# Start voltage



## gator do 65 (Jan 27, 2014)

What is more realistic, having low or high start voltage's? This is regarding diesels. 

Thanks in advance!


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## DavefromMD (Jul 25, 2013)

Start voltage is used to get a locomotive moving from a dead stop. It takes more power to get it moving than to keep it moving. You have to kind of play around with it to find out at what setting your locomotive will start moving. It will be different for different locomotives. Lets say you are using 28 step speed. You find out the locomotive starts moving at step 8. So you set that as your start voltage so that you don't have to crank it up to 8 to get it going. It will start moving as soon as you turn your speed control.

Then you can get into momentum which will tell it how fast to accelerate and decelerate. With momentum all you need to do is turn your speed dial to the speed you want and it will slowly accelerate to that speed. Beware of momentum on deceleration - if you need to stop in a hurry, it won't.

This may be more than you wanted to know.


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## CTValleyRR (Jul 26, 2014)

Dave nailed it with regards to starting voltage. On a couple of my locos, I have to crank it up pretty high to get the loco to start moving. This is largely a process of trial and error, but very satisfying to watch your loco creep along at 1-2 scale mph once you get it right.

Acceleration is an iffy thing. Up here in CT, we can watch the old Toasters (AEM-7's), HHP-8's, new ACS-64's, and of course Acela trainsets, go from 0-90 in seemingly nothing flat. Diesels and steam locomotives take much longer to accelerate and build momentum. Once you get the starting voltage set, you can experiment with speed tables to get it to accelerate at a rate that seems right. You can usually also set the max speed to something very close to the prototype (no 130 mph GP-8's). Again, this is largely a trial and error process.


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## tr1 (Mar 9, 2013)

*Jack rabbit starts?*

The lower the starting voltage,the more realistic the motion is.


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## CTValleyRR (Jul 26, 2014)

tr1 said:


> The lower the starting voltage,the more realistic the motion is.


While I'm pretty sure I know what you mean, the way you phrased it is incorrect. Starting voltage is basically the DC volts sent by the decoder to the motor at speed step 1.

Let's say I have two locos, A and B. The motor in A starts turning at 5vDC; the motor in B at 8. If I set them both at an SV of 8, B will look more realistic because it's initial speed will be slower. What the SV CV allows me to do is set loco A at 5v and B at 8v, so that they both crawl along in speed step one, gradually picking up speed as I increase the throttle.

So as nearly as possible within the limits of CV programming, you want to set the SV to the minimum voltage at which the motor moves the loco, and set it differently for each loco as necessary to get the best performance. This is just one of the advantages of DCC over DC: you don't have to crack your throttle open to 50% just to get a train to start moving.


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## gator do 65 (Jan 27, 2014)

Thanks for all the input!


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