I've seen on some shows that a lot of wooden coasters get their entire tracks walked by mechanics on a routine, if not daily, basis. So what about steel coasters? After the lift hill, there doesn't seem to be much opportunity to thoroughly inspect the track, esp on the bigger coasters. Is it that most of the stress occurs w/in the supports, which are easier to inspect?
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Steel coasters have fewer pieces, and hold up better in operation. With a steel coaster, the track inspection is more a matter of finding stress fractures, which are most likely to happen in particular areas of the structure. That, and with non-welded sections, looking for loose bolts, which is why the bolts are often torqued, and then painted with a mark so that a mechanic can visually determine whether the bolt has rotated at all since it was torqued.
Which reminds me...CALLING ALL BOLT EXPERTS:
I wonder if a bolt can stretch under load and come loose without rotating. Perhaps if it is over-torqued and has stretched beyond its elastic limit.....
Anyway, the inspection of a steel coaster track does not require as much detail as the inspection of a wood coaster track, and more often than not, the easiest way to do a quick check is to run a train and make sure it *sounds* right.
--Dave Althoff, Jr.
RideMan, yes a bolt can do that. However with the size of these bolts and the amount of forces required to produce a stretch in a bolt, you most likely wouldn't see that. Plus thinking, say 20-30 bolts around each support, these forces will usually be spread across them all and thus they most likely would come loose from vibrations before anything else.
Now a bolt shearing off, that is different, that one is a little more likely from the twisting of the round supports.
*** This post was edited by BeastFreak on 1/22/2003. ***
I'm not sure about coaster bolts, but for structural steel on some buildings the bolts have star shapes on the end of the threads. When you put an air ratchet on to tighen it, it will lock on the star and when it's tight the star breaks off so you can't over tighten it.
As for a bolt streching under a load and becoming loose...I have no idea. My guess would be if the two pieces of steel weren't completely flush, maybe a slight warp on one piece they may work loose or snap.
I worked with a guy a year or two ago who was leaving the job I was at to go to Hershey and go over all the bolts on the Great Bear. I guess they do that every spring.
All this info comes from an Ironworker who worked with very little iron but many tons of rebar! If you have any questions about footer steel I may be of better help. :)
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According to the Kar Products "Fastener Handbook", snapped bolts are more often caused by *underloading* than by shear loads, because an undertorqued bolt stretches when subject to force in excess of the clamping load, then when the force is reduced the bolt springs back, and eventually fails like a coat hanger bent back and forth a few times. Which sounds like the Chaos failure. All this has very little to do with coaster inspections, except that it demonstrates first of all why steel coasters get their bolts re-torqued each season, and why they often use lock nuts.
--Dave Althoff, Jr.
If you can walk the track safely, then that's how it's probably inspected. As we all know, though, many steel coasters have pretty convoluted layouts, prohibiting persons from walking their track. Usually a crane is rented and a few people go inch by inch over its course checking for problems.
Walk the track example: Mindbender (SFOG)
Use a crane: Georgia Scorcher
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*** This post was edited by Dutchman on 1/23/2003. ***
Here is the deal with bolts... In many high strength applications, "slip critical" bolts are used. What that means is the bolts do not act as a pin holding the parts together - the bolts are tightened so that they clamp the parts together. All the forces in the connection are carried by friction between the two parts.
If the clamping force of the bolts it too low (and therefore the friction force), then the connection forces *will* have to be carried by the bolt. The bolt is not strong enough to carry the load and breaks.
The clamping force of the bolt could be too low by a number of reasons... The nut has come loose (hense the paint lines to see rotation), too little torque on the bolt, bending of the connected parts, stretch of the bolt (although this is less common since most connections transfer shear forces, not tension forces)
Hope this all made sense... can you tell it is a slow day at work?
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