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#47
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Smoke test man.
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Posted 22 November 2006 - 06:06 PM
OK, OK .... I give in, No hair then, No hair now........................... 48
(my avitar pix was taken in 1990)
(my avitar pix was taken in 1990)
#52
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Smoke test man.
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Posted 26 November 2006 - 10:46 AM
Yes it has gone somewhere - however........
"Getting old has its own tensions"
"Getting old has its own tensions"
#53
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Posted 30 August 2013 - 02:59 PM
This is my first post.
I read earlier in the skilifts.org glossary that a top drive is slightly more efficient than a bottom drive. I am guessing that the reason for this is because on a bottom drive the motor has to pull down the down-going side and pull all of the slack out of it before the up-going side moves. A top drive pulls directly on the up-going side. I have noticed that on the Kaatskill Flyer at Hunter Mountain which is a Leitner-Poma six pack with a bottom drive that along the lower portion of the lift there is up to 15 feet of cable sag. It is also a rough ride over the towers, much rougher than most LP's I have ridden. On the Bear Peak Express at Mountain Creek, which is a Doppelmayr hi-speed quad with a top drive, there is almost no sag in any parts of the lift, even when it is fully loaded.
I read earlier in the skilifts.org glossary that a top drive is slightly more efficient than a bottom drive. I am guessing that the reason for this is because on a bottom drive the motor has to pull down the down-going side and pull all of the slack out of it before the up-going side moves. A top drive pulls directly on the up-going side. I have noticed that on the Kaatskill Flyer at Hunter Mountain which is a Leitner-Poma six pack with a bottom drive that along the lower portion of the lift there is up to 15 feet of cable sag. It is also a rough ride over the towers, much rougher than most LP's I have ridden. On the Bear Peak Express at Mountain Creek, which is a Doppelmayr hi-speed quad with a top drive, there is almost no sag in any parts of the lift, even when it is fully loaded.
#54
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Posted 31 August 2013 - 04:44 AM
Welcome to the forum.
You're correct about the efficiency of a top drive. There are several other factors involved as well, of course. A top-drive lift can run at lower tension because gravity assists in holding the rope tight against the bullwheel. This also allows the lift to use slightly less power as it isn't trying to overcome the added friction of a super-tight line. There are many places where a top drive isn't practical, though; consider access to power or practicalities of morning lift start-up.
You're correct about the efficiency of a top drive. There are several other factors involved as well, of course. A top-drive lift can run at lower tension because gravity assists in holding the rope tight against the bullwheel. This also allows the lift to use slightly less power as it isn't trying to overcome the added friction of a super-tight line. There are many places where a top drive isn't practical, though; consider access to power or practicalities of morning lift start-up.
Member, Department of Ancient Technology, Colorado chapter.
#57
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Lift Maint. Manager
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Posted 01 September 2013 - 01:33 PM
Economical or efficient ? top drive, bottom tension is the most efficient IMO. It has the lowest cwt. weight or hyd. pressure , and the top drive has the most tension. this setup is the easiest engineering wise.
"Maybe there is no Heaven. Or maybe this is all pure gibberish—a product of the demented imagination of a lazy drunken hillbilly with a heart full of hate who has found a way to live out where the real winds blow—to sleep late, have fun, get wild, drink whisky, and drive fast on empty streets with nothing in mind except falling in love and not getting arrested . . . Res ipsa loquitur (it speaks for it self). Let the good times roll." HT
#58
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Posted 02 September 2013 - 06:00 PM
Top drive is most efficient in terms of minimizing the required horsepower for both driving and braking. Gravity assisted tension at the top-drive bullwheel means lower tension at the bottom return, and thus overall. Having the return station provide tension means there is a lot less machinery that has to "move" on the tension carriage, making it cheaper to build.
Bottom drive requires higher tension on the bottom driving bullwheel (so the rope doesn't slip). This means that the tension at the top is much higher (gravity), and all that extra overall tension means way more friction, requiring more power to drive.
A bottom-drive lift that must provide 100% downloading is worst-case. Think of the tension required at the bottom bullwheel so the rope doesn't slip on the liner in the event of a 100% download E-Stop.
The electrical energy required to turn a top-drive ski-lift is often ridiculously small, considering the size of the machine. I also work in electric utility energy measurement, and many lifts require more energy to heat the machine-room & machinery, than to actually turn the lift. Building an energy-efficient lift may thus be more associated with designing and building a heat-energy-efficient structure for the drive-station machinery.
Bottom staging areas are often prime real-estate, so the smaller and quieter the bottom, the better. The capitalization required to run a power-line to the top (say $100/meter, or less) can often be justified by having a quiet & small bottom return station down in the village.
Bottom drive requires higher tension on the bottom driving bullwheel (so the rope doesn't slip). This means that the tension at the top is much higher (gravity), and all that extra overall tension means way more friction, requiring more power to drive.
A bottom-drive lift that must provide 100% downloading is worst-case. Think of the tension required at the bottom bullwheel so the rope doesn't slip on the liner in the event of a 100% download E-Stop.
The electrical energy required to turn a top-drive ski-lift is often ridiculously small, considering the size of the machine. I also work in electric utility energy measurement, and many lifts require more energy to heat the machine-room & machinery, than to actually turn the lift. Building an energy-efficient lift may thus be more associated with designing and building a heat-energy-efficient structure for the drive-station machinery.
Bottom staging areas are often prime real-estate, so the smaller and quieter the bottom, the better. The capitalization required to run a power-line to the top (say $100/meter, or less) can often be justified by having a quiet & small bottom return station down in the village.
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#60
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Posted 03 December 2013 - 04:38 PM
I have noticed that there has been a trend in where the drive and tension are located based on the age of the lift. The oldest lifts were always bottom drive top tension. I think that they chose this because they did not know how to tension a drive terminal yet and they didn't know how to put a drive terminal at the top. Then they figured out that bottom tensioning was more efficient and made most lifts bottom drive bottom tension. Then they figured out how to make a top drive and the choice was the customer's as to where the drive and tension was. Another thing I have noticed is that tensioning on a lift is almost always at the bottom. The only times it won't is if the lift is a bottom drive and the design requires tensioning at the return, or if it is a top drive and tensioning is required at the drive. Am I correct about these things?
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