GMTRCPLY - GeoMeTRiCPLaY - Magnetic Sticks

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Introduction

The classic Magnetic Stick sets come with plastic coated magnetic sticks, and ferromagnetic spheres. Other terms are Rods and Spheres, or Bars and Balls.

Usually, the ends of each stick have opposite magnetic polarity. But there are also sets where the ends have the same magnetic polarity, and therefore contain two types of sticks.

Desktop Size

Current "regular" sets come with short (~27mm) or long (~58-60mm) sticks. The balls have 12.0-12.8mm diameter.

The photo shows different Magnetic Sticks, from left to right...

• Generic brand, short
• Generic brand, long
• BANBBY, long
• Geomag, standard (long)
• Geomag PRO-L
• Goobi Magnetic
• Wisemag (out of production)

The table below shows the characteristics for some sets.

Brand	Type	Stick Length	Diameter	Weight	Magnetic Strngth	Ball Diameter	Weight	Notes
Generic	Short	27.1mm	6.7mm	3.9g	medium	12.0mm	7.2g
Generic	Long	58.0mm	7.0mm	6.8g	medium	12.0mm	7.2g
BANBBY	Long	58.0mm	7.0mm	6.7g	medium	12.0mm	7.2g
Goobi	Long	59.9mm	9.9mm	4.1g	high	12.8mm	8.5g
Geomag	Long	58.2mm	7.6mm	9.7g	high	12.8mm	8.5g
Geomag	PRO-L	58.2mm	7.4mm	9.8g	high	12.8mm	8.5g
Geomag	Original	27.0mm	7.4mm	4.6g	high	12.7mm	8.4g	Out of production
Wisemag	Short	30.9mm	6.4mm	5.7g	very high	12.7mm	tbd	Out of production
Magnetic World	Medium	39.6mm	8.9mm	1.4g	very low	12.0mm	6.9g	Junk, for reference purposes

For more information, see:   Stick Sets 

Floor Play

There are many different sets that are usually intended for toddlers. Because of the large size, the sets come with hollow tin balls of 30-60mm diameter. But the sticks can also be used with steel balls of appropriate size. When using solid steel balls, the magnetic attraction is stronger, but the weight of the balls increases by the power of three with the radius.

The market is flooded with cheap Chinese sets, but there are also high quality products. However, with increasing magnetic strength, there is also the danger of pinched skin.

Brand	Long	Medium	Short	Ball Diameter	Notes
Goobi Juniors, old size	144mm			60mm	Bipolar sticks; min. sphere diameter ~56mm
Goobi Juniors, new size	130mm			53mm	Bipolar sticks; min. sphere diameter ~45mm
Nexus Magne Sticks		81mm	60mm	54mm	Bipolar sticks; min. sphere diameter ~46mm
SmartMax	119mm	71mm		45mm	Monopolar sticks (indicated by warm/cold color); min. sphere diameter for long ~42mm, for medium ~36mm
Magformers Stick-O	115mm	68mm		45mm	Rotating internal magnets; min. sphere diameter ~45mm
Generic Chinese	87mm	52mm		35mm	Bipolar sticks; different detail design

For more information, see:   Stick Sets 

Steel Balls

You can combine any ferromagnetic sphere with the magnetic sticks. Below are some examples for 100Cr6 (1.3505) industrial grade steel balls that I have available.

Diameter	Volume	Weight	Density
9.00mm	0.38cm³	2.98g	7.80
9.53mm	0.45cm³	3.54g	7.82
10.00mm	0.52cm³	4.09g	7.81
10.50mm	0.61cm³	4.74g	7.83
11.00mm	0.70cm³	5.45g	7.81
11.50mm	0.80cm³	6.22g	7.81
13.00mm	1.15cm³	8.99g	7.81
14.00mm	1.44cm³	11.22g	7.81
15.00mm	1.77cm³	13.81g	7.81
16.00mm	2.14cm³	16.73g	7.80
17.00mm	2.57cm³	20.07g	7.80
18.00mm	3.05cm³	23.84g	7.81
19.05mm	3.62cm³	28.21g	7.79
20.00mm	4.19cm³	32.68g	7.80
21.00mm	4.85cm³	37.86g	7.81
22.00mm	5.58cm³	43.47g	7.80
25.40mm	8.58cm³	66.99g	7.81
28.00mm	11.49cm³	89.73g	7.81
30.00mm	14.14cm³	110.34g	7.81
32.00mm	17.16cm³	134.04g	7.81
35.00mm	22.45cm³	175.18g	7.80
40.00mm	33.51cm³	261.57g	7.81
45.00mm	47.71cm³	372.50g	7.81
50.00mm	65.45cm³	511.00g	7.81

If you want to calculate the weight for a certain diameter, you can assume a density of about 7.8.