Major Miscalculation

I was reading back through a thread on Railwire this morning. It was a Layout Engineering Report on Cody's PRR Northeastern Division. I came upon this posting and stopped...
"No problem with super elevation pulling 75 Atlas 55 ton hoppers up the helix with 3 atlas TrainMaster  but had to add a GP7  pushing to get it up. Would recommend when planning to use the outer loop for going up. Locos have a easier time on the outer loop going up."

It caught my attention because I understood the problem. The inner tracks travel a shorter distance than the outer tracks, so the grade must be steeper. It doesn't look it. All the tracks rise at the same angle...

"West Slope" Helix

How can that be? The inner tracks in a helix have a different overall length than the outer tracks. The distance traveled to reach a certain elevation is part of the grade equation.

Made me think about it. I was wondering about the inner tracks on my helix. I guessed the grade might be tougher as the overall length is shorter, but I never really looked into it. Up until now I've been using the outer 22" radius to figure grade etc...The total track length over three and a half levels is just a hair over 40'. A rise of 8" in 484" is about 1.2% (I think).

The innermost track is 18.25 " radius. Total track length is 16.75 feet. That's 8" in 201"...That's about 4%.  WOW! What a HUGE difference between the outer and inner tracks. How can my little locomotives climb a 4% grade. That would make the grade well over twice as tough as the real west slope! Am I going to need a fleet of helpers stationed at the base of the helix?

I almost threw in the towel at that point. I would prefer 22" be the minimum on the helix but space limitations demand the helix fit in 4' x 4' so there is no way. I can't make the westbound grade any easier...

Then BANG! it hit me. That's just it. It's the WESTBOUND grade, stupid. The trains on the inner tracks are going DOWNHILL. Although it's more extreme, it is a similar case to the eastbound trains descending The Slide. You need good brakes, not tractive effort. I didn't plan it that way, I just lucked out. Mr. Thomson built the real railroad that way :-)

Aside from reading Railwire threads, I've been going around "tweaking" the roadbed during breaks from anchoring the vertical supports. It may seem a tad late but I laid down the 16' foot long plan of Juniata on the pink slab. Needed to find out if the mainlines actually went where they were supposed to. They did not. At the west end of Juniata I was pretty close...

Close, But No Cigar.

Once again the flexibility of the spline came to my rescue. I undid the screws and simply realigned the roadbed with the plan...

Realigned Passenger Roadbed

I did the same thing for the freight mains through Juniata yards. The roadbed is not quite complete, but I grafted in a section....

Realigned Mains

East Altoona was a whole 'nother story. Missed by a mile...

East Altoona Misalignment

I used the same solution. But I may have to rework the curve on the freight mains. The alignment is just outside the splines "limit of flexibility". A new section of spline will need to be built...

East Altoona Mains Realligned, Sorta'

Now about this time, if not already, some guys are out there shaking their heads. "Better planning would have solved this before it happened". Yea, it might. But I'm not John Armstrong, if you take my meaning. I'm just some guy who likes trains.

Regards

Frank Musick

Chief Cook and Bottle Washer

Allegheny Eastern Railroad