Metal Wheelset Incompatibility

[jereising]

The bushing is hidden away on the right.  It is FVM - and it IS in gauge.  As I'm sure you know, FVM could be wide gauged but you'd likely see it, but could NOT be narrow gauged because of the way they're built.

And now the issue becomes apparent.  And yes, they're .540.  Hence the thread title.  Sigh.

[peteski]

So the bottom wheelset (with 2 insulating sleeves is BLMA?  Why is is riding off-center?  Or is there that much play between axle and the bearings?

To me the problem seems obvious: The BLMA truck assemblie's inside dimension seems smaller than other brand of trucks, and that causes wider-thread wheelset's wheels to rub against the inside of the sideframes.  There is nothging inherently wrong with either the FVM wheelset or with the BLMA truck.  They are just incompatible. Or am I missing something here?

Wheelsets with wider tread, by design, will be wider between the outside wheel faces than ones with narrow thread. 

[Mike C]

This should illustrate my dilemma:



Treads measure .0625 and .0760

Flanges are .0070 and .0190

The narrow wheelset with low flange is BLMA, and the wide with higher flange is FVM.  And that FVM is NOT the widest I have.

Putting aside temperature and humidity considerations, it is obvious there is a problem.

All I can do is try and find a wheelset with a wider tread (and higher flange than the BLMA.

  I think if it were me I would take a large woodworkers file ( fine tooth) to the backs of the truck frames . Probably wouldn't take more than a few swipes on each side . Assuming that the FVM wheelsets are corectly gauged.   ..Mike

[thomasjmdavis]

I suspect it is really just a matter of addition-
https://www.nmra.org/sites/default/files/standards/sandrp/pdf/S-4.3%202010.02.24.pdf

Per NMRA-    back to back dimension-             0.294
                 2 flanges @.024 ea                        .048
per Jim's measure 2 treads @.075                   .150

Total                                                            0.492

Which, if everything is within tolerance, leaves .024 of axle on either end to get into the little conical depression in the journal.

My trusty caliper measures the BLMA axle (from a BLMA 70 t friction bearing truck) as .539, but the inside measure of the space between the truck frames/journals as .465

So, I don't think a wide tread is going to fit.  Width over faces of wheels (if my addition was correct) is .492, space between journals is .465

[GaryHinshaw]

[I did the same exercise as Thomas while he was typing.  I get slightly different results.]

Okay, I decided to snoop around my collection and take some measurements.  I have a lot of 100T BLMA trucks and among them, I have at least four different types: two finishes and two sizes.  The two finishes are a matte and glossy (Delrin); I believe the matte ones are the first generation.  There are also two lateral frame-to-frame spacings, measured at the bolster: 0.450" and 0.457"; not noticeably different, but big enough to measure.  I have examples of all four finish/size combinations in my stock.  (I even have a new Atlas BX-177 car that has one of each size on the same car.)  The original reefers predominantly have the matte finish and the narrower bolster span.

The BLMA wheels have the follow measurements (uncertainty is ~ +/-0.001"):
axle length - 0.537"
face-face distance - 0.437"  (only about 0.013" clearance in the narrower truck)
wheel thickness, including flange - 0.067"
flange diameter - 0.265"

The FVM narrow tread wheels have:
axle length - 0.540"
face-face distance - 0.421"  (0.029" clearance in the narrower truck - no issues)
wheel thickness, including flange - 0.060"
flange diameter - 0.256"

I also have some FVM wheels that ship with their refurbished Red Caboose hoppers.  These have a larger flange and tread than the original FVM wheels, but I don't think they are as wide as yours.  Here are the measurements:
axle length - 0.538"
face-face distance - 0.439"  (similar to BLMA)
wheel thickness, including flange - 0.069"
flange diameter - 0.274"

It looks like you have the narrower BLMA trucks, and I'm guessing your FVM wheels have a face-to-face spacing of about 0.450", which will indeed rub on the frame.  The narrow tread FVM wheels (when you can get them) will work fine in these trucks, but they may or may not solve your derailment problem...

[jereising]

Good to know it's as crazy as I thought.

So as soon as the latest release of FVMs are out there, I'll do some serious replacing on that reefer train.

I would bet that will cure the derailment issue.  My trackwork isn't THAT bad...

I can easily run a 114 car earthworm with nary a problem - that train has mostly Intermountain, 18 exact Rail, 6 Scale Trains and two M-T.  All cars except the Scale Trains cars have the True Scale coupler.  That train will run all night without a problem.  There are no BLMA wheelsets on that train.

And my BLMA spines - both 3 and 5 - run flawlessly.  But those I suspect have different wheelsets and probably trucks as well.  I know the first reefer run had issues, and once I get them taken care of that should do it.

Thanks to everyone for digging in and pretty much confirming what I see.

[AKNscale]

I know I was having a problem with the BLMA trucks being unable to “flex” with my track. I replaced them with MT trucks and FVM wheels and haven’t had issues since.

[jereising]

One of my standard pre operation tests before any new car hits the layout is to make sure there is enough rock-ability in each truck.  That seems to work well.  I also check to make sure the wheels roll freely and there are no obvious problems like a dangling coupler trip pin.

I've had an idea and am trying something - necessary materials should be here Monday.  A report will be made...

[Boilerman]

I use Atlas code 55 track (about 350 ft.), turnouts (about 150 mix 5's & 7's) and use mostly MT low profile plastic wheels on my rolling stock and have had nearly zero problems with derailments other than when I do not have a switch thrown correctly for the direction of the train coming in to it.
I have moved my layout 2 time and have stored it for a couple of years between setting it back up and only had to replace track were I cut the benchwork for transporting.
I would suspect the rolling stock wheels and or trucks may be the issue of the derailments you are experiencing?

[jereising]

From earlier in the thread:  the culprit are the first run trucks from the BLMA ARMN reefers.

Which were factory equipped with BLMA metal wheels.

I would not return to plastic wheels for anything, let alone attempt putting them on those reefers...t'would be an abomination.

[jereising]

The parts got here earlier than originally thought - I noticed Tangent Models had 36" wheelsets, figured I'd give 'em a shot.

No joy, other than lightning fast service, and are beautiful. They are virtually identical to the original BLMA wheels and measure the same. 

I had hoped...

And yes I have done the filing thing, but I am reluctant to do this if not absolutely necessary.

So it's now wait until a restock by FVM.  Guess I'll keep the reefer train in staging until then.

Thanks everyone for the help and suggestions, much appreciated.

[sundowner]

I had this issue with the current run of Atlas/BLMA ARNM reefers and my solution was to put one MT bolster washer on the bolster to raise the car and give the truck some up and down movement. It bother me that the trucks by themselves would roll forever but when on the cars they were drag down. You barely notice the increase ride height but and you only need two locos to run a 24 car train.

And since the BLMA truck is the same as the Tangent truck I did the same to the Tangent hoppers because I was having a similar issue. Craig collaborated with the Tangent Folks on a few cars.

It looks to me like the BLMA truck is great for lowering othe manufactures cars but on there cars they make there cars too low.

[nkalanaga]

If you don't want to use the washer you can also scrape or grind a hole in the floor, if the problem is the wheels rubbing on the floor.  It will never show, and should solve the problem.

If the axle is rubbing on the draft gear, that's another matter, and the washer is probably the only solution, unless you can find a thinner axle.

[GaryHinshaw]

Jim, have you figured out why the BLMA wheels derail when/where the FVMs don't?  Just curious.

[jereising]

Jim, have you figured out why the BLMA wheels derail when/where the FVMs don't?  Just curious.

Gotta be either the tread width or flange depth.  The BLMA wheel profile is scale or nearly so, and because of this, both are the smallest in the hobby.  Unfortunately my - and I suspect most - trackage is not perfect.  This is an area where things simply do not scale down.

I need to catch it in the act, and have not been able to do so as yet.  It only happens when your back is turned.  It could be as simple as a car rocking a bit too much.