After some considered experimenting, I have found that the Branchline six wheel passenger truck seems to have maximum rollability when fitted with the Reboxx 0.990" axles. The improvement is quite significant.
The truck used for the experiment was taken from a new Pullman kit. When assembled according to instructions, the middle wheel is "trapped" by the bolster, and cannot be removed. To avoid this issue, I enlarged the bolster locating holes on the truck side frames with a sharp #40 drill (.098"). by making this simple change, a dry "slip fit" is created that is tight enough to still hold bolster to side frame extremely well, but which can still be easily drawn apart to change wheels.
I tacked each bearing insert into the side frame with a tiny drop of GOO. I checked each bearing cap for flash that could and would prevent these inserts from being "driven home".
The truck was tested on a roll tester (Reboxx RT200), in each instance three times, first with the truck "light", and then with a 3 oz. lead weight on the bolster.
The truck was first tested with the sintered metal wheel sets provided by Branchline in the kit. The axles measured almost exactly 1.000", a somewhat unusual length IMHO. (shorter than the NMRA nominal of 1.015"). When in place, however, they fit tightly with virtually no end play, a warning that longer axles (i.e. Reboxx, Kadee, IM and others) would not be likely to work as well.
The results are reported in the number of "rolls" back and forth that are attained in each instance, the count including a final roll even if movement was barely perceived.
Branchline Wheels:
- Without weight: 8, 8, 8. Poor.
- With weight: 17, 14, 14. Acceptable, better than average.
Reboxx 0.990" axle wheels:
- Without weight: 18, 17, 19. Very good- excellent.
- With weight: 23, 21, 22. Superior, near the top.
Conclusion: the 0.990" wheels seems to provide about a 50% increase in rollability- a not inconsiderable practical improvement, especially when we contemplate hauling these cars around with model steam locomotives that often have a hard time pulling their own weights. Note that the observed rollability of 21-23 is close to the maximum commonly, but *rarely*, measured (25-26).
The Reboxx wheel numbers are:
#36-1-0.990 one wheel insulated.
#36-2-0.990 two wheels insulated.
BTW, high grade wheels of the same axle length from other manufacturers would reasonably be expected to achieve the same results.
Did I try other wheel sets? I did try the Reboxx 1.000" axles, and by bench inspection alone I could see that they had little more rollability than the Branchline wheels (again, no end play). If I had had .0995" axles, I would have fully tested them, however.
In the final analysis the superior results already achieved would probably have made further experimentation a moot issue.
Notes on truck assembly/disassembly:
I will have to admit that assembling these handsome trucks "cold" was at times a very frustrating experience because almost none of the locating pins of the various parts would fit easily (or at all) in their respective receiving holes. This was made especially difficult because the tiny size of the pins and holes conspired with the black-on-black plastic parts so that even with sun-like lighting and a variety of Optivisor lenses and loupes, I simply could not see well enough to fit the parts (the urge to kill, but....who??).
I solved the problem to a great extent by then routinely opening all of the holes with sharp drills, all done by hand with a pin vise:
- Bolster pin holes in side frames: O.098" #40 drill.
- Brake hangers: 0.028" #70 drill.
- Brake beams: 0.024" #73 drill.
- Side bearing arch: 0.038" #62 drill.
I discovered that the thinner 0.088" thickness of the Reboxx wheels allowed the center wheel to escape the "trap" caused by the bolster (see above). In this regard, all wheels can be removed by only separating the bolster from one frame. To allow this in the future while at the same time keeping the truck tightly assembled, I have not glued the bolster to the side frame on one side. Instead, with bolster and frame held tight together, I have drilled through the frame locating hole collar right on through the bolster pin to the other side. I have then inserted through the hole a locking 0.015" brass pin with an L-shaped end left on for future extraction (if ever necessary).
The leaf springs also do not set in tightly because of the thickness of the paint on both the male base of the spring its female mount on the respective side frame. They will not lock or stay in place together by themselves. I scrape both to create a good gluing surface. Because of their feather weight, however, keeping the springs in place and in alignment while the glue or solvent sets can be dicey. What I have done is then to set the springs in place with the tiniest drop of GOO. Now, as the GOO wicks off and begins to dry, I can now apply some ACC to the joint from the inside of truck frame (which one can now do without the springs falling off!).
BTW, these trucks truly look great with these more scale-appearing wheels in place. If ever available separately, I would consider replacement of many brass trucks with these trucks, even if only temporary to allow free-rolling operation.
Now, I look forward to the rest of this wonderful kit!
Denny
