What is the MINIMUM curve radius required for an SD40T-2 in a yard?

J

JonMyrlennBailey

Active member
On level track, no grade.

This is an EMD/GM 68 foot long d/e engine with 3-axle trucks.

I have a curve in my yard 49 m. Is this too sharp? Would a 2-axle-per-bogie road switching engine as an EMD/GM GP9 better handle this?
 
In North America, equipment for unlimited interchange between railroad companies are built to accommodate 350-foot (106.7 m) radius, but normally 410-foot (125.0 m) radius is used as a minimum, as some freight cars are handled by special agreement between railroads that cannot take the sharper curvature. For handling of long freight trains, a minimum 717-foot (218.5 m) radius is preferred.
Click to expand...
Source:
https://en.wikipedia.org/wiki/Minimum_railway_curve_radius
 
I'm not sure how prototypical you want to get, but the general I use is if something doesn't look right, I change it.

I have also found that if a curve is too tight, a Trainz loco can and will stall on the tight curve. If the large wheelbase of the engine causes the engine to stall, then the curve is definitely too tight.
 
In North America, equipment for unlimited interchange between railroad companies are built to accommodate 350-foot (106.7 m) radius, but normally 410-foot (125.0 m) radius is used as a minimum, as some freight cars are handled by special agreement between railroads that cannot take the sharper curvature. For handling of long freight trains, a minimum 717-foot (218.5 m) radius is preferred.
 
However Trainz will allow you to lay and run locos/rolling stock around much tighter curves than the prototype, due to its model railway origins. You could, with care, persuade an Athearn SD40 to negotiate a 20" radius curve, which is around 45 metres radius at full scale.
 
What it really means is that not every physical phenomenon is simulated 100%. As an example, gravity and the strength of materials is just barely simulated. You can easily suspend an object in mid-air, without any visible means of support and it will just stay there. You can cantilever a very thin object a long distance and it will not sag. Remember that in Trainz, you are a god and are in charge. Place track the wrong way or with curves that are too tight and the trains will still attempt to follow the rails. Think of the Trainz world as an alternate reality where some but not all of the real world rules apply.
 
Indeed Martin, think of it as the trains are following a path defined by lots of little 0's and 1's, not really clinging to steel strips 4' 8.5" apart!! :)
 
Many years ago I had a HO scale DM&IR 2-8-8-4 which would negotiate a 18 inch radius curve. However - telling you what it looked like would violate the COC and its a good thing I didn't have telephone poles on the outside of the curve. The boiler overhang at the front would have snapped them off like toothpicks.

Model Trains like Trainz is quite forgiving (up to a point).

Ben
 
Indeed, if you look carefully, the trains are following an invisible guide way defined by the track geometry. The visible rails are just for looks.
 
Usually on a branchline a RR would use SW1500's or other small radius switchers, and also in yards for shifting cars.

The larger locos would be used to hook up to already made up trains, to take them over the mainline.

Some industrial tracks at industries are so tight that they oftentimes derail railcars.

I use FT tracks as curve guides, a 50m or 75m radius is for very tight curves like on trolley, backwoods logging RR's, and street running industrial tracks
 
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In arcade mode, the behavior around curves is probably very unrealistic but how is it in realistic (?) mode. Not at my gaming computer right now so can't test this.
 
For the 40T-2 specifically - from the manual:

193 Ft. Radius -- 30 deg Curve -
Single Unit With Single Shoe Or Clasp Brakes.
230 Ft. Radius - 25 deg Curve -- (No End
Footboards) -- Two Units Coupled.
359 Ft. Radius - 16 deg Curve -
Unit Coupled To Standard 50 Ft. Box Car.
Click to expand...
 
The 3 foot gauge Uintah RR had 66 degree curves which were so sharp passenger cars could not couple together - they had to run short flatcars in between them.

Ben
 
When I build a Trainz route, I think of it as a working model of a real-world railroad. I want to keep track geometry as close to real world as possible.
Having walked on real tracks passing industrial sidings, I have noticed some tight-looking curves from the switch to a customer's siding on the SP railroad in California. Trackside customers included feed companies with grain hoppers parked there. The GP7/9 roach-switching engines would work this Northwestern Pacific branch line. They were short wheelbase locomotives with 2-axle trucks so I suspect they could handle tighter turns when cutting trains to serve customers on sidings.
 
There is no reason a B-B diesel couldn't be designed for extra sharp curves. More clearance for the bogeys to swivel farther and making all connecting cables longer plus more flexible should do it. Particularly if is was a small industrial diesel with a shorter overall wheelbase.

Steam-wise the B&O dock sider (0-4-0T) went around very sharp curves. Think the wheelbase was 8 or 9 feet max.

Ben
 
JonMyrlennBailey said:
The GP7/9 roach-switching engines would work this Northwestern Pacific branch line. They were short wheelbase locomotives with 2-axle trucks so I suspect they could handle tighter turns when cutting trains to serve customers on sidings.
Click to expand...

certainly. here are a few more for example.

GP9 operator manual said:
Minimum Curve Radius Coupled To Car 150' (39 deg)
Coupled To Another Locomotive Of
Same Type With Type "E "Coupling 274' (21 deg)
Click to expand...

SW1 manual said:
Minimum curve radius 100' 0"
Click to expand...
 
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