Subject:
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Heavy Duty Track Connections for Public Display Layouts (ILTCO Article)
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Newsgroups:
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lugnet.trains
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Date:
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Thu, 25 Mar 2004 18:28:59 GMT
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Viewed:
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1859 times
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Reference http://www.iltco.org/library/articleShow.php?articleid=28
I noticed early on that there is a significant voltage drop between 9V track
sections. I put a large steam loco, which uses 2 train motors and 2 71427
technic motors, in a siding. When it was a metre from where the feed from a
standard Lego 9V controller met the track, it would hardly move at full
throttle, even with no wagons attached.
It was then that I decided to use a dual 30V 3A power supply to power my Lego
railway. 3 Amps is enough to power ten motors at a time, so if you have four
2-motor engines on the front of your scale-mile-long train it will cope.
For my British 8mm:1ft scale (8-10 wide) trains I use the extra current
capability to start one train and stop another simultaneously, since my trains
usually have up to four train motors each. The power supply seems happy enough
to supply the varying current while I'm switching over.
My large exhibition layout is currently 16ft x 12ft and each of two circuits has
a loop on either side, giving 3 trains each way. To swap trains I just change
the points at both ends of a loop simultaneously, using micro motors on modified
points, driven by standard Lego wires and polarity reversing switches.
The power feeds to the layout use standard Lego feed wires, connected to a short
9V wire cut in half. I put a 12V plug on this and used 12V wires from there to
the direction switches, which are small DPDT switches mounted in a 4x8 Lego
construction. The feeds to the layout are at either end of each circuit. This
gives redundancy and spreads the current, giving twice the current handling
capability. Because the feeds are opposite each other on the layout, the
maximum distance from a feed to the train is one quarter of the circuit length,
rather than half of it. Also, because of the redundancy there are two feeds
each one quarter circuit from the train, so I have actually divided the voltage
drop by four by halving the distance and giving two parallel paths. If I were
to remove a feed there would be a noticeable drop in train speed.
OK, the points of all this are:
1. that for big heavy trains a standard Lego controller just can't provide
enough juice;
2. that the location of redundant feeds matters - the more even the
distribution, the better the power delivery;
3. that for those a bit squeamish about soldering to Lego track, the use of 12V
plugs reduces modifications to Lego parts whilst providing nearly all the
benefits. I get round the one about corrosion by never removing the feed wires
from the track.
I also noticed the lack of chokes on the wires soldered directly to the track.
Presumably this is what the black cylinder is on a standard feed wire. I would
suggest winding the wire through a soft iron ring or similar a couple of times,
as one would with some computer cables, to reduce EM noise from the trains.
With all that said, I applaud your efforts - I'm sure your trains would say they
loved stretching their wheels on such a big layout if they had a voice!
Mark Bellis
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