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I've seen ski resorts use both top and bottom drive terminals on fixed grips. What are the advantages and disadvantages of both? Are some safer or cheaper then others? The only advantage of a top drive terminal is the higher elevation would keep the motor cooler. Are there any others?

The higher elevation actualy makes it harder to cool the motor/drive since the air is thinner. The top drive terminals are more efficient because they pull the chairs up the hill...the bottom drive lifts have a lot more tension on the light side of the lift. Often, the drive station is at the top unless it is too expensive to get power/supplies to the top...then they put the drive at the bottom. As far as safety goes, they both are very safe.

There is no reason why one couldn't have loading gates at the bottom if the drive is at the top. B-lift is a good example of that. I don't know to what you're referring but more than likely it was that topic about gates on FGs. Even there, as I mentioned in that thread, you can still have loading gates at the bottom when the drive is at the top. L-P, Doppelmayr, Riblet, it matters not.

Mike, on Mar 31 2005, 02:39 PM, said:

Top drive lifts have less tension overall because the tension on the bullwheel is always higher at the top terminal. At one point I remember hearing that R-lift ('82 Yan triple, bottom drive) had upwards of 75,000 pounds of tension at the bottom. It has closer to 40,000 now (75 was deemed excessive so a new counterweight was cast several years ago). Our detachable quads, all top drives, also have around 40,000 punds at the bottom even though they're much bigger lifts.

Some resorts that are in national parks can't have top drive terminals because the parks people don't want you tearing up the ground for electrical wires and other stuff.
This post has been edited by Zage: 04 April 2005 - 03:09 PM

Hey Zage, it's not so much the process of installing power lines under ground for top drive lifts, but rather the installation of access roads. By having bottom drive lifts, you don't need to have an access to the top, but it makes the job a lot easier of course.

I would also figure that top drives are desirable where real estate is clustered around the lift (like that never happens) since the noise level is considerably lower at the bottom.

Powdr

...or when real estate is clustered around the top, like DV's only bottom-drive lift, the Viking triple, that ends at Stein Eriksen's mega-bucks lodge

But if they had real estate at the top then electricity would already be there, and I would think that they would have a top-drive. I've never found noise to be too much of an issue, personally.

highspeedquad, on Apr 5 2005, 07:54 PM, said:

Then you have not been around to many lifts that are / were running off a diesel or a gas engine.

Exhaust is bad for real estate. You may not find noise an issue but high-rolling retreat owners do. Real estate does drive a great deal of lift-related decisions these days, like it or not.

Top drives allow smaller line machinery and smaller electric motors as you are only pulling the load uphill. In a bottom drive you must pull the rope on the downhill side, around the top bullwheel and then the uphill side to move the load.

I heard that top drives are more energy efficient why is that?

Instead of pulling the load directly from the top on a top drive lift, bottom drive lifts have to pull the load all the way around the whole lift, so it's a little less efficient. I don't know what I'm talking about, but I think that's basically it

Since you need a lower HP motor - it'll take less energy to power the lift.

I sorted through some old forums, I could not find one that described the difference between or preference for bottom tension, top tension or both. What are the characteristics of each?
This post has been edited by garthd: 13 September 2006 - 06:32 AM

I'm not sure as to the preference of both on which one is better at which end of the lift that you put it at, but from what I have observed over the years is that it depends on the profile of the lift, as well as it's length, and where is the easier place to have it in the event that you need to service or change that part of the lift. I have no idea if I have the right idea or not, but this seems to be a running trait in many installations. For example: the longer the lift is, the better the chance that it will have tensioning at both ends. The Slide Brook Express at Sugarbush, VT has tensioning at both ends to help pick up the slack of the cable over it's 2 mile length. Another example would be that here at Mt. Sunapee most of our lifts are tensioned at the drive (which is usually at the bottom for our lifts) for the accessibility to service it when it needs servicing.

It may also be for the need where there is space for it. I have seen a few instances in older Yan lifts that the tension block is out in the woods somewhere and is connected to the lifts through cables in order to minimize the amount of space the terminal takes up. I'm not sure about all this, but this is what I have always pictured for tension issues.

I’m no engineer, but I agree with Emax, the rope will fall down hill and you have to pull it up. With that said I’m not so sure it’s preference but more necessity when using top tension. One being space when using counter weight systems and one lift I know of that was top tension was because it was used when they bought it and it needed to be bottom drive because there was no power at the top, that made it cheaper in the short term. As with tension at both ends, you must mean one is active and one passive, I can’t imagine two active ends, one would think when you stopped both carriages would move up hill, and on start up they would move down hill. (Puzzled look now) Tensioning being at both ends (on a HSQ, Yan, Poma), one being active and one passive, is to take up rope stretch over time, particularly on longer lifts, not to react to loading. It also allows them to build nearly identical terminals, many top and bottom terminal sections on Poma and Yan are. You could put the drive gear at top or bottom with the same terminal, more so Yan in the earlier detach.

garthd, on Sep 13 2006, 07:32 AM, said:

Dead right on the top tension having to overcome rope weight. Bottom tension top drive is the best, given you have better rope traction on the drive (rope weight), you can get away with a smaller drive if it is a top drive. (I think we've all buried power lines in solid rock)

Most often it just doesn't matter, as design and utility location are big controlling factors.
Weight of haulrope is actually needed for bullwheel liner traction if the lift is a top drive.
Bottom terminal tension or counterweights can be somewhat smaller when comparing similar systems – however when using hydraulic tension this is immaterial because pressure of the tensioning ram is (somewhat) easily adjusted.
Interaction between number of towers, spacing, speed, size of carrier, and line terrain also play important parts…so we return to design and utility location.