2- track mainline curve radiius question

I KNOW  that there is sufficient spacing for a full-sized auto carrier between 89 and 96 diameter curves.  I really believe that would be true going down to an 80.  The only way too know for certain is take your longest two cars, place them on test tracks and check. You probably will be alright.

NOTE:  If you don't have a full-sized auto carrier, 22 inches long, or similar long car, DO PLAN that one day you will.  That will save you time, money, effort and dents in your walls where you hit your head if you don't plan accordingly!   

I know this may sound crazy but I would start at the Bridge and work my way out from each end of the bridge. I would purchase a few pieces of the radius you won't to use plus the next two radius down 80r 72r. Mix and match to get the spacing you won't than order the track you need….. I'am not sure if anyone would agree with my way of doing it…    good luck and………………Happy New Year…….

I would always suggest to anyone buy Gargraves Flex Track and make the radius you want!  Just don't purchase any of the manual hand cutting tools because they are all garbage.  Get a dremel tool with a 1.5 cutting blade that will give you a perfect cut every time, with a little practice at the very first!

John is right on with the GG Flex and the dremel. I just had no luck with flex but many people have great results…….

Stephen is right that you need to get the center rail-to-center rail distance at whatever the bridge requires.  What equipment will operate on the radii used to get the train to the bridge is the next consideration.  Big, articulated scale steamers, 21" passenger cars, etc. create a lot of overhang except on the biggest of radii.

MikeCT replied in a recent thread concerning this bridge and the center rail-to-center rail distance was supplied.  The issue in that thread was the member's distance was greater than the bridge's, and the member wanted advice on how to reduce his distance to meet the bridge's distance.

Bottom line:  No one can tell you that going from 089 to 080 will provide adequate spacing.  The bridge's center rail-to-center rail distance is the first consideration, and how you get there with the equipment you operate now, and in the future, is the next important consideration.  I've done similar work with GG flex and the Dremel with good results.  Similar results can be achieved using sectional track.

Way before the scale cars came out I did my mainlines with 0-89 and 0-96 leaving a bit more distance between the center rails on the curves which allows for the large over hang of the new auto racks and the soon to be 89' box cars. It is better to plan ahead for things like this then have to rip up track and road bed to change it.......Paul

thats my attitute towards it as well.  so respectively, an outside 089 and inside 080 should be ok then. also i will be using the atlas double track truss bridge for my duckunder, so i will check the rail spacing when i get it and plan accordingly.

080 /089 will be about 4-1/2" center rail to center rail. 

The Atlas truss bridge track spacing is 4.5 inches.  The O80/O89 curves will naturally create the proper spacing. 

Jan

thanks Jan.  so on a curve , two passenger trains (longer cars) shouldnt rub while passing each other with 4.5" ?

The Atlas # 7920 Truss bridge is the 2 rail version. Do you have the bridge yet or planning on obtaining one. Hopefully you just mixed the number up  # 6920 is the three rail version. The track spacing would be 4 1/2" center to center.

Try the search function and find MikeCT's reply on the use of this bridge that I mentioned previously.  He points out that some straight track must precede each approach to the bridge since any overhang close to the bridge stands a good chance of causing a collision between train and bridge.

Also, in Jim Barrett's article referenced earlier, he measured the overhang of a K-Line 21" passenger car on 072 track to be 2.5" from the center of the car to the center rail.  Larger radius/diameter track would yield less overhang.

Also, not all passenger cars from the various manufacturers use the same mounting point in the frame, nor do they all use the same pivot point on the trucks.  That is simply to say that not all 21" cars will have the same overhang.

In the Barrett article, he also measured the overhang of a Big Boy; it was 3" on 072 track.  So, the 21" car with its 2.5" overhang would contact a Big Boy and its 3" overhang on 072 track with 4.5" center-to-center distance because their cumulative overhang is 5.5".

Suggestion:  Start a new thread posing the precise question you want answered, including what passenger cars, freight cars, and locomotives you are running now and may run in the future, and the radii of the curves you are planning.