BLI T1 question

[ek2000]

I purchased a new BLI T1 and noticed that the wheels in the center don't make contact with the rails on some spots. I realize the center wheels don't have flanges but don't know if they should be this much off. Have you noticed this on your T1. Not sure if this is a defect or they all come this way. Thanks.

[glakedylan]

i do not see how that could be the way it was designed and produced to ride on the rails.
did you buy this from a hobby shop?
i would think it the very least it needs adjusting (i know nothing about the suspension
system on these and if they can be adjusted accordingly)
if a hobby shop purchase, return it for repair or replacement.
i personally would seek replacement.
hope it all works out for you


sincerely
Gary

[ek2000]

i do not see how that could be the way it was designed and produced to ride on the rails.
did you buy this from a hobby shop?
i would think it the very least it needs adjusting (i know nothing about the suspension
system on these and if they can be adjusted accordingly)
if a hobby shop purchase, return it for repair or replacement.
i personally would seek replacement.
hope it all works out for you


sincerely
Gary

Thanks, yes, I purchased from factory direct hobbies. I'll contact them, hope they agree to send a replacement. In some sections especially curves, I can see daylight between the wheel and track, they are off by a couple of millimeters, if not more.

[ek2000]

I checked the review of the T1 posted by MBK and interestingly, that model seems to have the same issue as well. Check out 1:24, 1:50 & 1:55 and either the blind/inner wheel facing the camera or on the farther side seems to be off the rail. Now I'm even more curious to know of this is a localized issue or prevalent across all.

[mmagliaro]

I don't own one.  I've just looked at a lot of photos of them because the PRR and the T1 have always been favorites of mine.  I'd say your center drivers look a little high, but the same as the ones in the MB Klein demo video you mentioned.  It's a design compromise.  The loco is rigid-framed, with large drivers, and a big gap between #2 and #3.  That gives it an unusually long rigid wheelbase that cannot negotiate reasonable curves without some sort of design "cheat".
Having labored to build one of these for myself many years ago, I cycled through all the possibilities.

1. Make the engine trucks or frame jointed in the middle so they can pivot a little to make it around curves.  I tried, but discarded this idea because it made the drive train (worms, motors, frame, and a pivot within a rigid shell) too hard to build

2. Blind the center drivers (like the BLI) model.  I had mine working this way for quite some time.  But the center drivers will drop inside the rails on curves and then get "stuck" trying to climb out when the engine exits a curve.  This can be fixed by making the drivers "float" a little above the rails, and by grinding the driver treads at a slight angle on #2 and #3 so that if they do get stuck, they can kind of slide up and out.  I have seen the BLI HO version and I'm pretty sure I remember noticing the driver treads having a slight angle to facilitate this.
But after a lot of testing and running, I found I had to make the drivers ride too high to reliably work, or put up with them sometimes getting stuck in a curve and causing a derailment.  So I discarded this approach

3. Leave flanges on all the drivers, and allow for enough side-to-side play in the drivers so that they can negotiate curves.  This introduces complications with the rods, making sure they can tolerate all that lateral motion without rods getting caught on crankpins and so forth.  But ultimately, this was the design that looked and ran the best, so it's what I ended up with.  It cannot handle less than an 18" curve, but that doesn't bother me.

I would think BLI considered all these options, and settled on riding the center drivers a little high.  It may not look so hot, but the rest of their engine is gorgeous and the running reliability is important, so floating drivers it is.  Plus, they probably don't want to restrict it to 18" curves because, you know, sales.  So lateral play was probably not a good solution for them.

[peteski]

I have this loco.  It has a rigid frame (no articulation), and the middle 2 drivers are blind.  I only ran mine couple of times and didn't notice any gaps.  However, since the drivers aren't sprung, I suppose that there can be slight gaps on uneven track.  As designed, those 2 drivers are pretty much cosmetic.  Since there are no flanges, you can easily see the gap.

I highly doubt the gap is "couple of millimeters".  That would be huge!  2mm would be 0.079"!  That is pretty much the height of Code 80 (N scale) rail.  If the center drivers were mounted 0.079" higher than the other drivers, I suspect there would be binding in the siderods and the loco would not run.  Your photo doesn't show those drivers being up over the rail anywhere near the height off the rail.

The 1:1 loco did not have blind drivers in the center.  That bothers me on this model.  I checked and I think that this mode has enough lateral play in the drivers to run well with all 4 drivers having flanges. I bought enough drivers to convert it too all-flanged drivers, but it turned out to be a more complicated than I envisioned it, so this became one of my unfinished projects. But I'll finish it someday.   

EDIT: I took my model out and on my workbench placed it on a brand new tangent (straight) piece of Kato Unitrack.  Even though this loco has 2 engines, lets call the drivers #1 - #4 (#1 is front).  On mine both wheels on #2 axle touch the rail.  On #3 axle the left side driver touches the rail, but on the right side there is a slight gap.  The gap is small - I can pass a piece of paper under it, but I feel resistance. So, the gap is probably around 0.004".  So I have to agree that your model is not quite right.

[thomasjmdavis]

Are the treads of the non-flanged drivers at the same angle to the face of the driver as the flanged drivers?  In my experience with other locos (I don't have a T1), the flanged wheels have a slight angle- that is, get increasingly larger in diameter, towards the flange, and then curve into the flange. And blind wheels have treads that are 90 deg. to the face.  If so, then it would be logical that on trackwork with tight gauge, or if the wheelset is slightly wide gauged, the loco would ride higher (although more likely a few thousandths than a couple millimeters). And even with everything precisely in gauge, the blind drivers would ride just slightly above the rails- because the inside of the driver, riding against the track, would be just slightly larger in diameter. And the longer the loco, the more pronounced it would be on curves. And I haven't done the math, but my instinct tells me that the larger diameter the drivers, the more notice-able.

Just to know how bad it is, I would suggest getting hold of a feeler gauge (I am sure there is one in my own garage, but I have no idea where- at some point it migrated to the wrong tool box).  If it is .005 or more, you could also get a close approximation by using various thicknesses of styrene or brass you happen to have lying around.

[ek2000]

Thanks everyone for your inputs. I watched more videos of the T1 including John Colombo's video on the speaker transplant, review in Trainworld etc and I see the Right side wheel on axle 3 being consistently higher off the rail. That seems to have been BLI's intent.

I also followed Pete's approach (pic attached) of laying the locomotive on a single section of track on a flat surface. I find that the Left wheel on axle 2 (from front, ignoring pilot) is very very slightly off the rail, hard to spot easily, but just a papers thickness while the rest with the exception of the right wheel on axle 3 are all touching the rails. The blind wheels in general seem to be slightly higher and that may be by design. While I wish that wasn't the case, I can appreciate it better thanks to the comments posted by @mmagliaro. Besides, when viewed from a distance, it can barely be spotted. The only other concern I have is performance on switches and turnouts, i'm not sure if the loco will have a higher tendency to derail or stall due to the blind wheels not making good contact with the rails.

A big shout out to Joe from Factory Direct hobbies, who responded promptly and agreeing to send in a replacement locomotive along with a prepaid label for shipping the one I have. This gives me an opportunity to compare the 2 locos together to see if the one I have is an exception from the rest. Many hobby stores don't accept returns or exchanges on dcc products and locomotives so I'm glad FDH agreed to. Best way to respond in kind to such consideration is through more purchases, and that's what I will do. I will try to post the comparison picture when I have the 2nd loco.

[muktown128]

I'll second the good customer service from FDH.  I purchased a Bowser PRR N5 cabin car from FDT (now FDH) a few years back that was damaged when it arrived.  I contacted them about the issue and Joe was very responsive and took care of the issue. 

[mmagliaro]

I'm curious.  Can you put calipers on your drivers and see if #2 and #3 are just a slightly smaller diameter?  I'm wondering if they implemented this scheme by using smaller drivers, or by having the same size drivers with no flanges, just set a few thou higher into the frame.  I suppose if I were tooling an engine from scratch, I would be inclined to use smaller drivers, because then the frame slots are all uniform, and the locaiton of the rod holes is the same on all 4 wheels.  It makes the whole thing easier to reliably build.

Peteski, when you said you bought extra flanged drivers with the intent of swapping them in for #2 and #3, I chuckled, because I was wondering if that exact thing might be possible.  Sorry it turned out to be more difficult than you expected.  Are the rod holes different or what?  I would have thought those could just swap in there.

[Jbub]

What I'm seeing when zoomed in to 500% on a 27 in monitor is that the "tire" size compared between the blind and flanged driver lines up above the rail. It seems to me  that the RP (can't remember which number) for wheel tapper is making the flanged driver bigger at the flange where the blind driver is being cut straight across. This makes it sit above the rail.

[peteski]

Peteski, when you said you bought extra flanged drivers with the intent of swapping them in for #2 and #3, I chuckled, because I was wondering if that exact thing might be possible.  Sorry it turned out to be more difficult than you expected.  Are the rod holes different or what?  I would have thought those could just swap in there.

No, it is little more complicated than that.  I'll document my conversion (when I get to it) and post a write-up here.

[glakedylan]

this is what i based my reply on
red lines are straight and parallel (90 degree angle to photo edges)
yellow lines show where the locomotive is following a curved arc
rather than a straight line, especially at the drivers
as for the rest of the yellow lines, there do not seem to be a straight
line on this locomotive, either by design or prototype
thus, i suggested their could quite possibly be an error in this unit's
manufacturing and/or assembly
never noticed a steam locomotive with all drivers not making
contact with rails
but the explanation of blind drivers and curved track makes much sense
this still seem to be somewhat extreme to my eyes
unless, of course, it is distortion in the camera lens and image mangagement


thanks!
Gary

[ek2000]

Here are the 2 pics. The one I originally had and posted about has 1 wheel on each side not making contact with the track while the replacement has both blind wheels on the same side not making contact and appears slightly better off than the first one