Random part of the day: Train Wheel, Dia. 50/60

Looking forward to see these in a MOC that can run on regular Lego train tracks.

Ah, the new super-driver that’s only available in this year’s 76405. I was about to tell a story about the smaller, formerly-large, flanged/blind/flanged trio that come in a bag together, but it’s good to see that brand new elements are occasionally getting picked for NSRPotD…

@HOBBES:
That might be difficult without a blind equivalent. The use of three of these per side pretty much guarantees the giant Hogwarts can’t handle curves of any but the most gargantuan radius.

Or people bought them from BaP.

@PurpleDave said:
"Ah, the new super-driver that’s only available in this year’s 76405. I was about to tell a story about the smaller, formerly-large, flanged/blind/flanged trio that come in a bag together, but it’s good to see that brand new elements are occasionally getting picked for NSRPotD…

@HOBBES:
That might be difficult without a blind equivalent. The use of three of these per side pretty much guarantees the giant Hogwarts can’t handle curves of any but the most gargantuan radius."

True. The pack you are mentioning had a wheel with no flange at all (I guess that's what you call blind) to allow the body of the engine to slide over the tight radius of the tracks.

But let's not discount the ingenuity of Lego train maniacs. I have seen people putting those on axles with a lot of leeway to allow the whole axle to move according to the tight radius of the track (look silly when you look at it on the curve but at least it works!) This set up also prevent the use of drive rod (which somewhat defeat the purpose of large wheels for steam engine).

I wanna see somebody make a Stirling Single with this piece.

https://en.wikipedia.org/wiki/GNR_Stirling_4-2-2

Looking at this part really makes me wish TLG or someone else would make a modern/solid version of something like this, for reeeeeally big diesels and diesel-electrics.

@HOBBES:
Yes, “blind driver” is the proper term for a steam driver wheel without a flange. I’m not a trainhead, but there are enough in my LUG that I quickly learned to stop calling them anything like “flangeless drivers”. Anyways, the two benefits of using blind drivers is it allows you to navigate tighter turns, and it allows you to bunch up the drivers until the “tires” (stupid as it sounds, that’s the rim that carries the weight on the rail) are just about touching. As you’ve apparently seen with MOCs, you can also put sliding axles in that will shift into the outside rail on tight curves, or articulated bogeys that will pivot to follow the path of a curve, both of which were done on real steam engines. All of this was done to put more powerful engines on the tracks, at a time when each one needed a full crew. To increase power, you could make the engine longer like the Big Boy, or make the wheels bigger like the Allegheny, but both solutions had their own problems.

@Murdoch17:
I want to say no, because it looks stupid with that one oversized driver, but until they make a blind driver to go with this, that might be one of the few engines that these are suited for. I know there’s a lot of interest in making the 1601 Allegheny that we display near at The Henry Ford Museum, but I think you’d need blind drivers to get the wheel spacing right, and even these wheels might not be tall enough to match the Stirling or Allegheny at minifig scale.

Completely unrelated to this piece, but using the smaller version of this part I recently put together Doc Brown's Jules Verne time train from the third back to the future movie. The wheels fold and it is my first custom Lego train as well!

https://www.instagram.com/p/CkNknB-p0KX/

If you forget realism and remove the drive rod which connects all the wheels on one side to the piston then each pair of wheels could be allowed to rotate in order to go around L-gauge curves. Motorizing all this could be an interesting build and fun to watch.

Even the Pacific in 7777, with much smaller wheels, articulated the front wheelset separately from the rear two.

I wonder whether an Atlantic (ie two wheelsets rather than three) would be possible with these wheels?

@PurpleDave said:
" @Murdoch17 :
I want to say no, because it looks stupid with that one oversized driver, but until they make a blind driver to go with this, that might be one of the few engines that these are suited for. I know there’s a lot of interest in making the 1601 Allegheny that we display near at The Henry Ford Museum, but I think you’d need blind drivers to get the wheel spacing right, and even these wheels might not be tall enough to match the Stirling or Allegheny at minifig scale."

Back in the day, those one driver locos were pretty sexy... and they got bigger than that! Some broad gauge trains (7 foot between rails) had eight foot wheels! https://en.wikipedia.org/wiki/GWR_Iron_Duke_Class

As for your Alleghany, it would be at least three feet long with these wheels! The real engine class' wheels appear to be around five feet in diameter, and mini-figures are too wide and too tall (like a elongated human) at the same time, so mini-figure scale is anything but easy to figure out. You're best bet is something in between: XL size wheels from Big Ben Bricks would be about right I think, vs. the XXXXL size wheels you want to use from LEGO... plus, BBB has blind drivers too! see here for a handy custom wheel chart I found: https://bricksafe.com/files/supertruper1988/train-stuff/Wheel%20Sizes%20Final%20with%20Scales.png

The wheels being discussed would be 15 on this chart.

@ambr:
Official curves are a problem for opposing wheels on a single axle (they need to rotate at different speeds as they travel different distances) and linked axles (mostly during transition into and out of curves as each axle experiences speed changes independently, but are forced to react to it in unison). You can mount each wheel fully independently using non-friction axle-pins, but then they wobble a bit, plus you can't exactly use them to drive the locomotive.

Real train wheels and curves actually have a very complicated geometry that causes the diameter of the bearing surface to change just enough that paired wheels can rotate the same number of rotations, while traveling different distances on curves, without causing one wheel or the other to slip on the rail. I don't know that LEGO trains got this geometry perfect, but they did try to emulate it. Regardless, another option is to remove the traction bands from select wheels to give them the freedom to slip, while their mated wheels cannot.

@Murdoch17:
But the Stirling you linked to has 8'1" wheels. 8'0" is smaller. Anyways, the driver diameter was 5'7" on the Allegheny. According to your chart, that would be pretty close to No11 (XL) for 1:48, and what would be a No14 (XXXL) at 1:38. XXXXL would be No15, so it's actually a tossup between that (slightly big) and the largest wheel on this chart (No13, slightly small) if you want to build to 1:38 scale. And look at a side shot of the full engine including the tender. The tender alone (which carried over 270,000 pounds of fuel, water, and sand) was about the size of many modern diesel engines. This would never be a petite thing. 3' for the engine and tender combined seems very reasonable.