Derailing truck through #4 turnout - UPDATE!

[tstage]

Hi everyone! 

I've got a slight problem and I'm wondering if you all can collaborate what I think may be happening.  I've been installing some new Atlas #4 turnouts in my yard this weekend.  This evening I was testing out the trackwork to make sure everything was working properly and discovered a consistent problem with one of my Proto 2000 0-8-0 switchers.

Circumstances Scenario

Whenever I back through the frog, the axle of the tender truck nearest the cab rotates sharply CW and derails.  (See sequence below)

Click picture(s) to enlarge

Observations

• I've tried this with another new #4 turnout and it does the exact same thing
• I ran the locomotive through the turnout forwards - no derailment
• I pushed an identical Proto 2000 0-8-0 tender backwards through the same turnout - no derailment
• I backed a 2-8-2 BLI Mike through the turnout - no derailment (added)
  
• I pushed a 40' boxcar through the turnout - no derailment
• Trucks rotate freely and don't bind
  
• Only that particular axle on that tender derails

Diagnosis Conclusions

My guess is that the flange on the axle closest to the cab might be slightly undersized; therefore it is not making contact soon enough with the frog and slips past it.  I haven't had a chance to measure the flanges on the axle with calipers to confirm this or not.

Am I way off base?  Or do you think it's an issue with the turnout(s) themselves?  I didn't have this problem with the Atlas Snap turnouts that have a sharper diverging angle.

Thanks for the help ahead of time.

Tom

[jeffrey-wimberly]

It may be simpler than that. Make sure that the wheels are centered on the axle, you may have a dog-legged truck. This will force the wheels against the rail and cause a mysterious derailment, just what you're having. Change out the wheels in that truck and see if that cures the problem.

[Vail and Southwestern RR]

I like Jeff's thought.  I had a boxcar that I was using on a 'test' train that derailed eveytime it went through a crossover.  Somewhere along the line the truck had gotten warped, so the two sets of wheels did not track the same line.

Also, check the gauge of those wheels, if it is a little wide, it might get forced to pick the frog.  I don't think I'd suspect the flange itself, of it is getting to the wrong place, it is getting directed there.  I'd love to see the sequence from the other side, to see if it is catching up on the guardrail somehow.

 

[tstage]

Thanks, Jeffrey and Jeff.

My initial thought was to change out that axle for a new set to see what would happen.  I thought I'd go ahead and post it anyhow to see what you all thought.  Getting a picture from the other side might be a challenge because these were taken from the edge of the layout.  If the new axle doesn't work, I'll see what I can do.

Tom

[jeffrey-wimberly]

I had a caboose that would do the same thing every time I backed it through a turnout, any turnout. Turned out to be a dog-legged truck. I changed out the wheels with another set and it never happened again.

[Vail and Southwestern RR]

Thanks, Jeffrey and Jeff.

My initial thought was to change out that axle for a new set to see what would happen.  I thought I'd go ahead and post it anyhow to see what you all thought.  Getting a picture from the other side might be a challenge because these were taken from the edge of the layout.  If the new axle doesn't work, I'll see what I can do.

Tom

I figured seeing it from the other side was probably hard, or you would have done it already!  If the problem is alignment of the truck, of course, changing one axle won't help. 

[tstage]

So Jeffrey...You changed out both wheels on your caboose truck and not the entire truck...and the problem went away?  I just want to make sure I understand you correctly.  Thanks.

Tom

[markpierce]

This is an example of what happens if one pushes the limit by operating a four-axle locomotive backwards through #4 turnouts.  If everything isn't perfect, you've got trouble.  Get it perfect, or get an "easier" turnout.

Mark

[jeffrey-wimberly]

So Jeffrey...You changed out both wheels on your caboose truck and not the entire truck...and the problem went away?  I just want to make sure I understand you correctly.  Thanks.

Tom

Yeah. The wheels were not centered on the axles. There was nothing wrong with the truck itself. I put in a set of wheels that were properly centered and the problem vanished.

[tstage]

Mark,

As I mentioned in the OP, I never had this issue with my Atlas Snap turnouts...and they have tighter diverging angles to them than the #4s.  I've also run 2-8-2s through them with no problem.

Tom

[tstage]

Yeah. The wheels were not centered on the axles. There was nothing wrong with the truck itself. I put in a set of wheels that were properly centered and the problem vanished.

Got it!  Thanks, Jeffrey!

Tom 

[tstage]

Okay, dumb question.  Standard 33" wheels (i.e. Proto 2000) should work fine for replacements?

Tom

[R. T. POTEET]

Please do not take this response as facetious but I thought that Jeff Wimberly's analysis of the troubles was reserved for N Scale because I have experienced just this trouble on numerous occasions. I don't ever remember encountering these off center wheels in my HO Scale days.

[jeffrey-wimberly]

Please do not take this response as facetious but I thought that Jeff Wimberly's analysis of the troubles was reserved for N Scale because I have experienced just this trouble on numerous occasions. I don't ever remember encountering these off center wheels in my HO Scale days.

I've come across it in many scales, including G scale.

 

Okay, dumb question.  Standard 33" wheels (i.e. Proto 2000) should work fine for replacements?

They should work fine. I usually use the Bachmann RP25 metal wheels myself. As long as the wheels are the same height. If you change out 28"'s with 33"'s there could be some trouble.

 

[markpierce]

Mark,

As I mentioned in the OP, I never had this issue with my Atlas Snap turnouts...and they have tighter diverging angles to them than the #4s.  I've also run 2-8-2s through them with no problem.

Tom

I have heard scores of times over several decades that Atlas Snap turnouts were equivalent to #s 4.5.  So, if you say they are sharper than #4s, what do you say they are?  (I am ignorant as I haven't dealt with sectional track for the last 50 years.)

Mark

[jeffrey-wimberly]

That's ok, I haven't used Atlas track for the last twenty years, mainly due to nightmares involving their turnouts back in the 80's.

[C&O Fan]

I may be seeing things but to me it looks like the chain holding the trucks gets caught between the tender step and the wheel and causes the truck to lock up and turn

[bogp40]

It does look like there is an interference, but this is after the truck has derailed.

One other posibility: When backing the drawbar or any electrical connections/ wiring could be lifting the tender even if is very slight the tracking of the truck will be affected. To test this, tempararily place a weight on the top of the tender over the offending truck. I had this trouble w/ an Athearn Mike- the decoder wiring to the tender was factory packaged curled in an upward shape and fairly stiff. Even if you don't find the actual cause if the weight works just add it permanently in the tender.

Possibility 2: I don't know if the electrical PU ar similar to other Heritage. One of the PU could be shifting the wheel/s within the truck giving the offcenter as Jeff mentions.

[georgev]

Sometimes Atlas turnouts have some excess plastic on each end of the frog that is higher than track level.  I have had many with this symptom.  The plastic will lift the wheels slightly.  Steam locos with rigid wheelbases would lift completely off the rails on that side breaking conductivity and stopping the loco (if that side of the loco was providing all pickup from the rail).

In this case it could be that the wheels lift slightly.  On the 3 axles that work properly there is not much force pushing the wheelset toward the frog.  But on that last axle, the drawbar is pushing the front of the tender toward the frog.  The wheel lifts, then then is pushed into the frog point and up over the point. 

If the plastic is high, just file it flat with the rail height.  Also check the flangeway with and NMRA gauge.  If the guard rail is too far from the stock rail, you may have to pad it with a thin strip of styrene or something.  That will pull the wheel away from the frog point. 

 George V.

[Anonymous]

I say take that derailing AXLE, put another proto 33" in there and see if you derail again.

Get a track gauge and examine the frog/Flange Gaurds paying particular attention to clearance between railhead and gaurdway.

Closer examination of the first photo and relationship between the rear axle on the first truck and the front axle already shoved way to the left and probably set to derail when it tries to cross the frog.

Either the axle is off to one side in the truck doglegging it or the Flangegaurd rail OPPOSITE the frog has failed to capture the LEFT wheel of the FIRST axle properly and shoved the whole thing to the right side of the engine and setting up for derailment.

If the axle is found to be in gauge and the truck is square, the fault is with the switch starting at the gaurd ways that are supposed to keep the flange and wheels against the railhead on the other rail away from the frog.

 

[Budliner]

Bog what a good idea

test this, tempararily place a weight on the top of the tender

as all the other ideas look at the track, and it was noted that other equiptment run fine.

and its cheep and easy

 

K

[Soo Line fan]

Tom,

Check the point-to-point length for the wheelset. It could be dropping down in the journal and causing the problem. I had problems with P2K wheelsets being too short and doing the same thing during backup moves.

Jim

[Autobus Prime]

Mark,

As I mentioned in the OP, I never had this issue with my Atlas Snap turnouts...and they have tighter diverging angles to them than the #4s.  I've also run 2-8-2s through them with no problem.

Tom

I have heard scores of times over several decades that Atlas Snap turnouts were equivalent to #s 4.5.  So, if you say they are sharper than #4s, what do you say they are?  (I am ignorant as I haven't dealt with sectional track for the last 50 years.)

Mark

mp:

Snap-switches and their clones and cousins are 18" radial type.  Atlas "no. 4" Custom-Line switches are about 4 1/2. 

tstage: Did you push a tender through *by itself*, or did you back the identical 0-8-0 through tender-first?  If the wheels and switch check out all right, perhaps the loco's rear overhang is forcing the tender and truck against the frog point.  You might lengthen the drawbar to fix that. Maybe the reason this doesn't happen with Snap-switches is that the diverging angle is constantly increasing, swinging the tender front farther to the right, bringing it closer to the loco overhang. 

[tstage]

Did you push a tender through *by itself*, or did you back the identical 0-8-0 through tender-first?

Auto,

I just backed the other tender through the turnout manually, by itself.  I should probably try and hook that tender up to it's loco and push it through connected to see what happens.

I haven't converted that one to DCC yet so I'll have to push it through manually.  The other 0-8-0 derailed whether I pushed it or operated it under it's own power.

---

Thanks for the suggestions everyone.  I'll let you know what I find out.

Tom

[J. Daddy]

Thanks TA462! I have had the same problem for a long time, even on a number 6 switch. never figured it out so I had to "retire my NP 0-8-0 to the shelf for an NW-1, so now I can fix it and get her back into commision. Do you have any pictures of what you did?

[loathar]

Tom, I had the exact same problem with one of my CNR Proto 0-8-0 switchers.  I thought it was a bad wheel or bent axle as well but when I replaced it it would still derail on #4 turnouts but only when backing up one way, to the right when backing up, never on a left turnout.  I loosened off the screw that holds the connectors in place on the loco and the tender as well as the screw that holds the leading truck on the tender and that fixed the problem.  Proto 33" rib back as well as the flat back fit, I tried both when I had my problem. 

That's what I was thinking. Try swapping the trucks. If it still does it, then it has to be what TA462 recomended. Some weight might help too.

[tstage]

I think the combination of not being able to flex up and down and the light weight of the tender is Toms problem. 

Well...at least the problem with my tender.  No reason to get personal, Dave.

Tom

[tstage]

Okay, I took another look tonight at the derailing issue with my Proto 2000 0-8-0.  I also took into consideration the suggestions that some of you had given me to try.  Here's what I did and what I discovered:

1. I removed the tender from the locomotive and manually pushed the tender backwards through the turnout - no derailment
2. I reattached the tender and locomotive, loosened the connector screws on both the tender and cab, and backed them through the turnout with my Power Cab - derailment
3. I removed the wheel axle closest to the cab.  The wheel did NOT appear to be not centered on the axle - i.e non-concentric with the axle.
4. I reinstalled the wheel set on the tender and backed the locomotive and tender through the turnout, with a small block of wood on top of the tender to add weight - NO derailment!  With the block of wood on top of the tender, I ran the locomotive backwards and forwards through the turnout serveral times - no derailments.  (Thanks for the tip, Bob & Dave! )
5. I also tried Point 4 on another #4 turnout - no derailment
6. I removed the block of wood and backed the locomotive and tender through the turnout again - this time observing the wheels on the opposing side of the tender.  I found out that the opposing wheel on the axle closest to the cab rose up slightly on the rail guide right before the other wheel opposite it derailed.
7. I took a look at the rail guides (See pics below for detail)

Atlas #4 turnoutClick picture(s) to enlarge

Atlas Snap turnout

The Atlas #4 turnout has rail spikes on the inside of the rail guide.  Notice that the Atlas Snap turnout does not come with any rail spikes.

It appears that the spike heads of the diverging track on the #4 turnouts are not uniform in size - i.e. some are very small (left side), while some seem oversized (middle and right side).  I'm guessing that the opposing wheel on the tender axle closest to the cab is hitting this oversized spike head, raising up, then forcing the wheel opposite it through the wrong side of the frog.

I've examined the other #4 turnouts that I bought and the oversized spike head on the diverging track rail guide is common on all of them.  I also observed the rail guide on the straight portion of the turnouts.  The rail spikes are either very low profile or practically non-existent.

Do you think if I remove or pare down the oversized spike head with a #11 X-acto knife blade that this should eliminate the problem?  Do you see any detrimental effects that I might be overlooking?  I'm tempted to try one and see what happens.

One last thing that I forgot to mention.  When I loosened the connector screws on the wire harness that connect the tender and locomotive together electrically, the connector on the tender side seemed to be slanted down slightly.  I'm wondering if the wires in the tender side of the connector are slightly short, therefore the connector is forced down to meet the connector on the locomotive side.  Could this also possibly exacerbate the derailing issue?

Anyhow, thanks again for your insight and thoughts.

Tom

[jeffers_mz]

The spike heads MAY be lifting the left front wheel of the truck, but much more likely is that that wheel lifts when the right rear truck wheel drops down into the frog gap. About the time the right rear wheel climbs back up on the far side of the frog gap,  forcing the left front truck wheel back down towards the rails, the right front wheel is passing the frog gap.

As the right rear wheel climbs back onto the railhead, it is forced to the left (as seen from facing towards the front of the locomotive). This creates a moment, a rotation of the truck, clockwise as viewed from above. The clockwise moment is applied during the time the offending right front wheel is down in the frog gap, and it "picks" the frog as a result.

The only direct cure is to change turnouts. Find one that doesn't have such a ridiculously deep frog gap.

Indirectly, you can improve the situation by adding weight to the tender, at the expense of total pulling power. The drawbar and wiring harness can apply lift to the front end of the tender, happens here with my Spectrum ten wheelers all the time. Not much lift, but enough.

At that point, the front of the tender rides a little high, not much downforce on the front truck bolster. this allows that front truck to pivot in the horizontal plane to a larger degree when tilting back and forth over Atlas' frog gap Grand Canyon. The truck is effectively suspended from the tender, hanging there.

Extra weight on the tender overcomes the lift from the drawbar and wiring harness and now the front truck, instead of floating under the tender, must lift the whole front end of the tender to pivot as much as it does when it's just hanging underneath.

As you know, adjust the weight to as little as possible necessary to overcome the effect, so as to maintain pulling power of the loco/tender package. 

[bogp40]

Atlas #4 turnoutClick picture(s) to enlarge

Tom,

If you decide that the molded spikes are the problem and want to cut them down some, Try using a file or better yet a cut down piece of a hacksaw blade. This inovative tool works great for our shaping the flangeways on handlaid turnout frogs and soldered guard rails. Should give you the control you need. I would CA the rail to the ties at this spot in case too much spike detail is removed. 

The hacksaw blade also works good for clearing the flanges of in street rail or cleaning out any scenery material from girder rail.

I still feel that adding  weight to the tender will help stop the problem as well.