What size are the standard Lego steam drivers in minifig scale?

[SteamSewnEmpire]

I'm just curious. I rarely use these wheels in designs (I'm not a snob - I just mostly build passenger steamers), but after creating my Reading 2-8-0 and lining it up next to diesels, I realized that it looks kind of short (rail head to stack-tip). This is generally not a problem for either my steam locomotives, or for RL late-generation (say, post 1910 or so) steamers - as you can see here, this 2-10-0 is basically the same height as a GE Genesis locomotive.

That engine's drivers are 56" IRL - so the proportions of the 2-10-0 should be relatively similar to my 2-8-0 with its 57" drivers. But... they aren't. My engine is a good brick lower than most of the diesels I have done (all of which are consistently scaled against each other).

So... does anyone know approximately what the diameter in inches (in minifig scales) the Lego wheels are? Typically, I go by the rough estimate that <60" diameter wheels are stock Lego; 60"-70" are Big Ben XL, and 70"+ are Big Ben XXL... but that seems to have broken down in this instance.

I have a feeling that, given how a lot of people here build their engines based on blueprints, someone is running around with this answer already :). I'm just not a strong math guy, and would rather leave it to the experts.

Edited July 26, 2020 by SteamSewnEmpire

[Daedalus304]

"Minifig scale". Nebulous thing. Also, in terms of precision, kind of meaningless. Minifigs don't fit cleanly into any scale. Scale off height, they're too wide, scale off width they're way too short. Scales where they look "Good" range from 1:38-1:55, really. You'll find dozens and dozens of models touted as "Minifig scale" that all look good with figs but are outrageously out of scale with each other. For something like train building, you need something more solidly defined or you'll end up all over the place.

If you're scaling at 1:48, which is pretty standard for 8-wide, then 57/56 inch drivers should be just shy of 9.5 plates. The LEGO train drivers are basically perfect for that.

In 1:48, you're looking at:
XXL = 80"-ish
XL   = 70"-ish
L     = 56"-ish
M   =  45"-ish

All of which are "give or take an inch or two". There are also wheels out there that are in between these sizes so you can get a bit closer to "perfect" as needed.

For scaling calculations I'd recommend using http://studs.sariel.pl/. Enter the scale you want to work with, enter the measurements, and it'll let you know what to shoot for.


 

[supertruper1988]

Here is a size chart I put together:

Most North American modelers seem to use 8 studs 10 feet which converts to 1 plate is 6" you can then do a little math and get the size. For reference, LEGO makes the S and L sizes. Big Ben Brick makes S, M, L, XL, and XXL. The other sizes in between were conceptualized and developed by @Shupp The XLL size was suggested by Matt Csenge and Developed by Scott Hoffmeyer. 

[SteamSewnEmpire]

How is an intermediate size - such as LL - mounted? If you drop down a plate from XL, that would force you to use L size, correct? So do LLs require special 'halfway' approaches, such as mounting in the bottom hole of 43857 set on its side?

Would that correspondingly require special mounting for the lead and trailing trucks?

What I'm talking about with 'halfway' mounting is something like this:

Is that what's required for an LL wheel mount?

Edited July 27, 2020 by SteamSewnEmpire

[supertruper1988]

There is honestly enough flex in the trailing or leading trucks normally that you will not need to worry about the half plate difference. If it is affecting the design, you would either need to mount the pilot and trailing trucks differently or use a size that is smaller but a whole integer number of plates from the driver size. like MS instead of S for the pilot wheels. 

Also the plate sizes mentioned above are the diameter. The center of the wheel is 1/2 plate different from its neighbor. If you have to have whole plate mounting height differences for your design, then you will need to use sizes that are multiples of 2 away. I hope that makes sense. 

[SteamSewnEmpire]

22 minutes ago, supertruper1988 said:

There is honestly enough flex in the trailing or leading trucks normally that you will not need to worry about the half plate difference. If it is affecting the design, you would either need to mount the pilot and trailing trucks differently or use a size that is smaller but a whole integer number of plates from the driver size. like MS instead of S for the pilot wheels. 

Also the plate sizes mentioned above are the diameter. The center of the wheel is 1/2 plate different from its neighbor. If you have to have whole plate mounting height differences for your design, then you will need to use sizes that are multiples of 2 away. I hope that makes sense. 

Yeah, it does. And after I put all that work in to make the "halfway" mount work on my next loco. Lol. :P Oh well. Regular mounting is more stable anyway. Thanks.

Edited July 27, 2020 by SteamSewnEmpire

[zephyr1934]

9 hours ago, SteamSewnEmpire said:

Would that correspondingly require special mounting for the lead and trailing trucks? 

If you use a technic plate and pin to attach the pilot/trailing trucks, there should be more than a plate worth of "play" and you might not even notice the difference.

If you use brick built trucks I believe if you build studs down you will get a half plate offset from studs up, so you could make up the difference in your trucks too.

 

9 hours ago, SteamSewnEmpire said:

What I'm talking about with 'halfway' mounting is something like this:

Is that what's required for an LL wheel mount?

This build has an even number of technic holes vertically, to get a half plate offset (really a 2.5 plate offset) just add or subtract technic holes vertically. As for the half stud offset horizontally, I think many builders use technic bricks and use either a 1x1 or 1x2 with two holes for the axles that are off by 1/2 stud. But if you can come up with a solution like you have above, I'm sure a half plate offset is nothing to overcome.

[zephyr1934]

On 7/27/2020 at 12:48 AM, supertruper1988 said:

Here is a size chart I put together:

Most North American modelers seem to use 8 studs 10 feet which converts to 1 plate is 6" you can then do a little math and get the size. For reference, LEGO makes the S and L sizes. Big Ben Brick makes S, M, L, XL, and XXL.

Is the minimum spacing between BBB XXL drivers 5 studs, the same as the XL drivers?

[supertruper1988]

On 8/23/2020 at 12:41 AM, zephyr1934 said:

Is the minimum spacing between BBB XXL drivers 5 studs, the same as the XL drivers?

No its even more 5 studs is 12.5 plates and the XXL are 13.5 plates. I woul recommend 6 studs center to center (so a 7 L beam)

[zephyr1934]

17 hours ago, supertruper1988 said:

No its even more 5 studs is 12.5 plates and the XXL are 13.5 plates. I woul recommend 6 studs center to center (so a 7 L beam)

Thanks, and yes, that makes sense. I was thrown off by the two sample images on BBB's webpage that show tight spacing between XXL drivers. There are obscured half stud offsets in there.

 

 

[SteamSewnEmpire]

Does anyone sell XLL drivers at the present time? I'm tinkering with a design, but don't want to move forward if I can't start with the right wheels. Thanks.

*Edit* Whoops, never mind. Found 'em. They're inexpensive, too!

https://www.bricktraindepot.com/product/3d-printed-xll-spoked-lego-compatible-wheel/

Edited August 31, 2020 by SteamSewnEmpire