Unless you use sectional track (and if you do, you mate the pieces exactly together with no fudging) it isn't always easy to create a perfect radius with flex track. The begining and the ending parts maybe spot on but in between there may be varients. That could be the issue here. Do you have one of those between the rails curve templates to check the radius? RibbonRail is one make.
Remember this -that the point of transition from a tangent to a "perfect" 24" radius curve involves a pinch-point which is more challenging for rolling stock than the curve itself. That pinch point is what we have in using sectional track from scale to Lionel. That is why the Lionel train lurches violently when hitting a curve.
That is why there are locomotives that could run on a perfect circle on 24" radius track which cannot handle the transition between tangent and fixed radius 24" radius, because the equivalent radius of that transition point is effectively much sharper than 24" radius. Is that where your derailments happen?
That is why real railroads have some sort of easement curve between tangent and fixed radius (degree of curvature; prototype does not use the radius vocabulary) curves, and John Armstrong's book on Track Planning for Realistic Operation makes a strong case that our layouts should have easement curves too, for good appearance but also for very practical operating reasons. it is in the part where he creates the wonderful phrase "the coefficient of lurch."
Armstrong makes the point that often easement curves allow us to run equipment on tighter curves than they are rated for, because the radius rating was calculated based on how they handle that pinch point. That is he shows how a locomotive rated for 22" radius might be able to run on 20" radius if you have easement curves.
There are complex math formulas for easement curves but as a practical matter there are also very simple mechanical means of adding easement curves - one is called the bent stick method (nail a stick to the tangent of your right of way, then bend the far end and trace it with a line - ir's an easement curve. Another mechanical method is to always have the meeting point between tangent and curve be in the middle of one seamless piece of flex track, because flex track cannot bend itself from pure tangent to pure 24" radius insgtantly, but creates its own easement curve to gradually get there.
Dave Nelson
I had this exact problem with a Bachmann GS4. It runs great, but is very sensitive to any kinks, bumps, or dips in the track. Once I fixed the track, it was fine. Also, just like you, I was able to run a Challenger and a Big Boy without these issues. Articulateds seem to be more forgiving on track with faults. Probably due to the fact that they don't have one very long wheelbase like a 4-8-4 or 2-10-4. As many of the other posts have suggested, I think some kind of track fault is your culprit.
I have a P3 PRR J1. It works on 26" curves but every track condition must be just right. The slightest variance in height, for example, and the front or third set of drivers derail. I replaced the traction tire wheel set with a steel set. That helped too allowing the rear wheels to slide laterally more easily. BLI didn't have those listed. I enquired, and they listed them. $10 each wheel set as with others. I don't see how it would work on 24" but don't have 24" to test it. I know from testing 22" does not work. No chance.
What is most important is if, when the locomotive is placed on a mirror or shiny countertop, you see that all the drivers and the truck wheels sit evenly and fully against the surface. A lifted wheel or axle suggests problems, either with a bent/broken frame or with poor suspension. BLI's steamers have springs under most of their driver axles, certainly the middle three on the J1, to allow the tires to maintain contact on uneven rails.
In addition to the up and down movement, when you invert the loco, check to see that the center three axles have some sideplay. You'll note the rather crude and sloppy arrangement at the crank pins for just this purpose...to allow lateral movement of both the axles and the rods and not have them run into each other.
I could see how that would be a problem, but the locomotive has had this problem pretty much since day 1 on 3 different layouts/trackplans. I don’t know the history of this loco other than I got it used. To see if It has a bent frame, should I take The boiler off and put a ruler against the frame to see if it’s straight or not? The when the locomotive fell, it landed the Tender on its wheels and The locomoive hangout off a box under the layout. All of the drivers seem fairly loose except one, which is the front set. I never thought to look and see if the frame was bent. If and when the part arrives from BLI, I will check the frame when I have the loco apart. I had to take the entire front half of the engine apart to take out the old piece! Thanks
NS6770Fan
One other general caveat that I somehow post about once a year, but it's intended for people newer to the hobby:
Our toys are fine products. They are engineered well and generally 'executed' well. But, they do have engineered tolerances and limitations. The importers state what they are. Those who have studied probability theory will know that as one incurs on the tails of the standard normal curve of a distrubtion (say mean time to failure of light bulbs, inclination to derail, lifetimes of a drive-train or a bearing, and so on), one encounters the extremes of performance.
What this means is that, when we place our BLI J1 on a 24" curve, and the manufacturer stipulates that the engine is good to that lower limit, they intend that it be so. But, that lower limit will also have more 'errors' in terms of binding in the motion, possibly, derailments, or just slowing in the curves due to friction. This is because the rails also have variations in their assembly.
A good rule of thumb is to add about 10% of the lower limit on stated minimums for curves on our railroads. For example, my Sunset Canadian Pacific 2-10-4 says it will work on curves down to 30". Fortunately, that's not a problem for me, but it might be since I use flex track and fashion my own curves. If I had a lot of supposedly 30" curves, I would be inviting the odd problem curve because of my natural variation in fashioning curves of all radii. So, to get around that problem, and reduce derailments due to minimums to a low, I don't have any curves less than about 33", with the extra three inches being my fudge factor to get around my 'errors' in laying the curves.
I don't necessarily recommend that practice, but................it helps.
I have two of the 10 wheeled BLIs, and my smallest radii is 26 inches for maybe a 12 inch length. They travel it easily.
I think 24 inch is pushing it even though its advertised to handle that curve.
One thing that might help is to assure you have easements to and from the tight curve. And as mentioned before, have the tender in the furthest hole, and also make sure the wiring between loco/tender isn't binding, and lead and trailing loco trucks are not binding either..........
ENJOY !
Mobilman44
Living in southeast Texas, formerly modeling the "postwar" Santa Fe and Illinois Central
A drop to the floor may render all of the track/blind driver/drawbar conversation moot. If this locomotive took a dive to the floor and you had to replace a cracked pilot, you may also have a damaged frame which none of the above suppositions will cure. Did you have problems with this engine from day one or, did they begin after the fall?
I don't own a BLI PRR J-1 but, I would definitely check to see if all drivers make contact with the railheads simultaneously. Place the engine on its flanges on a piece of plate glass and try to slip a piece of thin paper under each driver. If you can slip the paper between the flange and the glass, a distorted frame could be your problem.
NS6770fan ... Can I get thin wood to fix the track? (1/16“ or 1/32“ modeling wood) This may have been the probl all along... NS6770Fan
... Can I get thin wood to fix the track? (1/16“ or 1/32“ modeling wood) This may have been the probl all along...
If you have any clear plastic packaging from tools or other items, pies, you can cut little panels of that and slip it under the low spots...only the outside rail, though. I find that, it many cases, a single or a double layer of that plastic is all it takes to correct a height disparity. Wooden framing shims would also work, but you'd only want to use the barest bit at the sharp end...hardly an efficient use of your money.
[Edit-added: I shouldn't have said only the outside rail. The idea is that, if where are derailments, and one rail is measurably higher than the other, either reduce the height of the high rail or elevate the low rail. What you don't want is unevenness that makes one flange 'fly' and allows the opposite wheel to derail along the curve. Usually such derailments on curves are caused by a low rail height on the outside, but not necessarily. Figure out which rail it is.]
Check the track guage. Slightly narrow guage will cause problems with an engine that is operating near its limit. Widening the guage to the NMRA maximum or even slightly beyond may help if it doesn't cause problems with other equipment.
Mark Vinski
Please be aware that Challenger locomotives are much more forgiving of any minor track kinks, vertical or horizontal, than big 4-8-4's or 2-10-4's are. BLI purposely builds considerable end play into the steam drive axles to allow operation on tight radius curves. I, too, had to make minor adjustments to my trackwork to get 4-8-4's and 2-10-4's to operate reliably.
Thanks for pointing out the rail height! I noticed I have a few spots where the track dips down a few mm. I only have nails in foam currently until I get everything perfect. I just nudge the track a bit to adjust it. Can I get thin wood to fix the track? (1/16“ or 1/32“ modeling wood) This may have been the probl all along. I even thought to change the cracked pilot caused by a drop to the floor in the mindset that it was getting caught on the rail head!! I have emailed BLI and hopefully they have one. I will update once I work on the track next. Thanks!
I don't believe so. The driver that is blind on mine is the central axle. That configuration leaves only two axles on either side of it that have to negotiate the curve, which is 'doable'.
When you say you adjusted the track, do you mean you widened the curves? Often derailments are caused not by tight radius but by uneven track heights, especially when outer rails are somewhat lower than those on the inside. It often only takes a single mm to make a difference, something most of us don't notice until it's too late. When the flange on the outer wheel fails to meet restraining metal on the rail head, the wheel will work its way outward and derail. Softening ballast and prying up that outer rail, trying to shove a few grains of ballast under the tie ends, will often improve things to 100% reliability.
Is it possible to switch out another driver with a blank or would that cause issues? I adjusted some track areas but it still does it.
I have the original Paragon version of that locomotive. It was shipped with the blind driver axle in place, and it does go around 23" radius in that condition (neither quickly nor happily). So, you'll have to have the blind set in place for radii much less than about 28", maybe even 30" like my Sunset 2-10-4 Selkirk requires.
Just got home and I do have a blind center driver and there is some room to wiggle the drivers. I will have to get some Kato track.
I test all my locomotives for minimum radius with Kato Unitrack. I would suggest you do the same.
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If it passes the Kato check, you have a slight misalignment in your track.
Atlas makes 24" sectional code 83 track.
-Kevin
Living the dream.
Yes I meant “Derails” not ”Details” . I had theorized that the locomotive might have had a second set of drivers. I bought the locomotive from a dealer at the Greenburgs show in Lebanon PA back in December 2017. Where could one get the blind driver replacements? And I may look to pick up a pack of Kato/Atlas track, so thanks for the suggestion! I think I remember seeing photos of the loco with a blind center driver before. The tender is already in the last drawbar hole. Thanks!
Edit: I just looked on BLI’s listing for the paragon 2 J1a‘s and it says that minimum recommended Radius is 22 with 24 for S curves. I don’t have any S curves, but rather a 24” radius oval.
DOn't overlook other factors - if they specify 24" minum and that's what you have, that also assumes the tender is in the furthest drawbar hole, if you have it couped closer it can bind at the drawbar and force the engine off the track.
One of my original PCM Reading T1's had one of the driver bearings twisted int he slot - the front and rear set are sprung. With the twisted bearing, that axle couldn;t move up and down against the spring and it had problems even on 30" radius. It was very obvious the wheels weren;t moving freely, all I had to do was loosen the rataining plate ont eh bottom and shift the bearing so it was square in the slot. Never had a problem after than and it handles down to 22" radius if you go slow and with the tender in the furthest hole in the drawbar. 30" radius and #6 turnout it could take at warp speed.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
I assume you mean it "derails"? It's all in the details....
Does it derail at the same place? It could be there's a slight kink in one place that makes the curve be slightly tighter than 24"R. Atlas and Kato make "click track" curved pieces in 24" radius. Maybe get a pack of 24"R curves and a pack of straights and do some test runs. If the engine goes thru the Atlas or Kato track OK, it means it's your track that needs to be adjusted.
Also, make sure the drivers are free to move side-to-side; this allows the engine to take the relatively tight (for a big engine) 24" curves.
BTW I'll have to check, but I'm pretty sure my BLI (C&O) 2-10-4 has blind center drivers? If yours doesn't, did you buy it used (like Ebay)? If so, perhaps someone swapped out the blind driver for a flanged one.