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Henry 991

Lego Technic to 2 mm steel shaft adapters

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Hello all,

I’d like to reduce the frictional losses of my locomotives by installing ball bearings on all axles.

Has anyone thought about this before? I’m facing a challenge in connecting customer train wheels (E.g. Big Ben Wheels) to the 2 mm custom steel axle that are e.g. used in the Brickmodelrailroader’s wheelset (https://brickmodelrailroader.com/index.php/product/wheelset-w-bearings-full-assembled/).

I have considered three options:

  • 3D-print a Technic-axle-to-2 mm shaft adapter in hi-res nylon, ABS or resin. Then glue it onto the 2 mm steel shaft with epoxy resin
  • make adapters by drilling a hole into a standard ABS Lego Technic axle by using a jig. Otherwise the same as above
  • use a suitable hose (Lego 3 mm rigid hose?) to match Technic axle hole to 2 mm

The commercially available shaft adapter from Pololu (https://www.pololu.com/product/1001) does not work as it’s too wide. The adapter should not be more than one stud wide (8 mm).

Please let me know if you have ideas - much appreciated!

 Best,
H

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Posted (edited)

I would try the 3D printed option first, as you are more likely to get the steel shaft running true successfully, but it will take up more space than the second method. However, the second method is trickier to get working, as you'll have to get the hole for the steel shaft drilled straight and on-center - a mini lathe might be your best option here.

EDIT: Come to think of it, you'd probably want access to a resin printer, as the part in question is so small it wouldn't really work out well on a traditional hobby-level 3D printer. Now I'm not sure what the best option is.

Edited by Phoxtane

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Thanks for sharing your ideas!

On the 3D printed option, I haven't yet found the printing service in Europe that should be used. in Shapeways, there are basically two options:

  • "Fine Detail Plastic" that is their resin-based plastic. Supports wall-thickness of 0.2 mm
  • "Multi Jet Fusion Plastic PA12", or nylon (slightly stronger than ABS of Legos). Wall-thickness down to 0.5 mm

If you look at the geometry of Technic axle, the wall would be approximately 0,5 mm at smallest with the 2 mm shaft hole. So technically both would work.

I probably still go to the resin, as it's higher accuracy.

If anyone has tips, please let me know. I'll probably make the design available in Shapeways if this succeeds.

Best,
H

Axle - small.jpg

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30 minutes ago, coaster said:

Thanks!

Indeed, I have been looking at this. Didn’t know that it was you had made it. Already sourced the fitting bearings (156zz). The pros of this one are clear: you can have low rolling resistance bearings while still using the Lego axle.

However, to complement this, some applications require regular Lego brick/beam. There the steel axle and smaller size bearing and train wheel/Lego gear shaft adapter is handy.

I will probably end up using both solutions where suitable.

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