Train Wheel Size Naming

[supertruper1988]

Hello LEGO Train fans! @Cale, @coaster, and myself were recently discussing the confusing nature of the naming convention we have adopted for train wheels. It made sense for a time when only a few sizes were available. We came up with this solution where the size becomes a number. All of the wheels are XX.5 plates in diameter so the number would be whole integer number of plates that corresponds to the wheel size.

What are your thoughts? We will also be reaching out to Big Ben Bricks if this sizing scheme seems reasonable to most.

 

Edited December 5, 2020 by supertruper1988

[Jeffinslaw]

I approve!

-Jeffinslaw

[Andy Glascott]

Makes a lot of sense, though I’m curious about names for the three blue/proposed sizes, XS, XXS and Tiny? 

[mark6399]

I like it!

10 minutes ago, Andy Glascott said:

 three blue/proposed sizes, XS, XXS and Tiny? 

Hahaha! I propose XS, XXS and Itty Bitty, haha! 

[supertruper1988]

29 minutes ago, Andy Glascott said:

Makes a lot of sense, though I’m curious about names for the three blue/proposed sizes, XS, XXS and Tiny? 

Those sizes are what prompted the discussion actually. What do we call them? So we decided numbers were better than letters because they could be related to the actual Size instead of arbitrary letters. 

Edited December 5, 2020 by supertruper1988

[M_slug357]

I didn’t even know that LL and xLL were available options....!

Also, I think anyone and everyone that does 4-wide Narrow Gauge is interested in those proposed wheels...!

[moparacker]

Really neat idea!

I feel that the final image could be used for more than just size reference (especially to new builders) and could use a tweak. For the #2 and #5 wheels, the cross axle connection should be changed to a representation of the connection used by those wheels.

[M_slug357]

@moparacker Theres nothing wrong with the #5 wheel having an axle. Thats the standard wheel size from Lego. 

[zephyr1934]

I like the general idea, but there is a level of secret-language if you use N to represent N.5. It decouples the name from the meaning. With the current naming I never really spent much time thinking about the diameter of the wheels, just the stud spacing necessary for a given size (stepping up by half studs every so often). Naming the wheels accordingly to their actual diameter brings clarity and efficiency to their name.

I would suggest keeping the .5, so L would become "9.5" and the more verbose version would be "9.5 plate diameter". That way the name has a direct explicit meaning and as a newbe you do not have to learn that you need to add .5 to the number. More importantly, the language that develops around the wheel names keeps the connection to the plates (again, the verbose "plate diameter"). As a community we've settled into R40...R120 and beyond for curves because it makes intuitive sense. If we just called them a "40 curve", "56 curve", etc. the context would have been lost, especially if we called them an even more abbreviated #4, #5, .... If we go with integer names for the wheels it will quickly lose the connection to the number of plates, it will be clearer as to which size is larger than another (better than XLL), but still not clear as to why.

As a result, if integers represented half plate diameters in this naming scheme at some point someone will then introduce a 9.5 wheel that is actually 10 plates in diameter (or worse, some random number between 9.5 and 10.5) and completely undermine the clarity objective.

So I would strongly suggest keeping the .5. The advanced builders can then talk about a 9.5 wheel. The wheel sellers (and rod makers) can then talk about a "9.5 plate diameter wheel," in their product listings and everyone is a little more knowledgeable.

[ALCO]

I like it. And I think @zephyr1934 has an excellent point being the most prominent rod supplier. 

[supertruper1988]

5 hours ago, zephyr1934 said:

I like the general idea, but there is a level of secret-language if you use N to represent N.5. It decouples the name from the meaning. With the current naming I never really spent much time thinking about the diameter of the wheels, just the stud spacing necessary for a given size (stepping up by half studs every so often). Naming the wheels accordingly to their actual diameter brings clarity and efficiency to their name.

I would suggest keeping the .5, so L would become "9.5" and the more verbose version would be "9.5 plate diameter". That way the name has a direct explicit meaning and as a newbe you do not have to learn that you need to add .5 to the number. More importantly, the language that develops around the wheel names keeps the connection to the plates (again, the verbose "plate diameter"). As a community we've settled into R40...R120 and beyond for curves because it makes intuitive sense. If we just called them a "40 curve", "56 curve", etc. the context would have been lost, especially if we called them an even more abbreviated #4, #5, .... If we go with integer names for the wheels it will quickly lose the connection to the number of plates, it will be clearer as to which size is larger than another (better than XLL), but still not clear as to why.

As a result, if integers represented half plate diameters in this naming scheme at some point someone will then introduce a 9.5 wheel that is actually 10 plates in diameter (or worse, some random number between 9.5 and 10.5) and completely undermine the clarity objective.

So I would strongly suggest keeping the .5. The advanced builders can then talk about a 9.5 wheel. The wheel sellers (and rod makers) can then talk about a "9.5 plate diameter wheel," in their product listings and everyone is a little more knowledgeable.

I hadnt considered this point because as one of the creators the .5 in the size is intuitive to me but may not be for someone new.

Then the wheel sizes beyond this chart, which, to me, would not make sense as they do not fit in the "system" but there are new and creative possibilities with 3D printers becoming less costly every day. I will propose this change to those that helped ideate it and will likely be back with an updated chart. 

[moparacker]

15 hours ago, M_slug357 said:

@moparacker Theres nothing wrong with the #5 wheel having an axle. Thats the standard wheel size from Lego. 

The 2879 style wheel uses a steel axle, not the cross axle pictured.

[supertruper1988]

17 minutes ago, moparacker said:

The 2879 style wheel uses a steel axle, not the cross axle pictured.

that is really of no consequence the chart is more about diameter than mounting style. the mounting is variable because all of these sizes can be 3D printed with any mounting. 

[dtomsen]

In short: I like the new more sensible naming convention.

[moparacker]

1 hour ago, supertruper1988 said:

that is really of no consequence the chart is more about diameter than mounting style. the mounting is variable because all of these sizes can be 3D printed with any mounting. 

I apologize for seeing beyond the intended use of the chart and how it can be a general reference resource.

I'll go ahead and leave the conversation to prevent further derails.

[zephyr1934]

18 hours ago, supertruper1988 said:

I hadnt considered this point because as one of the creators the .5 in the size is intuitive to me but may not be for someone new.

...

I will propose this change to those that helped ideate it and will likely be back with an updated chart.  

Exactly that, once you are familiar with a good naming system (even if arbitrary, e.g., BBROYGBVGW) it becomes intuitive. Keeping the .5 just lowers the barrier to folks making the jump with your (all-ya-all's) great idea. Thanks for deriving and sharing it.

 

Once the details are finalized, please let us know where the official standard is posted.

 

16 hours ago, moparacker said:

I apologize for seeing beyond the intended use of the chart and how it can be a general reference resource.

I'll go ahead and leave the conversation to prevent further derails.

You did nothing wrong and no need to apologize or duck out. That was a perfectly logical and reasonable question you asked. These forums are meant for builders of all experience levels.

[supertruper1988]

22 hours ago, moparacker said:

I apologize for seeing beyond the intended use of the chart and how it can be a general reference resource.

I'll go ahead and leave the conversation to prevent further derails.

 

5 hours ago, zephyr1934 said:

You did nothing wrong and no need to apologize or duck out. That was a perfectly logical and reasonable question you asked. These forums are meant for builders of all experience levels.

As zephyr said nothing wrong here, just asking questions is totally fine. I was not trying to shut you out in my reply, I am sorry it made you feel that way. I was just clarifying that the point of the chart, especially in regard to the wheel size, was about about the size. The LEGO® wheel sizes listed are there for reference as a size not a mounting style, nor was this list meant to be a totally exhaustive list of all wheels offered at this time, which numbers in the hundreds.

[Paperinik77pk]

A nice work! I think is a good idea matching the real Lego part name to the new identifier.

Since it could become a comprehensive list of all possible lego wheels sizes, it would be nice in my opinion to insert also older parts sizes, just for reference.

For what I could measure with my hand tool and simple Lego plates, these are the sizes:

• 12v (mounted on 7865 motor) cone wheels (MS?)                                       - Outer cone 16mm (5 plates) / Inner cone 15mm / Flange 21,4mm (around 7 plates) - the rod hole center is around 6mm from axle center
• 4,5v (mounted on 107 motor) cone wheels  (MS?)                                       - Outer cone 16mm (5 plates) / Inner cone 15mm / Flange 21,4mm (around 7 plates)
• 4,5v flat traction wheels (used on older 100 motors to grip on rails)           - Wheel 17mm (around 5 plates) / Flange 22.4mm (7 plates)
• wheels used on wagons of Blue era (same as motor ones,flat wheels)     - Wheel 16mm (5 plates) / Flange 22.4mm (7 plates)
• wheels used on wagons of Gray Era                                                           - Wheel 16mm (5 plates) / Flange 22.4mm (7 plates)
• 7750 wheels                                                                                                  - Wheel 22mm (around 7plates) / Flange 28.8 (9 plates)

The 12v and 4,5v wheels have a smaller flange than wagon wheels and are a bit smaller than old "traction" wheels. But the smaller size is due to the fact that they needed to accomodate the rubber traction band, that brings them again to a diameter of 17mm.

I took all these measures since I'm attempting to 3D print those parts

I hope it can be useful!

Ciao,

Davide

 

Edited December 8, 2020 by Paperinik77pk

[supertruper1988]

On 12/8/2020 at 4:29 AM, Paperinik77pk said:

A nice work! I think is a good idea matching the real Lego part name to the new identifier.

Since it could become a comprehensive list of all possible lego wheels sizes, it would be nice in my opinion to insert also older parts sizes, just for reference.

For what I could measure with my hand tool and simple Lego plates, these are the sizes:

• 12v (mounted on 7865 motor) cone wheels (MS?)                                       - Outer cone 16mm (5 plates) / Inner cone 15mm / Flange 21,4mm (around 7 plates) - the rod hole center is around 6mm from axle center
• 4,5v (mounted on 107 motor) cone wheels  (MS?)                                       - Outer cone 16mm (5 plates) / Inner cone 15mm / Flange 21,4mm (around 7 plates)
• 4,5v flat traction wheels (used on older 100 motors to grip on rails)           - Wheel 17mm (around 5 plates) / Flange 22.4mm (7 plates)
• wheels used on wagons of Blue era (same as motor ones,flat wheels)     - Wheel 16mm (5 plates) / Flange 22.4mm (7 plates)
• wheels used on wagons of Gray Era                                                           - Wheel 16mm (5 plates) / Flange 22.4mm (7 plates)
• 7750 wheels                                                                                                  - Wheel 22mm (around 7plates) / Flange 28.8 (9 plates)

The 12v and 4,5v wheels have a smaller flange than wagon wheels and are a bit smaller than old "traction" wheels. But the smaller size is due to the fact that they needed to accomodate the rubber traction band, that brings them again to a diameter of 17mm.

I took all these measures since I'm attempting to 3D print those parts

I hope it can be useful!

Ciao,

Davide

 

First off sorry for the late reply. Holidays put a hold on my LEGO time. 

For all of these wheels, except the 7750 wheels,  would call those "S" sized. They are essentially the same design and diameter that has carried through to the current wheel designs. The sizes in the chart are the "nominal" sizes. The actual wheels from 2820c01 and 2820c02 are just under 17mm but are still "S" sized. 

The 7750 wheels are "M" sized as they are not quite big enough but the centers are mounted 1 plate higher than the other wheels of the time. This fits the original design pattern from Big Ben Bricks. 

 

Now to get to what @Cale, @coaster and myself feel is the final version of this chart. We heard the suggestions for exact sizes in millimeters and also pondered the problem of "what to do with the sizes in between?" 

For the naming convention, the .5 being omitted is purely for easy of conversing. The inclusion of it feels off when conversing about because there is no XX.0. Additionally, from a production stand point, the current sizes have to be mounted at 1/2 plate higher or lower than its neighbor. Anything less than that change is going to require some advanced SNOT to get at the "correct" height. I use quotation marks here because as soon as a traction band is added, the effective rolling diameter is changed slightly so any change less than 1/2 plate gets negated in the band diameter. We feel that anyone looking for that fine of detail in a model made of LEGO bricks is also advanced enough to print their own wheels that would not likely be produced on any scale. As noted above these are the nominal sizes so a change of a millimeter or two still fits in the system. 

We also added some scale guides for those modeling in the two popular scales of LEGO train building. 

@zephyr1934 asked about a spacing guide and while that is something that is feasible, it also will greatly depend on the prototype being modeled and will be unique for each model and builder. 

Here is the final size chart we have come up with and I have reached out to BBB about his thoughts. 

[M_slug357]

@supertruper1988 I think what  @zephyr1934 meant by a “spacing guide” was more along the lines of charting out the min&max distance between two same-sized wheels against the wheel type (B-B, B-F, F-F). And then maybe a suggested minimum radius that that arrangement could theoretically handle....?

My dream for this would be a website/app similar to @Sariel’s Gear Ratio calculator! ((it would take me too long to construct something like this)) A bonus calculation would tell you how many spm (studs per minute) the given wheel size outputs, which could then be multiplied by the theoretical rpm’s on the drive axle(s).**

This would help when determining scale, but also moreso the mechanicals going into a MOC.

 

**Back when xxL drivers where new, I made an engine that had geared up the drivers’ output speed to match that of a PF train motor in the tender. It crashed spectacularly. 

[Sariel]

@M_slug357 My Gear ratio app for Android does include a calculation of speed for a given wheel size. Granted, it doesn't have the result in studs, but I can try adding it.

[zephyr1934]

6 hours ago, M_slug357 said:

@supertruper1988 I think what  @zephyr1934 meant by a “spacing guide” was more along the lines of charting out the min&max distance between two same-sized wheels against the wheel type (B-B, B-F, F-F). And then maybe a suggested minimum radius that that arrangement could theoretically handle....?

Actually, I had meant that without the numbering system all we had was the minimum spacing in studs between wheels of different sizes and even that wasn't so easy to remember. With the numbering scheme, the "L" becomes "9" (short for 9.5 plate diameter). So if I have two of these next to each other (F-B) I need at least 9.5 plates from axle to axle, that rounds up to 10 plates which is 4 studs. Whereas the XL is #11 and thus, needs 11.5 plates between axle centers, which rounds up to 12.5 plates or 5 studs between centers. If you use two flanges (F-F) you will need a larger spacing, but that will vary by the size of the flange, most likely adding 2 studs between axle centers.

To get the distance per revolution, that is pi * d, or 3.14 * d. So the #9 wheels will travel just under 30 plates per revolution (12 studs).

Of course all of the above is rough since some wheels will have a taper to their profile and some will have traction bands.

Now thinking of the number as the minimum number of plates between axle centers, it might have been better to round UP to the next integer rather than down (so the #9 would become #10). That would give a safety margin for traction bands and tapers. But without it, the only potentially significant confusion would be #10 and #5, but I'm not aware of any bind #5's and #10's are likely to be uncommon forever.

 

[supertruper1988]

2 hours ago, zephyr1934 said:

Actually, I had meant that without the numbering system all we had was the minimum spacing in studs between wheels of different sizes and even that wasn't so easy to remember. With the numbering scheme, the "L" becomes "9" (short for 9.5 plate diameter). So if I have two of these next to each other (F-B) I need at least 9.5 plates from axle to axle, that rounds up to 10 plates which is 4 studs. Whereas the XL is #11 and thus, needs 11.5 plates between axle centers, which rounds up to 12.5 plates or 5 studs between centers. If you use two flanges (F-F) you will need a larger spacing, but that will vary by the size of the flange, most likely adding 2 studs between axle centers.

To get the distance per revolution, that is pi * d, or 3.14 * d. So the #9 wheels will travel just under 30 plates per revolution (12 studs).

Of course all of the above is rough since some wheels will have a taper to their profile and some will have traction bands.

Now thinking of the number as the minimum number of plates between axle centers, it might have been better to round UP to the next integer rather than down (so the #9 would become #10). That would give a safety margin for traction bands and tapers. But without it, the only potentially significant confusion would be #10 and #5, but I'm not aware of any bind #5's and #10's are likely to be uncommon forever.

I actually spoke to Ben of Big Ben Bricks and he had the same feedback about the .5 being included in the name. I was only rounding down because one of the original ideas was to start at the smallest size, #2 on the current chart, and call that a #0 then up from there as it is 1 stud (8mm) + the number of plates to get the size. The 8mm wheel is the smallest size that is feasible to be a driven axle with a gear in the frame, thus it made a good starting point. 

Ben also suggested we number them by stud diameter so it would start at #1.0 then #1.4, $1.8, #2.2, etc. 

Then he finally pointed out that the angled technic connectors have a number on them that is arbitrary. The point being that, if a system of arbitrary names or numbers is designed and accepted then that is the system and its meaning is easily communicated in a standards document (or chart) of some kind.

The more I think about it, I want the name to be the size of the rolling diameter in a LEGO unit of measurement so studs or plates. That is what will help people become easily familiar as they are already familiar with the LEGO system. 

Also the last point I wanted to make was that now that I understand what you wanted for a "spacing guide" something similar should be simple to added to the chart. 

[High_Admiral]

I personally think that the numbering of the diameters based on the plate diameter is probably one of the better options. The stud diameter is also promising I think, but it could get complicated with the various x.x designations instead of saying "Oh yes, this model uses #5 drivers" or whatever.

[coaster]

I'm partial to the whole numbers, and I like @zephyr1934's suggestion of switching to rounding up to allow for clearances. 

A note for spacing though gets a little tricky.  The LEGO versions of the "L" wheels can be nested, where the flanges fit behind the adjacent blind driver(s).  The BBB wheels do not allow for this though, so you would have a greater minimum spacing requirement.