Top vs Bottom Drive Lifts

Snowballs asked me about it in the take it all back thread.  I figured I'd start a new thread for it rather than going off topic there.


Top Drive:

Pros:  More efficient, much quieter at base area.
Cons:  More expensive and harder to install and maintain.


Bottom Drive:

Pros:  Cheaper and easier to install and maintain.
Cons:  Less efficient, noisier at base area.


Here are those pros and cons explained.  

Top drive is more efficient because the motor is in a much better position to move the heavy side.  It pulls directly up on it and gravity pulls the cable tight against the bullwheel meaning that the lift can run at a lower tension without slipping.  Lower tension means less friction and less energy to drive the cable.

Bottom drive is less efficient because to move the heavy side, the motor has to pull all the slack out of the light side and pull the cable around the top bullwheel before it can even think about moving the heavy side.  To keep tension on the bullwheel so there is no slippage, the tension must be fully applied by the lift's tensioners and gravity doesn't help at all.  More tension means more friction and more energy used.  There is also more wear and tear on the line gear.

Installing a top drive lift involves several tedious processes that are unnecessary with a bottom drive.  First is the fact that an underground electric line must be run all the way up the mountain.  This can cost over $1,000,000 extra to do if blasting is needed.  In hard to reach areas where a road cannot be built, it is literally impossible to install a top drive lift of any kind.  The drive components are too heavy and oddly shaped to be lifted in by helicopter, so there is absolutely no way to get them up there.  There also needs to be a 100 ton crane brought all the way up the mountain to install the drive components.  Maintaining the lift can also be complicated for similar reasons.  Say the motor burns out and needs to be replaced in the middle of the season.  Doing this means bringing a crane up to the top to remove it and install the new.

Installing a bottom drive lift is much easier.  No electric needs to be run up the mountain.  Bottom drive lifts can be completely installed by helicopter apart from the bottom drive terminal.  So let's say they are building a lift in an environmentally sensitive western bowl.  The tower blocks can be poured by helicopter, the towers can be flown in by helicopter, and the return terminal can be flown in and assembled by helicopter.  No need to grade terrain to build a road, just fly it right in.  Even a high speed lift can be installed this way.  Maintenance is also easier so if the motor burns out, no crane needs to go up the mountain to get it.

Top drive is quieter in the base for obvious reasons.  This is highly desirable in many cases.  Mountain Creek has no bottom drive lifts at South Base and it is almost silent once you get to the lodge deck.  At Hunter, the 6-pack is bottom drive and can be heard all the way in Hunter One.  Not a huge deal, but I'm sure basically anyone would prefer a return terminal to be in the base area vs a drive.

I could get into the merits of top vs bottom tension as well if you would like, and a bunch of other lift related stuff.

If you don't mind..... Spill kid, Spill !

Kid..Tell your dad to take you to the Alps.You will see every strange lift configuration you can imagine.

Become and Civil and Mech engineer and get a job with one of the big lift manufactures..

I've never really noticed or have been bothered by noisy lifts. Aren't most lifts, electric motor driven (with diesel or gas backups) which are quieter anyway?

The old Gore triple (AE1) was very loud especially when at the bottom of the race course for extend periods of time, it was very noticable.  Great info on the lifts, keep it up, interesting stuff!

The AE2 is also a bottom drive, but is much much quieter.  Newer lifts are usually quieter than older ones.  The AE2 also has a tire chair conveyor system which doesn't rattle like crazy when it runs unlike a chain system on the AE1.

Here is a pretty neat top drive lift for ya. This is at Powder Mills Park. This is the first lift I have seen with the tension terminal on the other side of a river.....

..... and it's slung over an old car rim. Hey, it works.

Snowballs asked me earlier what the merits of top and bottom tension are.  To put it simply, bottom tension is always more efficient.  This is because the tensioner doesn't need to hold up the entire weight of the line to apply tension like a top tension.  

On fixed grip lifts one typically orders a combined drive/tension for bottom drive lifts and a separate drive tension for top drive lifts.   This way, tensioning is at the bottom no matter where the drive is.  However, certain designs require a combined setup, so tensioning is at the top on top drive lifts.

Detachable lifts are pretty much the same, except some designs require separate drive/tension, so on a bottom drive lift, tensioning will be at the top.  Some detachable lifts have tensioning at both terminals as well.

Examples of different configurations.

Straignbrook quad at Gore.  Top drive, bottom tension with a separate drive/tension.

Summit quad at WF.  Bottom drive, bottom tension, combined drive/tension.

B Lift at Hunter.  Top drive, top tension, combined drive/tension required by design.

Main HSQ at Windham.  Bottom drive, top tension, separate drive/tension required by design.

AE2 at Gore.  Bottom drive with tensioning at both terminals.

Gondola at Gore.  Top drive, bottom tension, separate drive/tension.