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
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
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]