Kato FEF-3 problem with front truck deraling, and rear of the loco bobbing

[Ngineer]

Hello again,

I've checked and the front truck is in the right direction.

It will derail in a curve, it climbs out toward the outside of the curve. Backing up on Kato's double crossover will derail the front truck of the FEF, too. Going forward through a double crossover doesn't derail the loco. Weird.

Right now, I am using Kato Unitrack.

I'll try to weigh down the front truck (with lead?).

BTW, I was unable to detach it to take a closer look. I am afraid of putting to much force and breaking it.

   Javier

[peteski]

There should be a spring on the center post (on which the truck pivots).  That spring is supposed to exert enough downward pressure to keep the truck in the track.  Does your model have that spring?  Instead of adding weight, I would probably try to stretch that spring a bit, so it exerts more downward pressure on the truck.

The spring is in that truck photo I posted earlier  in the thread.

[Ngineer]

I made a close-up picture:



Looks like the spring doesn't go all the way up. Now I am really confused.

The truck IS attached, though it may look like it isn't.

How do I take the truck off without breaking the plastic?

   Javier

[peteski]

I'm surprised that the model has a problem in Unitrack. What you see is normal.  The truck is so free floating that not much spring pressure is needed to keep it on the rails. At least in most instances.  When the loco sits on the track, the front truck is much closer to the loco's frame and at that point the spring contacts the top frame surface and compresses slightly.  My model looks just like yours.




Maybe it would be worth stretching that spring slightly so it puts more pressure on the truck.

To remove truck, with one hand hold the loco while also pressing down in the center of the front truck (so it sits tightly against the frame). With the thumb and index finger of your other hand unsnap the wheelsets from the truck.  While there is some resistance. they will unsnap fairly easily.
Now you will be able to to rotate the truck frame 90 degrees from its normal position, that wil release the center post from the slot in the frame. Be careful not to lose the spring.

Stretch the spring slightly to make it longer,  then reinstall the truck's frame in the reverse order from the removal, then snap the wheels back in.

[Mark W]

The pilot truck will lift free when rotated 90 degrees.  It may be easier for clearance if you slide it a little to one side before turning. 

Also, before you add weight; I had some issues with mine early on and the solution was to REMOVE the spring.    In my case, I found the spring was introducing bias to the truck and forcing it off the rails. Removing the spring allowed the truck to steer itself. 

I would visually inspect the removed truck for wheel gauge, burrs on the tread or flange, and wobble.  Also look for roughness or deformity on the pin that feeds into the loco, and on the v slot that guides the truck between the cylinders. All these parts should be smooth and have free motion.  Anything that could hinder that motion would be a potential issue. 

[peteski]

The pilot truck will lift free when rotated 90 degrees.  It may be easier for clearance if you slide it a little to one side before turning. 

Also, before you add weight; I had some issues with mine early on and the solution was to REMOVE the spring.    In my case, I found the spring was introducing bias to the truck and forcing it off the rails. Removing the spring allowed the truck to steer itself. 

I would visually inspect the removed truck for wheel gauge, burrs on the tread or flange, and wobble.  Also look for roughness or deformity on the pin that feeds into the loco, and on the v slot that guides the truck between the cylinders. All these parts should be smooth and have free motion.  Anything that could hinder that motion would be a potential issue.

Interesting. I guess removing the spring would be the first thing to try.
The truck comes out really easily when rotated 90 degrees with the wheelsets removed (otherwise it is a bit of a struggle).

[nkalanaga]

If one doesn't want to risk over-stretching the spring, would it be possible to put a washer above the spring?

[randgust]

Just a thought - while you do have the front truck off, do a finger test of rolling it through any areas on the layout that have caused derailing issues with a finger on it.   You may feel something through the finger test you never noticed; rough edges on a switchpoint, hanging on a switch frog, finding a 'chip' on the gage surface of a curve on the outside rail, whatever.  Deliberately force it to ride on the outside rails, switchpoints, etc. looking for trouble - you may find it.   No sense messing with a locomotive suspension if it simply found something in your track that nothing else seems to care about.   

Any tinkering with a spring will undoubtedly decrease tractive effort, maybe not by much, but it will.   Adding weight to the truck will not, although it might increase drag just a hair.    I try to totally avoid springs if I can.   On my lead trucks, I've found out that a relatively tiny bit of soft lead secured with Goo can do wonderful things, generally just over the lead axle.    And there's a relationship between glitches and curvature here with an exponent; the harder your force a lead truck over with a spring on top, the more it tends to shift weight to the outer rail, unbalancing the inner rail to the point where the INNER flange can lift and the outer wheel falls inside, not outside. 

[nightmare0331]

check drivers one and two.

They are on a pivoting fulcrum and held in place with a press fit pin with a spring behind it.  I have seen the pin walk out and the spring behind it causes the fulcrum halves to press out against the inside of the two sets of drivers causing them to not have any lateral motion and generally causing things to slightly bind up.

The other thing that might be an issue...have you added sound or something that has wires going from the loco to tender?  this can cause the balance of the engine to get thrown off and for the unit to not track correctly.  It took me a bit to figure this one out when we started tossing sound in them and had terrible derailment problems with the early test builds.

Anywhoo...Hope this helps!

Kelley.
www.dufordmodelworks.com

[Jbub]

check drivers one and two.

They are on a pivoting fulcrum and held in place with a press fit pin with a spring behind it.  I have seen the pin walk out and the spring behind it causes the fulcrum halves to press out against the inside of the two sets of drivers causing them to not have any lateral motion and generally causing things to slightly bind up.

The other thing that might be an issue...have you added sound or something that has wires going from the loco to tender?  this can cause the balance of the engine to get thrown off and for the unit to not track correctly.  It took me a bit to figure this one out when we started tossing sound in them and had terrible derailment problems with the early test builds.

Anywhoo...Hope this helps!

Kelley.
www.dufordmodelworks.com

Are we talking left right balance or front back? I removed the light board in mine and ran wires from the tender for the lights and motor. I've had derailment issues when turning one direction but not the other on 381mm radius unitrack. Larger radius, no problems.

[nightmare0331]

I just shot a quick down and dirty video that may help explain the fulcrum setup/

I hope this helps!

Kelley.
www.dufordmodelworks.com

[peteski]

That model to me is a pinnacle of N scale steam design.  Just when I thought that GS4 was it, along comes FEF-3!  Thanks for the equalized drive #1 and #2 suspension, traction tire on the gear driven #3, and a "dummy" softly suspended #4 driver, this loco was carefully designed to maximize adhesion and pulling power.  I couldn't believe how war Kato took this design until I had one of those in hand and analyzed how it works.

GS4 design was similar, except the locos weight rested between #1, and gear driven TT driver #4 with #2 and #4 being "dummy" softly suspended drivers.  Equalization of #1 and #2 driver too FEF-3 to the next design level.

Of course the leading and trailing trucks are just for show in both locos.

[peteski]

Kelley's fulcrum fix video he posted in another thread reminded me of this thread.

@Ngineer  - did you ever get your FEF-3 problem resolved?