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Some questions about these train magnets:

https://www.bricklink.com/v2/catalog/catalogitem.page?P=73092

enter image description here

I'd like to know roughly how much weight two of those could lift or what force is needed to separate two of these...

According to BrickLink, the magnet was produced from 1980-2009, would there be a considerable loss of strength between magnets produced in the early days and later?

I suppose how they were stored or how much they were played or dropped would also influence heavily their remaining strength...

I suppose I could re-magnetize them with a neodymium magnet, anyone care to guess or experiment about how strong such rejuvenated LEGO magnet would be?

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  • 1
    Temperature also plays a role. Magnets lose their strength faster in warmer environment. Heat neodymium one to 80 degrees Celsius and it's gone.
    – Mołot
    Mar 23, 2018 at 10:42

1 Answer 1

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Test setup

  1. Take 20 magnets from my collection
  2. Build a test stand with a magnetically attached bucket containing an adjustable weight:image of an upside-down U frame, with a magnet hanging from the middle of the top beam and a LEGO bucket with six AA batteries hanging via 4 chains from another magnet
  3. Designate one of the magnets a reference (#0)
  4. Repeat for each one of the 19 other magnets:
    1. Attach the magnet to the bucket
    2. Carefully add Technic beams to the bucket until the combined weight of the bucket, batteries, beams and the magnet reaches the limit and the assembly falls onto the rug below: image of the frame straddling the bucket, which has fallen due to the eight of the added Technic beams
    3. Measure the weight of the assembly and note it: image of the bucket on a kitchen scale, reading 220 grams
  5. Measure the two strongest magnets against each other to get an estimate for the upper bound
  6. Measure the two weakest magnets against each other to get an estimate for the lower bound

Limitations

The magnets were mostly purchased between 1990 and 2000 and were stored for several years in a sunny attic room and then for a few additional years in a cold basement in various states of assembly (separated, joined in pairs or assembled into a column of several magnets).

The weight of the bucket was increased by adding Technic beams, which weigh 2-4 grams each, thus limiting the precision of the breaking point (but see the next paragraph for a more serious limitation).

The kitchen scale has a precision of about 10-20 grams.

All pairs were measured only once.

Care was taken to construct the bucket in a way that results in the center of mass being as close to the symmetry axis as possible, but the amount of deviation was not measured.

Results

The 19 pairs have resulted in the following measurements (all values in grams):

220 (#1)
240
220
220
220
240
250 (#7)
240
240
230
210 (#11)
240
240
230
240
240
240
250 (#18)
240

This results in an average value of 234 grams of force required to pull the magnets apart (including the weight of the lower magnet)

The two strongest (#7 and #18) together: 260 grams

The two weakest (#1 and #11) together: 200 grams

I'm aware of the inherent imperfection in this test method, but in my opinion, it represents a reasonable compromise between time investment and attained precision. I would welcome any critique aiming to improve it though.

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