# 2 or 3 axle trucks



## Mseav (Jul 30, 2015)

I have an 18'' radius track and 3 axle trucks have trouble on it. I am putting a 22'' radius track around it. What number of axles in a truck works best on the 22''? I am looking for a steam engine, will a 2-6-2 work on the 22'' radius or is there a better match for the 22''radius?


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## CTValleyRR (Jul 26, 2014)

There's no hard and fast rule on this. A lot depends on the manufacturer of the locomotive and rolling stock. As a general rule of thumb, your curve radius should be at least 3x the length of the longest piece of equipment that will operate on it (so an 8" long 2-6-2 would perform best on a 24" radius curve). Remember though, that this is a guideline, not a rigid requirement.

If you can get up to a 24" radius, that should handle just about anything. MOST 3 axle trucks should be fine on a 22" radius, but I'm surprised that a 2-6-2 won't take an 18" radius. I have a Bachmann Prairie 2-6-2 and an IHC Command XXV Pacific 4-6-2, both of which could handle the 18" curves on my old layout.

BTW, don't forget your turnouts, too. A #4 turnout imposes roughly the same operating limitations as an 18" curve; use a #6 on your 22" track.


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## Mseav (Jul 30, 2015)

CTValleyRR said:


> There's no hard and fast rule on this. A lot depends on the manufacturer of the locomotive and rolling stock. As a general rule of thumb, your curve radius should be at least 3x the length of the longest piece of equipment that will operate on it (so an 8" long 2-6-2 would perform best on a 24" radius curve). Remember though, that this is a guideline, not a rigid requirement.
> 
> If you can get up to a 24" radius, that should handle just about anything. MOST 3 axle trucks should be fine on a 22" radius, but I'm surprised that a 2-6-2 won't take an 18" radius. I have a Bachmann Prairie 2-6-2 and an IHC Command XXV Pacific 4-6-2, both of which could handle the 18" curves on my old layout.
> 
> BTW, don't forget your turnouts, too. A #4 turnout imposes roughly the same operating limitations as an 18" curve; use a #6 on your 22" track.


Well, I didn't mention that the 3 axle truck was on a car and derailed on every corner. I didn't want to invest in an engine that would have issues . Great info on the turnouts, I would have messed that up.


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## CTValleyRR (Jul 26, 2014)

Do you have a couple of pieces of 22" track you can test your rolling stock on? Maybe just pick up a pack of True-Track, EZ Track or something else cheap and build a test curve. Most locomotive manufacturers will give you a minimum radius for their equipment.

I believe the issue with the 3 wheel truck. Most locos have some play in the wheels; cars often have less. I have some Spectrum heavyweight cars that used to derail if you so much as looked at them. The issue is that the chord formed by the front and rear wheels of the truck doesn't fit within the radius of the inner rail (18" is the radius at track center), thus forcing one of the wheels out of the track. I have an ALCO PA that would handle the curves OK, but at the top of a grade, the rear wheels of the truck would still be on the incline, leaving the front one hanging in the air. Clunk. Derailed.


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## grashley (Aug 27, 2015)

My layout is basically a double oval, 18" inside loop diameter and 22"outside loop diameter.
I have not found any cars or locos that have trouble on the outer loop, unless other issues are present, like coupler screw too tight or bad truck / coupler. About ½ of my cars do NOT like the inner loop. My 6 axle PA loco absolutely will not run on the inner loop. It will run flawlessly all day on the outer loop. Many "longer" cars (50 ft or longer) are a problem. My 4 axle F3 and GP50 run fine on either loop. Some cars only work well when coupled to certain other cars - not all! I test run cars on both loops, then keep records of what runs on either or only outer loop.

There are no hard and fast rules, as stated above. Just test the cars / locos to see what works and what does not.


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