MF Track Question

Hi guys, I have always wondered why Millennium Force has tri track in some areas and quad track in other areas. If any of you know please tell me.

Triangles are much stronger than squares. The most stressful parts of the track (the bunny hop near the end of the ride) have triangle track to support all of the stress. The box track is not triangular, and not quite as strong. Anybody knows that triangles are the world's strongest shape. The main hill and first turn (not so stressful) are made out of box track because of the low levels of stress.

Actually, i'm not sure if that is entirely correct... I was under the impression (i'm not sure where i read it) that Intamin developed the box track specifically for MF and their mega coasters. The box track was much sturdier and could thus have supports further apart from one another.

I would hesitate to further assume that the box track is thus used at higher points of the ride to allow fewer larger supports and support structures = Cheaper. Since there is obviously more material and engineering required in the box track it's not ideal at lower heights where more supports and triangle track would be cheaper - bunny hop. I'm pretty sure the first drop and banked turn pull the highest G's in the ride, so it wouldn't make sense that this point had the least stress. I'm also pretty sure that vibrational issues need to be dampened by more supports, so this would be another reason for using triangle track - if you need more supports to dampen the vibrations, then why use more expensive track... I just don't know too much about vibrational resonance and so forth. however, i'm pretty sure that banked turns (the tunnels) cause higher vibrations. Again, most of that is a SWAG.

In the case of Intamin, 4 rails is sturdier and has supports less spaced out but in reality, triangles are the strongest shape. on a square, only two sides support the pressure, whereas, a traingle has pressure evenly distributed on all three sides. Look at most structures out there, they all have trusses (basicly many traingles). Bridges, Building like the John Handcock, Eiffel Tower, rolle coaster supports (A frame or shape), etc.

Thanks guys for the answers.

While a triangle has always been considered the strongest shape (and its pretty good) I remember reading somewhere that a hexagon or a octagon was actually the strongest shape with triangle coming in a close second. When one factors in the ease of designing though, the triangle reigns supreme and the strongest practical shape.

I beleive that while a triangle is the strongest shape, the square box section is actually stronger track than tri because of the fact that it has more to it. The top two rails are still the same distance apart, so there is more steel involved in the track. The tri-rail track isn't as sturdy as quad because it uses less steel. If they both used the exact same amount of steel, trhan yes, tri would be stronger.

Think of it this way...

A five foot long peice of track. Assume all rails are the same size and there aren't any special peices on the track (support connections, chain track etc.) and rails are placed ever foot to connect all rails together. each

For a quad track, all rails are spaced 1 foot from each other.

You have 5ft. X 4 for the four rails = 20 ft of railing.

Also there is 1ft per connection X five connections per side X five sides = 20 ft of connections.

Assume connections and rails are the same size, you get 40 ft of connection.

For tri, top connections are one foot long and bottom are 1.25 ft long.

5 ft per rail X 3 rails = 15 feet of railing.

1ft per top connection X 5 connections = 5ft

1.25 ft per bottom connections X 5 per side X 2 sides = 12.5 ft of connections

Total for tri = 32.5 feet of connections.

Now, this is assumong all rails and connections are say, 1.5 inch diameter. So if the triangular track used the sae amount of steel as the square track did, it would be stronger. however, because of it's dimensions and the necessary distance between the two top two running rails, The square is stronger.

Tri-rail track is obviously cheaper to use, however, at higher elevations, the it is quite a bit less expensive to use less support connections and the more expensive quad rail track and leave more of the track unsupported.

That's all just speculation, of course :P

maybe it makes sense, maybe it doesn't. That's just how I figured it would work... And I'm no engineer.
*** Edited 8/8/2007 8:27:35 PM UTC by IntiMANIAC***

^that made no sense, and I'm an engineer.

My take on it is this. The triangle is the sturdiest shape because it allows 0 degrees of freedom in the plane of the triangle. The square, however, does allow for some movement. But that's why there are cross-members on all sides of the square track forming small trusses. So even though it is a square cross section, it is practically made of triangles. See picture below.

http://www.pointbuzz.com/Gallery.aspx?i=3794

I think the square structure therefore is indeed stronger in this case, because it distributes the load better. In the triangular sections, all of the vertical load from the train is being applied directly on the single beam below the two track rails, whereas in a square-track section, the vertical load is split between the two parallel rails below the track rails.

It probably doesn't make any sense, and I'm no engineer, but let me put it to practical use.

Say you want to build a bridge with 2X4s from one concrete block to another. You could do it one of two ways.

A) use a limited amount of wood and build the bridge with a strong geometric design.

or

B) Use a Crapload of wood in a random design.

Now if you decide to build the bridge with a strong geometric design, chances are it's going to be stronger if you use more wood than it would be if you used less, no matter how strong the design was.

Does that make any more sense. (hopefully I'll learn more in Arch II this year :P)
*** Edited 8/9/2007 1:50:12 AM UTC by IntiMANIAC***

Haha that's more understandable, but its also a lot more general. See my post above.

^^ It's a good thing structures is a very small part of Architecture educations. :)

The box track is most certainly stronger and is certainly made of triangles. It tends to be used by Intamin the most in places where there are longer gaps in the support structure (see: Storm Runner, MF over the lagoon).

Isn't it about time for some red box track to start piling up near Breakers?

I'd rather see some of this in any color than red box track.

Well if you want to see that, check out Mantis and Raptor. ;)

Yeah, but those are already assembled. I'd rather see the track piling up at breakers.

Hey...you left out the 2 rail track...

All track is 2-rail, except for the 4-d, which has 4 rails.

^lol.

The 2-rail track on Intamins is just for areas of minimal stress, i.e. brake runs, launches, loading/unloading platforms.

Good point! Just don't touch the 3rd rail.