Making B-Trains Run Slower

[ZIArail]

hello, I'm new to your forum and like just about all trains in general (and MOST scales)   I came on here as this group seemed the most knowledgable on this question.  I model HO and HOn30.  HOn30 is NARROW GAUGE trains of HO scale running on N scale track (HO 30 inch wide track)    I have a few of the Bandai B train units (2 axle) power units.  I and others that model HOn30 like these units alot, BUT... they run TOO FAST.   Has anyone in this group had any like of any sort to get these models to run MUCH slower?  really about HALF the speed of how they run new out of the box.  Any suggestions are appreciated and yes the short trains you all have on here are cool.. I especially like the scenery and paint jobs.  Thanks Mark

[CaptOblivious]

Welcome to our forum! I've split your topic off into its own thread for clarity.

 

I would think that one thing you might try is wiring resistors—large wattage resistors, mind—in series with one of the motor leads might work. Same idea as the current-limiting resistors on LEDs. But you'd want to get, I'm guessing here, a 1W resistor or larger, as they will put off a lot of heat! But it would have the effect of reducing the voltage going to the motor at any given throttle setting, and hence a reduction in speed. The size of the resistor would depend on the current draw of the motor, which you'd have to measure, but then I could do the calculations for you.

[The_Ghan]

Hmmm .... when you say it's running too fast I'm guessing your minimum voltage on your controller is too high ... so you have 0, fast, and extra fast with burning smell, right?

 

I think it's a little more complicated than just a resistor in series.  You need one in parallel too, so that some of the current bypasses the motor altogether.  This is the correct way to step-down the voltage.  You need to know R2 in order to start.

 

KenS did some experiments about how much current is drawn by a motor car, to be safe, lets say 150mA.  We'll call this value I.

 

Next you need to know your maximum input voltage.  So, if your controller does 0-15v the value is 15.  Let's call that value E.

 

Using good old Ohms Law, enter the values for I and E. The resistance, R2, will be calculated as 120 Ohms.  The power P..will be calculated as 1.875W ... so we should use a 2W resistor.

 

We have calculated two important things here: R2 being the resistor in parallel and the fact that we could be drawing 2W of power.

 

Now it's time to use your gut feeling.  Let's take two examples: ¹/₂ voltage and ¹/₃ voltage.  So, you want to step down to 7.5v or 5v from the 15v in.

 

Go back to the voltage divider in the first link in this post.  

 

For ¹/₂ voltage: Enter 15 for input voltage, 120 for R2, and 7.5 for output voltage.  Press calculate.  The resistor in series R1 will be calculated: 120 Ohm - so you need 2 x 120 Ohm 2W resistors

 

For ¹/₃ voltage: Enter 15 for input voltage, 120 for R2, and 5 for output voltage.  Press calculate.  The resistor in series R1 will be calculated: 240 Ohm - so you need 1 x 120 Ohm 2W resistor and 1 x 240 Ohm 2W resistor with the 120 Ohm used as shown in position R2.

 

Hope that helps.

 

Cheers

 

The_Ghan

 

Edit:  Oops!  Sorry Cap'n ... I didn't see your offer to calculate ... since I've just had a go, do you mind checking?  It has been 20 years !!!

[keitaro]

Ghan the motors in these run on very low voltage.

i.e. 6v is like running them on 12.

 

i recently got some tomytec motor units they also run fast at low volts i.e 50% almost makes the unit fly of the table.

 

best suggestion is a tram controller theres one running max 9v i think theres another lower than that.

[Nick_Burman]

Erm...DCC? My Tomytec chassis have all been "tamed" when operating on DCC...

 

Cheers NB

[The_Ghan]

Ghan the motors in these run on very low voltage.

i.e. 6v is like running them on 12.

 

i recently got some tomytec motor units they also run fast at low volts i.e 50% almost makes the unit fly of the table.

 

best suggestion is a tram controller theres one running max 9v i think theres another lower than that.

 

Hey keitaro,

 

Yuh, I didn't know ... which is why I've included a couple of examples.  In that case, the ¹/₃ voltage should work.  It will give a max output of 5v.  Remember this circuit will scale whatever voltage is coming out of the controller ... so, if you're 9v controller is set at ¹/₃ voltage it will be putting out 3v ... which then goes through the ciruit and is scaled to ¹/₃ voltage again ... output will be 1v, with a maximum of 3v.

 

One should be prepared to do some testing.

 

Cheers

 

The_Ghan

 

PS: keitaro, I know you don't like to convert the circuitry on lighting boards for operation with 3-wire DCC setup, so I'm looking into it for you.  I might come up with some kind of intermediate circuit to go between the decoder and the light board.

[Mr Frosty]

I am considering swapping the transformer in my controller to reduce the available voltage to a lower level.

[keitaro]

the tomix n-400 was max 8.5v but yeah bit hard to find.

 

again though if the voltage was 9v max you have more play with the dial before it gets fast.

 

Good luck.

 

nick not everyone does dcc!

[dabsan]

Hi, I use a KATO UNITRACK 22-014 CONTROLLER for running B-Train's and that seems to work fantastic!

[Guest Closed Account 1]

Try the ModelSpeed app.

 

It's a stopwatch that tells you the train speed per your gauge and track length.

 

No guesstimating.

[cteno4]

another option thats used to reduce voltage on engines is diodes. you get a voltage drop across them and you can add more to reduce the voltage in steps. i think less heat dissipation than a resistor. you could wire these onto the controller to drop the voltage and isolate it with a dpdt switch so you only turn it on when you have a train that needs the slower speed on that throttle. you get like 0.6v per diode pair (need this for reversing). bridge rectifiers would be another way.

 

folks use diodes to try to match up engines internally in n and ho so they will run about the same speed when run together w/o dcc to do this. but no need in this case for the btrains probably, im not sure how easy it would be to isolate the motors in a btrain mechanism.

 

jeff