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[Anonymous]

Hello fellow RR fans. After lurking for several weeks and being a rail fan for about the last 30 some years I figured Id say hello.

First off Ive loved trains since I was about 4yrs old and was an avid model railroader until that fateful day I discovered drag racing. Since then Ive been an "arm chair" model railroader but I have still managed to collect a fair amount of HO rolling stock and motive power for a free lanced Western Maryland layout when time permits (retirement hobby maybe?). I grew up ~100ft from the Laurel Bank division of the former WM in WV and regularly witnessed 8 unit lash ups of 4 axle geeps struggle with sixteen 100 ton hoppers en route to the summit of Cheat mtn. I actually became such a regular along the right of way that I was invited into the cab of the lead unit by the engineer and was allowed to man the throttle/engineers seat for a while during one of those slow hard drags out of Laurel Bank. For a ~13yr old train nut getting to regulate the throttle between run 7 and 8 to maintain the 10mph speed limit up the grade is something I'll NEVER forget and it still brings a smile to my face [:D] .

So, what are my questions? Let me start off by saying I now live a stones throw from Norfolk & Southerns main line heading east out of Roanoke, VA and have noticed a couple of things that being a drag racer/engine builder have me wondering about when they occur every few months when a drag is making its way up the grade out of Roanoke. Keep in mind these things Ive noticed are a little tough to explain in written text considering they are sounds rather than actions but I will describe them the best I can.

The first thing I have a question about is when a lash up of 4-6 units are at what sounds to me like run 5 or 6 one unit seems to have an incredibly loud exhaust note. The unit doesnt sound like its turning anymore RPM than the other units but the exhaust note is really, REALLY loud to the point I usually walk out of the garage to a point where I can see the units going by expecting to see flames, lots of exh smoke, or something obviously wrong with the unit only to discover no visual issue at all. Also at the same time the same unit is doing something I cant figure out at all even being a seasoned race engine builder. The previously described unit also sounds like (this is hard to explain so bear with me) someone is in the unit VERY rapidly opening and closing the throttle in approximately one second intrevals. To my well trained gasoline engine ears it sounds like someone is cutting the fuel supply off, letting the prime mover slow down one or two hundred RPM, then fully opening the fuel supply back up again and again. The best way I can describe it is to take a normal passenger automobile and perform a WOT (wide open throttle) accelleration test and just before red line turn the ignition switch off while still holding WOT, wait for about one second, switch the ignition back on, then repeat over and over again. When the unit is doing this I listen well after the train has passed and this "throttle cycling" never ceases or changes in any way. Ive listened until the train was far enough away that normally I cant really hear it anymore but when one of the units has this cycling ailment I can still hear it quite well. So, guys (and gals?) what is going on with this unit? Is there a problem or is it a normal mode of operation of some type? Personally, I highly doubt its "normal" since it occurs so randomly happening only about once every 6 months or so.

My second question is about a sound that while not quite as dramatic as the above has me curious none the less. Every so often when a lash up is dragging up grade I can hear an incredibly loud "whine" that gets my attention quite easily when Im in the shop working. It isnt the high pitched whine of a turbo or supercharger but more like a bad bearing in an automotive alternator only on a MUCH larger scale. My present vehicle I race is a twin turbo montrosity that even with open 5in exh right off the turbos and at 30psi of boost during WOT dyno testing isnt even close to how loud the "whiney" locomotive is. The casual passer by would probably pass it off of as "oh thats just the turbo" or something along those lines but I know what a very loud turbo sounds like as well as a supercharger and this is different. Turbos sort of whistle where as this is a combination of a VERY loud whine/moan and doesnt sound like a healthy locomotive at all. So, guys....whats your verdict on this one? An educated guess tells me its an issue with either the air compressor or the generator for the traction motors (maybe a traction motor issue too).

Thanks in advance for any light that anyone can shed on the above curiosities of mine and while I will lurk most of the time I hope to contribute every now and then should there be a question an arm chair modeler can help with [:)] .

[Anonymous]

I will try to get some road numbers from now on but it may take a while since its such a random occurance.

Thanks

[Anonymous]

Well, the reason the engines throttle sounds like it's goin up and down may have to do with the tonnage on the train and how hard it is working.

[M636C]

myclone,

I don't think I've ever heard what you describe but thinking about what it could be, I an reminded of a feature of older Alco locomotives that used to do that sort of thing in idle, sit there going "vroom, vroom" at about one second intervals. I was assured that this was caused by a governor problem. These units used an electro mechanical Woodward governor which had an oil filled damper to prevent "hunting", oscillation about the chosen RPM. If the unit had run a while since maintenance, the oil level in the governor would drop, and the damper stopped working. What you describe sounds like this problem occurring under power (which I'd been told wasn't a problem with this particular governor fault). However it does sound like a governor failure, and I'd suspect it would be with an older unit with this type of governor.

Remember that diesel engines don't have a "throttle" in gasoline engine terms. A gasoline engine is controlled by limiting the air through the carburettor. A diesel doesn't have a carburettor, and the governor and fuel system control the speed. I hope this can't happen with a microprocessor controlled unit, GE Dash 8 or EMD SD50 or later but it might just be possible.

So I'd say a governor problem, maybe a worse problem than that I heard on Alco units.

EMD Turbo locomotives use a gear train to drive the centrifugal compressor (which is direct coupled to the exhaust turbine) at speeds below notch 7 or so (when the Turbo takes over and the drive uncouples). I'd expect that a really loud whine could be due to a fault in this drive, maybe as simple as worn gears.

If you are really unlucky, the over-running clutch might not let go and the turbo might be trying to drive the crankshaft through this gear train. That should sound like an amazing whine (whith the force all going the wrong way) until it failed, which might not be too long.

The final drive gear in this train has damping springs to prevent too much shock being passed back down the gears on connection and disconnection, and can sometimes be heard as a "bling bling bling" noise at idle.

Anyway, those are my guesses!

Peter

[Anonymous]

Peter,

Thanks for the explanation/thoughts as thats exactly what I was looking for. Ive been around gas engines for over 15yrs and stuff like I described gets my curiosity up as to whats going on.

The governor issue you describe, or some form of it, is probably what Im hearing and I figured it wasnt a healthy sound. I was a young teenager when I was last around units working hard and those were GP30s, GP9s, and GP35s which never made such a noise that Ive been hearing since moving close to NS trackage 4 yrs ago. I thought it could possibly be something the new generation of units were possibly supposed to do but common sense told me it wasnt due to the randomness of it occurring.

Also, thanks for the explanation on how the centrifical supercharger and turbo are tied togeather. Im used to centrificals and roots style superchargers on racing engines being belt driven (they whine too but nearly as loud) so the noise coming from the interconnection gearing never crossed my mind.

Excellent info and thanks again.

Now if I could just quit getting out bid on that WM SD40-2 in the circus paint scheme that pops up on ebay every now and then Id be a happy fellow for a while [:D]