# Inertia/Momentum circuit



## doublereefed (Jan 3, 2008)

Greetings,

I would like to add an inertia, momentum circuit to a small 4 axle locomotive running on 3V. I'd also like to do this to a larger locomotive like and Bagley Drewry that probably requires 12V? 

I'll be using a simple on-off-on toggle switch, but would like the locomotive to ramp up on voltage as the switch is thrown. While the inertia will look cool, I really just want the sound card to cycle the engine up and down. (The sound card would always be powered, the motor would receive the output of the switch and inertia circuit, sound card would read the voltage across the motor and respond with sound. There would be a master switch in front of all of this.)

Is there a product out there that does this? 

Thanks,

-Richard


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## Greg Elmassian (Jan 3, 2008)

finding something that works at 3v will be a challenge. Perhaps some battery-powered toy would have a sound card at this voltage.

Greg


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## dbodnar (Jan 2, 2008)

doublereefed said:


> Greetings,
> 
> I would like to add an inertia, momentum circuit to a small 4 axle locomotive running on 3V. I'd also like to do this to a larger locomotive like and Bagley Drewry that probably requires 12V?
> 
> ...


Richard - some years ago I wrote an article that may give you some ideas - it used capacitors to slow down deceleration and thermistors (NTC) to slow acceleration - have a look & let me know if you have any questions
dave

*Your Trains can Accelerate and Decelerate Smoothly* 
 Give Your Engines the Capacity to Ignore Dirty Track

  Thermistors, the Magic Behind Smooth Acceleration


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## David Leech (Dec 9, 2008)

Richard,
I will start this off by saying that I know nothing about electronics and how or why circuits actually work! 
A friend of mine left a British DMU (Diesel Multiple Unit) with me many years ago so that I could look at it's 'electronics' to see how it works.
It had two switches, one for direction, and the other was on-off.
When one turned it on, it would 'think' for a couple of seconds, and then slowly accelerate down the track, and then when you flicked the switch off, it would slow down gently to a stop.
Just what I needed for my RDC that I was building.
So, I opened up the panel underneath and found this tangled mass of wires and transistors and things.
It was horrible, no nice circuit board or anything.
I carefully followed each wire and drew an actual wiring diagram and noted all the numbers on the various parts.
So far, so good.
Now, of course all the numbers were British, so when I looked around (This is pre internet days) for parts, non of the local suppliers had a clue. Some books gave alternate numbers, but somehow I managed to get what I thought were replacement parts.
I wired up my test circuit, but there was no pause or acceleration - so I gave up!
Now live steam I can understand!
Cheers,
David Leech, Delta, Canada


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