Lego GBC Balls
GBC Balls are a quintessential part of Lego Great Ball Contraption, without them it would just be a bunch of strange contraptions.
The typical ball is a Lego sports ball most often recognized in their soccer and basketball printings, however, these balls have not been produced for many years and although plain orange and white counterparts are still produced they can be expensive to procure in large quantities.
So I set out to do a comparison of Lego vs some non-Lego balls as well as compare the UV properties.
Properties of the Lego sports ball
Lego sports balls have two key properties that impact GBC modules design,
- Diameter: 14.00 mm
- Weight: 1.50 grams (~0.05oz)
Depending on your module style will depend on how much these can be varied when using non-Lego balls.
Module styles that are NOT tolerant of ball changes
Modules that are designed based on ball geometry and weight can have varying levels trouble with non-Lego balls.
These modules are
|GBC Module Style||Weight matters||Size matters|
|Picking / Grabbing||Possibly||Yes|
For my comparison I wanted to test size and weight and also the UV properties of some of the non-Lego balls
- 14mm UV Beads
- Lego Sports balls
- PV-Productions UV balls
- 14mm plastic beads
- Lego UV parts (a spider and a ghost)
Size and Weight Results
For weight I used gram scales and took the average of several measurements for each item.
Dimensions was the same process, although this was a little harder as none of the test balls was perfectly round.
|TestItem||Weight||Weight % of Lego||Diameter||Diameter % of Lego||$/100|
|UV Bead 1||1.38||92%||13.9||99%||$6|
|UV Bead 2||1.41||94%||13.8||98%||$6|
|LEGO Soccer Ball||1.51||101%||14.08||100%||$40-$120|
|PV-Productions UV 1||1.67||111%||13.9||99%||$60|
|PV-Productions UV 2||1.64||109%||13.85||98%||$60|
|Bead – blue||1.31||87%||13.6||97%||$20|
|Bead – green||1.42||95%||13.6||97%||$20|
|Lego UV – Spider||0.36||24%||20||142%||$48|
|Lego UV – ghost||3.02||201%||40||284%||$150|
For UV testing I did three separate tests where I changed the amount of time the items were under UV light, these were for
- 1 second
- 5 seconds
- 10 seconds
However when I compiled my discharge results there was no consequential difference between a 1 second or a 10 second soak, which means when “charging” balls for night time running soaking a ball for long periods is not required.
|Test Item||Time to discharge (seconds)|
|PV-Productions UV Balls||120|
If your are designing Chain or Stepper based modules, all of the balls here would work fine (the spider may not roll very well)
For Shooter and Picker modules even a 0.1mm change in diameter or a 0.1 Gram (or 0.003oz) difference can change the behavior of the module and I would strongly recommend acquiring genuine Lego sports balls for testing and tuning these kind of modules.
For glowing UV balls PV-Productions are excellent outlasting Lego’s on UV materials by a factor of 2 and Lego aren’t producing UV soccer balls anytime soon, make a worthwhile investment.