A week of wheels: FVM wheels in at Scaletrains

[sp org div]

Snip-   …but even the dreaded slinky effect mostly disappeared. It seems the consistent rollabilty and lack of uneven friction smoothed out the descent. I need to do some more testing, but so far so good.

Otto

This is something that has really baffled me with the slinky comments over the years
I see very little slinky (if any) also with all metal wheels, nor did I when I changed all my pizza cutter cars to low profile delrin way back when I first went to code 40
Some have posted video at low speed of serious issues (I agree Yuk!)
The gunk that builds up on wheels seems to be the main culprit for slinky if you ask me
I get stretch and run in like the prototype but no bobbing of cars like I used to see with the old dirty wheels
I am meticulous about keeping my track clean which is the only reason I can attribute to this not being a recurring problem…
Thanks for confirming this is not just a theory Otto

[nkalanaga]

I've also often wondered if the slinky effect was more a rolling friction problem than a spring problem.  One doesn't have it with springless draft gear, but it seems to be much less common with free-rolling wheels, and good electrical contact.  I saw much less, even with the same wheels and couplers, after switching to locos with flywheels, due to smoother pulling.

I actually had very little "slinky" with my ancient Minitrix F-units, after I wired four units together.  32-wheel pickup, spread over more than a foot of track, makes for very smooth running!

[bbussey]

Plastic wheels always become a problem.

[Cajonpassfan]

I made some more progress with my two all FVM/Scale Trains wheel set "test trains" on my mountainous Cajon layout.

The good news, they helped me find less then perfect trackwork in a hurry. I kind of knew where the marginal spots were but now I know know, in the words of Donald Rumsfeld. A parrot in the mine/rose in the vineyard...

The other good news, the dreaded slinky pretty much disappeared where the bouncy bouncy was bugging me before, especially on the downhill grade. The cars roll so freely, they simply bunch up against the engines and ride downhill nice and tight against one another.

The not so good news is that these relatively heavy free rolling cars, weighted close to NMRA standards, put an inordinate amount of downhill pressure on the engines' rear coupler, and the least amount of hesitation derails the first car or two. This is especially prevalent on the 3% descending section with several 18" radius curves. And on the uphill stretch, having a break-in-two results in an instant runaway of the rear section of the train...not a good sight.

So maybe the the super free rolling quality is not optimal for my hilly layout. I'm pondering putting "brakes" on the cabooses, or leaving a bit of paint on the axles a la Grant Eastman. They should roll freely, but maybe not this freely?

The saga continues...
Otto K.

[peteski]

A parrot in the mine/rose in the vineyard...

Funny, the version I always hear is "canary in a coalmine" (including a song by the Police).  I wonder if it is a regional thing?

Good to know the FVM/Scale Trains wheels are making such a big difference.

[sp org div]

Snip - “put an inordinate amount of downhill pressure on the engines' rear coupler, and the least amount of hesitation derails the first car or two.”

Im guessing talgo mounted couplers adjacent to the locos?

…sees flashes of a beet rack runaway…

[bbussey]

I’m guessing that as well. If all of the equipment in the consist contains body-mounted couplers, there shouldn’t be any derailments because the load of the train is transmitted through the floors/underframes and not transmitted to the trucks, which are pushed to rotate and the smaller wheel flanges don’t keep them on the rails. The ESM well car is the perfect example. It admittedly is well under NMRA weight recommendations (not much that can be done about it). However, the combination of body-mounted couplers and the model’s center of gravity being below the coupler centerline keeps the car on the rails whether loaded or unloaded, pushed or pulled, the first car or the last. The model up to now has been equipped with FVM 28” wheels.

We load-test all new models before we sign off on the tooling. The GSC test always has been my favorite, because it proves that body-mounted couplers and center of gravity are far more important than model weight.

I'm having trouble getting the video to play as embedded here, some internal YouTube error.  It does play on YouTube directly if it won't launch here.

[sp org div]

Bryan did well articulating what happens there with the compression scenario. A buffer car in the lead with body mounts (BM) is a good way to mitigate concerns. Also why helper ops can be so delicate with talgo couplers. Fortunately many manufacturers are falling in behind now on the BM trend (kudos ESM).  I only have half my fleet converted as it can be a pita. For now, paperwork directs crews to block cars per destination in the long trains as a cover for keeping those body mounts where they need to be.

Then stretch also has its own baggage. I have found when pulling a long train uphill on sharper curves (<24”) with a talgo equipped lead car it can also cause issues. Particularly six axle diesels with BMs adjacent to a car with talgos will cause the lead truck with low profiles to ride up over the railhead as the couplers are kicked to the outside of the curve.

Hope were kinda staying inside thread drift parameters…
 

[bbussey]

That is an accurate assessment regarding talgo- mounted couplers behind motive power, since all nearly motive power available today are now equipped with body-mounted couplers.

Body-mounts on everything is the way to go.  Removing the load passing through the trucks allows for smaller wheel flanges and reliable operation, as long as the track work is decent.  And by decent, it doesn't have to be immaculate.  But it does have to be in gauge and unkinked with level joints.

[nkalanaga]

If you're running unusually long, or heavy, trains, compression derailments are prototypical.  In effect, our trains go downhill with "dynamic brakes" only, as all of the braking is in the locomotive.  On the prototype, steep grades, especially with curves, and all of the power on the head end, almost required the use of some train air brakes, to keep the weight of the train from squeezing the head-end cars out.

[Cajonpassfan]

Thank you gents, for the comments,  observations, and the video. There's no argument from me that bodymounts are the way to go. I'm in the process of slowly converting and upgrading my cars, but it takes time and money when dealing with several hundred cars, all the while building a large layout.

The cars derailing behind the engines on the 3% downgrade are not talgos, they are properly weighed BM's. I'm still testing and experimenting (and have no desire to criticize the fine FVM/ST or any other fine wheelsets; I'll be buying more). I simply note my experience with a two-pound, very free rolling train on a 3% downgrade and 18" curves on my layout, and believe the dynamics  of a heavy train on a steep downgrade are very different from uphill or flat running. But perhaps this discussion belongs on my layout engineering thread instead....that's where the grades are...

Again, thanks for the feedback,
Otto K.

[nkalanaga]

"the dynamics  of a heavy train on a steep downgrade are very different from uphill or flat running."

They are, definitely!

[MetroRedLine]

I've also often wondered if the slinky effect was more a rolling friction problem than a spring problem.  One doesn't have it with springless draft gear, but it seems to be much less common with free-rolling wheels, and good electrical contact.  I saw much less, even with the same wheels and couplers, after switching to locos with flywheels, due to smoother pulling.

It's definitely a combination of both. I notice it less with metal wheels, and on faster speeds. Also, weight is a factor - a lighter weight car will do the herky-jerky more than one that has a little heft to it. I tend to put my die-cast rolling stock on the tail end and it doesn't bother me much anymore.

[GaryHinshaw]

With operating sessions starting up again, I recently made a pretty big push to convert some more cars to FVM wheels with one resistor-equipped axle per car.  As I started dipping into my newly acquired Scale Trains branded FVM wheels with .540" axles (3601s), I soon realized that these do not roll in the 100-ton BLMA/Atlas trucks!  (Nor in my MTL 1035 trucks, though they do seem to work fine in the MTL 100T trucks that ship with the TBOX cars.)  The axle length does indeed check in at .540" on the nose with my callipers, but the BLMA wheels are more like .537-.538" and that seems to make the difference between rolling and not rolling in those trucks.   I'd be curious to know if anyone else has experienced this.

[DeltaBravo]

With operating sessions starting up again, I recently made a pretty big push to convert some more cars to FVM wheels with one resistor-equipped axle per car.  As I started dipping into my newly acquired Scale Trains branded FVM wheels with .540" axles (3601s), I soon realized that these do not roll in the 100-ton BLMA/Atlas trucks!  (Nor in my MTL 1035 trucks, though they do seem to work fine in the MTL 100T trucks that ship with the TBOX cars.)  The axle length does indeed check in at .540" on the nose with my callipers, but the BLMA wheels are more like .537-.538" and that seems to make the difference between rolling and not rolling in those trucks.   I'd be curious to know if anyone else has experienced this.

I had this issue with a recent batch of Intermountain wheels. I ended up spreading the trucks. You could also ream out the axel point cavity.