How strong are Lego axles when braced by 1/2 bushes?

[nerdsforprez]

By now probably pretty much everyone is familiar with The Brick Experiment (TBE) channel on YT.  This little video submission is in no way supposed to copy that, only to extend one of the channel’s popular videos a little further:

 

As can be seen in the video, Lego axles begin to experience permanent damage at about 180  mN m  of force applied in twisting motion (axle length of 10L unbraced).  My little video replicated this, which is fairly remarkable given the variance in motor productivity, battery power, etc.  Also it should be noted, which was not noted in TBE channel is that axle durability is a function of its length.  A longer axle will twist with less force, a shorter one with more force.  So, in keeping with this I used the exact same length of axle as TBE channel, although the braced versus unbraced length was slightly different at ~180 mN m of force (we both used a slightly different configuration).   But these differences are so slight I believe any effect is very small to negligible (TBE channel’s exposed axle length was ~2 studs shorter than mine). 

In the TBE video at 300 mN m the 16L axle twisted so much it began to curl and eventually pulled from the fixed end (opposite from motor end).  At this point there was extreme twisting of the axle but it also was no longer even straight.  Unrecognizable.  Looked like black licorice.   In my little experiment at this level of force, but with braced axles by 1/2 bushes there was slight damage to the axle but it was very mild and the overall shape of axle was not compromised (it was still straight).  The extreme difference between the braced versus non-braced axles at 300 mN m of force is probably the most significant part of the experiment.  

I did not go further than 300 mN m of force.  As can be seen in the video, looks like the method of bracing axles indeed does strengthen axles, surprise, surprise, right?  I saw the same amount of damage (actually a little less) at 300 mN m in my experiment (braced axle) as was seen in TBE video at 180 mN m.  So, I guess one could approximate that the method of bracing axles with Technic bushings roughly doubles their strength.   Certainly an approximation, but it is something. Hope you enjoy!

 

 

 

[howitzer]

Akiyuki Kawaguchi did a somewhat similar experiment, though with 32L axles and about non-permanent twisting:

All this work to find out about the ways around the limitations and shortcomings of Lego is very interesting, so kudos to you and others for doing the experimentation and sharing the results!

[Seasider]

As an engineer this result is no surprise to me, you’ve changed the effective cross section on the axle significantly along it’s length.

[nerdsforprez]

4 hours ago, howitzer said:

Akiyuki Kawaguchi did a somewhat similar experiment, though with 32L axles and about non-permanent twisting:

All this work to find out about the ways around the limitations and shortcomings of Lego is very interesting, so kudos to you and others for doing the experimentation and sharing the results!

Oh this is interesting.  I did not know about this video.  Thxs for sharing.  This set-up is much more scientific than mine... though the use of a 32 inch axle surely makes them less robust. 

Perhaps one additional iteration I should have done, or someone else, is like 3L or 2L connecters all linked together by 2L axles. I am sure there would not be any twisting, but they would disengage at some point.  Be interesting to know what that point is.... 

[Andman]

But why would you embrace an axle that way in the first place? IF possible, i would replace that shown setup with alternating 2L axles and axle connectors.

[nerdsforprez]

33 minutes ago, Andman said:

But why would you embrace an axle that way in the first place? IF possible, i would replace that shown setup with alternating 2L axles and axle connectors.

Yes, exactly, that is what I mentioned in my last post:

2 hours ago, nerdsforprez said:

Perhaps one additional iteration I should have done, or someone else, is like 3L or 2L connecters all linked together by 2L axles. I am sure there would not be any twisting, but they would disengage at some point.  Be interesting to know what that point is.... 

Admittedly this wasn't an experiment for practical purposes.  Or at least not typical purposes.  Rarely are there applications where there is an exposed/unbraced axle of any real significant length.  Especially ones that are subjected to the amount of force needed to damage.   Fun to do nonetheless.  Got the idea from the Brick Experiment Channel, which really isn't into doing things for practical purposes anyways 

[1974]

1 hour ago, nerdsforprez said:

Rarely are there applications where there is an exposed/unbraced axle of any real significant length

Boom extension on mobilecranes both in sets and MOCs

[Andman]

5 minutes ago, nerdsforprez said:

Yes, exactly, that is what I mentioned in my last post:

Oh, sorry. I should have reloaded the thread. Had it open for some time and haven't seen your post.

[nerdsforprez]

8 hours ago, 1974 said:

Boom extension on mobilecranes both in sets and MOCs

Yes, that is a good application.  Outriggers too. Again though, probably not going to be exposed to the forces that will twist axles.  Unless we are talking about @Jeroen Ottens's large mobile crane... or something similar.  But any vehicle with extending something... outriggers, boom, etc. would be a good application.  

 

8 hours ago, Andman said:

Oh, sorry. I should have reloaded the thread. Had it open for some time and haven't seen your post.

  NP