K-27 front truck

[BobHuddleston]

Running outside on Code 250 track and having problems: the front truck jumps the track on the slightest excuse: any little bump and it jumps, always to the right so as soon as it reaches a right hand switch, the truck goes right while the drivers try to go straight.

I have watched it carefully: it does not happen every time, but it will not go more than 2 or 3 trips without the problem.

The truck will jump on the slightest excuse. I have seen it jump going over a flange way on a switch. It lifts going over the switch points. Once it jumped on a rail joiner.

Are the wheel flanges too deep or too wide?

I am about ready to truncate the K-27 into a 0-8-2 -- at least it will go around! Anyone got a better solution?

[JerryB]

If the front truck is derailing at several places, it could be that the wheels are out of gauge. Use a caliper to check the back to back spacing of the lead truck wheels. The target value is 1.575", with a tolerance of +0.019" and -0.015". Press the wheels in or out to get the proper back to back dimension.

See:
http://www.nmra.org/standards/sandrp/pdf/S-3.2%202010.02.24.pdf
For trackwork standards.

And see:
http://www.nmra.org/standards/sandrp/pdf/S-4.2%202010.02.24.pdf
for wheel standards. Use the dimensions for Fn3.

If you have "bumps" in your trackwork, they need to be fixed. Even more important with code 250 rail.

You also need to check that the switches are level with the earth and the nearby trackwork.

Check to see that the lead truck is free. Since you report that it derails, ". . . always to the right so as soon as it reaches a right hand switch, the truck goes right while the drivers try to go straight", it would seem that something might be biasing the truck. I don't have a K-27, so can't advise on the truck installation, but I have not read of any major problems in that department. If spring centered, check to see that the spring is not biasing the truck.

A couple of good sites to get more information are Large Scale Central and My Large Scale. Lots of K-27 owners there.

Happy RRing,

Jerry

[Loco Bill Canelos]

Here are some thoughts if your wheels check out ok for gauge.
While I don't have a K-27, I find I have similar problems with my pilot truck steamers regardless of brand unless my track is very well maintained and I use the heavy track not the nice small track you have.  Diesels and shays and heilslers all work fine but the 2-8-0 have problems .  Be sure that the front truck is floating properly and that the pivot is lubed.

If you have had a lot of rain like I have, you may need to relevel you track.  My first clue is that my steamers start to derail while everything else is running fine.  This year I have had to relevel my track 4 times, because of heavy rain.  Sometimes I have trouble due to small debris sticking to a wheel.   

I relevel my track by first using a four foot level to make sure I have no bumps.  Bumps are a killer even on my large track,  Bump near switches must be eliminated, especially if you have a tight curve leading into the switch.   Once all bumps are eliminated then level the track from side to side with special attention to the switches. I first level the switches at both ends and then level the track leading away from the switches next.

I have an indoor layout and when I suspect the problem is with a loco I take it from outside and run it inside to see if the same thing happens.  this give me a great way to troubleshoot a specific situation.  If all else fails set up a temporary track and switch on a level spot on a bench and see if the problem persists, if so you will know it is the loco or possiblely the depth of the flanges.

Friend s who use code 250 track have far greater problems than I do, related to track leveling.

Hope this is helpful in some small way.

Bill

[Kevin Strong]

As others have suggested, check the gauge first. If it's too wide, it will look for whatever excuse to climb. If the back-to-back is 1.575", try narrowing it just a bit (to around 1.565" or so) and see if that solves the problem. Wheels with thicker flanges may need slightly narrow back-to-back spacing than wheels with thinner flanges. (Not that the K's flanges are overly thick, though.) I don't think your issues are related to flange depth unless you turned down the wheel flanges.

Next - spin the front wheels and look at them from the bottom to make sure they're square to the axle. Sometimes, Bachmann's wheels have a wobble to them which causes them to be in gauge on one side and out of gauge on the other. This wobble causes the wheels to climb the rails. If they do wobble, try narrowing the gauge just a bit again, so the wheels have some lateral play between the rails even on the widest part of the wobble.

One thing that may also help is to increase the downward pressure of the spring that keeps the front truck on the track. You have to remove the front truck assembly for this (not difficult), then remove the housing that holds the little brass plunger (one or two screws). Stretch the spring a bit and re-install it. This will give a little more downward pressure on the front truck. If that's not quite enough, then take a thin sheet of styrene (.040" or so) and glue it to the underside of the platform where the plunger rubs. This will add a bit more downward pressure, keeping the truck that much more firmly in contact with the rails. Don't worry, you're not going to reduce any traction by doing this.

The other thing to look at is the switch points where the truck derails. Many modelers file a small taper on the very ends of the points so they taper into the side of the rails, reducing the "bump" that tends to catch flanges. I've done that to most of my switches, and it really cut down on derailment issues.

Later,

K

[Loco Bill Canelos]

Kevin  makes a great point on making a small taper on the switch points, something I do as soon as I get a new switch.  It does resolve many problems, especially when there is a tight curve leading into the points.!!!

[MAELLIS]

I have two K-27's. I've not had any issues with the front trucks but I did notice how you could lift the truck off the track without lifting the drivers. As I have switches  that are sprung, I wanted to be able to run thought these "against the spring". I took off the trucks and made a small plastic bush to fit over the pin that is supposed to keep the truck down on the track. The limits the upward movement and now the truck will push the switches over without derailing.

I would also check the back to back to make sure the gauge is correct as well. Other than that, check all switches have a nice smooth path and the track for unevenness.

I hope you get the problem sorted. The K-27's must be one of the best models on the market so it's a shame if yours is not behaving itself .

[Wjkroebig]

I am having the same front truck derail problem. When I took the truck assembly off to inspect it, I found that the truck itself was badly warped. I used some heat to soften the plastic and straightened it as well as I could. That helped a little, but I ordered a new truck assembly to see if that works better.