Re: The Fantasy Lift Shopping List...

**Hipennine Wrote:**

I'm not convinced about this Hi speed detachables use more power than fixed grip argument.

For the same uplift capacity, a fixed grip (because it runs slower) needs many more carriers and passenger on the line than a detachable express. The load being hauled at any one time is therefore greater than a detachable, therefore requiring more energy to balance the extra power input to run at higher speed of a detachable.

Arm chair physicists...

There are a number of flaws in that reasoning. Firstly a chairlift is a semi balanced system. If we consider a fixed grip chairlift that has no passengers the energy required to lift a chair from the bottom to top station is recovered as it comes back down. The losses are rolling resistance on bull wheels, sheaves etc. and air resistance. There is also the energy required to overcome the inertia of the system when starting it up.

However a detachable chairlift also has decelerate and then accelerate every chair as it goes through the top and bottom station. This is a huge energy expenditure and as far as I can tell no detachable chairlift has a kinetic energy recovery system aka KERS to offset this cost.

With passengers added into the mix all chairlifts have to expend energy to accelerate the passengers to the line speed. This is dependant on the square of the velocity of the line speed of the chair. So a typical detachable chair operating at 6m/s compared to a fixed grip at 3m/s requires four times the energy to accelerate the passengers to the line speed.

We also have the fact the power required to overcome aerodynamic drag is related to the cube of the velocity. So with the above example line speeds that is nine times the energy to overcome aerodynamic drag. Now admittedly you will be exerting it over a shorter period of time, but it still adds up to more energy required to operate a high speed detachable than a fixed grip.

Note the number of passengers on the line at any one time is a red herring. What you need to look at is the energy required per passenger. As I have pointed out previously the limit on the number of passengers per hour for a chairlift is dependant not on the line speed of the chair, but the loading interval. This changes very little if at all between a fixed grip and detachable chair. You do get slightly more on a detachable due to end effects but it is negligible over the day.

Roughly you need four times the energy to accelerate each passenger, a bunch of energy to accelerate each chair twice, four and half times the energy to overcome aerodynamic drag and more to overcome "rolling" losses in the system. Consequently the energy required to run a detachable chairlift is much higher than that of a fixed grip.

The other consideration with big (ie 6 plus seaters) is uplift capacity. The Bochasses lift in thge Yearbook has replaced 3 T bars and still added additional capacity to the area they served. That is a significant reduction in operating costs, particularly wages.

Sure read my notions of doing similar things at Glenshee on Sunnyside. However this is separate from the fixed grip/detachable argument.