This dimmer came out of a Knights of Columbus meeting Hall. There were several feeds to it. It would control 6 sets of large chandeliers. You would turn on each chandelier and then control all 6 using this large dimmer. It is about 2 - 2-1/2 foot in diameter. It weighs about 5-10 lbs.
This reminds me of some of the old theatre equipment I worked with some years ago. I used to be involved with a couple of amateur dramatic groups doing the lighting and sound for them. This was back in the early 1980s, and in one village hall we still had a lot of old 1940s/1950s equipment, which I assume had been donated to the village when it was replaced by my modern gear at a big theatre.
We had a whole bank of rheostat dimmers for the lighting, linear arrangements rather than rotary, with the largest master dimmers being almost 3 ft. long as I recall. Everything was installed in the control booth high up at the back of the hall -- A small enclosure which must have been no larger than about 12 x 6 ft.
When the lights were running on reduced power the heat from the dimmer bank was collosal.
Harold: This looks like a very nicely preserved example of a Ward Leonard "Vitrohm" dimmer. These guys were very widely used in theatrical stage lighting practice (and elsewhere, of course) beginning in about the mid 1920's. In smaller installations, they would be outfitted as this one is, and simply be mounted on the surface of a wall, usually with a piece of asbestos behind it - you could fry bacon on these things when they were properly loaded and had its resistance in the circuit. In larger installations, these dimmers would be mounted sideways in a steel frame, usually in one or two rows along the top of a switchboard in order to dissipate heat and protect workers from the live parts (even though early switchboards typically had dozens of exposed knife switches within too-easy reach) . In place of the handle shown, a rack and pinion gear connected to an extension rod and a vertical pivoting handle would be used to move the contact arm to impose the proper resistance. In some installations, the smaller handles could be interlocked together and be moved in unison with one large handle (or with a worm gear and crank handle affair on very large boards). These dimmers were made typically in 250, 500, 1000, 2000, and 5000 watt varieties. Loading them below their maximum rating meant that the lamp(s) could not be dimmed completely out (unless a "phantom load" was connected somewhere to fill it out). Loading them above their rating created the risk of burning out the resistance elements in the dimmer. These dimmers were rapidly replaced when autotransformer dimmers (built in the same general physical style and capable of dimming any size load up to its maximum capacity with virtually no heat) were developed.
It's kinda interesting to note that, as late as the mid 1970's these resistance dimmers were still in use by touring production companies. The dimmers were arranged along with knife switches, fuses and receptacles in large sheet-metal lined boxes referred to as "piano boards" (owing to the size of the box which resembled a shipping crate for an upright piano). I remember having to hook three of these boards up to power sources (called "company switches" in theatrical parlance) backstage at the old Music Hall in Houston when I was working with the IATSE in 1975.
"Loading them below their maximum rating meant that the lamp(s) could not be dimmed completely out (unless a "phantom load" was connected somewhere to fill it out)."
I remember seeing that. My father was a set & costume designer and when up in NYC for rehersals he would let me hang out with the master electrician. Lucky him - I was only about 9 years old! Anyway the electrician once showed me a concrete room with many stage lights set up and there were two huge 48in fans installed in the walls. He said these were to balance the dimmers. This BTW was in the late 1960s. Not until many years later while in EE courses did I understand what he meant.
[This message has been edited by Gus1999 (edited 05-09-2003).]
that do bring me memories with grand dimmer switches yeah they are pretty picky to run it and also one jobsite i was working they use large dimmer switch for wound routor motor ( the armture is controlled by dimmer) to change the speed aka early speed controller for variable speed motour i see that in one compaine to use that for milling machine the motour rather is large (450 HP ) and use big stacks of it. it was about 12 dimmers with common shaft with wormgear motour with back up hand crank . i will expain more later on the time how that run
Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)
It is a Ward Leonard dimmer. You can see it on the metal dimmer itself in the picture. YES, it was mounted in a wall behind a metal door and it was mounted on a piece of asbestos. Yes, it did get very, very warm and the bulbs never did dim all the way out. I am surprsies that anyone knew about this dimmer. I just figured that it was old and neat looking. Plus I like to keep some of the old devices that I would work with.
Since I have you on here, I have a question. I was told that in USA we have what we call a 3-way switch. This is a switch that can control a light from 2 different locations. If you wanted to control a light from 3 or more locations, you would use a 4 way switch. Now most people asked me, why a 3 way switch would only work from 2 locations, and a 4 way would work from 3 or more locations. I was told that ther terminology came from England and the original "3-way" switch was call a "3-point" switch. That was because it had 3 screws on the body of the switch. A "4-way" switch was called a "4-point" switch because it had 4 terminals on it. Have you heard of anything like this?
Like the numbering of floors in a building, this is one area where American and British terminology differ.
What you call a 3-way switch in the U.S. is known as a 2-way switch in England (i.e. the common wire can be connected to either of two others). A typical stairway light controlled from both top and bottom is frequently called a "2-way lighting circuit."
Where extra control points are needed, the switches you call 4-way are generally called "intermediate" switches here (derived from their location on the travelers between the two 2-way switches).
I don't know when the 2-way terminology came into being, but it's certainly found in British electrical books right back as far as the 1920s.
I've never seen the 3-point and 4-point terminology, although it's possible that it was in use in the early days.
There are quite a few instances in our shared language where America retained a word/term/spelling which later fell out of use in England.
I read that story somewhere here a long time ago about why we called it 3 way switches because it was you terminology. Guess it just goes to show you that you can't believe anything that you read. As for believing what you read, my great-great grandfather came from England. I am not sure what city. He was a coal miner from what I hear. Someone told me that there is a large forest in lower England called the forest of Dean. ( This again is only hearsay passed down through my family) Someone thought that he came from this region. That is why my last name was ENDEAN, the "en" could mean from and the Dean meant from that forest. Eh, what the heck. It sounds good to me.