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Author Topic: Is there a way to equalise the speed of two different locos  (Read 189 times)

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Offline DaveEssex

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Is there a way to equalise the speed of two different locos
« on: March 15, 2019, 04:50:53 PM »
I am planning a DC shuttle with a Y junction at one end so two different locos can run alternately down the single track.  A layout at my club has a similar arrangement and has the problem of the different locos running at different speeds for the same speed setting on the controller.  I was wondering if there was a way to do something to the faster loco to slow it down to match the slower loco, possibly by padding it in some way.  Any suggestions of doing this or is there a shuttle control system available that allows for each loco to have its own speed control?

I hope this is the right forum to ask, if not please point me to the correct one.

Thanks,  Dave

Offline PLD

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Re: Is there a way to equalise the speed of two different locos
« Reply #1 on: March 15, 2019, 05:07:52 PM »
Simplest way is to add a resistor in series with the motor of the faster loco, but it will take some experimenting to get an exact match and I suspect the values needed will be fairly small.

Offline Newportnobby

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Re: Is there a way to equalise the speed of two different locos
« Reply #2 on: March 15, 2019, 05:12:37 PM »
It's certainly a bugger to do with DC as even 2 locos of the same model do not run at the same speed unless you're lucky. Good luck in finding a solution.

Offline kenbury

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Re: Is there a way to equalise the speed of two different locos
« Reply #3 on: March 15, 2019, 07:19:01 PM »
one way is to use two controllers switching with a double pole switch on the y point

Offline ntpntpntp

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Re: Is there a way to equalise the speed of two different locos
« Reply #4 on: March 15, 2019, 08:11:52 PM »
I prefer to use a string of inverse-parallel diodes to drop the voltage. Each diode has a natural voltage drop of about 0.7V across the semiconductor junction, without generating as much heat as a resistor does.  Just be sure to use diodes rated for the expected current.

I tamed a speedy Tomix chassis this way using 4 diodes in each direction, to bring it more into line with other locos and units I run on  my automated shuttle.

In the end I split the diode strings either side of the motor (as per the lower diagram) purely for neatness of the installation in the chassis.





« Last Edit: March 15, 2019, 08:33:29 PM by ntpntpntp »
Nick.   2016 celebrating the 20th anniversary of "Königshafen" exhibition layout!

Offline Mr Sprue

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Re: Is there a way to equalise the speed of two different locos
« Reply #5 on: March 15, 2019, 08:16:01 PM »
I prefer to use a string of inverse-parallel diodes to drop the voltage. Each diode has a natural voltage drop of about 0.7V across the semiconductor junction, without generating a load of heat like a resistor does.  just be sure to use diodes rated for the expected current.

I tamed a speedy Tomix chassis this way using 4 diodes in each direction, to bring it more into line with other locos and units I run on  my automated shuttle.



Neat work!  :thumbsup:

Offline DaveEssex

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Re: Is there a way to equalise the speed of two different locos
« Reply #6 on: March 15, 2019, 09:19:13 PM »
Thanks for the details about using diodes. I had thought about that but was not sure exactly how to configure them... Your useful diagrams gave me the answer... Many thanks..

Dave

Offline Newportnobby

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Re: Is there a way to equalise the speed of two different locos
« Reply #7 on: March 15, 2019, 09:20:56 PM »
Glad you got it, Dave. It just short-circuited my brain cell :dunce:

Offline ntpntpntp

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Re: Is there a way to equalise the speed of two different locos
« Reply #8 on: March 15, 2019, 09:49:45 PM »
Thanks for the details about using diodes. I had thought about that but was not sure exactly how to configure them... Your useful diagrams gave me the answer... Many thanks..

Dave

You're welcome.  It took me a little trail-and-error to work out how much voltage drop I needed (around 3V  in this case).  I bought a bunch of 100 SMD diodes for 99p from Ebay. Fiddly to solder together to make the string but a litttle smaller and neater than "normal" diodes of the same current rating.  Should last me a while!  I have another similar chassis that will get the same treatment.

https://www.ebay.co.uk/itm/100PCS-LL4007-M7-1N4007-DO-214-SMD-1A-1000V-Rectifier-Diodes-NEW/253048346409
« Last Edit: March 15, 2019, 09:51:10 PM by ntpntpntp »
Nick.   2016 celebrating the 20th anniversary of "Königshafen" exhibition layout!

 

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