What is a "pantograph"?

[jacon12]

and how does it relate to a cantery (sp?)
Jarrell

[NZRMac]

It's the springloaded mechanism atop electric loco's that makes contact with the catenary wire.

Ken

[Anonymous]

Jarrell,

Google GG1 and look on top. Those are pantographs. They are spring loaded pick up devices that push up against the wire to make contact. They have a flat surface on the top that contacts the wire anywhere on the width of the pantograph. Alignment is not as critical as trolley poles where the pole is actually riding on the wire in a groove in the pick up shoe on the pole.

[Medina1128]

You've heard of an EKG, or electro-cardiograph? It's a graph showing the action of your heart. Well, a pantograph measures your dog's breathing. [:)]

[nedthomas]

The contact area for a pantograph is wide because the catenary wire is installed in a zig-zag patten over the center line of the track. This causes the contact to sweep from side to side to even the wear on the shoes. If the wire rode at one spot a groove would be cut in the shoe reducing the life and causing problems with side sway of the engine.
I beleive the contact shoes were made of hard carbon much like a motor brush.

[claycts]

QUOTE: Originally posted by nedthomas

The contact area for a pantograph is wide because the catenary wire is installed in a zig-zag patten over the center line of the track. This causes the contact to sweep from side to side to even the wear on the shoes. If the wire rode at one spot a groove would be cut in the shoe reducing the life and causing problems with side sway of the engine.
I beleive the contact shoes were made of hard carbon much like a motor brush.

THat I did not know, thank you. I have a GG1 and will try to run it from the "CATS" now I will not put it in the CENTER of the rails. You probably just saved me from causing damage to my BLI
George P.

[ndbprr]

the original "shoes" on GG1's were carbon. Later the PRR switched to steel shoes for longer life. at every stop the engineer and fireman checked for grooving and problems. Practice was to use the rear pan in case it snagged so it would not tear off the front one. Double pans were used when sleet and ice was on the wires to help cut it off and maintain contact

[dehusman]

The Reading had a huge bus line across the roof of the electric MU cars with a spring loaded contact at each end, so they only had to put a single pantograph up.

The actual name "pantograh" comes from a drawing instrument that is used to duplicate or reduce a copy of a drawing. It is a series of links arranged so when the user moves a pen (or pointer), a second pen moves in the same pattern, depending on the distances between the joints on the links, the size of the copy will vary.

There are two general styles of pantagraph, one is a diamond shaped frame, generally used on preWW2 engines and cars and the other is a jointed arm (Faivley? (sic)).

Dave H.

[jacon12]

Thanks for the education. Guy, I also learned this from the page:
"Why is it called the GG1?
The Pennsylvania Railroad had a standard system for identifying locomotives by wheel arrangement. For example a 4-6-2 was a K, a 2-10-0 was an I, a 2-8-2 was a L. subsequent models would get a number such as K2, K3, K4. Of importance here, is a 4-6-0 was a G. When articulated locomotives were introduced, either electric or steam, it was classified as two locmotives back to back. The GG1 is a 2-C+C-2 in Diesel terms, but a 4-6-0+0-6-4 in steams terms, so it was two G lomotovies back to back, hence GG. First revision makes it the GG1 (there was no GG2, but all electrics got a trailing number, although all steamers did not.) "

JaRRell

[Anonymous]

George,

Don't worry about the wire wear on models. I ran locos off of catenary for 30 years and wore out exactly one set of pantographs during that time. That was because the springs wore out, not from wire wear. Cool info from Jarrell and Ned. Thanks guys.

[rrinker]

Jarrell, the next Space Mouse? Early on, tons of questions, those things those of us who've been doing this for a long time think are rather obvious - so obvious the answers usually aren't even given in the beginner's books. A few months down the road - The Mouse is ANSWERING the tough questions, and his modelwork is excellent - witness the great job on the Climax.
I see great things ahead for Jarrell as well.

More! More!

--Randy

[nedthomas]

One more item about the pantograph. In 3rd-rail electric areas some locos had short stuby pantographs on the roof. This was really a third rail pick-up shoe. (some Lionel models come to mind). In complex track areas -double-slip, crossovers, etc,- the third rail was moved overhead because of the long gap in the outside third rail. The truck mounted shoes could not bridge the gap. The rail was supported on the ceiling of tunnels and steel structures above ground. The rail was rigid (same as the outside rail)
and had supports ever few feet. It was not caterany. The above ground structures looked like short snowsheds.

[Jetrock]

Catenary wire is a sort of trolley wire that is supported by an upper structure a "catenary" so the wire hangs very straight--this is used in places where electric trains are expected to run fast. On city streets and other low-speed locations, simple trolley wire hanging is used, as it is expected that the wire will dip a bit between supports. Catenary hanging is more complex and expensive (model and real-world) but required for fast electric lines!

Modeling the zig-zag used for pantograph-based trolley lines would probably be a bit difficult, although kind of a nice touch--but, as mentioned above, not strictly necessary.