Power Tower Cable Snap

They are little black fins?

You answered your own question, Keith! LOL

MrScott

I think they had a cable snap the year it opened, I remember someone from PTC telling me about it.

Keith,

The "black fins" are there to keep the cable(s) from banging into and wearing against the tower structure. The less the cables contact the structure, the long the service life they will have.

I've never heard of a wire rope seperation on Power Tower. I've watched maintenance tighten them before though.

Each tower has 4 load cables, 4 tension cables, a ride unit, 4 yellow cylinders, and a large air receiver (tank) in the center of the tower (Red or teal).

There are 4 of the same circuits for the cables, one for each side. The load cable runs from the cart up to a pulley at the top of the tower's track. The load cable is diverted 180 deg. into the tower and enters the yellow cylinder. Inside the yellow cylinder there is a piston. The piston also connects to the tension cable on it's bottom side. It returns down to ground level to another pulley that diverts the tension cable outside of the tower and up to the cart.

There are 4 black plastic guides that keep the cable from banking into the tower. They carts are far enough away to just clear those guards.

When the cart is on the ground, the piston is near the top of the tower.

How the ride works:

Space Shot:
After the ride is dispatched, the cart is raised a few feet. The pressure in the cylinders is measure and the weight is calculated with the known cylinder size. The control system sets a require pressure to launch. Valves open in the launch tanks and the pressure builds to that pressure. As soon as the pressure hits the target, the valves from the launch tanks to the cylinders open and the ride immediatly launches. The unit launches upwards with the valves at the bottom open and the top fed with the launch tank. As the cart reaches the top, the valve at the bottom closes allowing pressure to build up, the launch tank cuts out, and the cart slows down quickly. When the cart begins to move downwards, the bottom valve opens. Sometime after that, the decending valve near the top opens and allows the cart to decent at a relatively quick rate. This allows the pressure to build and fall causing the dampened harmonic motion while the cart decends. When the cart nears the bottom of the tower, the valve closes slowing the decent rate as the cart approches the hydraulic cylinders then contacts them. The ride unit is lowered with the hydraulic cylinders.

Turbo drop:
The cart is weighed in the same way. Instead of launching, it's lifted to the top. There are brakes at the top which hold the cart up while the launch is prepared. A set pressure launches the ride downwards then the ride goes through the same decent as the space shot.

The pressures for the turbo drop is about 30 PSI while space shot is roughly 80 PSI.

-------------------------------
Onto Millennium Force.

That ride had exactly 1 cable seperation. On Sunday, September 2, 2001. A good first hand account by Steven John (7-19-03) MF forum:

Here's what happened on that fateful day... It was sept. 2nd 2001, After a long, hard and very fun summer of working MF I woke up late (which honestly was rare for me) My alarm clock just never went off.. I franticly showered and put on my uniform and ran to my ride thinking "well, some things are just out of my control." This was soon to be proven to me in a much grander way! I arrived, we were just starting test runs with loaded trains...MF ride op's and sweep's. I took load platform controls over so a fellow co-worker could have a ride. I picked up the red phone and apologized to my lead for arriving late... dispatched blue, then yellow. Then a friendly co- worker jumped off and said I could hop on ( how nice of her ) I jumped in my very favorite seat..last car, last row, left side. Thumbs up all around and off we went. Great way to start the day usually.
There was no warning. All was well up there in the beautiful blue morning sky as the train was about to crest the lift. Then WHAM! the train slammed backwards into the anti-rollbacks. I looked at my friend next to me and I believe we comunicated telepathically for that split second when our eye's met. We had all been on a block stop sitting up there.. even sometimes alone. It was a routine check every morning...But this wasn't your usual drop back and engagement of the saftey system. We hit hard and the lift was vibrating. I don't believe a word was said. Then I hear a fimiliar noise... It was the sound of the catch car rolling back down the lift. So familiar in fact that I still hadn't come to my senses that this was very bad! That is until I put two and two together and my co-worker and I seeing as we were in the very last seat looked back down the lift to witness the catchcar, or sled as Intamin calls it, sliding out from under us and taking off back to terafirma ripping apart the track itself as it sped through the box track faster than it was ever intended to. We watched our co-workers on the platform scramble for their live's and ambulences arriving not having any Idea what was going on down there. Meanwhile, I was a bit fearful to say the least. One girl was crying. My friend was laughing.. saying "we'll, this they won't be able to fix today." Her enthusiasm helped me a bit I have to admit. We waited, Most people were laughing and goofing off. I on the other hand was well aware that the only way for us to get down was to unload this train angled at 45 degrees stepping across to a service car that doesn't meet up with the train very well... and that a lift evac on MF had never occured before. Well, the boats were watching us now, as I later was informed that the counter weights for the elevator system crashed creating a bang that could be heard across the park and apparently the lake also. The park was just opening and people were entering the park. Management arrived..zipped there way up to us and made sure everyone was o.k. They agreed to take the girl who was crying down immediatly.. It took some talking her into it with soothing vocal tone's and such..but she climbed out just fine and sat down immediatly in the service car. Next up to unload was us they were uloading from last car to front. I watched my friend climb out carefully because the first girl to unload didn't seem to be grabbing for the safest parts of the train and service car. I made note of my order of steps and grabs in order to ensure my safety but what I didn't expect is the frantic grabbing from my kind supervisor trying to pull me to safety. Needless to say I'm still here and I made into the service car safely. We had one car unloaded, 4 employees, a manager and a maintance worker. 6 total when they started moving up to unload more. when I noticed a small sign inside the service car that said 7 person maximum. I figured we should be on the safe side and said Let's just go down now. They agreed. one car at a time. When we reached the bottom it was far from over for me. I was very concerned about this and very uncertain that everyone was sure to make it down alright. It took a while it seemed to me, but we all did and no one on the load platform or under it were hurt. We were all split up to work different rides while they fixed it. They fixed it in pretty good time and they repaired it so well that I was unable to tell anything ever happened when I returned. Routine blockstops were cool, that day wasn't. So there you have my story. And I have to let it be known that MF still remains the greatest rollercoaster ever built in my book. Peace.

The cable was replaced during the week before and on Friday September 19th and the afternoon of Saturday September 20th.

Ralph Wiggum posted a thread titled "Cable Work?" on 9/19/03: (The date is a typo from what I see)

When I was at the park tonight (9/18/03), there was a sign saying that MF would be closed for the night. There was another sign saying this was due to wind, but after taking a look at the ride, it looks like they may have been working on the cable. The sled was parked at the bottom of the hill, and it looked like there was some sort of bar across the top part of it. I figure that given the length of time the original cable lasted, they were about due to replace the current one. Anyone know more about this, or am I just reading too much into it?

The cable was in fact replaced. I was there that weekend too and watched maintenance do work in several places on the lift. I even watched one maintenance guy go down in the fanicular and run into the crane cables that went throught it's track as he went down. I guess he wasn't paying any attention. He then had to climb the rest of the way down on top of the track. That was one of the more interesting weekends I've been to.

I have not heard anything about a cable replacement since. I don't know if it has or has not been replaced since 2003 nor if a new cable will be used this summer. Maybe they found a way to extend the life of the cable. By that I mean fixed the problem the caused the damage to the cable and not the use of duct tape.

Wire rope is practically guaranteed to give a large amount of warning before failure. It was puring Cedar Point at fault for each wire rope failure on MF and TTD. Wire rope is very expensive to both buy and the manhours and downtime required for replacement. While Cedar Point will not put off replacement on Sky Ride or Power Tower, they have done it on MF and TTD. The worst that has happened is minor scrapes on TTD. Millennium Force's cable was in terrible condition before it snapped. Apparently management kept the ride open dispite. After the first cable failure on Dragster, Monty Jasper stated that the cable had a kink in it and he thought it was fixed. OSHA states that a wire rope that is bent is permanatly damaged. Regardless of what has happened, It seems the Cedar Point now has TTD and MF under control and are keeping close watch on these factors.

I have educated guess on the cable minimum break strengths:

Power Tower: Each of the 4 cables are about 50,000 lbs min. break tension. S&S requires that the cables are replaced if a single wire fails.
MF: The single cable has a min. break tension of about 400,000lbs. A fully loaded train weights up to 32,000 lbs (overestimate). My guess is that the max tension at any point in the cable is no more than 50,000 lbs unless it gets shock loaded.
TTD: Two cables that appear to have a min. break tension of about 100,00 lbs each. The trains weight up to 17,000 lbs (overestimate). The peak launch tension would probably be something like 40,000 -60,000 lbs distributed over the two cables for a matter of miliseconds as the catch car and train break static friction.
I'd say something about Sky ride, but I don't know too much about loading on the splices. It certainly has a higher saftey factor than MF or TTD.

The loads are educated guesses from running through a huge number of various statics and dynamics problems as well as knowlege about various sizes of wire rope. For example to find the static forces that the track and the cable needs to support MF's train, you would need the angle of inclination A and the train weight W:
Cable Force = WSinA
Track Force = WCosA

Say a given train has 30,000 lbs on MF's 45 deg. angle.
Cable Force = 30,000 * sqrt(.5) = 21,000 lbs
Track Force = 30,000 * sqrt(.5) = 21,000 lbs

Of course when the train accelerates, Newton's F=MA also applies and kinetic friction is added too. That turns it quickly into a dynamics problem and I just guessed instead of crunching through the numbers.

A few pieces of info about MF that might be helpful to you CP_bound is:
MF's lift motor puts out 800 HP, though it is not really a peak, but a max average load. The motor draws up to 2,150 amps during acceleration near full speed at some power factor. I'd guess that it's .7-.8. The motor turns proportionally to the pull speed of the cable, But when the motor turns 1,500 RPM, the pull speed is exactly 6 m/s. The drum is approximently 2 meters wide. The full speed is 6 m/s and the slower speed when the next block is occupied is 4.5 m/s.

rathofdoom, I've personally seen it launch from inside the building. The interesting part isn't watching the cables but the motors. They whine very loud (maybe 100 -110 dB) and the gearboxes as well as all of the motors torque quite noticeably when the launch starts untill is slams into the support bar. Then it falls back when it stops. It certainly was quite interesting to watch. *** Edited 4/8/2006 2:47:11 AM UTC by ForgottenEE***

We can always rely on ForgottenEE to give us the answer to any question of this sort.

That was interesting to read about MF cable break. Never read that before.

FEE, nice and informative. Thanks for the info.

If I remember right from Ultimate Thrill, PT's cables are about 39,000 pounds. The show shows them doing a stress test on one where they basically pull it till it breaks, which is right about 39,000 pounds.

Interesting information you have there too. My guess wasn't too far off after all.

Destrutive testing is rather interesting. It's even more fun to get paid to break stuff. "We just bought this very expensive part" said the boss, "I want you destroy it."

I am frequently in an automotive plant where destructive testing is going on all the time. Lots of fun stuff there.

I guess S&S does this with every batch of cable too. So they have one guy whose job is to break cables.

I used to help build temporary barrier wall (for construction sites - you've surely seen them if you live or travel in SE MI), and random sections had to be pull-tested to insure they were strong enough. I can't remember the exact requirement, but I do remember it being quite a massive force necessary to break them. It was quite a sight to see.

Thanks for all of the info you folks provide. It is very interesting to us that enjoy seeing the man behind the curtain.

MrScott

PS: Will SkyHawk have similar cables?

Wasn't there a video of the hydralic room durning launch on the net somewhere? I thought I remember seeing it years ago. It may have been from Xcelerator cause I don't know if Dragster was finished when this video was made. You couldn't really see the motors jumping around (if I remember correctly) but you could see the hydrolic lines jumping all over the place and hear how loud it was

Sorry to drag this back up, but I found one of my old data logs from the 2003 season while cleaning.

CP_bound said:
Yeah, MF's trains weigh 28 tons empty, while PT's cars are probably no more than 1-2 tons.

I have 2 records for launches of empty cars on the Shot East Tower...the 1st has the weight of an empty car at 377 lbs and the 2nd has the weight at 363 lbs...in both cases, the car was launched with 71psi.

Just to round out the weight issue, the heaviest launch I have recorded was a loaded car with a weight of 2806 lbs and launched at 92psi

ForgottenEE said:

The pressures for the turbo drop is about 30 PSI while space shot is roughly 80 PSI.

Considering all my data is between 71psi and 92psi, your estimate of 80psi is spot on.

You engineers amaze me.

MrScott

Very much indeed, very interesting...

Let's hope PB lives well on into this decade, and I'll be posting this kind of stuff :)

MrScott said:
You engineers amaze me.

MrScott