Joseph Rampolla says in his article “Make a Smoother-Running Rail Truck”, “It’s critical that you choose a quality, electrolytic capacitor rated for 50 volts. A good rule of thumb is to use a capacitor rated at approximately triple the maximum voltage it might receive.” It is not at all critical. In fact, there is no benefit to derating an electrolytic capacitor for voltage. If you use it at a lower than rated voltage, it will gradually lose its ability to operate at that voltage, effectively resetting its rating to the voltage it actually sees. You will have used a more expensive, bulkier capacitor with nothing to show for it. Especially in a situation where you want as much capacitance as you can cram into the space available, use a capacitor rated at or only slightly above the voltage you have. Twenty or 25 volts should be plenty for an application like Rampolla’s rail truck.
He also shows a 600-volt, 6-ampere bridge rectifier, which is a considerable overkill. You could justify the ample current rating as useful keeping the rectifier cool; but there is little point to the high voltage rating. Fifty volts would be more than enough.
Neil Besougloff makes a common terminology mistake in his article, “Old transformers: which terminals to use”. He calls the transformer return a “neutral or ‘ground’”. “Ground” could be excused as slang for “common” or “return”. But the neutral is a completely different concept, involving cancellation of return currents. While many are familiar with the fact that residential power-wiring neutrals are grounded, that doesn’t mean that the words mean the same thing. In fact, those who take pains, often unnecessarily, to get their transformer outputs in phase with each other, actually guarantee that the transformer common will never function as a neutral!
Bob, thanks for educating those of us “less informed”. I had thought of the “neutral” thing as being bad, but was not aware of the capacitor issue. Perhaps we could use a “Flux Capacitor” on the Delorian[;)]
We struggle with terminology because our magazine audience ranges from electrical engineers to folks that are concerned that electricity will “pour off” the rails at the dead end of a track spur and onto the floor (I’m not exaggerating). We also cope with terminology that Lionel used decades ago that was inaccurate but has become accepted jargon (postwar “trestle” bridges instead of truss bridges, for example). The Lionel “U” terminals drive folks nuts, because “U” on one transformer is “A” on another.
What word would you like to see used for the wire going to the outside rail?
“Common” to some of our readers can suggest the wire is being shared, which in some wiring diagrams is true, but in others is not. “Ground” to toy train hobbyists gets confused with the ground on extension cords or “earth ground” for metal bridges, etc., on a TMCC layout. “Return” suggests, again to typical hobbyists, that AC is a one-way street.
Neil, I actually do understand your dilema. I recall a similar discussion with regard to turnouts, etc. Perhaps, you could on the first common term word, put parenthesis around the correct word next to it, or vise versa. Then continue with the rest of the article. This would, I believe, subdue the critical observer, and also educate the less informed. I for one have a lot to learn and that is the main reason I return to the forum as there is a wealth of information to be gained in it’s pages.
Regardless, I appreciate your time and efforts…y’all (all of you) at CTT do a wonderful job.
I feel your pain, Neil. Strictly speaking, something like “layout common” is correct; but, unfortunately, there are other commons, like the common terminal of an SPDT switch for example, which are likely not to be connected with that layout common but will be confused with it. “Ground” has a certain appeal to me. It is actually legitimate (in the ANSI and IEEE standards) to use that term for the frame of a vehicle. Furthermore, in a sense, the outside rails can be said to be modeling the (literally) grounded rails of an electrical-railroad prototype. But, as you say, some will infer, not unreasonably, that we mean an actual connection to the earth (which, by the way, is not a bad idea for a layout, though not strictly necessary).
My best suggestion is one that I have tried to follow here on the forum and is actually right there in your question, “What word would you like to see used for the wire going to the outside rail?” It is, of course, “outside rail(s)”, or perhaps sometimes “the transformer terminal connected to the outside rails”. The latter is a bit wordy, but probably doesn’t need to be repeated very often, while “outside rails” compares favorably to “neutral or ground”.
I was thinking about this… why not refer to it as ‘Transformer Common’? That would indicate that the terminal(s) are not always ‘U’ or ‘A’ or ‘whatever letter they use tomorrow’…
It would read something like this: “Connect the outer rails to ‘Transformer Common’, then connect the center rail to ‘Transformer Variable’.” This makes a heck of a lot more sense to me!
The problem with switching up the ‘A’ and ‘U’ as common can create a real hazard IMHO. Just look at the older CW and the new CW. Since they switched them, you can no longer connect ‘U’ from the old CW to the outter rail, you would have to connect it to the center rail and connect ‘A’ to the outter rail, then on the new CW you connect ‘U’ to the outter rail and ‘A’ to the inner rail… switch them with two CWs powering adjacent blocks and well… damage to equipment is quite likely to occur…
I also can’t figure out why they aren’t labeled ‘O’ and ‘I’, for the ZW it would be ‘O1’, ‘I1’, ‘O2’, ‘I2’, ‘O3’, ‘I3’, ‘O4’, ‘I4’… that would make more sense to me! [:)]
Here’s another one for the “electricity pouring off the end of the rails” concept.
A few years ago, a CTT reader set up a loop of track for Take a Train to Work Day. He told me that one of his younger co-workers was absolutely stunned to learn that the track was actually electrified. The co-worker had never heard of such a concept and presumed the train was battery-powered.
I have not had that happen to the layout indoors, but several people have asked about the type or size of batteries I use for the Gardern Railroad LGB Mogul. [:D]
BTW, if you put a 5 gallon bucket at the end of the track, you can catch some of that electricty pouring off and use it to run the trains onboard radar so that it doesn’t wander off the track. [swg]