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Curve maximum speed.
- Thread starter Ben1337
- Start date
Yes. All/most railways would have had a data table that was used to calculate the maximum curve speed for a given curve radius for a standard train with a standard load operating under set track conditions. This could vary from one railway to another and between different sections of the same railway depending on the track conditions.
For one layout I created based on a real railway, I found the table they used in the 1950s. It was as follows.
This table does not take into account super-elevation - it did not exist on that railway in that era.
I put the above data into a spreadsheet and used a Lookup function to provide the correct speed for a given curve radius which was calculated from the curve chord length and perpendicular distance from the centre of the chord line to the track - as measured by the Surveyor ruler tool.
So, if the curve radius was 12 chains (for example) then the corresponding curve speed would be 30mph
For one layout I created based on a real railway, I found the table they used in the 1950s. It was as follows.
| TGR Curve Speed Data 1950s | ||||||
| Radius (chains) | 3 | 5 | 7 | 10 | 15 | 21 |
| Max Speed (mph) | 10 | 20 | 25 | 30 | 35 | 40 |
This table does not take into account super-elevation - it did not exist on that railway in that era.
I put the above data into a spreadsheet and used a Lookup function to provide the correct speed for a given curve radius which was calculated from the curve chord length and perpendicular distance from the centre of the chord line to the track - as measured by the Surveyor ruler tool.
So, if the curve radius was 12 chains (for example) then the corresponding curve speed would be 30mph
For those living in... well... most of the world :hehe::
1 “chain” is 20.117 meter.
Wait, so you are saying that an Australian going 60mph would think he was traveling 479.95 cph (chains per hour)? Or does that only apply to pware?
cascaderailroad
New member
I usually don't drive more than 35 - 45 mph on the mainline ... and in yards I usually drive 1 - 5 mph
MTH_ELECTRIC_TRAINS
7 Year Trainz Vet
I do about 15 MPH in yards. 5 MPH is more for engine facilities and things like that. Its way too slow for switching, nothing would get done at that speed.
I read a rough and ready calculation that in the real world, you divide the curve radius in metres by 5 to give the speed in km/h. So for example 100m radius curve gives a maximum speed of 20 km/h. or a 300m radius curve 60 km/h. Convert to MPH as necessary. For 100 MPH (or 160 km/h) you would need a minimum radius of 800 metres. That I believe was for uncompensated track, superelevation adds a little more but it is only eye candy in Trainz and does not affect whether or not your train stays on the track. Indeed you could drive a train at 100 MPH round a 30m radius curve, so long as that was the posted speed limit probably wouldn't derail, just look silly and at a more reasonable implementation is the only way you could get away with faster speeds on a model railway. A 2ft radius curve in HO is equivalent to around 54m in real life which would impose a speed limit of around 12 km/h or 7.5 MPH which is not going to be particularly interesting to drive or watch!
Wait, so you are saying that an Australian going 60mph would think he was traveling 479.95 cph (chains per hour)? Or does that only apply to pware?
That would depend on a more complex formulae involving the distance between pubs, alcohol % (by volume) and number of drinks per hour.
How about track speed up to 100MPH?
Since centrifugal force determines speed, the latter can be calculated from the formula:
Vmax = k * sqrt(R)
where
R is arc radius in meters
sqrt(R) is square root of radius
k is coefficient to return result in km/h. It equals 4.5 or 4.6 on most European railways.
Vmax is maximum speed
To get result in mph, use coefficient m = k/1.609 = 2.8
For example, to calculate maximum speed a train can negotiate an arc of 600 meters:
Vmax = 2.8 * sqrt(600) = 69 mph
Conversely, to calculate minimum radius of an arc for traveling at 100 mph:
Rmin = (100/2.8) ^ 2 = 1275 meters or 4183 feet
But there are two bigger issues than speed limit on an arc:
1/ Balancing centrifugal force by track tilting. There is no track tilting option in TS12. Maybe there is in TS19, but I don't use this version, so I can't check.
2/ Reducing sudden jump in centrifugal force from zero to some value when trains leaves straight section of the track and engages an arc. On real railways this is solved by laying track in a parabola, but I found plotting parabola in Trainz quite challenging and never seen a route implementing it accurately. So, there is always room for improvement in future versions of Trainz.
How much does TRAINZ adhere to these curve speed specs? Can you derail by taking a curve too fast? The reason I am asking is that I was trying to create a T:ANE version of a local n-scale model railroad club and they had a 180 degree turn that was only maybe a two-foot radius, but I calculated to be High-speed in real life it would have to be close to a half-mile radius, or a mile for the complete turn. That left me with a lot of unused space that wasn't in the real n-scale....
narrowgauge
92 year oldTrainz veteran
Don't weight, height, loading gauge of vehicle, and track gauge play a part in the calculation. What assumptions are made/used in the formula?
Interesting.
Peter
Interesting.
Peter
How much does TRAINZ adhere to these curve speed specs? Can you derail by taking a curve too fast? The reason I am asking is that I was trying to create a T:ANE version of a local n-scale model railroad club and they had a 180 degree turn that was only maybe a two-foot radius, but I calculated to be High-speed in real life it would have to be close to a half-mile radius, or a mile for the complete turn. That left me with a lot of unused space that wasn't in the real n-scale....
I believe Trainz is very tolerant, so you can have consists traveling with speed of 60 mph on arcs with radius of 300 feet or tighter, as in the model railway scale HO, TT, N and others. But if you set derailment option to Realistic there will be a limit and when you reach it, trains will get off the track occasionally. This is one of the reason I moved away from a single board design to multi board design. Real estate in Trainz is so cheap, I often lay track in radius of 5,000 feet or even 13,000 feet for speeds of 60 mph and 100 mph respectively.
Since centrifugal force determines speed, the latter can be calculated from the formula:
Vmax = k * sqrt(R)
where
R is arc radius in meters
sqrt(R) is square root of radius
k is coefficient to return result in km/h. It equals 4.5 or 4.6 on most European railways.
Vmax is maximum speed
To get result in mph, use coefficient m = k/1.609 = 2.8
For example, to calculate maximum speed a train can negotiate an arc of 600 meters:
Vmax = 2.8 * sqrt(600) = 69 mph
Conversely, to calculate minimum radius of an arc for traveling at 100 mph:
Rmin = (100/2.8) ^ 2 = 1275 meters or 4183 feet
But there are two bigger issues than speed limit on an arc:
1/ Balancing centrifugal force by track tilting. There is no track tilting option in TS12. Maybe there is in TS19, but I don't use this version, so I can't check.
2/ Reducing sudden jump in centrifugal force from zero to some value when trains leaves straight section of the track and engages an arc. On real railways this is solved by laying track in a parabola, but I found plotting parabola in Trainz quite challenging and never seen a route implementing it accurately. So, there is always room for improvement in future versions of Trainz.
So if I go around a curve with a radius, not arc radius, of 75 meters, I can go 24 miles per hour?
Don't weight, height, loading gauge of vehicle, and track gauge play a part in the calculation. What assumptions are made/used in the formula?
Yes they do. Railway engineers (the actual engineers, not the train drivers) would produce data tables that indicate the maximum track speed for a given curve radius, train weight (although the weight is distributed along the length of the train - but probably unevenly), track gauge (narrow gauge tracks can have tighter curves). But perhaps not vehicle height (tunnels and over-bridges would "take care" of that issue) but trains with an unusual loading gauge would probably be restricted to a much lower speed anyway.
narrowgauge
92 year oldTrainz veteran
I thought that would be the case, it just seemed that the formula in the previous post seemed to be rather limited. If it was aimed specifically at Trainz where none of the values I mentioned need to be applied, mine was a needless question.
Peter
Peter
So if I go around a curve with a radius, not arc radius, of 75 meters, I can go 24 miles per hour?
The textbook I copied this formula from states no arc should have radius smaller than 190 meters on normal gauge (1435 mm) railway. Some locomotives with axis arrangement Co-Co have problem negotiating arcs tighter than that. If 24 mph seems to be too fast, you can lower the coefficient. In my routes I use coefficient of 1.8, e.g.
R=75m, Vmax=15mph
R=200 m, Vmax=25 mph
R=400 m, Vmax = 36 mph
R=800 m, Vmax = 50 mph
and so on.
This formula does not apply to curves with variable radius (like parabola).
The textbook I copied this formula from states no arc should have radius smaller than 190 meters on normal gauge (1435 mm) railway. Some locomotives with axis arrangement Co-Co have problem negotiating arcs tighter than that. If 24 mph seems to be too fast, you can lower the coefficient. In my routes I use coefficient of 1.8, e.g.
R=75m, Vmax=15mph
R=200 m, Vmax=25 mph
R=400 m, Vmax = 36 mph
R=800 m, Vmax = 50 mph
and so on.
This formula does not apply to curves with variable radius (like parabola).
The curve I'm inquiring about is in a yard so I won't be going that fast anyway but I wanted to go ahead and ask.
EDIT: On curves that have a variable radius, I use the 'get radius' feature and find the average radius by adding the highest number (largest radius) and lowest number (smallest radius) and divide by two. I then plug that number into your equation to find the speed limit for the curve.
Last edited:
EDIT: On curves that have a variable radius, I use the 'get radius' feature and find the average radius by adding the highest number (largest radius) and lowest number (smallest radius) and divide by two. I then plug that number into your equation to find the speed limit for the curve.
To be realistic you would take the smallest radius value and plug that into the equation. By taking the average value your trains would be exceeding the safe speed limit for about half of the curve.
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