An Oil Waster?

I'm sorry if I don't know what I am talking about here, but since Dragster's launch is made by pushing oil through pistons or whatever it has to do with oil, how much oil is used everytime it launches? I know the oil prices are at an all time high and I'm wondering if Cedar Point is paying a lot of money for this oil.

I also have minimal knowledge of the system, but I'm pretty sure hydraulic oil is very different from motor oil.

Plus hydraulic fluid isn't as expendable as gas or regular oil. They use it over and over,I'm sure it has to be replaced eventually,but not very often I would think.

I asked the CP website the same question and they said its changed, I believe it was, once a month or something. They said it's a quick procedure.

Once a month is about what i would expect. I know it's filtered beyond belief so no metal shavings get into it.

How would metal shavings get into it?

The oil isn't burned, it's pumped into a container that in turn compresses "air." When the valves open, the compressed "air" pushes the oil out through the hoses which turn the "fan blades" in the motors and make it go.

I forgot to add that obvious fact which may have been his original question. It isn't an engine that uses oil to burn,it's a hydraulic motor like Jeff said.

As for metal shavings, the first year they had problems with shavings,I know they fixed it,but I would assume some sort of breakdown would occur on the piston just during normal use right? I am not a hydraulics expert so I may be wrong.

The oil used when compressed decreases in volume of .5%@1000 PSI and 1.3%@3000 PSI. The system uses pressures of over 4500 PSI. To compare, air has a volume reduction in the range of 5000%@1000 PSI.

Pumps and motors get cavitation from air in the oil. In the pumps, the pressure instantly changes from 0-4500+ PSI and the reverse happens in the motors. Pumps get air implosions and motors get air explosions. The pumps and motors actually contribute to the contamination. When the oil is contaminated beyond specs already, they rot away quickly.

TTD lacks adaquate contamination control so the pumps and motors have a short life expectancy. They may prevent ingressed contamination, but that isn't enough. Having damaged pumps and motors in the system will undermine any steps taken to reduce contamination. With proper contamination control and all good parts will the system be able to last.

I've heard stories about factories and inadaquate routine maintenance of the hydraulic systems. There are cases where the maintenance costs double or even triple because of failure. This doesn't include production losses due to downtime. Some machines equate to thousands of dollars lost per minute. Of course a factory has more incentive to poperly upkeep their machines than an amusement park.

EE, I'm not sure that is true.

A factory has incentive to keep their equipment running properly, because the equipment allows them to produce product.

But at an amusement park, the operation of the equipment *IS* the product, and if that isn't a pretty significant incentive, I don't know what is!

I need to check my notes, but if Dragster is running at 4,500 PSI, then it has surpassed the Witches' Wheel as the highest pressure hydraulic system in the park! I think that thing is only about 2,000 PSI; again I have to check my notes.

Here's an interesting question: EE says, "TTD lacks adaquate contamination control...". This year, is it finally more accurate to say, "TTD lacked adequate contamination control"?

--Dave Althoff, Jr.

Ignoring maintenance costs: Say factory is producing a product at a rate where the items produced times the revenue per part is $1000 per minute. If a pump fails causing the line to go down for an hour, the company will produce an hour worth of product less. The revenue is $60,000 less. Continuing failures can lead to greater problems such as missed deadlines and loss of clients.

TTD had terrible downtime in 2003 yet the park still managed to get the expected attendance increase. It may have had a negative effect financially of somewhat less returning guests, but nothing compared to a factory. The maintenance costs of replacing 6+ pumps and over half of the motors in a season more than offsets installation and maintenance of a highly integrated contamination control system. Contamination control rated at 5000 PSI is expensive, no doubt about it. The cost of replacing pumps and motors as they are is ridiculous.

At this time, I don't know of any additions of dynamic contamination control. I heard a rumor that the hydraulic system was rebuilt over the winter, but I don't have confirmation of it.

The pressure actually varies from around 290 to over 320 bar (4200-4600 PSI roughly). It has a stepping that permits the system to change pressure either to a default or according to the last train's time. Cold weather will clip the upper limit of the pressure. The results are reduced speed over the hill and rollbacks. If it's cold or windy enough, the trains won't have a chance to make it over. Servo valves hate contamination at such pressures. Contamination problems weren't nearly as bad in 2004 compared to early 2003, but they were still too high.

So with the extra maintence and procedures being done to the Top Thrill Dragster will that mean minimal breakdowns?

I guess that remains to be seen. Last year was an improvement, but the ride was still down probably over 30% of the time. That is kind of a drag on Monty's uptime stats. :( While it improved substantially over 2003, the ride failed to top one million riders last year and we know it wasn't because of lack of interest. Millennium Force, a ride with failrly similar hourly capacity did 1.5 million. Magnum and Raptor were both over two million.

For anyone who forgot that Dave spent a little bit of time making this:

http://www.pointbuzz.com/ttdtech.htm

I was impressed that CP was able to get the ride running every day for 2004. Not counting weather or the week that those injuries were caused. If they can get rid of the 20 minute downtime periods throughout the day it'd be a lot better.

In 2003, changes to the system caused the system's problems to go from inoperable to just bad. This had to do with a problem with the reversing action on the system. It would create a vacuum causing some of the oil to turn into a vapor. This caused cavitation of the pumps and motors which in turn jammed the sevo valves with steel and bronze particles from the pumps. After the hydraulic problems of June rolled into the catch car problems of July. They fixed part of that problem with the ghetto water cooling system. Works great but isn't the most pleasing fix. The nylon in the catch car track was also replaced.

In 2004, the is some caviation to the pumps and motors causing damage. None of the pumps and most of the motors did not make it through the 2004 season. If the pumps and motors were in fact replaced over the winter, this would give better performance overall. It won't save the system from contamination problems though.

Now, the problems that could be improved are better deaeration, reducing solid contamination of over 2,5,15 microns, and reducing the absolute maximum contaminate size. This will extend the life of the pumps and motors significantly. This would reduce the hourly downtime over 100 hours during the season. 30% downtime seems reasonable for last years performance. Better contamination control would give it around a 5% improvement.

The cables and catch car are responsible for 15-20% downtime in 2004. One of the reasons it's so big is the unfortunate injuries and the downtime that followed. The reason the cables have had a hell of a time is that they suffer abrasion wear in the channel. The catch 22 is the cables that have better abrasion resistance will be damaged by the small radius of the tension pulley at the begining of the launch. The problems with the catch car and cables will exist untill the entire launch is re-engineered.

Interesting. I always thought that the tension pulley seemed to be on the small side.

Are some of the contamination problems caused by sludge formation because of high oil temperatures?

No.

The worst thing you can do to a hydraulic system is allow the oil to burn. Burnt oil will damage the system faster than cavitation. The maximum operating temperature is usually 130-140 deg. F. There are temperature sensors in the room and in the oil that are directly connected to the PLC. If the temps go over a set point, it will shut the ride down.

If they really wanted to improve the system... they need to get rid of the gear pumps and use piston pumps. the gear pumps are not famous for smooth reveresals(SP). and they will feel alot better about the -32 return lines once the leakage around the crimp sockets are eliminated. It is not air that gets compressed in the accumulator, its nitrogen.

As far as oil temp goes, ForgottenEE is correct. There is also a chiller system, wich uses glycol in it to transfer the heat from the oil. the oil circulates through a heat exchanger, the heat exchanger has tubes running straight through it while the glycol is circulated through the cavity of the exchanger,removing the heat from the oil.