IronBeltKen
Lazy Daydreamer
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Grade transitions
- Thread starter DairyStateDad
- Start date
RCShadow
Member
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I don't eat corn, I write it.
Selector
Well-Known Member
To address an 'empirical' best guess about the length of a transition, my own 'formula' is to allow 6" for each 0.5% of change of grade, up or down. This would be functional for many applications, but not all of them. For example, a 2-10-4, whether in brass or plastic/diecast metal, might struggle to keep traction on that sharp a vertical curve leading into a grade. I currently have an Atlas twin track truss bridge in a single span across my river. As an imperfect model builder, the upper half of the span and the next 14 inches or so are in a exceedingly shallow of a negative curve with an average radius of maybe 150". My Sunset brass CPR Selkirk, a 2-10-4, spins far too much for my liking with a modest trailing tonnage behind it. I will have to use Bull Frog Snot on a couple of drivers...there's no help for it because no other engine spins as much as it does, not even the BLI PRR J1 2-10-4.
You would be wiser, as a general rule for most applications, to use a 8"/half percent of grade change.
You would be wiser, as a general rule for most applications, to use a 8"/half percent of grade change.
DairyStateDad
Mumbling in the corner
Thank you, Crandell. It turns out someone has created an Excel spreadsheet to help calculate. I am going to try that out and for that go with the 8 inch/0.5% you suggest, and see if I can get to the height I need to in the more challenging segment without exceeding 2.5 percent, with 2.75% as a fall back. (of course, as noted, that will require more transitions!)
Edited to add: In fact, I now realize that the spreadsheet was linked to here on this site sometime last year!
Unfortunately, the spreadsheet's ability to add additional rows has been disabled, so after 12 segments you have to start over...
Edited to add: In fact, I now realize that the spreadsheet was linked to here on this site sometime last year!
Unfortunately, the spreadsheet's ability to add additional rows has been disabled, so after 12 segments you have to start over...
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scroggin
Member
Is there anything you could put on the track or do to the track to make the track grippy at that point, rather than the wheels?............ just wondering
I create track plans as a job and that's way more complicated than anything I do.
No offense meant, but it seems like you might be trying to pour 10 pounds of sugar in a 5-pound sack.
Don't be afraid to acknowledge that it just doesn't fit and you have to start over -- a grade that is too steep (or deck-to-deck clearance that is too tight) is a pain that keeps on giving for the life of a layout.
RCShadow
Member
Byron has a good point.
I just did a "re-do" that by-passed a bridge with another whole section of track to solve a way-to-steep grade that my loco's could make in an A-B-A setup but with 15+ cars, a BAD decouple would happen and boy, you don't want that to happen on any kind of steep grade. That will make for one tightening of the bottom moment let me tell you!
DairyStateDad
Mumbling in the corner
Perhaps, yet in the dimensions I'm working with I would seem to be well within standard parameters for most medium to small layouts.
It's a twice-around loop in a footprint of about 11 feet by 8 feet. The upper section is at one end of the 11-foot dimension.
The upper track will rest of 1/4 inch cork on top of 3/4 inch XPS foam on top of 1/4 inch Luan, with lots of support wherever there is NOT track below it. (I am intending to build the upper portion as a "drop in" sort of thing). So On top of train clearance below (3 inches, per NMRA) I need to allow another 1-1/4 inches for railhead to railhead. So that's a total of 4-1/4 inches.
I'd actually like to get higher, but that's not looking very likely...
Running in one direction, I have a total of 230 inches to rise from 0 elevation to high enough to clear the rails below. With no transitions built in, the total 230-inch run would be just under 2%.
However, the run is complicated by a couple of things. First, there are a couple of switches along the way. One of them I'm willing to put on the grade (very carefully) but I am restricting it -- and about 8 inches leading in one direction & 11 inches in the other -- to no more than 0.5%.
Second, there's about a 38-inch segment where there are two facing switches (with another 14-inch length of track between them) that create crossed spurs. I've decided it's probably safest for that entire segment (St. Matthew) to be level.
So here's what it ends up looking like:
Before the first switch (the one with the 0.5% grade limit) there's about 43 inches of track. That rise alone will be about a half inch. With no transitions, the grade would be 0.76%.
Taking the transition rules into account, here's what I've come up with:
Run Grade
two segments of transition:
8.0 0.50%
8.0 1.00%
Peak grade for this run
11.0 1.50%
Transition back to the designated 0.5% segment (where the switch is)
8.0 1.00%
Designated 0.5% segment (middle 12 inches is the switch)
8.0 0.50%
12.0 0.50%
11.0 0.50%
All this just to get up to 1/2 inch.
After St. Matthew (which is level at 1/2 inch) comes the rest of the run, with 8-inch transition segments.
Just to get 4 inches railhead to railhead -- strictly speaking not high enough -- and with all the transitions, I end up going up to 2.75% for the main run.
This for a run that, with no transitions, would be nominally 2.13%:
8.0 0.50%
8.0 1.00%
8.0 1.50%
8.0 2.00%
100.0 2.75%
8.0 2.00%
8.0 1.50%
8.0 1.00%
8.0 0.50%
Now, don't get me wrong, I am NOT saying "fooey on transitions". (or is it spelled Phooey?)
Just trying to figure out if I'm really doing this right...
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RCShadow
Member
I honestly think you will be ok. Just don't have any transitions where the wheels are raised off the tracks. With those grades, I think you will be just fine. I think you might be over thinking it at this point. If you were talking something in the 4%-6% range I'd be nervous, otherwise, I think you will be good. Again, just don't have any transitions where wheels raise off the track.
It may not apply in your design for other reasons, but turnouts can certainly be on a grade with no problems. You just want to avoid changing grades within a turnout or directly adjacent. So in your first example, you might be better off with a consistent grade through the turnout.
Best of luck.
Best of luck.
Selector
Well-Known Member
Placing a turnout near a grade transition is asking for a lot of heartache. I have done it, but it takes a lot of patience and tuning to get it to work reliably. I would recommend placing the turnout's through route in a steady grade, and have a transition on a divering route only, starting about one car length from the frog. This is especially critical for steam locomotives with longer driver wheelbases, such as the eight-coupled and ten-coupled. If your transition is abrupt and/or too close to the frog, you run the risk of having a steamer entering the appliance still oriented to the average grade on the diverging route and the lead drivers being forced to run both high and aligned to the axis of movement. That means their flanges will not 'bite' and that pair will want to run right over the frog and closure rail.
DairyStateDad
Mumbling in the corner
I guess I figured that planning for a constant grade of 0.05 percent starting 8 inches before and continuing 11 inches after the turnout would address that issue.
Who, ME?
I *never* do that! From the DairyStatePhone
From the DairyStatePhone
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At my club they recently did a bit of trackwork restructuring to remove a troublesome slip joint turnout that fed all fiddle yard traffic through it. This required bringing two tracks from further away in onto the yard ladder at seperate points and relaying a couple of turnouts about 15' before that. This being all fairly level going. I run a number of 6 axle diesels, often double headed and on one of these turnouts they always derail (I have to use the other track that is now available since the modifications). The reason for the derailments are that the offending turnout has a very slight peak right at the join where the lead-in track attaches to the turnout and causes each truck as it passes over this peak to pivot about on the centre axle.
So, the reason for mentioning this is to illustrate what can happen if turnouts are laid where either of the diverging lines was placed right on the change of grade, might be OK in 1-1 scale but not in the size we work with. The diverging track would I would think need at least a full car or engine length before changing the grade direction.
So, the reason for mentioning this is to illustrate what can happen if turnouts are laid where either of the diverging lines was placed right on the change of grade, might be OK in 1-1 scale but not in the size we work with. The diverging track would I would think need at least a full car or engine length before changing the grade direction.
RCShadow
Member
Who, ME?
From the DairyStatePhone
From the DairyStatePhone
LOL...no offense with my comment at all. I am guilty of over thinking stuff too sometimes. I do understand it's important though with what you are doing. I still feel you will be all right. If you are that stressed about it, test it! Set it up on a temporary basis and see how things work out. If I had the room, that's what I would do.
DairyStateDad
Mumbling in the corner
And absolutely no offense taken!
I've been looking again at the Woodland Scenics incline sets and think that they might be the best bet, at least using the starter segments.
On the issue of turnouts and other more complicated trackage on grades (and again, completely understanding the issue of NOT putting turnouts on transitions)...
I've wondered whether, if using XPS subroadbed (or I suppose any subroadbed), whether it makes sense to build the entire segment on a single slab of subroadbed, then set the whole slab in place at the desired grade, to avoid exactly that issue.
So, for instance...
This segment
...would be built on a single slab of subroadbed, then placed on the layout at a tilt corresponding to the grade. (The Blue track represents the main, which would connect to other pieces of track; the white tracks are spurs.)
My thinking is that this approach -- if I take care to avoid any bends in the subroadbed itself -- will minimize the possibility of a *change* in grade anywhere in the relevant segment of track.
DISCLAIMER: Yes, it's *very* clear to me that either end of the main will have to very very very carefully match the connecting tracks in either direction!
I've been looking again at the Woodland Scenics incline sets and think that they might be the best bet, at least using the starter segments.
On the issue of turnouts and other more complicated trackage on grades (and again, completely understanding the issue of NOT putting turnouts on transitions)...
I've wondered whether, if using XPS subroadbed (or I suppose any subroadbed), whether it makes sense to build the entire segment on a single slab of subroadbed, then set the whole slab in place at the desired grade, to avoid exactly that issue.
So, for instance...
This segment
...would be built on a single slab of subroadbed, then placed on the layout at a tilt corresponding to the grade. (The Blue track represents the main, which would connect to other pieces of track; the white tracks are spurs.)
My thinking is that this approach -- if I take care to avoid any bends in the subroadbed itself -- will minimize the possibility of a *change* in grade anywhere in the relevant segment of track.
DISCLAIMER: Yes, it's *very* clear to me that either end of the main will have to very very very carefully match the connecting tracks in either direction!
