A) Dowel driven into a copper collar
1. Alluminothermy Welding
After drilling the rail, a tapered dowel is driven into a cylindrical copper collar using a sledgehammer, the cable having been previously welded to the collar.
As the connection is made by uncontrolled strikes from a hammer, certain disadvantages are inevitable:
B) Dowel driven directly into the rail.
After drilling the rail, a threaded tapered dowel is driven into the rail by means of a sledgehammer. A terminal lug is connected to the pin.
The electrical resistance of the connection does not permit high amperage currents to flow and so this system can only be used for signaling currents.
There is a risk that violent shocks on the rail might harm its fatigue strength.
There are large stresses in the rail, the penetration of the pin results in permanent deformation of the drilled hole.