CrashCoaster
CF Legend
How does the anti-rollback system on an SLC's lift hill work? It just looks like a fin that runs the whole way up the lift hill, but does anyone know how it actually functions? 
Vekoma SLC ARBs
- Thread starter CrashCoaster
- Start date
CanobieFan
Strata Poster
There are spring loaded pads on the train top that clamp shut onto the fin you can see on the lift. When the train is in the station you can see the clamps, if you know what you're looking for.
I've struggled to find a good quality image after a brief look through RCDB. Best I could find was this POV:
@CanobieFan is right - it's a mechanism very similar (identical?) to how some lift/elevator emergency brakes work.
It's a device a bit like this:
When the train moves up the rail, the friction on the pads acts to push them apart. As soon as the train begins to move backwards, it pulls the two pads together and they grab the rail. From that image you can sort of see how this would work if you imagine the fin sliding in between the two pads.
Have to admit, I've never spotted it in real life (I think I'm too busy praying at this point), but I'll look out for it next time!
@CanobieFan is right - it's a mechanism very similar (identical?) to how some lift/elevator emergency brakes work.
It's a device a bit like this:
When the train moves up the rail, the friction on the pads acts to push them apart. As soon as the train begins to move backwards, it pulls the two pads together and they grab the rail. From that image you can sort of see how this would work if you imagine the fin sliding in between the two pads.
Have to admit, I've never spotted it in real life (I think I'm too busy praying at this point), but I'll look out for it next time!
Antinos
Slut for Spinners
If I remember correctly, Millennium Force actually uses a ratcheting system, except they made it "smart" (because we need to keep up with all the trendy buzzwords these days). Again...if I remember correctly...a mechanism (magnet?) holds the ratchet away from the track. Onboard sensors are constantly measuring the train's speed and if it senses a drop in speed, the mechanism will release the anti-rollback dog allowing it to engage with the track.
Again...my memory might be fuzzy on this though.
Again...my memory might be fuzzy on this though.
CanobieFan
Strata Poster
If Millennium Force is like El Toro, it's pretty.. uh, terrifying when it stops on the lift. The train actually slides backwards a few -feet- before the rollback kicks in... I've been, uh, lucky, to have it happen on Toro, twice. Pretty much everyone on the train screamed/gasped. haha
Snoo
The Legend
You can hear it as well when it starts up. Being it's normally half way up the lift, it echos around the area. You certainly know when you stop and when you start that train.
Doom_Disciple
Roller Poster
I know it's a bit of a thread mine, but I was cleaning out my phone and I found this for you. Direction of travel is away from the camera.
They are two sets of spring loaded curved shaped jaws that have no clearance (so they will spring back and touch each other like in the photo if the rail isn't passing through), effectively meaning they only have one direction of travel. The rail runs through and rotates the jaws backwards, opening the gap, and each side just drags along the rail as it travels the lift. If there is a stoppage, the train rolls back slightly which turns the jaws in the opposite direction causing them to close the gap and the teeth bite into the rail. The arb system is always in contact with the rail and you get very little roll back. If you have ever seen an SLC arb rail up close, it has all these little teeth marks along it from all the lift stops during operational checks and any break downs.
In the event of a stoppage, there is also the pair of chain dogs that are fully engaged with the lift chain until they pass over the top too. You can sometimes hear a small clunk as each of the dogs disengage from the chain as they have very strong springs and will raise up as far as they can travel once free of the chain.
They are two sets of spring loaded curved shaped jaws that have no clearance (so they will spring back and touch each other like in the photo if the rail isn't passing through), effectively meaning they only have one direction of travel. The rail runs through and rotates the jaws backwards, opening the gap, and each side just drags along the rail as it travels the lift. If there is a stoppage, the train rolls back slightly which turns the jaws in the opposite direction causing them to close the gap and the teeth bite into the rail. The arb system is always in contact with the rail and you get very little roll back. If you have ever seen an SLC arb rail up close, it has all these little teeth marks along it from all the lift stops during operational checks and any break downs.
In the event of a stoppage, there is also the pair of chain dogs that are fully engaged with the lift chain until they pass over the top too. You can sometimes hear a small clunk as each of the dogs disengage from the chain as they have very strong springs and will raise up as far as they can travel once free of the chain.
Nicky Borrill
Strata Poster
It actually seems like a really good system... Wonder why it’s not ‘industry standard’ given the noise constraints on many parks?
Two possible answers to that one:
a) I think it is actually reasonably common nowadays. I definitely don't think new coasters (on the whole) make as much racket at older ones. But also, maybe:
b) If it ain't broke don't fix it.
Nicky Borrill
Strata Poster
I would say that with woodies you're in a slightly different game there. For the same reason the brake runs are on a slope, there isn't the accuracy of track construction with wood as there is with steel, and so relying on a fin that has to be fairly well aligned between two contact surfaces when you have more tolerance in your structure may be a perfectly valid reason why GCI still use the cruder (less precise, no less safe) anti-rollbacks.
RMC? Well they're just a bit janky aren't they? No surprises there.
Nicky Borrill
Strata Poster
Far be it for me to disagree, but I don't buy the accuracy thing at all. If they're accurate enough to rely on brake fins as the single safety mechanism for bringing the train to a halt, from speed, then accuracy cannot be a factor here, when lining up a similar mechanism at a very slow speed, in a straight line.I would say that with woodies you're in a slightly different game there. For the same reason the brake runs are on a slope, there isn't the accuracy of track construction with wood as there is with steel, and so relying on a fin that has to be fairly well aligned between two contact surfaces when you have more tolerance in your structure may be a perfectly valid reason why GCI still use the cruder (less precise, no less safe) anti-rollbacks.
RMC? Well they're just a bit janky aren't they? No surprises there.
I'm sure there are very good reasons. For example I thought of putting the calipers on the track itself, and utilizing the fins already underneath the train, but this would add wear and tear to those fins, especially when used (as in the picture above.)
It also occurred to me that perhaps this method increases the rolling resistance of the train too much, adding additional strange and unnecessary forces to the lift hill structure as the chain lifts the train. Then I decided that was nonsense, if the structure couldn't stand a bit of friction it really wouldn't be safe.
I don't know, I'm just typing b*!!*cks now (and I'm completely sober to boot) but that brings me on to my next completely random and off topic point...
I had a look at your website earlier, (or was it yesterday?) really impressive stuff, I've seen some of your photography before, obviously, but it's nice to see a lot of it together in one place, it genuinely is fantastic stuff to look at.
I also got to find out that my chosen CF background for the last year or so is one of your photos Doom_Disciple
Roller Poster
Friction brakes are outdated and everyone is starting to retrofit where they can. They have largely been confined to safety or holding brakes now and are being used less frequently with eddy current (mag) brakes becoming the norm in trims doing most of the braking.
The problem with using a fin is maybe due to the above eddy current brakes. The brake fin material tends to be a lot softer than previous steel ones used with copper based friction material. Wear becomes an issue and anything even slightly harder than the fin material destroys it instantly. It literally tears big gouges in the fin which then tears your friction material too. So a lift isnt somewhere you really want to be replacing brakes frequently due to poor access/working from heights on a lot of coasters.
Reversing it so the braking unit is contained within the train would be difficult as it would need to be a purely mechanical system to provide both redundancy and due to lack of power or hydraulics onboard.
So you would end up needing a secondary braking system just for the anti roll back, and packing in another set of fins or some holding system probably just overcomplicates things like Hixee said. A spring loaded arb tooth or hook is easier to fit and implement into a train and keep the rail or track on the lift. The slc style one works for suspended coasters as the arb isnt the tallest part of the train, so it doesnt poke up very high. Might be more difficult with flat bottom style train designs, probably need two channels running underneath, one for the rail and one for the existing brake fin or mag brakes.
The problem with using a fin is maybe due to the above eddy current brakes. The brake fin material tends to be a lot softer than previous steel ones used with copper based friction material. Wear becomes an issue and anything even slightly harder than the fin material destroys it instantly. It literally tears big gouges in the fin which then tears your friction material too. So a lift isnt somewhere you really want to be replacing brakes frequently due to poor access/working from heights on a lot of coasters.
Reversing it so the braking unit is contained within the train would be difficult as it would need to be a purely mechanical system to provide both redundancy and due to lack of power or hydraulics onboard.
So you would end up needing a secondary braking system just for the anti roll back, and packing in another set of fins or some holding system probably just overcomplicates things like Hixee said. A spring loaded arb tooth or hook is easier to fit and implement into a train and keep the rail or track on the lift. The slc style one works for suspended coasters as the arb isnt the tallest part of the train, so it doesnt poke up very high. Might be more difficult with flat bottom style train designs, probably need two channels running underneath, one for the rail and one for the existing brake fin or mag brakes.
Sorry, maybe I didn't really explain myself. In order to make sure the brake fins enter the brakes properly, wooden coasters often have banked (to the left or right) brake runs. This means that they can precisely measure the distance from one rail to the brake device and then be sure they line up. If the brake run was level, the tolerances between the two rails means they couldn't be sure that the brake fin would enter the brake cleanly. I was hypothesising in my previous post, but I wonder if similar alignment/tolerance issues mean that a 'old school' anti-rollback is easier to implement.
Thanks man - I appreciate it.I had a look at your website earlier, (or was it yesterday?) really impressive stuff, I've seen some of your photography before, obviously, but it's nice to see a lot of it together in one place, it genuinely is fantastic stuff to look at.