Heavy Us Freight Downhill Braking

Although TSW does not at present model coupler failure, you can still experience that standing wave effect if you drive rough, especially on Clinchfield for some reason: your loco gets repeatedly shoved forwards and jerked back as the "Slinky wave" runs up and down the consist.

 

Oh yeah that happened at SPG for me recently with the journey expansions - hell of a ride but I managed it, learned a lot in the process ;-)

I knew what was happening but felt I need to practise a lot more (which I did), it’s difficult to anticipate the right actions

 

Just when I think I have braking all figured out, I read a thread like this and realize I’m doing it all wrong.

I do Sand Patch Grade a lot. I had been using the Dynamics as my main/only braking and then adding air brakes only on spots where my dynamics couldn’t keep up even in notch 8. It always gets the job done but from this thread it sounds like the correct method if I am reading right would be to have the entire train in minimum application for the entire descent and then use the dynamics for fine tuning. I will try this on my next run.

A question I have with combining dynamics and automatics: on the SD70ACE the dynamics don’t work in combination with the air brakes unless you bail off the loco. On the AC4400 and I think the C40-8W you can have the dynamics work in concert with the automatic brake without having to bail off the locos. Is that a inaccuracy where in real life those should also require a bail off? Or does the real life GEs just behave differently than the SD70? I am in the habit of always bailing off the loco as soon as I apply dynamic because of the SD70 behaviour but it doesn’t seem necessary on the AC4400.

 

I just did a downhill run on SPG after reading through this thread.. service N402 which is a loaded coal train with 43 cars, 5,510t. I did it with an AC4400 lead with 2 C40-8Ws trailing.

I just did this service yesterday too so it was a perfect one to try with what I learned in this thread.

My old way: basically come down the entire hill with the dynamics screaming in notch 8. Then when the speed was about to hit or exceed the speed limit, add air/automatic brakes. Then cut them when speed was reasonable and repeat that process. It worked fine to get me down the hill but wasn’t correct based on what I read here and was pretty janky leading to lots of speed limit exceeds.

Today I ran it this way: climb the hill to Sand Patch, then when over the summit and heading downhill (about when passing through the tunnel), put auto brake into minimum reduction, bail off loco brake, and then use the dynamics for adjustments all the way down. This ended up being the smoothest descent I’ve ever done in 500 miles using this route, I didn’t go overspeed once. I decided to try to keep the train at around 25mph regardless of the parts with higher speed limits. This seemed to work well. Instead of screaming with the dynamic brake in notch 8, it stayed in 0-5 the entire run and was able to keep myself close to the speed I wanted most of the time just adjusting the dynamic. There was one part about 7mi from Hyndman where the grade flattens out to about 0.8 and even with dynamics at 0 the train was slowing down quite a bit due to the air brake application. I was tempted to release the air brakes there but decided to ride it out and see. It did slow down to about 15mph but by that point the grade got steep again and my speed climbed back up to my target 25mph and I kept everything going all the way down to Hyndman where I finally released the automatic/air brakes and continued to Cumberland using just dynamics when needed.

This definitely seems like the right way to do downhill in US freight routes… always learning new things in this game. Just in time for Horseshoe Curve I guess .

 

Dynamic brakes are most effective at 25-30 mph.

 

pveezy Way to go!