Report says design flaw led to Re-Mix accident

Posted Thursday, October 10, 2002 6:21 AM | Contributed by RideMan

A flaw in the design of a ride at the Ohio State Fair was to blame for one of its cars falling about 15 feet, injuring two men in August, according to a final report released Wednesday. The Ohio Department of Agriculture, which is responsible for inspecting amusement rides, said that cracks caused the welded metal to snap where the car joined an arm of the Re-Mix.

Read more from AP via The Akron Beacon Journal.

Thursday, October 10, 2002 7:05 AM
The seat on the Re-Mix has a piece of tubing attached to the top which connects to the end of the turret. Instead of connecting that tube directly to the turret, Tivoli concocted a seat adapter consisting of a square block that attaches to the turret, with a tube sticking out the same size as the tube coming off of the seat. Those two tubes were butted together and welded all the way around. In fact, here is a photo of the joint between the seat and the turret. It's not the connection between the tube and the rectangular block that broke; it was the seam in the middle of that round tube.

--Dave Althoff, Jr.

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Thursday, October 10, 2002 8:06 AM

Why would there be a seam in the middle of the tube?

I rode one of these rides and wasn't too impressed, but now that this has happened I think I'll be staying away from them for good. Orbiters which seem much sturdier are my ride of choice between the two. Orbiters go much faster with far more Gs.

-Ride_Op

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Thursday, October 10, 2002 10:10 AM

If that really is a butt weld between 2 piece of tube, I'm like Ride_Op, I don't quite understand why it is there rather than using one piece of tube then welding it to the block. The only thing I can think of is that the want to be able to inspect the fillet weld of the tube to the block inside and out since it can't be X-rayed well, then did the blind weld as a butt so that it could be x-rayed. The newspaper article makes it sound like there was also an internal corrosion problem.

The whole thing without further details makes me wonder if this was really a design error or a fabrication error. Properly make between 2 pieces of tube, the butt weld should be as strong as the tube. However, if things aren't done right it can be much weaker especially in fatigue which there would lots of. Then again there is the mention of corrosion.

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Thursday, October 10, 2002 12:47 PM
When I heard about where the failure happened (and subsequently when I looked at the remains of the ride from the midway and took the photo) I wondered the same thing: Why would they put a joint there instead of using a longer tube. I've heard that they did flange the ends of the tubes before welding them together, but I don't know how accurate that is. But perhaps there is an explanation: The seat assembly appears to be identical to the seat assembly used by KMG on the Fireball and the Move-It (and by Tivoli on the Spin-Out). Is it probable that KMG supplied the seats with a too-short mounting tube, so Tivoli welded an adapter onto the seat hanger to attach it to the ride. As Jim Fisher suggests, done properly, that weld should be as strong or stronger than the unwelded pipe, so Tivoli didn't designate it as an NDT point.

This sounds suspiciously like the (in)famous Spider sweep crack that propogates from the end point of a pair of welds on the sweep, and starts on the inside surface of the tube.

I tried to determine whether there was a similar seam on the KMG rides at the Ohio fair this year, but I couldn't see that tube on the KMG ride because there is a reinforcing gusset plate wrapped around that tube on the KMG rides. At least I think that's what I'm seeing in this photo.

--Dave Althoff, Jr.

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Thursday, October 10, 2002 5:45 PM

There are two different types of tubing, seamless, and seamed. Seamless tubing is extruded,and if I recall correctly, seamed is rolled. The seam is fused shut in the manufacturing process. The latter is less expensive to make than extruded, and in some cases they can be interchanged with the seamless in certain applications. Apparently this isn't one of them.

Many of the smaller European ride builders have components built by the same fabricators, thus sharing certain subassemblies.Thus KMG and Tivoli using the same seat assemblies and other components is not unusual.

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Friday, October 11, 2002 5:15 AM
This failure though was apparently in the butt weld (the circumferential weld in Rideman's photo), not in a longitudinal seam in the tube. A failure in a tubing seam would most likely have resulted in the tube buckling with the assembly sagging, not coming off.
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Friday, October 11, 2002 6:01 AM
I agree. It makes suspect Tivioli's welding procedures.
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Friday, October 11, 2002 6:07 AM
I don't care to much for fairs i just don't think they have the same standerds of regulation for there rides as the big parks do. This just also proves my point that fair rides are not as well made a stationary rides.
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Friday, October 11, 2002 6:17 AM
Right. Unfortunately, that part of the ride was rotated around to where I couldn't see it when I took my pictures, but from news video (WCMH-TV) it looked like a clean break along that circumferential weld.

Thing is, that weld would have a starting and ending point somewhere along the circle, and the point where the start of the weld and the end of the weld meet would be an inflection point in the weld. My guess is that the overlap point of the weld is probably where the crack started. I don't know that; it's just a guess at this point. But it's consistent with what I know of Spider sweep cracking, and this sounds like a similar problem.

--Dave Althoff, Jr.

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Friday, October 11, 2002 9:28 AM
While weld failures can be associated with starts and stops, there are several other types of defects that can start a weld failures. Unless this weld was welded on a roatating jig there were probably several starts and stops with some overlap at each. Most commonly defects that cause weld failures are inclusions, lack of fusion, poor penetration, and cracks. I could only tell you which was the problem if I had a chance to examine the actual weld. The location of the the defect also is an issue. If the area of the defect is in compression, you can probably get away with it. If defect is in tension you are in trouble. *** This post was edited by Jim Fisher on 10/11/2002. ***
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Friday, October 11, 2002 2:24 PM
what is a turret?
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Friday, October 11, 2002 4:45 PM
A turret is a device for rotating something. In this case a group of seats.
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Monday, October 14, 2002 12:15 PM
"I don't care to much for fairs i just don't think they have the same standerds of regulation for there rides as the big parks do."

As Dave has pointed out many times, it varies from state to state and in many cases fairs and carnivals are better regulated than parks.

"This just also proves my point that fair rides are not as well made a stationary rides."

Really? I would advise you to check out rides from KMG and Mondial before saying that every ride made to move is inferior. You should also contact several parks and tell them they have dangerous rides. For instance, all of these parks operate dangerous portable rides:

Myrtle Beach Pavillion- Huss Top Spin, Mack Petersburger Schlittenfahrt, Mack Calypso, Zierer Wave Swinger

Cedar Point- Schwarzkopf Wildcat, Mack Calypso, Schwabinchen and Matterhorn

Knoebels- Zamperla Power Surge, Dartron Downdraft, Eyerly Roll-o-Plane, and Sellner Tilt-a-Whirl

I am sure most of these manfactuerers would be insulted at the insinuation that they build rides to lower-quality standards when building for a carnival or indepedent operator as opposed to a park.

Adam
http://history.amusement-parks.com

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