3B Scientific Tyndall's Bar Breaker - Manual (Page 4)

Elwe Didactic GmbH ▪ Steinfelsstr. 6 ▪ 08248 Klingenthal ▪ Germany ▪ www.elwedidactic.com
3B Scientific GmbH ▪ Rudorffweg 8 ▪ 21031 Hamburg ▪ Germany ▪ www.3bscientific.com
Subject to technical amendments
© Copyright 2009 3B Scientific GmbH
4. Technical data
Bolt holes: 10 mm dia.
Length of abutment: 290 mm
Stand rod: 65 mm x 12 mm dia.
Weight: approx. 1.3 kg
5. Accessories
Set of 10 cast-iron bolts U8442110
6. Operating principle
As the metal bridge is heated, it expands to such a
degree that its tensioning screw needs to be tight-
ened up. When it cools it contracts back to its origi-
nal length. However, it no longer has the play to do
this, since the tensioning screw has been tightened
at one end and the bolt prevents contraction at the
other. Eventually, the resulting tension in the metal
bridge becomes so great that it snaps the bolt in two
with a loud bang.
7. Operation
The following equipment is also required to perform
the experiment:
1 Stand base, A-shaped U8611160
1 Stainless steel rod, 470 mm U15002
1 Universal clamp U13255
1 Cartridge burner
1 Gas cartridge
• Set up the experiment as in Fig.1. Check that the
bolt is not aligned towards any viewing persons.
• Secure the bolt with its fastening screw before
heating it.
• Heat the bridge for about 5 minutes in a naked
gas flame. As the bridge heats up, keep tighten-
ing the tensioning screw to match the expansion.
• Take away the burner and allow the bridge to
cool.
Some time later, the bolt will break apart.
Fig. 1 Bar breaker experiment set-up