# Electrical Engineering/Escalator Design.

Question

Escalator
QUESTION: Dear Cleggsan

http://en.wikipedia.org/wiki/Escalator
http://science.howstuffworks.com/transport/engines-equipment/escalator.htm
http://www.reedconstructiondata.com/documents/FS/specdata/143100_10001243_01_SD_

Escalators, like moving walkways, are powered by constant-speed alternating current motors and move at approximately 1–2 feet (0.30–0.61 m) per second. The typical angle of inclination of an escalator to the horizontal floor level is 30 degrees with a standard rise up to about 60 feet (18 m).

1. Is the Angle of inclination of 30 degree standard to the Horizontal floor and standard rise of about 60 feet standardized in all escalator designs  while manufacturing ?. i.e. Can the Angle of inclination differ to 45 degree or standard rise to say 80 meters
or speed vary i.e.  2-3 feet (0.61 m - 0.91 m) per second ?.

2. Is the Load carrying capacity (weight of the Riders) in a escalator set to a maximum limit ?. i.e. Every Escalator designed
has a maximum load carrying capacity similar to a Elevator device ?

In this case, how safety of the passengers is ensured if overload happens ?. what is the overload protection mechanism
inbuilt within the escalator ?. As soon as there is a overload of
extra weight, the escalator device stops moving upwards (Step Up Motion) or downwards (Step Down Motion) ?.

3. In events of electric power breakdowns where escalator comes to a standstill, how passengers safety is ensured as they is a chance of losing balance while moving up or down ?. Is the escalator machine battery powered up in case of mains power failure ?.

Thanks & Regards,
Prashant S Akerkar

ANSWER: I am not an expert in escalator design so all I can offer is my personal opinion on your questions.

1.  I suppose the angle of inclination is based on experience, testing and intelligent application of engineering principles coupled with mathematical optimization of power input, efficiency of movement, balance of human being response and ergonomic factors.  During the first few years of escalator usage it was necessary for human guards to stand at the starting point of the entrance to watch that humans did not fall down as they were whisked away with the first step!  There were many accidents during the first years of their use; now days you rarely here of accidents as people have grown accustomed to them.  Some of the escalators in the London tubes and the Marta in Washington DC are very, very long. I don't know how long but I have ridden them and they are frighteningly long/tall.

2.  Overload protection is quite straight forward engineering.  There are many ways to detect over power draw, high temperature, strain and load.  Whilst I do not know the exact electrical principles and mechanisms used, there are classical text book solutions to motor design, control circuitry and safety measures for fire, heat rise, over burden of load, etc.  The greatest failure of escalator motors is burn out and wear I think.  Just my opinion.

3.  Yes, that is a vexation to the designers of escalator systems on how to handle immediate stoppage.  They never go back down from my experience as there is probably a braking system that prevents them from reverse movement.  And, I have been on an escalator when it failed and some people tended to lose balance but quickly emerged and the people on it continued manual stepping to get to the top. I have personally been on the long Washington DC escalator when it failed and walked up the steps to the top.  I was exhausted by the time I got up and out!....

Interesting question. Hope you get all the answers you need for your project. Hope this was helpful to you.

---------- FOLLOW-UP ----------

QUESTION: Dear Cleggsan

Thank you.

1. if a Comparison between Escalator and Elevator Systems is done in terms of  Manufacturing, Installation, Maintenance Costs, Escalators will
be more expensive (i.e. Cost incurred for Manufacturing, Installing and Maintenance) than Elevators ?

2. Can we implement Escalators in already built structures viz Shopping Malls, Departmental stores, Buildings, Airports, Metro Rails etc.

Thanks & Regards,
Prashant S Akerkar

ANSWER: 1.  It is very difficult to answer the question because of the building codes, legal requirements, architectural designs and such.  The cost would take into consideration of foot print and structural differences as well as the actual machinery, stairs, cages, lighting, hydraulics, etc.  It seems to me a detailed analysis would be necessary for a given set of designs to give a good answer to this question.  For small, tall buildings an elevator may be the only practical solution.  For buildings with many floors, again, elevators have much higher velocity in moving humans from floor to floor.  In buildings with lots of floor space and not so many floors like a shopping mall the escalator is a better choice.  For large crowds the escalator keeps people moving all the time but elevators require long waits and can handle only a small group at once.

2.  Escalators are easily added to existing building given sufficient space to include the drive systems and the moving stairs themselves.  Elevators can be added as well but they require some serious cutting into floors and building of a hydraulic piston or chain drive into the basement area to host the up and down movements.  I would think that all other things being equal adding an escalator would be more practical and less costly than adding elevator shafts.

---------- FOLLOW-UP ----------

QUESTION: Dear Cleggsan

Thank you.

Do you feel Specific Sky walks if replaced by Horizontal Auto walks could be more useful for people flow ?

http://en.wikipedia.org/wiki/Mumbai_Skywalk_Project

Thanks & Regards,
Prashant S Akerkar

Many airports bus depots and train stations are using them. I like them personally.  Some people would rather walk on their own. If the walkway is too narrow it bottle necks because some humans are fast walkers and some are slow. If the width does not allow easy passing then they are not so friendly to a smooth flow of people.  A study of traffic flow, number of persons/hour, etc. would be the tool to determine the usefullness of moving walkways  (inclined and flat).

Good Luck.

Electrical Engineering

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#### cleggsan

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