Minimum radius for a steam loco

[aet]

I received a model power mikado as a gift, having already secured my track down on my layout , I ran the engine and noticed that when it went around a section of curved track, it would topple over and derail. I am assuming my radius is too tight?

I am using Atlas code 80 black ties

What should I do or use to correct this

 

Thanks

Art

[TomDiehl]

I received a model power mikado as a gift, having already secured my track down on my layout , I ran the engine and noticed that when it went around a section of curved track, it would topple over and derail. I am assuming my radius is too tight?

I am using Atlas code 80 black ties

What should I do or use to correct this

 

Thanks

Art

First, we need to ask a few questions: Is this HO or N Scale? Is it flex track or sectional? What is the radius in the area in question?

[wjstix]

You could check Model Power's website for their recommended minimum radius. Generally an HO mikado should be able to do an 18" radius curve; 9-3/4" for an N-scale mike.

It could be even if your curves are large enough you may have a kink in the trackwork (like where two pieces of sectional track join) that is creating a short stretch of tighter radius curved track...or it could be two pieces of track aren't connected properly, one rail joiner isn't connecting to both pieces of track or something.

It's not unusual when you get a new engine that you may need to "fine tune" your layout to let it run flawlessly on it. New engines sometimes find an imperfect piece of track that your other engines don't have a problem with.

[pcarrell]

Being that the OP stated that it's code 80 track, I'd say he's probably in N scale.

[dstarr]

   Derailments are caused by either the track or the rolling stock, or both.  On the locomotive check for free movement of both the pilot and trailing truck.  If if either hits the locomotive frame in a turn it will cause trouble.  I have several steamers with extensive Dremel work hogging out the frame or cylinder head assembly to give clearance to the trucks.  A piece of flash, or a bit of foam carton material stuck underneath can cause interferance.  While you are at it, check all the wheels for cracks, lumps, bumps, and bits of stuck on crud which might interfer with smooth rolling.  Check the tender.  If the tender hits the cab on turns it will force the engine off the track.  Check pressure on the pilot and trailing truck.  Sometimes tightening up the spring, or adding weight will improve tracking.

   Steamers are a bit more demanding of your trackwork than diesels.  Check the track gauge.  Use a long straight edge to make sure the track is level, no humps or bumps.  Make sure all rail is properly inserted into the rail joiners.  It's easy to have the joiner slid under the rail leaving a crooked joint. Run your hands down the track feeling for rough spots, track nails standing proud of the ties, too high uncoupler magnets, solder lumps from feeder wire soldering, anything that might interfere with the train.

   Eyeball down the rail for kinks in the track at the joints.   Make sure the track radius is a solid 18" (no cheating in tight places) for HO.  Less for N.  It is easy to bend flextrack into a tighter than allowable curve. HO snap track is nearly always 18" or bigger.  There is a little bit of 15" curve track out there but it's uncommon.  

In HO, just about everything will get around an 18 inch curve.  An 8 driver Mikado is pushing it but it ought to work.  In HO there is strong market pressure to make every thing run on 18" radius, 'cause 18 inch is the train set minimum radius.  If your product will handle 18" then every kid can buy it and not bring it back for a refund after it derails.  If it needs more than 18" then the market is limited to the more advanced hobbists, so marketing puts great pressure on the engineering dept to get everything to run on 18 inches.  Check the instructions and packaging.  If it says something like "22 inch radius" then you need 22 inches.  If no mention of minumum radius is made, then it's safe to assume the maker believes it will run on 18 inches.

       

[aet]

N scale flex track

[markpierce]

I received a model power mikado as a gift, having already secured my track down on my layout , I ran the engine and noticed that when it went around a section of curved track, it would topple over and derail. I am assuming my radius is too tight?

I am using Atlas code 80 black ties

What should I do or use to correct this

You should be using track with brown ties.

Mark

[markpierce]

 In HO, just about everything will get around an 18 inch curve.  An 8 driver Mikado is pushing it but it ought to work.  In HO there is strong market pressure to make every thing run on 18" radius, 'cause 18 inch is the train set minimum radius.  If your product will handle 18" then every kid can buy it and not bring it back for a refund after it derails.  If it needs more than 18" then the market is limited to the more advanced hobbists, so marketing puts great pressure on the engineering dept to get everything to run on 18 inches.  Check the instructions and packaging.  If it says something like "22 inch radius" then you need 22 inches.  If no mention of minumum radius is made, then it's safe to assume the maker believes it will run on 18 inches.     

A lot of my stuff requires more than 18" radius, including a majority of the locomotives.  Except for the four-axled diesels, geared locomotives, conventional steam locos up to three driving axles, and freight cars up to 50' long, I don't expect anything of mine to negotiate 18".  In fact, I'm concerned that my planned 30" won't be enough for everything to stay on track.  And if one is concerned about appearance, almost all of us have compromised a great deal.

Mark

[TomDiehl]

N scale flex track

It sounds like your radius is too tight for the loco, or you have a kink in the track (not a smooth curve). Another thing to look at would be to check if the rails are level from side to side (left rail to right rail). And if you weren't careful when nailing down the track, you may have put a dent in one of the rails with the tack hammer.

And yes, that is the voice of experience.

[dstarr]

  On 18 inch radius I operate 2-8-0 Bachman Consolidations, six axle E8 Proto2K diesels, and 80 foot IHC passenger cars.  Maybe not out of the box; I had to weight the cars up to NMRA standards, and convert some to body mount couplers.  But they run now.    The new layout will have 22 inch curves, giving me a bit more margin. 

 

[jeffrey-wimberly]

My layout is quite tight in the curve department. 18" radius curves and the turnouts are #4's and #5's. I've run a 2-10-2 T2-a on it with no problem. I always check the turn radius of a loco or car before I buy it. If it won't take 18" radius out of the box or with minor modifications I don't buy it. I've run locos ranging from tiny 4 wheeled switchers to a giant 16 wheel monster that EMD calls a DDA40X. If you have tight curves and buy a rigid loco that won't take them you might as well set your money out on the street corner for every Tom, Dick and Harry to pick up.