

Magnetic models

Introduction

Strong magnets have become inexpensive - and their use as modelling materials has now become practical.

Galleries

Strut length limitations

The pure-neodymium route provides that capability without much effort - since cylinder magents are available in widths down to half a millimeter thick - allowing for strut lengths to be varied with that sort of granularity without much difficulty.

Magnet strength tests

Stronger magnets help when building bigger models.

I did some strength testing of the various magnetic modelling materials I had available:

Name 6mm

Rod 6mm

Cyl Uni

Mag Geo

Mag Sup

Mag Mag

Stx Sup

Sml 3mm

Rod Stx

Bls Mag

Max Wit

ka Strength Strength 11 10 10 9 9 8 7 7 7 5 5 Mass/l 2.08 1.43 1.77 1.98 1.14 0.68 0.76 0.51 0.48 0.43 0.43

These tests all used 6mm ball bearings as the test weights.

Note that the strength scale is non-linear - the further away each ball is, the greater increment in magenetic strength it represents.

The mass/length figure doesn't make any attempt to factor in the weight of the steel ball bearings. They make up a lot of the weight in many kinds of model.

I dissected a couple of rods - to see how they were made:



Supermag

Geomag

Supermag uses a single 5mm diameter solid magnet.

A few notes in summary:

The "raw" neodymium magnets are strongest. They also have configurable lengths - and some have reasonable weight.

Of the commercial systems, Unimag was the strongest I tested.

Supermag scores highly in both strength and weight. It comes in a range of lengths - and has a neat ability to fit many rods around one ball.

Contention

Typically the magnets know which way around they are best positioned, and they leap from your fingers onto to the model while adopting that configuration. Sometimes they leap to the wrong location - but they can be pulled off again without too much bother.

Hollow cylinders

Some magnetic strength is lost in the process of removing the magnet's core - but the hollow tubular magnets seem preferable to the solid cylindrical ones overall.

Scaling



3mm neodymium magnet spaceframe



3mm neodymium magnet ring



Making the components larger or smaller seems unlikely to make much difference to the range of models which could be constructed.

Size does make quite a difference to construction cost, though. Neodymium magnets are not yet so cheap that cost is a negligible factor.

Unfortunately, there are some disadvantages to using smaller magnets:

They are more difficult to manipulate with your fingers;

Hollow cylindrical versions are not easily available much below 6mm;

The thinnest magnet is still 0.5mm thick - so there are more length-quantization issues;

The modeling stratgey would benefit somewhat from the use of hollow ball bearings.

However, unfortunately, hollow and light ball bearings do not yet seem to be widely available.

Spheres



Neodymium magnetic spheres



Modelling with magnetic spheres is also possible.

See the neodymium magnetic sphere page for more details.

Hazzards

Some people have sensitivities to nickel. I don't seem to be one of them, and am not too concerned about absorbing heavy metals through my fingers from these components.

Magnetic modelling can be fun - and doing too much of it might waste your time and or give you RSI. Nontheless, I rate magnetic modelling as a fairly low addiction risk activity - and a moderate-to-low RSI risk hazzard.

If you have small kids, you might want to think twice about leaving these components lying around.

There are a number of other potential hazzards with magnets - read the warnings and take appropriate care.

Links

Neodymium modelling

Magnet suppliers

Bulk magnet suppliers

Plastic magnetic kits

Models pages

Non-magnetic construction kits