Can someone provide the background for construction of the new 2006 Tampa line using double overhead with no wire frogs at turnouts on most of the system?

Wesley

I believe the wires are directional. The motorman moves the pole from one wire to the other at the end of each run. They have been talking about going to pantographs so I wonder how they would work since the pantograph would contact both wires.
-JH

There shouldn't be a problem with a pantograph on 2 wires. Two wires reduce the probability of the trolley pole going down the wrong wire and coming off the wire. I did notice that the newest construction - on the west end of the line - used frogs. I can't recall if the carhouse used frogs or not.

It's perfectly reasonable to have two contact wires near each other. Not least, tie them together frequently and you double your ampacity because the other wire is your feeder. In fact if you plan pantagraph operation you should tie them together often. If they are separated, it becomes possible for a "perfect storm" scenario of a rocking car, high winds, pantagraph up-pressure etc. and you have one wire getting under the pantagraph horn. You have 0.00% chance of noticing this in time, and 0.00% chance of stopping the car in time even if you do. TRUUUUUST us on that (at the western railway museum).

I'm not sure what the value is to having 2 wires instead of a frog, but I could certainly see it for routes which converge onto the same rail then diverge not far later. It would eliminate two trolley frogs. They are expensive and high-maintenance and can be temperamental, a problem frog can de-wire half or all the poles that diverge through it. That's a 30 second delay 98% of the time, the other 2% it damages a pole or the wire. Either case, your line is plugged up until it's fixed. If you can get the pole down, you can switch to the other pole, but you can't back-pole very far or very fast without the 100% certainty of pole or wire damage-- which condemns you to going the other direction to get in the clear. Dewirements are a hassle.

Sacramento Northern used poles on passenger cars. Mainline siding wire came out and ran alonside mainline wire for a short distance. When passenger cars had to go into a siding, crews had to move poles to siding wire. They could do this with cars in motion as shown in movies. SN used frogs in yards and city strrets.

SN passenger cars operated at up to 65+ MPH. Poles would bounce when they hit a frog at this speed and occasionally come off the wire.

SN freight locomotives used pantographs so switch wiring made no difference.

Tampa Electric Company Line does use frogs for the car barn leads from the main tracks. The 2006 extension is single wire with frogs at the 1 new passing siding. I guess that means that there is a frog at the passing siding near the old end of track.

Here is an interesting solution to the trolley frog problem http://www.youtube.com/watch?v=qZAQ3y58Qco

dual wires close enough won't interfere with pans. If your running singe track with passing sidings you always take the right side pass, not an issue with the wire following the proper path.
Pans have drop off ends to pick up wire moves in and out. So splitting off wires is not an issue.

Switchable wire frogs is not new, has been done.

Here are a couple of photos of the Tampa/TECO line taken while attending the ARM spring meeting in 2008. Tampa actually uses some electric trolley bus overhead fittings including at least one movable point crossing frog. I believe that is the device shown on the trolley wire directly behind the Birney car. Trolley bus overhead curve segments are used in the carbarn yard. One lead to or from the carbarn is shown in the foreground in this photo.

The other photo shows the double overhead with the car having just passed over the diamond with the CSX and Amtrak into Tampa. Double overhead was relatively rare, mostly used where overhead wire frogs were avoided for whatever reason. Having double wire does help with the ampacity of the overhead but it also costs double to hang. Generally, railways had one or more heavy (e.g., 750,000 or one million circular mil) feeder wires with taps to the overhead contact wire every 1,000 feet or so. Generally, the heaviest overhead contact wire used by a standard street or interurban railway was 4-ought wire--pretty big stuff and usually used on mainline railroads or very heavily travelled lines such as in a big city downtown where it was prudent to have heavier wire because of the rush-hour loads and to reduce the frequency with which the trolley wire had to be replaced because of wear.

Speaking of wear, the Pacific Electric actually used steel overhead contact wire in several locations to try to cope with the wear problems they were having.

Thanks!

I have never seen the Tampa operation, but in looking at Jim Vaitkaunas' photos, I was astonished at the complexity of the trolley wire! It appears to me that the designer was familiar with catenary design for pantograph operation on electrified railways and light rail lines, but was completely unfamiliar with streetcar wire design. The use of a trolleybus type powered wire frog tells me that he felt uncomfortable with the use of rigid streetcar wire frogs, and went to the double trolley wire to avoid their use. There are several ways to provide ampacity that are less expensive than double trolley wire, including using 4/0 rather than 2/0 trolley wire, or using a relatively small feeder, such as 4/0.

Having been in Tampa for 10 days attending a conference, I have had time to further study the wire system. As Art and others suggest, I now think the mainline wire system was possibly designed for pantograph and feeder use, but with a traditional pole and bracket support system to give a vintage look. Note that the later extension to downtown includes a traditional wire frog and single trolley wire instead of including the dual wire to the terminus as is the case at the Ybor City ternimal. By the time this opened they were using the Gomaco cars with trolley poles. Also there are "shunts" between the two trolley wires at regular intervals that support the notion that the dual wire has a feeder purpose as well. I have not yet had time to stop at the yard and look at the wire system installed there.

Wesley