1 stud wide coupling rods: alternatives to 1L axle with stop?

[Freak_NL]

I am designing a steam locomotive where the body is 7 studs wide, and the coupling rods and steam chests fit in an 8 stud wide bounding box. For this to look good I want the coupling rods to have a combined width of just 1 stud, and stay within that 8 stud wide limit.

I've managed to do this using red thin Technic beams, but without the elusive 9 stud long one, this means getting creative. This is the best I've come up with:

This is all fine and functions with a minimum of friction. However, due to the limitations of the available short half-width beams, one way or the other I end up with an axle hole in the place where this reddish brown 3L axle with stop now sits in this CAD drawing. In my real life mock-up of this model, this 3L axle had an appointment with a utility knife to become a 1L axle with stop, and frankly, that works great.

But if I want to turn this MOC into a set of instructions anyone can use, that might be a sticking point. Is there another solution here that might work within the same constraints? Or should I just accept that sometimes a minor modification of a cheap part is tolerable?

[Stereo]

Older part, but 1x4 Technic plate with holes on both ends could have a stud pressed into the back layer 7L beam and not need modifications.  So then I guess it's cheaper vs. no modification.

[Freak_NL]

4263? That could work there. but I'd probably need a spacer for the pin in the rear driving wheel.

[Sven J]

You could also use the old Flex Cable parts for the coupling rods, they are only 0.5 studs wide.

[Freak_NL]

14 hours ago, Stereo said:

Older part, but 1x4 Technic plate with holes on both ends could have a stud pressed into the back layer 7L beam and not need modifications.  So then I guess it's cheaper vs. no modification.

Huh, that actually works fine without a spacer in a real life test. I might just go that route. Thanks.

2 hours ago, Sven J said:

You could also use the old Flex Cable parts for the coupling rods, they are only 0.5 studs wide.

Certainly an option, thank you. I think I'll see where 4263 brings me first though.

[JopieK]

Great work, will you also share the end result?!

[Freak_NL]

1 hour ago, JopieK said:

Great work, will you also share the end result?!

Certainly, if it turns out good enough.

[LEGO Train 12 Volts]

I guess cutting the axles (or a pin 2736) is not an option for you... or maybe it is...

[Stereo]

5 hours ago, Freak_NL said:

Huh, that actually works fine without a spacer in a real life test. I might just go that route. Thanks.

I would guess the original design's axle is also optional in real life, as long as the left and right drivers are paired properly, 90 degrees different on the same axle.  I'm not sure if all 3 rows of drivers need to be connected; I suppose I can test that for myself.  On actual 6 or more driver trains, the side rods have a pivot so the suspension can work.

Edited November 1, 2024 by Stereo

[Freak_NL]

4 minutes ago, Stereo said:

I would guess the original design's axle is also optional in real life, as long as the left and right drivers are paired properly, 90 degrees different on the same axle.  I'm not sure if all 3 rows of drivers need to be connected; I suppose I can test that for myself.  On actual 6 or more driver trains, the side rods have a pivot so the suspension can work.

I've left the blind wheels off the drivetrain to decrease friction and give me some space for the upwards bevel gear pair. They're rotating freely on pins instead so they do need the rods to turn (supported on either side to prevent jamming).

1 hour ago, LEGO Train 12 Volts said:

I guess cutting the axles (or a pin 2736) is not an option for you... or maybe it is... 

Possible, but I found cutting the 3L with stop worked well and left the stop neat and flush. Fortunately the 4263 solution above makes it a moot point.

[Selander]

Perhaps a silly question...but can't you use 4586 (from Orient express) which effectively is a 9L thin beam...?(!)

Edited November 3, 2024 by Selander
Spelling mistake

[LEGO Train 12 Volts]

I assume he wants the red piston rod...

[Selander]

13 hours ago, LEGO Train 12 Volts said:

I assume he wants the red piston rod...

Yeah, that might be true, although it is not specifically stated..

Anyhow, 4586 + red striping looks the part, I've got that on my little Knapsack tanker engine 🚂 

[LEGO Train 12 Volts]

This seems like an excellent solution to me...now I'm looking for the locomotive you're talking about

[Freak_NL]

@Selander Yes, red was a requirement. That part is otherwise perfect.

I've finished the MOC this was intended for using 4263: