Track radius

[Suncoasttrains]

So please explain the radius terms for G scsle. What is r1 and r3.. how wide is 8ft radius. How wide a half circle be to accommodate a g auto rack or challenger.

[Rayman4449]

From LGB's web site (in terms of diameter, not radius)

R1 = 1200 mm
R2 = 1560 mm
R3 = 2390 mm
R5 = 4640 mm

 

Translated into imperial:

R1 - 47.2" diameter (2' radius)
R2 - 61.4" dia (2' 6' rad)
R3 - 94.1" dia (3' 11" rad)
R5 - 182.7" dia (7' 7"rad)

 

I can't speak to the USA Trains Autorack but the MTH Challenger is said to need 8ft diameter minimum.  I personally suggest going with 10ft minium.  8ft radius works out to 16ft diameter.

 

See this for explanation for diff between Radius and Diameter: https://www.mathsisfun.com/geometry/circle.html 

 

[enginear joe]

Keep in mind that the minimum stated track radii to operate on is a recommended size. Just like any toy train scale, the biggest curves you can get will look and work the best. I have ten foot diameter track in the basement on the inside mainline. I wish that was larger.

Outside I'm running around 14' diameter and larger curves. I still can't even look at the USA bigboy as it needs 20' diameter as it's minimum!

[Suncoasttrains]

The mth site says the challenger is r3 which is about 8 ft. That should be about right . My layout room is 35x19 . Maybe not big enough for the autorack but I'm tired of 3 rail. Time to rip up O scale??

[Sean]

Ok

 basic math we all have forgotten.

R= measurement from the center to the edge of a circle

D= measurement from edge to the other edge of a circle

[ssculptor]

Ray, Thank you for this info. I was about to ask his question myself.

However, I still would like to know what is meant when they give us the degrees. 

For example, a listing on eBay says LGB 1608 Right & 1615 Left Hand Electric Switch R3 22.5° ~ G SCALE

Now, thanks to you I know that R3 means the radius is 3''-11" (7'-10" diameter). But what does the 22.5 degrees mean?

 

I started to construct my outdoor railroad and was looking to make it large enoiugh to accommodate the big mallets. However, two years ago there was a fire at my home and my library burned. Well, that happens. But I wanted to construct my own switches and especially on a curve. I remember I had an article on how to make my own but its is all ashes now. 

Is there any source where I can get plans and instructions on scratch building my own switches in G gauge? 

Thanks again,

Stephen

[grsman]

Garden Railways Magazine had a two part series on building turnouts. It was in June 2009 & August 2009 issues.

Tom

 

[nscaler711]

Well it doesn't help that past O scale HO and the smaller gauges use radius when it comes to curves... O and G gauges use diameter... Which to some (including myself) can cause confusion, and LGB makes it worse by using R1, R2, etc.

 

As for the Degrees that is the angle of a single section of curved track. So you can divide that number by 360 (or vice versa) to get how many sections you would need for a complete circle. 

[du-bousquetaire]

If you intend to operate live steam standard gauge locos the minimum safe radius is a bit over Ten feet, with fourteen being coinsidered much better. Usually outdoor there is n't the same accute space problem as indoors. Samre with pointwork on any main line points I use N°8 points at least. I only have two shorter ones on very small sidings not much used and on the engine runaround track at the end of my indoor terminus.

 It works better and looks much better.

[Alan Crosson]

I am designing a G Scale track and I am planning on purchasing an SD40-2, which has 6 axles. Does anyone know the min. radius you can run a 6 axle locomotive without derailing it?

[Sean]

8' 

[Oldsalt]

G Guage MTH Big Boy.

I bit the bullet and have obtained a Big Boy even before I have started my Layout.  So, I see the engine is rated for a LGB R3 curve which is a bit less than 8-foot diameter.  I have the room so I will adopt the 10-foot diameter.  Being a highway engineer as well as the son of a railroad yard foreman, I would like to know thoughts. about super elevating (banking) the curves also.  

Also, I noted that in this tread someone was asking about what a 6 or 8 or so on switch meant.  A number six switch has a departure from the mainline tangent of 6 degreed.  In other words, the larger the switch number is, the sharper the turn off angle is from the mainline. 

[Rayman4449]

10ft diam is a good minimum to go with on the MTH One Gauge Big Boy.  As a general note to others reading, keep in mind that any stated minimum diameter curve (like 8ft in this case) that an engine is supposed to be able to take, doesnt mean it might not struggle/bind going through a curve that tight.  So going with curves wider than the minimum is a wise move to avoid issues.

 

I would avoid super elevating your track.  In the real world they are trying to compensate for heavy weight loaded higher in the cars to compensate for that tendency tip over towards the outside of the curve if you go around a curve to fast.  In the model train world you have the exact opposite risk.  In really long & heavy G scale trains, the cars are relatively light weight and you be more apt to pull them off on the inside of the curve because so much force is exerted on the cars in the curve itself that they will lift off the track.  So super-elevating your track to the inside only stands to make that risk worse.  I would just go with as level a track as possible.   Unless you plan to run shorter trains at super high speeds then I would leave them flat.

[blid]

I’m afraid you have not observed the difference between the European and US notification of curved tracks. In Europe the radii is measure in mm to the center of the track. LGB R3, the 18xxx, are 2363 mm. This gives a diameter of 4726 mm or about 15.5 feet – if I am correct.

I have a picture of my Big boy on LGB R2 showing the ridiculous overhang, but I can’t find it right now.

[Sean]

Go as large of a curve as space will allow ! You might end up with stock later that will be happy with that  decision . 

[Rayman4449]

For reference, the details on LGB and Piko R* values (which are different)

 

Track Curves - LGB:

From LGB's web site (in terms of diameter, not radius)

https://www.lgb.com/fileadmin/media/lgb/produkte/produktinformationen/LGB_Gleissystem-Info.pdf - LGB website

    - https://www.lgb.com/products/product-information/overview-of-the-track-system/

Direct link: LGB_Curve_Calculations.pdf

 

R1 = 600 mm (Radius) / 1200 mm (Diameter)
R2 = 780 mm (Radius) / 1560 mm (Diameter)
R3 = 1195 mm (Radius) / 2390 mm (Diameter)
R5 = 2320 mm (Radius) / 4640 mm (Diameter)

Translated into imperial:

R1 = 23.6 inches (Radius) (1.97 ft) / 47.2" (Diameter) (3.93 ft)
R2 = 30.7 inches (Radius) (2.56 ft) / 61.4" (Diameter) (5.12 ft)
R3 = 47.05 inches (Radius) (3.92 ft) / 94.1" (Diameter) (7.84 ft)
R5 = 91.35 inches (Radius) (7.61 ft) / 182.7" (Diameter) (15.23 ft)

 

 

Track Curves - Piko

        Piko website: https://www.piko-america.com/collections/g-scale-g-track  (see R curve & MM values listed on each curve)

R1 = 600 mm (Radius) / 1200 mm (Diameter)
R2 =  ??mm  (Note:  MTH notes R2=1560mm/61.5 inch/5.125 ft - Diameter)
R3 = 920 mm (Radius) / 1840 mm (Diameter)
R5 = 1240 mm (Radius) / 2480 mm (Diameter)

R7 = 1560 mm (Radius) / 3120 mm (Diameter)

Translated into imperial:

R1 = 23.6 inches (Radius) (1.97 ft) / 47.2 inches (Diameter) (3.93 ft)
R2 = ??  (Note:  MTH notes R2=1560mm/61.5 inch/5.125 ft - Diameter)
R3 = 36.22 inches (Radius) (3.02 ft) / 72.44 inches (Diameter) (6.04 ft)
R5 = 48.82 inches (Radius) (4.07 ft) / 97.64 inches (Diameter) (8.14 ft)

R7 = 61.42 inches (Radius) (5.12 ft) / 122.84 inches (Diameter) (10.24 ft)

 

[blid]

I was wrong. What I called R3 is in fact R5. R3 has a diameter of 7.86 feet. About 8 feet as you wrote.

[blid]

I didn't find the pictur but made screen dump from a video. It shows Big Boy on LGB R3.

To me it looks like the hole width of the engine sticks out from the center of the tracks.

 

If you intend to place the tracks along walls the clearance have to be added to the equation. So for R3: 2(1198 + 120) mm = 2636 mm, about 8.7 feet.

 

Suggestion for he curve using LGB. One R5 18000, thre R3 16000, one 18000, three R3 16000 and one 18000. My track planning softwre calculates the center track distance to 2758 mm. This gives 2998 mm or 9 feet 10 inch with clearance as above. This will look so much better and the clearance need by the straight tracks will be less. Besides, if you look at a train in a sharp curv from the inside it will look much better than from the outside.

 

If you don’t go for LGB tracks; check the code. MTH made “pizza cutter wheels” on purpose. They will not run on Marklin/Hubner tracks. The flanges are to deep. I don’t know the required code.