derailing question?

[chpthrls]

I am modeling in HO and recently added incline (and thus decline) on a 22" radius curve. I fashioned this up and down ramp from two inch foam board and used wood shims as transitions from level to up and down. My problem is this, when running my Atlas Dash8, when the engine has cleared the down side, the second car uncouples, always the second car. Could the coupler heights be off a bit (Athearn SD60 works fine, Athearn GP38-2 works fine, likewise Atlas GP40-2)? Or could it be negative draw-bar pressure? Also, the journal box (?) on the Atlas GP40 is hitting the Atlas switch machine on a couple of turnouts. Would it be sacrilege to do a bit of trimming so they clear?

 

[dstarr]

 If you are having uncoupling trouble near the beginnings or ends of your inclines first try easing the onset of the incline.  If your roadbed goes from 0% grade to the full grade of your hill at once, you have a vertical kink in the track.  You want to ease into the grade of some distance.  Go from 0% grade to 0.25% grade to 0.5% grade to 1.25% grrade and so on.  If you are still having problems, do more easing. You mentioned wood shims as transitions.  Try more shims to ease the transition more.

   After doing all the easeing you can, check your couplers heights.  Get or make a coupler height gauge and check all your rolling stock at both ends.  You will find that the Athearn blue box cars always need a washer under each truck to jack the couplers up to standard height.  After checking all the rolling stock against the coupler gauge,  couple up a train and  get your eye down close to railhead height.  Inspect each coupling to make sure both couplers are at the same height.  

   You have to fix any places where rolling stock hits stationary stuff (switch machines, bridge abutments, station platforms, what ever).  At least if you expect the trains to stay on the track.  I'd start with some Dremel work on the offending switch machine.   After you get it whittled back enough to clear, a coat of grimy black paint will make the surgery invisible. 

 

[Mr. SP]

Are you coupling a short 40 foot or so car next to a long car such as a 72foot centrebeam? The difference in car lengths will also cause uncoupling. Correct coupler height is critical and could be part of the problem too. Check your couplers with a gauge.

The main cause is as mentioned in the previous post a quick change in grade. Also at the summit of the grade allow for some level track before going down the other side.

[gerhard_k]

On the subject of vertical grade transitions, which so often make problems on beginners' layouts, I was very disappointed that in the new book "102 Realistic Track Plans", Andy Sperandeo, one of my favorite model RR writers, says not one word about this topic in the section on "Figuring Grades and Clearances" (page 48). I know that a 2-page article can't cover everything, but it should at least have been mentioned as an important factor. Any comment, Andy S? My guideline is to allow one car-length of track for each percent of grade change, so if you use 60-foot passenger cars (8.3 inches long) and go from level to 2.5%, allow 20 inches, or 2 feet to be safe, for the transition. At a summit, going from 2% up to 2% down, that's 4% total change, with 85-foot scale-length passenger cars (12 inches long), you would need 4 feet. Vertical transitions are often ignored in mountain-type track plans, where sometimes 3% up and down grades converge at a turnout frog. You'd think by the time authors (and editors) publish track plans, they'd know better... - Gerhard