Why should DCC operate at lower voltages resulting in slower running trains when I have bullet trains in my layout. Whats the point of DCC then.
The voltage available to the track all the time is a whopping 15-16 volts. It just happens to be AC current with DCC. Adjust your speed tables to get the maximum speed your engineered drive train can provide your locomotive and you should find your trains running plenty fast. Also, if you want TGV speeds, you had better have curves wider than 50".
Crandell
alloboard,
Maybe you should read (or re-read) Tony’s Train Exchange primer on what DCC is and what advantages it offers. DC is fine, too. It just depends what you want to accomplish with DCC.
Tom
Oh my 50’ curves not even 22 radius curves! I 'm guessing that the speed tables have something to do with CV’s (configuration variables) with I find very intimidating when I’m looking at them in the Digitrax manuals. In other words I have not tampered with CV’s. It looks like one of those mathematical equations that rocket scientists decipher. It would be nice to find an illustrative easy to read and understand hands on article on how to operate these stuff.
With your move into signalling etc, do yourself a favor and get a PC interface for your Digitrax system PR3 or Locobuffer USB and start to use the free Decoder Pro application. It is far and the best way to look at programming decoders and gets you right away from CV’s. Speed tables are very simple when looked at on Decoder Pro.
Also responded to this question on your other thread.
Trains can run plenty fast on DCC. Do some measurements and compare your scale speeds to the actual prototype top speeds and you may be surprised.
From the primer mentioned above:
The section on speed control is listed at the link at the bottom of the page.
Tom
What could possibly be intimidating about changing CV’s? Keep track of what CV’s you change and what you change them to. Then if there’s a problem just change the problem CV back to what it was. After you’ve done it a few times you’ll find it’s easier than shaving.
On the subject of bullet trains, the fastest is the Frence TGV at 200 mph (highest recorded speed 357.2 mph). The Japanese bullet trains on the long lines have maximum speeds from 149 mph to 186 mph. The shorter line (Mini-shinkansen) run at a maximum speed of 81 mph.
If you’re running Japanese Shinkansen they should have their own separate (and fully grade separated) right of way. They run on rails spaced 14.5 inches wider than the rest of Japan’s major railways.
Even the fastest of Shinkansen aren’t that fast in HO - just 2 (full scale) MPH, or semi-slow walking speed.
Chuck (Modeling Central Japan in September, 1964 - without Shinkansen)
I have a question for the electric experts.
What’s the difference if DCC operates at lower voltages? So what?
Can’t you still achieve the same speeds as DC by just increasing the speed steps?
Or, will the same engine run faster at top speed in DC than it will in DCC?
Rich
Once you understand the concept (pretty much a form of binary), it’s quite easy. I actually enjoy it! (but then again, I’m a huge geek)
Looking at some MR product reviews, it appears that straight DC locos will run faster than DCC versions of the same thing. I believe that this might be due to the DCC decoder using some of the available voltage before it gets to the motor. And no, you can’t increase the speed by changing the speed step CVs, assuming that they have not been changed from the as-supplied number. All the locos I’ve speed matched have had the highest speed step CV set at the default maximum value.
No, that’s not what I meant. When I asked, Can’t you still achieve the same speeds as DC by just increasing the speed steps? , I meant to just crank the throttle up to the highest speed step (e.g., 28).
Rich
Jeffery!
“After you’ve done it a few times you’ll find it’s easier than shaving.”
You don’t shave! At least, if your avatar is correct, you have a beard!
Sorry, I couldn’t resist.[}:)] Please forgive me!
I totally agree with you that adjusting CVs is easy to do. Your advice to keep track of CV values is essential. If all else fails the decoder can be reset to factory settings.
Dave
Unless your decoder has a built-in step-up transformer (they don’t), you will only get something less than the maximum voltage the rails get from the power supply and base control unit. So, if your Brand Y DCC system provides a mean value of 15.5 volts to the rails, your decoder will only be able to provide a little bit less than that to your can motors. Assuming two locomotives with the very same engineering, parts, and assembly, and both trailing the same weight, they should both move the same speed in DC. If you place them on parallel rails, but one on DC and the other DCC, the DC one will move faster at max throttle if the voltage is higher than the DCC system can put out at max throttle.
If you can accurately measure the output of a decoder to the motor, and the input to the motor on DC rails, and they are the same, I would bet that both locomotives would move very close to the same speed. If you could measure the input to the motor on a DC locomotive, and the voltage input to a DCC decoder, you would probably see a difference in speed between them, the DCC locomotive being the slower, if both those readings were the same.
I sure hope we get some experts confirming this because I would not like to labour under any illusions if I am wrong.
Crandell
Crandell,
I suspect that you are right.
From my observations of engine speeds of HO scale locomotives in both DC and DCC, the DCC equipped locomotives run pretty darned fast, such that a DCC decoder has little slowing effect on a DC locomotive.
Rich
I believe that the answer is still “no”. When MR tests locos, many times they give the scale speed results using both DC and DCC. On DC they use 12 volts, and on DCC they report the results using speed step 28 (that’s 28 on a 1 to 28 speed step scale). Now I recognize that the top speed set at step 28 can be clamped lower by adjusting the appropriate CV for that step, but the default value for that speed step is usually the highest value. So you cannot increase the speed at step 28 any more than what the decoder allows.
As an example, the June 2010 MR had a review of a Bachmann GP7 with a dual mode decoder. Running in DC mode, the top speed was 80 smph. In DCC mode, the top speed was64 smph. Certainly the gearing and motor did not change during the test, so I have to assume that the difference had to do something with the decoder. I can only conclude that the decoder was using some of the available voltage before it got to the motor.
I did not go through every issue of MR to look at all the loco reviews, but I think you’ll find that at best the top speed is the same DC to DCC, but often the DC speed is higher than with DCC.
Check the voltage setting on your DCC system and then your curves on your decoders.
David B