Is "Spitters on Shutdown" a Real Thing?

[tehachapifan]

Sort of a proto question, but refers to at least one sound decoder manufacturer's approach to "spitters". My observations are that spitters are on all the time when the loco is running.....at least with modern locos anyway. Is/was there a prototype out there where the spitters only activated once the loco is powered down? At any rate, I currently reprogram the decoders so that the spitters come on and go off with F8, if that loco is believed to really have spitters. When did spitters, I believe AKA automatic air dryers, come into play anyway?

[jdcolombo]

Hi Russ.

Yes, they are a real thing.  They are valves that open to expel water condensation from the main air reservoir tanks on a diesel, so that only "dry air" goes to the brake lines.  You'll hear spitters more in high humidity situations, or in the winter time, than in dry climates, because there is little condensation in warm, dry climates (think Arizona). 

And according to a friend who works on the CN, yes, they indeed continue to spit even after engine shutdown, to make sure that the air in the reservoirs stays dry.

However, I've always found the sound of the spitters going off while the engine is sitting "dead" in my yard to be a little weird.  So I ended up turning the "spitters on shutdown" sound to zero on my LokSound decoders.  But in fact that is NOT prototypical - spitters continue to operate for a time after engine shutdown.

John C.

[tehachapifan]

Thanks, John. To clarify, I do know spitters in general are a real thing and the overall purpose of them. My questions were specific to the preset decoder programming of spitters only activating once the loco is shut down. This arrangement seems odd to me and I question it's prototypical accuracy.

[Steveruger45]

Hi Russ,
To my understanding if the thermionic valves are purely mechanical, that is not operated by a electronic solenoid then they will work when the loco is powered down as they will release in the presence of moisture in the air system only.  I would imagine that when powered off the compressor is not running so the accumulation of moisture caused by compressing the air is removed, but the compressed air is still there in the system even when not being recharged and more moisture can accumulate by changes in ambient temperatures.  In short purely mechanical spitters can still spit with the loco powered off.  Just not as often.
https://www.dayton-phoenix.com/productCategoryDetail.php?categoryId=112

[tehachapifan]

More good info! However, I think there's a misunderstanding as to what I'm asking/referring to. The preset programming in many sound files I've used is spitters only upon shutdown. My impression is that there are no locos in the real world that do this.

….I do see that my initial post excluded the word "only", which was somewhat misleading as to what I was asking.

[Steveruger45]

Ahh!  Now I get it.
While I’m not a locomotive engineer I would think your suspicion is correct. I cannot think why it would be desirable to only have spitters work on shut down.   These things keep the air in the brake system dry and as moisture can build up relatively quickly in use, when the compressor is running, I would think it logical these things work in operation too.  In fact, the purely mechanical spitters will work anytime moisture is present to trigger them, running or not.

LOCOMOTIVE ENGINEERS OUT THERE HELP. 🙄

It just occurred to me the meaning in the sound file of “spitters only upon shut down” may be that this is the only sound the decoder plays when shut down at some random rate, presumably to simulate a real shut down loco that has mechanical spitters occasionally spitting when it is parked and all on its lonesome.  I think this then would be prototypical.  However, my models do this too but I must admit it seems to do it too often to be prototypical. 

[RBrodzinsky]

Russ, there is also a function key to manually turn on the spitters.  I believe that other setting is for the random sounds (i.e., randomly fire spitters if prime mover is off).

[fire5506]

Spitters operate whenever they sense moisture whether the locomotive is running or shut down. They will operate until the air bleeds down too low for them to work.

 

[tehachapifan]

(duplicate post)

[tehachapifan]

Russ, there is also a function key to manually turn on the spitters.  I believe that other setting is for the random sounds (i.e., randomly fire spitters if prime mover is off).

Yes, thanks. What I do is program the decoder so they come on and go off with F8.

[RBrodzinsky]

Yes, thanks. What I do is program the decoder so they come on and go off with F8.

What I meant was that many of the Select sound files have spitters on F21, too.

[MetroRedLine]

I think the other issue is at hand are sound levels/ratios. In the prototype world, the sound of spitters is only really audible close to a locomotive, and can hardly be heard from a distance, wheras on our models, the sound is usually almost as loud as the horns. So it does sound weird coming from a turned-off locomotive because the volume level is disproportionately loud.

[tehachapifan]

I agree they're preset too loud. I typically turn them way down as well.

Thanks for the replies and info!

Interesting that I lose respect points with this thread.

[MK]

Interesting that I lose respect points with this thread.

That's crazy!  Fixed it for ya'. 

[tehachapifan]

Ha! Thanks!!