Questions for Rich and Hot Water

I can't remember NKP 700s having back pressure gauges.

SP4449 does indeed have back pressure indication, as part of the main steam chest pressure gauge assembly (the back pressure reading is in its own little 'window' down at the 5, 6, 7, o'clock, bottom portion of the gauge).

The way Doyle runs 4449, as he learned from the late Neil Voden, back pressure GENERALLY does't exceed 6 to 10 pounds when accelerating at heavy throttle. He pretty much prefers a steady 5 pounds at higher speeds, but once the throttle is reduced for cruising speeds (above 50 MPH), and the power reverse gear is LENGTHENED in order to bring that "crack" back to the exhaust sound, the back pressure drops to only 1 or 2 pounds on the gauge. At this stage, Doyle is primarily running her by his ear!

As far as maximum back pressure, I have only see one instance when the power reverse had to be dropped closer to the "corner", in order to get 4449 to accelerate on the 2.2% ascending grade of Cajon Pass, back in 1989(for the 'side by side' operation with UP8444, after the 50th anniversary of LAUPT). That took 25 to 30 pounds of back pressure, for a short period.

I know watching the videos of the 765, that Rich has referred to back pressure readings. I'm thinking on one comment he made, was something like 175# in the steam chest, and 12# back pressure... this was on the ~.48% of the New River Gorge..

Dave

The 765 does have a back pressure gauge. When working hard, the 765's "sweet spot" is when the back pressure is around 5-7% of the cylinder pressure. With the throttle wide open, 230 psi in the cylinders at 10-15 mph we'll have 15 to 18 psi of back pressure. Cruising along at track speed of 40-60 mph on level ground and a 15-20 car train, we'll be down at only 3-5 psi of back pressure, still enough to make a nice "crack" at the stack.

The highest back pressure I have ever run in the 765 was around 20-22 psi during hard acceleration, back in the 90's before the overhaul. We had to run the cutoff longer back then to keep the rods quiet and cool. The running gear was worn out then, with a lot of slop in the rods.

The highest back pressure I've ever witnessed was in another locomotive with another engineer who shall remain nameless. I saw the back pressure gauge pegged at 40 psi for quite a while. The locomotive was making a tremendous amount of noise, but we weren't accelerating very fast. WAY too long on the cutoff.

Thanks guys,

I sure hope someone is "writing this stuff down...."

There is NO substitute for firsthand experience!

Rich Melvin!  I thought you might enjoy these photos I took while your guest on 765 up in Owosso, MI, in 2009.  It was a real treat.  You and your crew are first class!  Great meeting you and best Regards, -Scott Nauert