# Roberval Balance

## 3D model description

The Roberval balance is a weighing scale with two horizontal beams one above the other connected to two vertical beams supporting the weights to be compared.

Because the beams form a parallelogram, no matter where the weight is placed in the plates the balance works properly, compared to a simple beam scale which is sensitive to where the weights are placed in the plate. See it in action at https://www.youtube.com/watch?v=Bg7IBTMdyf0

Use this tool to compare the weight of any two small objects! It shows differences as small as 1 gram.

See https://en.wikipedia.org/wiki/Roberval_balance for more historical and scientific information about the Roberval balance.

## 3D printing settings

Printer Brand:
RepRap

Printer:
Original Prusa i3 MK2

Rafts:
No

Supports:
No

Resolution:
0.2mm

Infill:
10%

Notes:
Print the base, top bar, bottom bar, riser, 2 plate holders, 2 plates and 2 plate sleeves. The full model is not meant for printing, just to show the assembly.

Print all parts plat.

Assembly
Using super glue, glue the plate holder to the bottom of the plate. Pay attention to the orientation of the plate holder: the end the farthest from the holes goes into the plate. Make sure the plate holder is square with the plate. Slip the plate sleeve on the plate holder and glue it to the bottom of the place.

Using M3 screws attach the plate holders to the top and bottom bars and the bars to the riser. I had some partially threaded screws (meaning the lower half of the screws have threads and the upper half is smooth) so I used that but regular screws work too.

Glue the riser into the base. M3 10mm partially threaded screw

Overview and Background

Kindergarden: Describe and compare weight. Which object is lighter and heavier.

Grade 1: Measure weight indirectly. Order 3 objects by weight.

Grade 2: Measure weight in standard units. Add standard weights to find the weight of an object.

Grade 3: Solve problems involving weight measurement.

Kindergarten
Describe and compare measurable attributes

Directly compare two objects with a measurable attribute in common, to see which object has "more of"/"less of" the attribute, and describe the difference. For example, directly compare the heights of two children and describe one child as taller/shorter.

Measure weights indirectly

Order three objects by weight; compare the weight of two objects indirectly by using a third object.

Express the weight of an object as a whole number of weight units, by putting multiple copies of a lighter object (the weight unit) on one balance plate; understand that the weight measurement of an object is the number of same-weight units that balance the scale. Limit to contexts where the object being weighted is balanced by a whole number of weight units with no gaps or overlaps.

Measure and estimate weights in standard units.

Measure the weight of an object by adding numbered standard weights to balance the scale.

Measure to determine how much heavier one object is than another by adding numbered standard weights to balance the scale, expressing the weight difference in terms of a standard weight unit.

Solve problems involving measurement and estimation.

Measure and estimate masses of objects using standard units of grams (g), kilograms (kg), and liters (l).1 Add, subtract, multiply, or divide to solve one-step word problems involving masses that are given in the same units by using the balance to represent the problem.

Materials Needed

Scale, objects to measure, units weights of 1 g, 5 g, 10 g, etc.

• 3D model format: STL