I'm running an auto rack from Cumberland to Rockwood. I have two big AC locomotives up front, 50 auto racks in the back. No helpers in the rear. I've made it through the tunnel at sandpatch and now I'm headed down hill towards Rockwood. I'm controlling my speed with dynamic braking, and that's working out just fine except I noticed my speed oscillating quite a bit. So I try and apply some independent braking to let the train bunch up behind me. It doesn't seem to make any difference. So I applied a little train brake, no difference. Can anyone explain to me why my speed is oscillating?
Maybe the on/off of brakes is "rippling" through the train like a slingy toy and all the cars are bouncing each other around?
Are you applying any auto brake? Give it a minimum application or slightly more, then bail off the independent brake before you use the dynamic. The dynamic is only applying to the locos, so the cars will be jostling due to the wave mentioned by the previous poster. Once you've done that do not release the auto brake until you've got to a level grade. Control your speed by adjusting the dynamic brake.
I experienced exactly the same thing on a recent SPG run a couple of days ago. The engine was literally bouncing forwards and backwards while the dynamic brakes were constantly applied. Their force differed without changing the lever, resulting in higher braking force at lower speeds. But every few seconds - again without changing anything - the braking force reduced itself automatically and the train gained speed again, giving a delta of about 7 mph where it constantly bounced between during the whole run. The whole ride felt like a permanent fuzzling around with the accelerator of your car in 1st gear. Unfortunately I wasn't able to capture this on screen because as a final bonus the game crashed - most likely out of memory - in Cumberland Yard on Series X only half a mile before the final destination... 2 hours that will never come back.
As I said earlier, You need to apply auto brake - try about a 12 pound reduction at first, for the 1.5% ruling grade from Sandpatch tunnel, then put your dynamics notch 3 -5 and control your speed using the dynamic, this way you can get a constant speed down the hill. If you don't apply any (or enough auto brake) your cars are unbraked and will be troublesome - jostling into the back of each other and into your locos. See below for a test I just ran using the 2 locos + autoracks. Do not release the auto brake until you get to the part where the grade flatterns out. Hope this helps! The slight wave at the beginning was just after I applied the auto and tried a few different setting to sort out the speed, after that I didn't need to do a lot to keep a steady 29mph
Thanks for the reply! I know this isn't simulated ingame but wouldn't a constant apply of the auto brake result in overheating IRL which is why the dynamics are used to maintain speed as often as possible?
Don't want anyone to be mistaken - I am not an expert, not even remotely so, what I am saying is a conjecture, and I am not claiming to be a real locomotive engineer or something. I think this is an exaggeration of the effect of the consist "bouncing" behind you, I noticed it happens on a lot of older american freight trains, and it is one of the main reasons I didn't play any - I think Cane Creek and the freight services on Peninsula Corridors are the two prime examples that come to mind. I believe at heart it is realistic, but just way too noticeable, for example I remember from playing Peninsula Corridor that by just releasing the brakes and applying notch 1 power you almost get a whiplash (the moving camera gives that effect) from the consist moving behind you, and again it's not like you just went straight to notch 8 or something. Considering how this doesn't happen on SMH, with the reworked physics, I would say that I believe it is a bug. Keeping in mind the disclaimer above, so far most of the people I've talked to about american freight trains seems to agree on the idea that dynamic brakes only is always preferred, and a running release is actually not that standard of a manouver, and the air brakes are used almost exclusively when you expect to completely stop the train.
If you need auto brake to keep your train from running away, you need to use it. You shouldn't be using more that notch 4 or 5 of dynamics as you'll cause damage to the loco. So if you're in notch 4 dynamic brake going down a grade, and are still increasing speed, start adding more air brake. Probably fair to use just a light dynamic on a small downhill grade but once you get to >1% grade you need air and dynamic. I am not an expert in US operations, but that's info that I've gleaned and seems to serve well.
I'd agree with this too, the physics are probably a bit exaggerated! I just imagine though - on a steep hill, those heavy cars are going to want to roll through the locomotive, as effectively they're going faster than the loco. The only thing stopping them is a knuckle - so you need the auto brake applied on anything fairly steep to stop that from happening.
Like FD1003, I’m no expert on US freight (although find it intriguing!!) but having had a looking through the Norfolk Southern locomotive engineer’s manual sometime ago (i think you can find it on google as a pdf), using only the dynamic brake is the usual method of controlling the train speed on gradients or even for reductions in speed. Using the air brake is highly discouraged and when it does have to be used, it should only be a minimum reduction (10psi) and the locomotive brakes must be bailed off immediately. Even coming to a stop can be done pretty much exclusively using the dynamic brakes because US locos have resistors that step in as speed reduces thus allowing dynamic braking to maintain its braking effort upto almost a stand. Beyond a certain number of wagons (I think it might be a 100), the rules are that if you have to use the air brake at all, you must let the train come to a stand before releasing so using the air brake really is a last resort.
The often quoted video tutorial for Run8 was done by a real NS engineer if I recall correctly. We can be pretty sure that the use of the auto brake on grades as a standard is prototypical.
