It’s going to be while before I’ll be ready to get my first engine, but I had noticed this issue, so thought I’d asked the question:
I notice in the MR loco test reviews that the slowest maintained speed always seems to be higher in DCC than DC. Why is this the case? Seems like the decoder ought to be able to control the DC output from the track–but gather this must be a consistent issue–at least in HO, I’ve noticed it on every test loco.
Seems like this could be a problem?
Thanks,
Jim
can be from what i’ve heard but i’m no expert in dcc
Just a guess on my part, but it’s likely the presets on the DCC decoder CVs are not optimized for slow speed running. If I were the manufacturer, I would preset the CVs so that even the worst running loco of the batch would visibly start moving on speed step 1. That way I would avoid the complaints (and some returns) about the loco “not working” when the end user cracked the throtte (speed step 1) and nothing happened. Those with the knowhow and desire can easily reprogram the CVs for the loco to run more slowly.
Again, a guess on my part. From what I have seen/heard, you are correct, slow speed operation on DCC after CV tuning should be better than with filtered DC.
yours in tuning locomotives
Fred W
I’ve noticed that too about the DCC/DC comparison. Odd, but it’s not a huge amount - plus keep in mind that is on level track, on DC an engine will slow down and speed up due to grades, on DCC (if the decoder has Back EMF “cruise control”) it will run the same speed up and down hill and on level track.
Ideally a decoder when first installed should be ‘transparent’, that is, the engine should run about the same on DCC as it did on DC. Then it’s up to the modeller to adjust the CV’s as noted above.
One reason that I think that the manufacturers do not do this is as the model gets broken in the engine will loosen up and then it might move too fast in speed step one.
I have found this on several engines I have set up for myself and others and had to go back and make s minor adjustment to the V start CV.
BOB H – Clarion, PA
Depends on the decoder and how it is configured. A decoder with good back-emf control should be able to maintain a slower speed than pure DC power. A good example is the comparison of the QSI-equipped locos - they all seem to have a rather high starting speed, because as currently available the QSI decders do not use Back-EMF to control the motor - they do apparantly use it for the sounds, especially steam, but not to control the motor. And it shows. My Loksound-equipped PCM T-1 will crawl so slowly that it takes more than a half hour to circle my layout.
-Randy
They obviously haven’t tested any ZIMO decoders [:0]
Regards,
Art
Zimo Agency of North America
http://www.mrsonline.net/
You have been reading too many reviews of the QSI equipped locomotives… [;)] As stated above, the QSI decoders don’t have BEMF (or speed control) enabled, so any locomotive with this setup in it will have erratic slow speed performance when compared to BEMF equipped models. The only exception to this are the Lionel Challenger and Veranda which both have the QSI system and BEMF enabled. These models crawl along at <2 smph while pulling trains no problem.
But as a general rule, any current generation decoder equipped with BEMF will outperform straight DC in any slow speed task (loaded or unloaded). While the locomotives mechanism performance is always an issue, I’ve yet to see a non decoder equipped locomotive crawl like any of my ESU equipped models will.
Jeff
Well I have to say my Stewart DS4-4-1000 with the Canon motor crawled quit nicely even before I installed a decoder… Low speed on my P2K Geeps is better with the decoder though.
–Randy
I have a Bachmann Spectrum 4-8-2 Heavy Mountain that I installed an NCE N14SRP decoder into that crawls. I also have several of the cheap Bachmann diesel loco’s that came with factory decoders that also crawl. Bachmann uses Lenz LE1014E decoders in their’s according to the literature that comes with the locos.
I just bought a Proto 2000 SD50 from TTX that they installed a NCE N14SRP decoder into and it crawls.
I can’t get any of them to move as slowly on DC as I can on DCC.
I don’t have any complaints.
Bill