coupling on curve - radius?

[gregc]

what is an acceptable radius for a curved siding to avoid any potential problems with coupling cars together?

instead of making the siding with two straight parallel tracks, i was thinking of making the siding with a gentle curve (> 48")

[superbe]

If you can couple cars on less than a car and a half length of straight track please let me know.

Thanks,

Bob

[richhotrain]

Dunno, 48 inch radius may work, but I can tell you from experience that 32 inch radius won't.

Rich

[cowman]

Take a piece of flex track and bend it to various radii on a flat surface.  Put cars on the track and try to couple them.  Let us know what your experimenting finds.

Have fun,

Richard

[Doughless]

Its going to depend upon the characteristics (quality) of your couplers and the length of the cars, with shorter cars being easier.  The sharpness of the angle between car ends is what generally prohibits coupling.

There is math involved with the car length and geometry that other members may offer. 

Having said this, I'm pretty sure you'd be safe with greater than 48 inch radius in all situations. 

[BRAKIE]

48" curves should work without problems..44" and 40" curves may also work since these are sweeping curves.I wouldn't want to try anything less.

 

Now,you can couple cars on curves less then 40" if you don't mind manually lining the couplers like the prototype.

[charlie9]

my experience has shown that if the cars are not the same length, then, it will be difficult regardless of the curve radius.

charlie

[CTValleyRR]

I guess we're all assuming that you mean "coupling without any operator intervention". All my rollong stock has Kadees, ProtoMAX, McHenry or EZ-Mate couplers (not many of those last two types left), and it generally refuses to couple on my 22" curves. I just use the loco to push the cars together, then stick an uncoupling pick made from a bamboo skewer in ther and hook up the couplers (this simulates the conductor / brakeman jumping down and hooking things up).

[farrellaa]

I have trouble coupling on 36" radiius, especially 85' passenger cars. Generally, curves are a problem when it comes to coupling, but 48" may work. As suggested, try a section of flextrack and see what works.

   -Bob

[tomikawaTT]

Quick rule of thumb:  cars will usually couple reliably on a curve with a radius five times the car length or more.  Reduce the radius and the reliability drops.  Anything less than three times the car length will almost certainly require active operator intervention.

Note that this assumes reasonably uniform car lengths - no Minnesota ore cars coupled between Pullmans or hi-cubes.  On my 610mm radius curves I have to position a medium-length car between the 6-wheel tender (which has the geometry of a Buckeye truck with truck-mounted coupler) and the 20 meter container flats and/or auto racks.  Otherwise the tender will take the long car right over the inside rail.

I use a semi-permanent test spiral to determine what will (and will not) run together, and plan my consist building accordingly.

Chuck (Modeling Central Japan in September, 1964)

[Paulus Jas]

Hi gentlemen:

The LDSIG (Layout Design Special Interest Group) developed a rule of thumb relating radius to length of longest cars.  The rule is fairly conservative.  But it does allow pretty quick evaluation of the practicality of a given curve radius in light of planned operations (the intent of the rule of thumb).  All the empirical and anecdotal evidence I have seen suggests that the 3X minimum is right on for long trains and operations with a helix.

Here are some curve radius guidelines based on the lengths of your longest pieces of rolling stock.

2X - Some model equipment may be able to track reliably on 2X their length, but this is generally considered pushing it.

3X - Making your curve radius at least 3X the length of your longest cars gets reliable tracking around curves, but looks toylike.

4X - If you make your curve radius at least 4X, your longest cars will look much better on curves.

5X - If you make your curve radius at least 5X, your longest cars will couple easily with minimal manual fiddling of the couplers.

This measurement is based on the length of your longest car (coupler to coupler).

[BRAKIE]

CTValleyRR

(this simulates the conductor / brakeman jumping down and hooking things up).

Actually we used our foot to line the couplers--sorry couldn't resist that tidbit.

We never jump off of moving equipment-we swung off..Trailing leg first!

[richhotrain]

Paulus Jas

5X - If you make your curve radius at least 5X, your longest cars will couple easily with minimal manual fiddling of the couplers.

This measurement is based on the length of your longest car (coupler to coupler).

I have found that it is difficult to couple cars on anything but straight track.  As soon as cars enter a curved area of track, the reliability of coupling diminishes with the radius of the curve.

Rich

[Train Modeler]

Length of car and the difference in car length is more critical as the radius pulls the longer car to the point of some mid point overhang.   I agree with the poster that trying it is important.    I couple/uncouple passenger cars with Kadee couplers on 36" radius track on occasion, but need a pick to help.  The biggest problem there are the diaphragms.   If you want reliable totally hands free coupling/uncoupling using magnets for example, then I would stay with straight sections.   I like the 5X rule as a guide too.

Richard

[CTValleyRR]

Brakie -- at the risk of a thread hijack... that's why there are a lot of 9 toed brakemen out there. and I apologize for my imprecise terminology: I swing off moving cars myself, just like you do trailing leg first.

[Schuylkill and Susquehanna]

The ability of cars to could on a curve is a combination of curve radius and car length.  Two 40' freight cars can couple together on a 24" radius curve, but if you try coupling a 40' car to an 80' car on the same curve, it will never happen.  The problems are the overhang on the couplers and the angle of coupling.  The overhang on the 80' car is substantially more than that on the 40' car due to truck position, and the longer car increases the angle of coupling.  If you run exclusively 40' and 50' cars, you can get away with a 30" radius curve on the siding/spur.  If you run longer cars, then the radius will need to be increased.  A safe bet is in the 36" to 42" range for reliability and a bit of "slop".

When you curve the tracks, you will also need to increase the track spacing to resolve any overhang issues.  On a 42" curve, a spacing of 2 1/8" should work.  Check NMRA's site for their recommended practices on curve spacing.

S&S

[mactier_hogger]

Nowadays we'd be fired for using our foot to line the coupler!