Ninja at six flags st. louis?

It says in my book that Vekoma and Arrow built the coaster.Why would two rival coaster companys work together?
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"Whenever you dream You're holding the key,It opens the door To let you be free" RJD

May I ask what book?
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Flying High Again.

Vekoma designed & built. Arrow supplied the trains. http://www.coastergallery.com/SF/STL14.html

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Current favorite coasters:
Wooden: 1) Beast 2) Raven 3) Son of Beast 4) The Boss 5) Timber Wolf
Steel: 1) Raging Bull 2) Millennium Force 3) V2 4) Wild Thing 5) Mr. Freeze
Visit: http://www.dynamicgroove.com

The American Rollercoaster by Scott Rutherford.

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You will never forget the name........GOLDUST

Why do you think that just because to they are different companies that they are rivals? Look at B&M and Intamin. I know that B&M broke off from intamin, but Intamin let them build the trains for Flashback. Companies can work together, its not like there is anything wrong with it.

Who built NINJA at SFOG?
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Is there somthing more, then what I've been handed, I've been crawling in the dark looking for the answers!- Hoobastank

Ninja at SFOG was built by Vekoma.
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Intelligence is a God given gift: Know how to use it.

Trains are often supplied by a comnpany different from the company that built the coaster.  This is particularly true for woodies.  Phily Toboggan has made their core business supplying trains for other's coasters.

Also, in some other cases a coaster is designed by one company and built by another due to financial or other problems.  Drachen Fire may be the most famous example of this.