How exactly are the LIM's fired?

Friday, November 9, 2001 2:14 PM
Does anyone out there know exactly (or roughly) how the LIM's are activated to produce the types of acceleration and deceleration that they do on these rides?

For instance: V2 or Superman Ultimate Escape - the LIM accelerates forward, then backward, then acts as a brake. I am currently trying to design a scale LIM system and I need to know what sort of charging/discharging/switching sequencing is required.

Anyone interested in learning more about LIM's can look here:


~Tocci Yohiro

Friday, November 9, 2001 2:17 PM
an AC/DC charge is applied, pulling and attraicting
Friday, November 9, 2001 2:19 PM
actually, the brakes are seperate from the LIMs.  you can see them pop up and down at different times during the ride.  they're in between the LIMs, but not in the station.  the brakes seem to be no different than Intamin's other magnetic brakes.  I'm not sure of exactly how the LIMs work, but good luck with the model.
Jay and Silent Bob have left the building ~Jay and Silent Bob Strike Back
Friday, November 9, 2001 2:23 PM
janfrederick's avatar Sounds like a question for Rideman. Sorry that I do not have a link to his site (lost my favorites recently).

From previous discussions about this, I think a scale model would be incredibly difficult. It is hard enough as it is for a rollercoaster company with a full time staff of engineers to do it.

"I'll bet that thing hits 5 Gs going through that loop.....faaar ooouut!"

Friday, November 9, 2001 2:32 PM
As for the AC/DC charge thing.....most of the pulling and attracting is done by Brian Johnson and Angus Young.

I was kind of looking for greater detail in the calculating of timing sequences...

coasterjedi: Thanks, I hadn't noticed that. That could simplify things a bit. I'd like to see if I can pull off the braking with the same LIM anyway...just for kicks!

janfrederick: Yeah, RideMan is THE MAN! (I got his site bookmarked of course!)

This project may be ambitious...but so am I.  I am an engineering student and this whole project is kind of going to be my "thesis".


Friday, November 9, 2001 2:39 PM
"Furthermore, in a double-sided LIM (one with two sets of stator coils with a gap in between for the reaction fin), the active coils will actually attract each other when the fin is not present, and so will attempt to collapse the mounting brackets. For those reason, some switching of the LIMs is required so that the amount of time they are active with no fin in place is limited. So the LIM installation is complicated a little by that requirement. That level of sophistication is desirable anyway because firing the LIMs in sequence will reduce the amount of power needed to operate the motor. Further control over a LIM launch comes from controlling the line voltage, which, in an AC circuit, is typically done with a high-speed switch."


"Footnote 1: For you electrical engineers--If you really want to, you may substitute "-84.85v to +84.85v (-155.56v to +155.56v)" for accuracy, but bringing up the difference between instantaneous and RMS voltage is, in my opinion, not critical to a qualitative description, which is what I am trying to accomplish here."

RideMan.....what would we do without him?

Thanks RideMan!

*** This post was edited by Tocci55 on 11/9/2001. ***
*** This post was edited by Tocci55 on 11/9/2001. ***

*** This post was edited by Tocci55 on 11/9/2001. ***

Saturday, November 10, 2001 4:08 PM
LIMs are fired by sensors that precisely detect the position of the trin and fire each LIM at the proper time.  The sensor systems are especially apparent on the Intiman inverteds that are LIM powered.  Look for the pieces that resemble real coarse steel combs.  These are what the sensors detect to know the position of the train.

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