Home Elevator Drive Systems
One of the most important decisions you can make about a home elevator is the drive system. Let's look at the pros and cons of the six major types.
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Cable winding drum
- Moderate intial acquisition price
- Consumable parts (the cables)
- High maintenance costs
- Less smooth ride than other systems
If asked to sketch an "elevator," most people would probably come up with something like a winding drum system, where the elevator cab is suspended with thick steel cables from a reel at the top of the shaft. This is the most basic elevator setup, and the one typically advertised by price-conscious installers due its comparatively low cost.
The outstanding drawback of winding drum systems is the one common to all systems that use cables: Every cable, no matter how thick, twisted and tough, will eventually stretch and have to be replaced – typically every three to five years in the case of a winding drum elevator. In many cases, the attending higher maintenance costs more than counterbalance the initial savings over the life of the elevator.
In addition to the drawback of maintenance, winding drum elevators generally deliver a ride that's less than smooth. Some folks don't mind this, but it's good to find out about it before making a purchase decision, rather than discovering it the first time you use your home elevator.
Noise quality is another big issue with this system. A winding drum requires a big 220V motor - larger and louder than other types. And, while it might seem like cables should be smooth and quiet, they're actually quite noisy compared to other systems.
If initial acquisition price is the all-important factor and you can put up with some noise and roughness on the ride, a winding drum system may be right for you. For a long-term investment, however, a winding drum drive system is not usually the best choice for your home elevator.
- Quiet operation
- Somewhat smoother ride compared to other systems
- More expensive than other drive systems
- Consumable parts
- High maintenance costs
- Prone to mechanical difficulties
A hydraulic drive system works almost exactly like the automotive jack in your garage: A piston in the bottom of the shaft is pushed up and down by pressurized hydraulic fluid to effectively carry the elevator cab. When used in this application, a cable system is added to the hydraulic jack, doubling the elevator cab's travel and reducing the shaft depth needed to contain both cab and drive system (this is a little difficult to wrap your head around, but it works – really).
Hydraulic elevators have more consumable elements, and require more maintenance, than any other type of home elevator. To start with, a tiny amount of hydraulic fluid escapes from the piston every time the elevator runs, even on the most well-made hydraulic units. This natural slow leak can easily be multiplied into a fast leak by the mere intrusion of a single tiny particle – a grain of sand, for instance – between the piston and the seal. Even if this doesn't occur, the hydraulic fluid still needs to be changed annually.
As discussed above, a hydraulic elevator uses steel cables to mulitply the travel distance of the cab vs. the piston – like any elevator cables, these have to be changed every five years or so, and this job is much more difficult on a hydraulic elevator than a winding drum, because of the increased complexity of the cable paths. Also, hydraulic hoses have to be replaced at the same interval as the cables.
The main selling point for hydraulic elevators is quiet and smooth operation, and it is indeed true that a well-built hydraulic system is a little quieter than most other drive types. As to the ride, descent in a hydraulic home elevator is unquestionably a very smooth experience, though this benefit is somewhat counterbalanced by a slight roughness on upward travel.
A hydraulic home elevator may be the right choice if noise level and ride quality are extremely important to you. The comparatively higher acquisition cost plus the maintenance issues mean that a hydraulic elevator will cost you much more over its lifetime than some other systems.
Chain drive counterweight
- Reasonable acquisition cost - about the middle of the home elevator pricing spectrum
- Low maintenance
- Lower lifetime cost than cheaper systems
- Good ride
- Low noise
- Not quite as smooth riding or quiet as hydraulic
- Not initially as inexpensive as a low-end cable winding syste (but substantially less expensive than hydraulic).
- Requires an access door at the top of the hoistway.
Rather than using cables or a hydraulic cylinder to move the elevator cab, this type of drive uses a chain (much like a very large bike chain) to transfer torque from the motor with a system of gears. One might think this would be really noisy, but it's actually rather quiet – almost as quiet, in fact, as a hydraulic cylinder system.
Chains have a very significant maintenance advantage over cables: They don't stretch as easily. Where cables need replacement every five years or even less, a well-maintained chain can easily last for twenty years without replacement.
Unlike winding drum or hydraulic systems, a chain-driven home elevator typically uses a counterweight - essentially a stack of steel blocks equaling the weight of a 40% loaded elevator cab, hung on the other end of the chain opposite the cab itself. This increases mechanical efficiency and also provides additional security against free-falling.
Considering all factors, we recommend chain drive for most home elevator systems. It's relatively inexpensive, quiet, reliable, and low maintenance.
Inline gear chain drive
The inline gear system is an improvement on the basic chain drive concept which places the motor assembly at the top of the shaft – instead of on top of the cab like a standard chain drive. This allows for less headroom on the shaft, reducing construction costs, and also provides faster access to emergency controls outside the car, increasing safety. Inline gear systems are also somewhat more energy-efficient than standard chain drives.
Gearless traction drive
- Very quiet
- Popular in commercial applications
- Most expensive system short of vacuum tube
- Multiplies the problems of cables with more length and complexity
When you ride an elevator in a hotel or office building, gearless traction is very likely to be the drive system you are experiencing. This type of drive combines the cables of a winding drum system with the counterweights of a chain drive, resulting in a whisper-quiet installation.
On the downside, cables are still cables – only with a traction elevator, there are 2-3 times as many as there would be with a comparable winding drum, and they are more difficult to install and remove. Since all elevator cables need to be swapped out every five years or so, this means a large increase in maintenance costs.
A gearless traction drive home elevator is a good choice for high-end installations, but you should keep in mind that, with its associated maintenance expenses, traction drive is an expensive gift that keeps on taking.
- Visually stunning
- Great view from cab
- Very quiet
- Orders of magnitude more expensive than other drive types
- Requires an unusually large opening for the door
Vacuum tube elevators are a great choice for any installation where money is no object, particularly for new construction where the hoistway can be planned ahead of time to include larger opening for the doors. While the system is beatiful (a "work of art that happens to carry passengers" according to some), quiet and smooth-riding, its price tag is easily two or three times that of a chain drive or hydraulic system.