LIM vs LSM

[madhjsp]

I searched and couldn't find a topic for this, so I apologize if someone's already posed this question.

Simply, what are the relative practical advantages of one type of electromagnetic launch over the other?
I'm not a physics whiz by any means, but I've read enough to understand the basic principles and mechanisms underlying each type, and as far as actual application goes, they almost seem interchangeable to me. Just looking at Intamins as an example, we see that Maverick and iSpeed use LSMs, while Volcano and California Screamin use LIMs. Even Premier, who introduced the first LIM launch and specialized exclusively in them for a long time, opted to use an LSM launch for Sky Rocket. Would anyone know the determining factors that a manufacturer uses to decide which type of launch is appropriate for a design they're working on?

 

[Anonymous]

You could make the comparison between the two with:

LIM:
Is a basic brute force implementation of magnetic drive, it works by making powerful magnetic field by running a 3 phase currents through 2 series coils with an air gap in between, and it will accelerate a plate (that you connect to the train) that is put in that air gap. The system is relatively easy to control, more or less a switch on and off. It's relatively cheap, but it will require a separate braking system since it can't work as a brake. The air gap have to be really small (20 mm) or else you will have a drop in efficiency.

LSM:
It's a way more efficient system, but it require a complex control system to make it run. The polarity of the magnetic field that is generated by the coils (inside the white fins) must correspondence to the permanent magnets that is connected to the train, so that you get a "push-pull" scenario. And since you are accelerating the train the speed isn't constant which makes controlling even harder. LSM units can work as brakes themselves and newer versions (Freishütz) are able brake the train and convert the kinetic energy of the train to electrical power to reduce the power need for the next launch. Are allowing for larger air gaps (40 mm) which gives designer a lot less limitations in lateral movements in the train.

If you take a look on RCDB and search for the different propulsion types and sort by opening years then you see that early installations are almost all LIM, and sometime around 2003 it seems like the LSM technology have it's major breakthrough in design and control making it a much more viable option compared to LIM's which dominated the market before then. LSM installations before then are just massive (ToT and STE) and are not the nice small white plates as we know them today. There are almost no new installations (only 2 today) that are using LIM's since 2006 which could be the point when IntraSys started to make LSM units to everyone instead of only Intamin (or other company's had their LSM "breakthroughs" at that point), since all non-Intamin LSM coasters (after the 2003 "breakthrough" opened 2007 or later.

RCDB - LIM
RCDB - LSM
RCDB - More LSM (Intamin Halfpipes)

Another great article about this subject can be found at Coastersandmore.de, which would be in German but Google translate could probably fix that for you...
Coastersandmore.de - Linear Inductions Motors

The first LIM installation on a coaster wasn't made on a Premier, but on BTMR at Disneyland Paris, where they use it as a set of "kicker wheels"...

So the consensus behind this whole thing is that LSM is the future, it just took some time to find the solutions to the complex power regulation of the LSM control system but since they got past it then there is not really an option to go back to LIM's unless you are making some kind of clone of an existing ride...

I hope that this made some sense after all...

 

[mouse]

This might help a bit:

LIM and LSM coasters use propulsion via electromagnets, which utilize large amounts of electricity to propel the coaster train along its track into the ride elements (e.g. inversions, twists, turns and short drops). Five design companies managing these types of rides are Vekoma Industries, Intamin AG, Premier Rides, Maurer Söhne and MACK Rides.

Electricity is transferred into a motor so that it controls the speed at which it will urge the car forward. LIMs are mainly used in Premier Rides roller coasters and Intamin AG impulse coasters. However, LIMs are also used for transport systems and the Tomorrowland Transit Authority in the Magic Kingdom for low acceleration, unlike what most roller coasters use for high acceleration.

Source: http://en.wikipedia.org/wiki/Launched_r ... IM_.2F_LSM

 

[madhjsp]

That's good info, thanks guys! I guess U hadn't noticed that LIMs weren't being used for new installations anymore, so that would certainly seem to support loefet's conclusion that they're being supplanted by LSMs as the system of choice.

 

[Anonymous]

^ Well there are actually 2 new coasters (Mummy at Singapore and CLICK which is a slightly redesigned version of a Mr Freeze) with LIM's, both of them are "clones" of similar rides that were originally built with LIM's so I don't think that Premier would completely redesign the coaster just so that they can put LSM units instead. But I guess that this would be the only times that we would see LIM's new versions on old designs...

 

[Thekingin64]

I thought that LIMs were more powerful than LSMs and that was the difference.

 

[Anonymous]

^ That might be true, as in it may be easier to construct a more powerful LIM system than one based on LSM. But LSM have more advantages over LIM which makes it a more desirable technology on rides...

 

[choluby]

I thought LIMs were low power high accelerating
and LSMs were high power low acceleraing

and by the way I do not like war or anything like that eg Call of dutie and monster games!

Smilies removed, they were pointless and unnecessary and most of all annoying - Hixee

 

[Anonymous]

^ That might be the case, but in this application it doesn't really matter...

Also please go easy on the smiley's in the future, they are a bit of an eyesore...

 

[AmusementSci]

My question has always been how they are able to control the direction in which the train travels when the systems are fired up. For example, on the Intamin Inverted Impulse coasters, what keeps the train from traveling backwards rather than forwards. It would make sense to me that it would be a 50/50 shot of it traveling forwards or backwards when initially launched, but obviously this is not the case. Anyone know what is keeping it from doing this?

 

[Hixee]

^As far as I understand it, they pulse the electricity in a 'wave' down the track in the direction they want the train to go. They set up an 'attraction-zone' just in front of the train and a 'repulsion-zone' just behind it. (These aren't the technical terms, they're just easy to explain, **** knows that the technical terms are!).

That way the train has no option but to move forwards (in this case).

 

[Martyn B]

A bit off topic, but I've always wondered why Vekoma dont use LSMs/LIMs on their Boomerangs, especially on the second spike...

 

[Anonymous]

The technology wasn't ready/available at the time Vekoma designed the Boomerang. And now it's pretty pointless to update it since almost all "new" Boomerangs are relocated ones. However a complete overhaul of the design could bring it back to life, maybe with a whole new layout...

They did however try to run the inverted boomerang (Hang Over) with LSMs back in 1996, so they have though about it, but they never got it to work and the whole ride stood dormant for a year (believe me I know, I stood beside oogeling it ) before they opened it in 1997 modified to run with a a lift system similar to that found on Boomerangs...
The screw up cost them an S&S shot tower...

 

[AmusementSci]

^As far as I understand it, they pulse the electricity in a 'wave' down the track in the direction they want the train to go. They set up an 'attraction-zone' just in front of the train and a 'repulsion-zone' just behind it. (These aren't the technical terms, they're just easy to explain, **** knows that the technical terms are!).

That way the train has no option but to move forwards (in this case).

Okay this makes sense then. I'm alright with newtonian physics, but when it comes to magnets and electrical fields my knowledge is lacking....I always found myself in line for LIM powered coasters wondering how the hell it worked. Hoping, for just one time, to see Wicked Twister take off in the reverse direction...

 

[lakeccrunner]

LIM:
Is a basic brute force implementation of magnetic drive, it works by making powerful magnetic field by running a 3 phase currents through 2 series coils with an air gap in between, and it will accelerate a plate (that you connect to the train) that is put in that air gap. The system is relatively easy to control, more or less a switch on and off. It's relatively cheap, but it will require a separate braking system since it can't work as a brake. The air gap have to be really small (20 mm) or else you will have a drop in efficiency.

What is a 2 series coil?

And I know that the units on the track are the stators, but is the wire coiled inside just like it is in the stator of a traditional electric motor?

 

[Anonymous]

^ Looks like I forgot an "of" in that sentence...

Inside those "white" things that are used in LSM and LIM drives there are, as you said, coiled up wire.
It's pretty much like any electric motor, just in a linear motion rather than a circular one.

 

[lakeccrunner]

^ That makes more sense.

Another question though, why 2 wires and not 3? Just wondering because of the 3 phase current.

Oh, and one more. What would happen without a 3 phase current? If it was just one current, without the constantly changing magnetic field?

 

[Anonymous]

I said 2 series of coils with an air gap in between, nothing about what type of coils they are.
But it would be most likely that there were 3 wires in each coil (unless they want to use 1 phase)...

 

[neo]

^Not three wires in each coil.

Assuming something like Wicked Twister uses three phase LIMs, inside each motor there will be three coils (one coil for each electrical phase). The coils will be arranged so that a wave of magnetism is produced in the motor's air gap. This wave can be reversed to provide either a braking or reverse acceleration force by simply reversing the motor’s electrical connections.

An impulse coaster constantly reverses its motors to accelerate/decelerate the train depending on train direction and the desired ride cycle. In many ways this can be best visualised on old HUSS Pirate Ships where the drive tire reverses its direction upon each swing.

There’s a useful linear motor animation about 2/3 of the way down this page:

http://www.animations.physics.unsw.edu. ... otors.html