Decoder

Yes it is. Just add a 100 ohm resistor across the two motor leads. I have put a SoundTraxx LC decoder in a loco tender. The loco had it's own motor only decoder. I did not want to take the loco apart.

There are sound only decoders also.

Google the subject. You will find many responses.

Rich

Heat

Make sure you use a resistor of suitable wattage just in case the decoder's motor control is accidently notched and goes unnoticed (how would you know?). A 100 ohm resistor on a 14v DCC rail will dissipate 2 watts. A two watt resistor is not an itsy bitsy size resistor.  Thick film resistors are real thin and probably well suited to placement inside a locomotive shell.

Thanks 

Thanks 

Dummy decoder

I've installed Tsunamis in several de-motored P2Ks with no resistor. No problems at all, but when using the programming track to set the unit number, I have to put a powered unit on the track with it for resistance, then reprogram the powered unit's number to its original value. 

Speed Table

By setting up a custom speed table with all CVs set to zero, even if someone notched the throttle, no voltage would go across the resistor. I still would put in an adequate sized resistor, if possible.

GregW66

Mr DCC

Bruce explains this in the link. I forgot to mention a 1/2 watt resistor.

http://www.mrdccu.com/curriculum/soundtraxx/tsunami.htm

Rich

Heat Build-up

Just to reiterate what the others have said about the resistors. I did this with one locomotive and used too low a wattage resistor, it heated up so much that it melted a hole in the plastic shell. So beware, use a sufficiently large (physically large that is) resistor and try to locate it so that it is next to something metal rather than the plastic shell!

Both, not either

Ah, makes sense. Bruce says a resistor and speed steps to zero.

From the 50s

Back in the 50s Model Railroader magazine printed a series of articles on two guys building a layout. In one episode Linn Westcott made some trackplan suggestions. Their response was, "If Linn says we does it, we does it." 

When it comes to DCC, if Bruce says we does it, we does it. If Bruce knew how much I admire Linn Westcott, he'd take that as a huge compliment.

GregW66

I do, I do.

Greg -

I don't know the level of intimacy that you had with Linn, but I take ANY reference that puts me in tha same paragraph as high praise.

Good Idea

Given the tiny space inside N Scale Loco's and given my collection of N scale loco's that I'll probably never convert to DCC driven this sounds like a good idea to make good use of old locomotives.

I'm just starting my DCC journey so I'll have to come back to this thread much much later but I will want to look seriously at this option in the future.  If anyone does this project be sure to blog it with pictures please. 

On a remotely related note;  not that long ago I read somewhere about mounting the speakers on the end of a tube to amplify the sound. Could this be done inside the shell of a de-motored locomotive?  I wish I could recall where I had stumbled across that article.