Turnout Basics: #4 vs #6 vs #8 — Where Each One Belongs
New to turnouts? The frog number tells you how sharp the diverging route is: a #4 spreads 1 unit for every 4 units forward (sharper); a #8 spreads 1 for every 8 (gentler). Lower turnout numbers save space; higher numbers run smoother—especially with long cars and big steam.
Quick Turnout rule of thumb
- #4: Compact, industrial, yard ladders, tight shelves
- #6: General-purpose mainline, crossovers, run-arounds
- #8: High-speed mainline, passenger terminals, long modern freight
Approximate HO “radius” feel (varies by brand): #4 ≈ 16–18″, #6 ≈ 28–32″, #8 ≈ 40–50″. Treat these as feel, not exact geometry.
Where each Turnout size excels
#4—Space Saver:
Choose #4s for industrial spurs and yard ladders where you need many tracks in little space. Short diesels and 40–50′ freight cars glide through them, and switching stays lively. However, 80′ passenger cars and long steam may look awkward and can pick points at speed.
#6—Do-It-All:
A #6 is the default for many layouts. It balances footprint and reliability, making it ideal for mainline crossovers, passing sidings, and staging yards. Moreover, it handles mixed fleets—50–89′ cars, six-axle diesels, and medium steam—without eating the whole bench.
#8—Mainline Turnout Smoothness:
When you want passenger-train elegance or modern 89′ autoracks to snake through cleanly, #8s deliver. They’re excellent for visible mainline junctions and station throats where appearance and low-speed reliability matter. The trade-off, of course, is length.
By scale (practical guidance)
- N scale: #4s work for yards; #6 for mainlines; #7/#8 for passenger or long intermodal.
- HO scale: #4 for industry/ladder; #6 for most mainline needs; #8 for long cars, big steam, or showcase scenes.
- O/S scale (2-rail): #6 minimum for mainline feel; #8 where appearance counts. (Three-rail often uses curve diameters instead of frog numbers.)
- G scale: Favor larger frogs (#6/#8) outdoors; #4 only for tight industrial scenes.
Reliability tips that pay off
- Straighten the S: Insert a short straight between opposing curves or stagger ladder tracks to reduce coupler bind.
- Mind the frogs: “Live” (powered) frogs improve DCC pickup for short wheelbase switchers; consider a frog juicer or micro-switch.
- Gauge and height: Check wheel gauge and coupler height; many “mystery uncouplings” are geometry, not magic.
- Turnout mix: It’s normal to run #4s where space is king and #6/#8s where trains need to breathe—use each where it shines.
Bottom line on
Pick the smallest frog that doesn’t compromise your longest equipment on its intended route. That way, your yard stays compact, your mainline stays silky, and your trains stay coupled. For a more detailed explaination, check out the video below.
