DCC Impulses Column - 6
set to 28 speed steps – see Mr. DCC's Workbench at the end of
this column. Adjust CV 2 (7) until the loco just starts to move
at speed step one on the throttle. Because of stiction, the best
way to accomplish this is to set CV 2 to 0 and then run your
throttle up until the loco runs, and back down to speed step
1. If it continues to run at your desired minimum speed, all is
well. If not, add one to the value in CV 2 and try it again. If you
overshoot, subtract one from the value in CV 2 and try again.
Note:
if you are planning on using speed tables, make sure CV
2 is zero and adjust CV 67 instead (9).
Now check for stiction. Set your throttle to 0. Move it to speed
step 1, without overshooting. Does the loco move? In my
experience, BEMF decoders will overcome stiction, given time
to sense that the loco isn't moving. Non-BEMF decoders and
excessively sticky locos may need kick-start or dither adjust-
ments here. See the manual for your specific decoder.
Tsunami users note: If BEMF is going to be used in your
Tsunami decoder, CV 2 should ALWAYS BE ZERO. Frequently,
locos will run too fast with a Tsunami on speed step one. The
Tsunami BEMF is doing too good a job overcoming stiction in
these cases. There is a way to fix this, but it is beyond this col-
umn. Check it out on my website in the middle of the Tsunami
page
for instruc-
tions and a video.
QSI users note: sometimes the loco will continue to run after
you bring the throttle to 0, especially with the Q2 series decod-
ers. There is a fix for that available on my web site:
With the Q3 software, a lot of issues have been
fixed and the tendency to run-on is reduced.
Limit top speed
Many folks stop at this point when adjusting their decoders. I
press on and limit the top speed.
Sixty MPH is 88 feet per second, or roughly the length of a
road switcher per second. So, if your loco moves past a fixed
point in one second, it is doing about 60 SMPH. If it takes two
seconds, it is going 30 SMPH. All but the largest layouts with
long mainline runs would benefit from speed limiting in the
30 to 40 MPH range, in my opinion. This means that the loco
will take about 1-1/2 to 2 seconds to pass a fixed point with
the throttle wide open.
The side benefit of limiting top speed is that the entire throt-
tle range controls the loco from creeping to maximum. It is so
7: DecoderPro screen: Setting start voltage in BASIC
SPEED CONTROL tab. Note: this is a Tsunami file
which doesn’t support mid or top voltage (CVs 5 and 6).
7
MRH-Dec 2013
