Newbie issue - 8601 Engine derails on 90 degree crossover

Got a picture? (start typing and you'll see an attachment tool & paperclip at the lower right of the box, in blue.  After finding pic, check the box "insert large size" that appears AFTER "processing & success" is done. Then hit finish, then type again (if any), then finish by hitting post.)

"Special" tracks don't always play well between brands, or even within them. Lionel on Lionel has issues at times too, usually pickup placement in certain turnouts. Prewar "Fat wheels" are another compatibility issue with special tracks. Marx prewar electric turnouts seem the most universal Ive used if/when you start thinking about those. (they kinda need 4-5 extra track pins strategically added for a mod. Real simple, insert & squeeze

Marx pickups were long flat ones that wouldn't "drop" into gaps. You likely nailed your issue. The pickup drops and snags in the wide gap. Why wide...

With old "fat drivers" the wheel's gear is as large a diameter as the flange, making gear wheels wider than those on the other side of the loco; so the flangeway gap for the cross traffic, may simply be too wide ... ? 📸 ?

So... first solution is just remove the front pickup totally. That will prevent "pole vaulting". But the rear pickup alone may, or may not, provide enough contact through turnouts or even the 90°. Some extra speed might solve that ...?

or

I think you might be able to limit the drop distance if you could fabricate a stiff strip/leaf to add into the spring slot, and it's (long) exposed end sitting under the pickup. A longer strips end sticking out limits the drop more. I've done this with a small modern Erector set strip on a slip in roller, but because that plastic at the pickups hole had melted from being run hard and heavy as possible  for many hours. A little weight goes a long way. 

 To remove it, poke/ press the brass backing/contact spring I'm expecting and it can be fished out. (Im pretty sure that that those shoes can be replaced with a roller; same exact slip fit for both I think.)

and/or

Adding weight might be needed (especially if it is a plastic 90 with a spring loaded piece between rails like the plastic turnouts have)  Adding some weight anyhow, will  imrove any wheelslip for pulling more cars... fishing sinkers (lead concern?) or better IMO are peel & stick automotive tire balance weights (harbor freight/tire shops) Add it as low as possible, but high up mounting of weight usually beats none. Don't forget front to rear balance may be a factor too. 

And/or

Modifications to the 90° might be another solution. A strip (4) of plastic, tapered to a long triangle, laid in the slots, peaks centered to the center rails.

  The taper guides the wheel flanges rather than being something the flange can crash into head-on, causing a climb. The peak of the triangle closes the gap more to catch the pickup higher.

You will need to leave a gap between the peak and center rail for the 90° traffic's flanges to pass, so you basically have to make a frame-like"filler" around that center square, but also leave enough flange gap. Good guide rails at the (4) entrances/exits and that taper might not even matter.

Doit temporary at first. These wont be as prone to "upset" as you might think.    Use two sided tape, regular tape, a small dot of caulk or something else temporary until you are confident in shape, placement, and function. Then gel super glue or 5 min JB Weld, etc. to glue it permanently. A Dremel tool and reenforced cut off wheel can easily grind it off even years later too

and/or

*I have a prewar Saki with the same issue. It's center "diamond"/"guideils thingy is round, so an O ring works to fill the gap. I'm not sure if that will work for you though.. (picture? even a "borrowed one" from online ) 

I love it becase if I can run tiny dia K-line rollers, then simpls pull the ring off the center of the 90° and it can run fat wheel trains.

"O-27 ".  O gauge 27 inch (outer diameter of a circle of it, other tracks may measure on center rail to center rail dia. vs OD. If in doubt ask).. but 0-27 works too. I think Lionel used both... in old metal typesetting, you might run out of O or need the fraction of an inch for line justification. Context wins there if it is understood without thought   Searching online, use both.

Don't pay top dollar for a 90° IMO. The shipping might be more . There are simply thousands unused Lionel 90° out there.

Welcome  

"Guideials" or whatever, should be "guiderails". Kinda important or I'dve skipped it.

"Spellwreck" has been hating using "r", and other random deletions.

And "vindictive text" protested "up" following pickup...repeatedly; it just wouldn't listen.

Basically that took two hours to write, no joke.

I screwed up the s for an e all by myself and forgot because I was on a good roll

But I just kind of realized this also contributes to my long post habits, and to "scattered paragraphing". I have too much time to think and jump around in the various thoughts a bit deeper, when I'm busy convincing the composer I don't want it's "help".

Adriatic,

Thanks for the detailed response! It's obvious from your post that there are a lot of factors that could be at play here. 

I did read elsewhere on this forum that someone had issues with the trolley bumping up when going over a 90-degree crossover, due to its short wheelbase. I think that is the issue with my train, being an 0-4-0. I was able to run a 2-4-2 over the crossover with no issues at all, so I think it must be the weight being so centered on those 4 wheels on the 0-4-0 that are making it jump up when the front slider contact hits the rail.

Makes sense to a point, but the gap may still be the root issue I think.

Does the other loco have rollers? A roller would climb out of a gap easier.

Is it cast metal? The pilot and trailing truck would have little effect. Overall weight might though. Balance I need to think on more, but I think the driver wheelbase would have more impact. 4 driver motors do have different wheelbases... not much, but do. Longer wheelbases are obviously more stable.

Done thinkin'.. Marx E locos used to add lots of weight up high, above the loco frame. Bare, no shell they are 0-4-0 and the weight keeps them planted and bouncing less than unweighted steam versions of the same motor. I don't think driver size saves the diesel. I don't think it would change the relevant weight & angles to fulcrum points enough. It is a lot of weight (a pound? Maybe more?)

I don't have an example of either Marx 90° to narrow my guesses. I don't even know which era 90 it is yet. Early speculation often negates a need to see, but not this round.

I think that loco can roll easy without power or gear damage(like worm gears). Moving it (or them, both)thru the 90° by hand, you may be able to feel if there is a hangup to really be concerned about, or simply a need for weight, or "it is what it is" and it is wheels bouncing over gaps or bumping guide rails, etc.

Removing the fwd pickup for a TEST  may stop it bouncing.  If it still bounces then it isn't the pickup.

It won't even matter about losing power, your testing for smoothness. If it doesn't need the pickup, then it doesn't need it. Save it incase you do need it some day. (zip lock, pill bottle, parts box, etc. will keep it from vanishing easily)

The photo I was going to show was lost to googles intrusive updating PS services while I was composing emails that eve (12 pics, 4 vid gone from mail, gallery, & cloud).

   But this one at least shows a fat wheel to see that the gap must be about 3/16"- 1/8" wider for them to pass.  Seen from behind or ahead, it is  more dramatic.

 I need to set up a new example shot.(or you can use the advanced search option here with "fat wheel" & .jpg & my name (option down low)  I had posted it once before within the last month.)..in fact, if you find it, copy paste the url adress here to create a link so I can recover it please. (links auto-form once you post, that menu doesn't work often for android)

.(yes this runs without derailing...magic or something 🤔 )

Here is a thought. If loco #2 has the same pickup plate but rollers, steal the rear roller off #2 and swap with the #1's front slider, put #1 slider on #2's rear, so each has a roller in front.

Not sure if I missed it in a reply post. (Way too much text )

Guessing the wheel gear is striking the inner guard rail when going over the crossing.

Close Bobby. He has normal wheels, but (likely) a 90° designed for the fat wheels. That design has a wider gap between guide rails.

I'm being even a bit more long winded because the poster is new and I have no clue what their experience or tech ability is.(not that I'm "short but sweet") 

I don't even know for sure if the turnout is pre or postwar yet. I'm hoping for more info from the Orig. Poster so I can tighten up the focus.