Tightest Radius

[Anonymous]

What is the tightest radius possible for an HO layout when the maximum length of rolling stock will be scale 50' and the largest loco will be a gp7?

[Anonymous]

How big is your layout?

[Anonymous]

5x9 but Its for a siding on the inner line I need a really sharp turn

[IRONROOSTER]

http://www.nmra.org/standards/rp-11.html gives recommendations of minimum curves. If that's not tight enough, truck mounted couplers means even tighter curves. If you're willing to tinker with the rolling stock, extra long shanks, truck mounted could be tighter. Radial couplers like the streetcar folks use can go even tighter. You may have to sacrifice under body detail at the ends to allow for coupler swing.
Enjoy
Paul

[Jetrock]

Personally I'd recommend 15". I have suggested turns as tight as 12" for 50-footers and GP-7's before, and feel free to give it a try but it can be tricky if things are that tight. The engines want to wedge themselves into the track and at the edges of 50 foot boxcars *just* barely miss each other at a 12" radius--15" is pretty tight while still leaving a margin for error.

[Anonymous]

I'm assuming you're using sectional tack. For reliable operation, I wouldn't think of using anything less than 18" radius for the rolling stock you mentioned. I used 15" radius for a industry spur on my previous layout and anything longer than 40' or a switch engine (SW1500) would derail every time. If it's too tight, don't bother putting it in. Take a look at the replies to a question I asked, How Many Layout Have You Built and What Did You Learn From Them". Most say one mistake was using too tight of a radius.
Save the 15" curves for trollys and street cars.

[Jetrock]

Maybe in O scale...a good HO trolley can manage a 6" radius curve!

Four-axle diesels and 40-50 foot rolling stock can run reliably around 12" curves as long as the track is carefully laid, and the operating speed is kept low--they won't barrel around that 12" curve at 150 scale mph, but at yard speeds they'll putt around just fine. If they won't, either the track is poor or there's something wrong with the trucks.

15" is a comfortable margin of safety for conventional equipment.

[orsonroy]

Using a 15" radius will restrict the spur to MAYBE a 50' car and a SHORT four axle diesel switcher (or a 0-6-0T). Gp's or anything larger won't negociate the curve with a 50' car because the couplers will swing out too far, derailing the car. I'd use no less than an 18" curve and rethink the spur if necessary.

[Jetrock]

MAYBE. I suppose it depends on whose GP-7 one is using--in my own experience, one can run an Athearn GP-7 with 50' cars (connected with Kadee couplers, body-mounted, on the cars) around and around a loop of track with 15" radius on one side and 12" radius on the other (this was my test-track layout) for several hours (at a relatively modest rate of speed, maybe 30-40 scale mph) with no derailments.

The main hitch in this spur is having a straight length of track at the end, so you'll be able to couple and uncouple that 50' boxcar--uncoupling on a curve, especially a 12" curve, is a pain...

[Anonymous]

I have an Athearn GP-7 with body mounted Kadee couplers(with uncoupling rods CUT OFF!!.see "Pet Peeves" topic) with 50' cars through a 15" radius switchback ( S turn ) full throttle, all day long without ANY derailments. Hope it helps.