Large Scale Central

JMRI question re sidings

After reading Daktah John’s operations topic I noticed he had multiple industries/stops on one siding. This could really work well for me. For example, I would like to have a stockyard and a freight depot on the same siding. Each could hold two cars. It sounds like I should label them as separate spurs in JMRI. I could limit the stockyard to stock cars only so nothing else gets spotted there. I would make the spur lengths just long enough to handle the two cars each. Am I missing anything?

By George, I think you’ve got it (

I make my spur length about a half car longer than I need in case cars grow in the future. Not sure if that helps anything; it’s just theory.

I’m definitely using this! Thanks!

My cars are 15-16 inches long, so how do you setup JMRI spur length to handle one or two cars only? What scale factor do you use?


Jay Root said:

My cars are 15-16 inches long, so how do you setup JMRI spur length to handle one or two cars only? What scale factor do you use?


You can really use any scale factor you want, just be consistent. If you use inches, use inches for car length, train length, siding length, etc. If you use feet, same thing, be consistent. It really doesnt care if “250” for a siding length is in feet or inches, it can fit 10 cars of “25” length. (actually, probably 9 cars because of coupler hang, etc)

I find I have to tweak siding lengths anyway. I did a full measuring of the railroad, but then had to go in and see why cars wernt getting dropped off like I thought. Takes a bit of twiddling.

Following up on Bob’s post, here’s how I calculate the length of my siding for two spurs with two-car capacity each, a total of 4 cars. Keep in mind that JMRI adds scale two feet on both sides of the car body for the couplers.

Boxcar length (body only, no couplers): 18.25 inches

JMRI coupler length (4 feet x 12 inches per foot / 20.3 scale): 2.4 inches

Total car length: 20.6 inches, I will round up to 21 inches

Total cars per spur: 2

Length of spur: 2 x 21 inches = 42 inches

Add buffer of 6 inches (for variability in car lengths, but less than the length of one car)

Total length of spur: 42 + 6 = 48 inches

Total length of siding for two spurs: 48 x 2 = 96 inches or 8 feet

I noticed that JMRI lets you set your scale at “G” but does not specify any finer detail such as 1/32, 1/29, 1/24, 1/22.5 or 1/20.3. It doesn’t need this information to operate. It is up to the operator to do some math.

Since JMRI operates in scale feet, I am converting all my measurements to scale feet in 1/20.3 basically for consistency.

Thank you Bob and Joe. I am in the process of setting up JMRI with a scale of 20.5 and will see how it works. Most of my cars are 15" (26’) the Log cars are only 11" (19’).


Daktah John said:

By George, I think you’ve got it (

I make my spur length about a half car longer than I need in case cars grow in the future. Not sure if that helps anything; it’s just theory.

Oh yea, my cars grow. But, its the number of cars I have that is somehow growing, not the length of each car. (

I now have JMRI working, I think. May not be correct. I now have a layout, usint JMRI Layout Editor. How do I print this layout out and get it so you can see if I am doing things right or just beating my head on the desk? I have 14 cars on the layout and about 16 destinations, not counting the Round House, most hold only one car. Location Varina is the is a Yard and is the begining and end of the run. The Manafest picks up the engine, and I have to sort the order of the pickups from the Yard to get the train in dropoff order. I have one car that moves between the Grain Mill and the Yard only. It has not moved to the Quaker Oats siding. The build report sees the QO but does not move the car there.

This is a challenge for this old man.


Hi Jay. One thing I noticed about JMRI is that it will make sure you have room on your siding before assigning a car to it. If you have a siding that can handle two cars and the siding has two cars on it, then you cannot move another car to the siding even if your manifest starts with a pickup from that siding. In other words, it adds to current cars plus reserved set outs together, even if the current cars are picked up as part of the manifest. JMRI can run in “aggressive” mode and this might cure it. I haven’t tried it yet.

You might also consider setting up a switching train for your yard. It can move cars from yard tracks to spurs within the yard.


I will try extending the length of the siding and see if that helps.



Things are working well??. I have one problem that is the same for two locations. The Grain Elivator @ Apex will not send the covered hopper to the Quaker Oats spur @ Rawls by way of the Yard. The Yard just sends it back to the Grain Elivator. The covered hopper is only allowed at these 3 locations. The willow spring location can accept box and water cars. The spur has received the same box car all the time from the Yard. Back and fourth.

Both locations are at the end of the run, just before returning to the Yard. The build report get the other locations filled befor it gets to these last two locations. I only have 3 box cars and 1 covered hopper.

Any suggestions?


You might need more cars. Or you could just run a train that skips the other locations (delete the other locations) then does that last spur. What it does is fills the demand for cars at the first locations, if it runs out of cars, the other locations won’t get any.

I am running JMRI in a circle. Yard to Yard. Not sure if this is the best way to run the program with my limitted space. I have 6 locations plus the yard and a total of 17 spurs. I have 14 cars, all on the layout. The build report starts with the last car returned to the yard. There are 6 spurs that can accept the 6003 box car, the last being the one that it came from. That car has a low move count but that should not cause it to be returned. The grain car is simular set up. It has only 3 spurs available but does not move. The build report only looks at two locations?


Now I did it. I tried to restore to a previous date and now when I open JMRI, it comes up with the railroad name but does not have the settings tab? What have I done this time.