Kato FEF and Peco code 80 - oh dear.

[bobthebear]

Hi Guys.
I'm sure it's problem with undersprung equalization on the rear driver as suggested by Doug.
As I reported, forward travel is OK now - I can put up with the "frog diving" as long as I stays on the track! It's just those rear drivers rising up too far in reverse. Back to work next week (been off with an op), but when I get back I may investigate further with a view of stiffening the springing on that rear driver. Oh, and replacement rear truck works fine.
Cheers, Bob.

[Doug G.]

So, after reading Pete's last post, we can conclude that the FEF CAN run through Peco code 80 switches. The dropping of wheels through frogs and all that is due, of course, to some incompatibility due to the FEF being designed to finer standards.

I wonder if the inside edges of the rails of Bob's switches have somehow had friction added over the years so the flanges grab on them instead of just being knocked sideways. Are the edges sharp, Bob? Possibly from repeated cleanings?

Doug

[bobthebear]

So, after reading Pete's last post, we can conclude that the FEF CAN run through Peco code 80 switches. The dropping of wheels through frogs and all that is due, of course, to some incompatibility due to the FEF being designed to finer standards.

I wonder if the inside edges of the rails of Bob's switches have somehow had friction added over the years so the flanges grab on them instead of just being knocked sideways. Are the edges sharp, Bob? Possibly from repeated cleanings?

Doug

I wouldn't say so, as it happens with new turnouts too. And the "new rear truck" doesn't like reversing either, so I have gone back to the one I doctored with pizza cutter wheels.

[mmagliaro]

Can you crawl that engine in reverse, through that turnout, and stop it just as the wheel starts to climb up the rail, and take a picture of it like that, really close up?
Can you take a photo from both sides?  (the side with the climbing wheel and the other side that is presumably still on its rail?

When it gets like that, and is stopped, see if you can take a toothpick or something and just nudge that driver inward, and see if it drops back down onto the rail without shifting the locomotive itself in any way ?
Here's where I'm going with this.  I've had engines climb like this, thinking the rails were too narrow, when it turned out
to be caused by 2 other factors.

1. A spot where the rail gauge was actually a little too wide so that one wheel dropped DOWN IN, thus causing the opposite-side wheel to lift up and ride up the rail.

or...

2. over the whole length of the engine, the geometry of the two rails is such that the engine isn't free to slide back and forth between the rails like you think it might be from just looking at it and measuring the gauge.

See if, when you stop it with the wheel halfway up the rail, can you gently take the engine and swivel it a little back and forth a little between the rails?

Unless that axle is getting hung up somehow, preventing it from sliding over, it really should not climb that rail, and that would be true even if there was no spring action on that driver at all.  That axle should be able to slide over like oil over glass.

[peteski]

One more thing to ponder is that I ran my engine with only one aux. water tender (we didn't have time to set up a full passenger train).  If Bob is backing up the loco with several cars being pushed by it, that  additional load exerted on the drawbar might be creating a sideways force pushing the d#4 driver to the outside of the curve.

I suppose we could ask Bob if the problem disappears when he is runnign the loco with with no cars, or one car (like I did).

[bobthebear]

One more thing to ponder is that I ran my engine with only one aux. water tender (we didn't have time to set up a full passenger train).  If Bob is backing up the loco with several cars being pushed by it, that  additional load exerted on the drawbar might be creating a sideways force pushing the d#4 driver to the outside of the curve.

I suppose we could ask Bob if the problem disappears when he is running the loco with with no cars, or one car (like I did).

Doesn't make any difference as a light engine or with 10 cars attached, the rear drivers still rise up.

[peteski]

Doesn't make any difference as a light engine or with 10 cars attached, the rear drivers still rise up.

The difference in behavior of our (supposedly identical) models is odd.

[victor miranda]

the problem is that the drivers lift instead of turning the chassis
or at least moving the axle set sideways a bit.

causes.... three drivers going one way and that last one gets no choice....
(my guess in this case) (tryanny of the majority...)
the bearings being snug enough that they don't like to move sideways.
absolutely no weight on the driver.
this can be from chassis lift or a lack of the bearing holding it down
when the other bearings are fully weighted.

there being enough pull from the train to straighten the loco.
(this often looks like 'lift')

this one is hard to fix because one has to chase a lot of details
to eliminate them.

the equalization means that all four front drivers have equal weight btw.
victor

[peteski]

Your explanation make sense Victor. But that I don't understand is why the same loco going through the same switches (located on another layout) behaves differently.  So the only variable is possibly the way the track is laid?

[bobthebear]

I understand what Victor is saying.
But Iit is only in reverse where the problem lies, and there is no equalization therefore. I'm sure the springing is too light on this axle. On mine there is a square hole through the chassis just at the spring height and I'm wondering if I have something missing!
I'm back to work tomorrow, so won't be around for a week, but will investigate when I return.
Cheers, Bob.

[craigolio1]

Could it be that there is more weight over the front drivers than there is at he back, so when entering a turn running in reverse, the heavier front of the loco stays put between the rails acting as a pivot. The tourque on the front of the loco will either push it over to the side, or because of the light weight in this case it just climbs. Would adding weight move the Center of gravity to the middle so it pivots more in the middle allowing the rear to push over instead of climbing?

Craig

[victor miranda]

Hi peteski,

the logic is correct by my thinking.
the ...resolution is finding the magic reason for the loco acting different
here from anywhere else.

uneven track is high on the trouble shooting list.
(it can be perfect in the problem spot and everywhere else
the problem track helps guide the drivers....)

one of the posters said to look for sharp edged railhead.
I would check that too.

the possibility of a missing spring definitely catches my attention.
(I guess it is possible that Kato made a mistake in assembly... strange as that is.)

pushing may lift the chassis a bit.  That may be enough to get the driver onto the top of the railhead.

the drawbar could be leveraging the chassis and that could be enough as well.

as Max points out; observation is the key.
I am guessing because I can't see it.

victor

[peteski]

Craig, the rear driver is strictly cosmetic - it supports almost no weight.  It is just there to look good. All the rear weight rests on the only driven #3 driver.  So #4 driver coudl then easily ride over the rail on a curve or s-curve  that was too sharp for the loco's wheelbase.  But Bob and I ran our locos through same brand of switches and mine did not derail.  It sure is odd, and as Victor said, there is obviously something different between Bob's and mine.

Victor, I have not disassembled mine yet - does the spring for #4 driver consist of a single piece of metal or are there separate left and right parts?  If it is the latter then Bob's model would be missing both pieces.

[bobthebear]

SORTED!!!!
Hi Guys.
The 2 springs that form the suspension for the rear drivers. Just rearward of their mounting point is a rectangular hole in both sides of the chassis. I put a thin strip of plastic through the holes, above the springs to increase the spring tension. I can now reverse through Peco curved turnouts at almost warp speed. Traction has not been affected. I would be interested to know if there SHOULD be something in that hole! Easy to get at. 2 screws on the underside and lift the rear drivers out. As I said, I'm away from tomorrow, so I will leave it to you Guys to inspect yours!
Cheers, a very happy Bob.

[nkalanaga]

Great!  At least it was an easy fix, and if there is something missing, hopefully Kato will issue a repair kit.