International Society of Large Scale Model Railroaders by Stephen Podwojski

USA trains and 4 ft Diameter Curves by Stephen Podwojski

Invariably everytime you buy a locomotive that is Large Scale, the one question you should ask is:  What is the minimum diameter curve that it will negotiate?  Only recently has some of the Large Scale manufactureres been letting you know what that minumum curve is.  I have personally yet to see it labeled on boxes.  LGB has stated that they will design no locomotive that will not negotiate their smallest 2 ft. radius [4 ft. diameter] track.

An overhead shot of the GP-7 easing around the curve.  The track is LGB 1200 track which has metric diameter of 600 mm [3.973 ft].  Actually none of the diameters are truly measured in feet.  The R3 or 1600 LGB series of track is  described as 8 ft. diameter but it is actually smaller.  None of the foot measurements actually equal their generic names.  10 ft diameter Aristocraft track is actually 9.8425 ft. Again, because the big manufacturers [LGB, Aristocraft, USA trains] all make their curved track to Metric daime

On the left, you can see a USA ,GP-7, creeping around a 4 ft.curve. These 2 axle truck locomotives will make it around the curves. If you have 4 ft. or 5 ft. diameter curves, make sure you ASK if the engine and trailing cars can make the turns!  When you build your outdoor layout, put down the largest diameter curve that you can!  I would suggest no less than 8ft. Small curves do put strain on the motor blocks of the Larger engines.

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In looking at the photo on the left, you can see the immense off-center line as the USA train pulls an Aristocraft, 1:29 scale 40 ft. box car.  The hook and loop couplers are at the maximum stretch.  The hook on the GP is all the way to the left side of the box cars loop. The engine will go fine through the curves but remember that engines are supposed to haul freight.  A string of cars can be pulled on the 4ft. diameter track - but in this case, reversing the train caused derailments over 50% of the time.  Knuckle couplers would not fair any better.  Body mounted Kaydees would not work at all. If you are going to use Aristocraft knuckle couplers, you are going to need to modify them so the knuckle can pivot side to side more freely by removing the centering spring.  Metal wheels are also great in keeping the car hooked to the engine.

Note the above photo of the engine straining to go around the track. Hook and loops are more forgiving on smaller curves.

This page was last updated on: March 2, 2003