) over really crappy trackage. The thicker and deeper flanges, wide treads, and larger diameter wheels were required to keep it on the track. The heavier track was needed to handle the weight of the locomotive and heavier cars. Speed was as fast as possible in many cases which really stressed the track conditions.

I guess the point I am making here is that comparing 2' gauge full sized equipment with 24" gauge park train equipment is like comparing pumpkins with oranges. Its simply not the same thing. Loads are different. Wear and tear of the track is different. Equipment weight is different. Number of wheels is different. Center of gravity is different.

If speed was an issue at the zoo, wider wheels and better flanges would have made no difference at all.

Hope this is helpful,
J.R. May
Wall, NJ

If the Chance/CP Huntington trains are so poorly designed, why aren't there more accidents and derailments? They are by far the most popular park trains out there, and many of them are in daily service, either during summer or even year round in warmer climates.

I don't know the total number in operation, but I do know it's a lot, and chances are good that when you see a park train it will be a Chance/CPH. They rack up an impressive amount of operating hours and miles each year.

So, if the design really is flawed, why aren't we seeing more problems? Why isn't the track record (sorry, bad pun) a lot worse than it would seem to be?

I'm inclined to think that it becomes a matter of how the ride is operated. I have reasonably close experience with 2-3 such sets (one's for sale at the Maryland Zoo in Baltimore), and two of them are/were operated at quite modest speeds (a combination of real-estate-saving curves and stretching out the ride so they haven't paid $2 for two minutes), and the third runs at a good 25-mph clip but is laid out on a huge, sprawling layout with curves that could probably take a UP Big Boy if one were operable in that gauge/on that track, and operated by an amusement park that by now considers itself an amusement park preservation outfit.

IF someone is operating a Chance train on a compact layout in a manner so as to hurry up and squeeze out the most trips possible, then I could easily see the "Casey Jones" syndrome of exceeding design parameters.

So what you're saying is pretty much the same as the others have suggested, that when the train is operated in accordance with the design parameters (slow speeds in most cases) it works well. That's been my observation too, though I've never been directly involved with the operation of any of the Chance trains. Of course, if that's really the case, then it would seem that the design isn't flawed after all...

I'm curious as to what Amusement park it is that has the large radius curves and generous track layout. Which one would that be?

If you want a track record for this location, look in the comments at the end of this early report on the incident: http://www.wlky.com/news/19625792/detail.html.

There you will find multiple people zoo employees, operators and riders complaining about how the train tended to derail in this location, and others reporting how with some of the operators the ride tended to approach that of a roller coaster due to the tilting of the cars under speed in this location. Also that some of the time the train went so fast that it had to stop early to wait for the other train to leave the station, when they were supposed to be 1/2 of the route away. To me that makes it sound like two things happened, first it derailed on the curve and either rolled when the inner wheels hit the outer rail or after the wheels jumped the second rail and hit the dirt with all the cars wanting to continue on their own radial paths.

Just my observation,

Rich C.

Not true, flange radius and taper have everything to do with at what speed the flange climbs the rail head.

There are, and often. There was a big one a few years ago at St. Louis, Ft. Worth has had a few big ones, now this latest one.

IMHO & from what I read, the KY incident was from over speed, its that simple but, They (C.P's) are still junk and prone to being off the rails.

I don't think we can say for sure the flange climbed the rail My experience would tend to say the cars would be in a much bigger mess. Can't say anything for sure really.

Stuff happens. We all try to prevent it, but sometimes it happens even with an experienced crew on board. The 489 out in Colorado comes to mind. And its not junk.

J.R.

Here is a link to what appears to be a power point presentation, but looks to have a lot of the boilerplate "CYA" notes that manufacturers recommend. Page 52-54 concerns curves.

http://www.recreationengineering.com/Do ... ANDOUT.pdf

I assume Chance has a process where they approve track layouts and installations?

At the risk of dragging this out any further, the following video is on youtube and reportedly is from the zoo about a year ago. Its probably the fastest I have ever seen a Chance CPH run.

http://www.youtube.com/watch?v=r1gjUm470sA

Of course I've been called a chicken before. Just seems awful fast to me.