Damian De Sabbata

Tripod Fossicking Stand with water capability.

Made by Damian De Sabbata. Owned by the club. Field tested by John and Isabella Heenan

Thanks

The club is extremely grateful to Damian for making the tripod sieve stand upon request by the club

Design

The stand is based on a popular design once used in parts of QLD and for which there is no known documentation or images.

Images

Please click on images to enlarge

Portability

The stand, sieve and chains above weigh 10 kg. Carrying the folded stand balanced on shoulder is practical and is not uncomfortable. Carrying by hand is not practical over long distances.

Construction

The outer legs were made from three 1.3 metre lengths of galvanised 25mm x 25mm RHS steel with 2mm wall. The length was chosen to be convenient to fit in a vehicle

The inner legs were made from three 1.1 meter lengths of painted and galvanised 20mm x 20mm RHS steel with 2mm wall. If there had not been spare steel, RHS galvanised 1.2 metre lengths would have been chosen.

The ring at the top and all the nine hooks (three at top and six at side) were made from the same section of 6 mm steel rod. The six holes at the top for the ring are all 8 mm diameter.

Precut 5 cm x 5 cm x 0.3 cm steel plates (with a central hole) were welded to end of inner legs.

A MIG welder was used

To clamp the inner legs, 8mm holes were drilled in outer legs at the bottom for a M6 nut and bolt set. The nuts are welded to the outer legs, so larger M6 nuts were used. The bolts had heads suitable for screwdrivers but the slot for a screwdriver was used to weld in pairs of washers. This avoids requiring a screwdriver in the field.

Those assisting Damian (thanks John and Isabella) quickly cleaned off the welding slag and added polishing with a 40 grit zirconium flap disc, followed by a paint job.

Characteristics

The tripod sieve stand has six major and probably unique outstanding design characteristics:

  1. It extends from an extremely compact foldable size in both height and width
  2. It has a versatile geometry to work under different conditions, including uneven ground. There are three independent geometry types: tripod leg length, angle of leg and height of sieve
  3. It is very easy to vary the geometry and to fold away
  4. It can be used to sieve with water
  5. It can be manufactured from cheap raw materials with inexpensive tools (Damian’s main raw materials were RHS steel and 6 mm steel rod and his main tool was a MIG welder)
  6. It can be used to boil water or cook with!

It cannot be considered lightweight by today’s standards and if lightweight may not work due to the locking mechanism.

Design Principle

The key design principle is unexpected. It is based on gravity providing a non obvious way to lock the sieve stand. The gravity lock is very easy to release and so makes it very easy to vary the geometry of the stand and to fold away the stand.

Water-sieiving vs Dry-sieving

Water-sieving, if water is available, is more efficient than dry-sieving to both separate out and identify.

When water is available but severely limited then starting with dry-sieving with a lightweight stand and finishing with wet-sieving with this tripod stand is an option.

Field Test

John and Isabella field tested the tripod stand on 4 October 2020 at Glittering Star on Mt Gibson fossicking area. These are their findings and recommendations.

  1. The tripod stand’s single biggest disadvantage is its carrying weight.
  2. The above disadvantage is more than overcome by its advantages if the stand does not needed to be moved too far or too often.
  3. The tripod stand is far easier to use, in practice by orders of magnitude, than single leg stands.
  4. No energy is required to move the stand against single leg support frictional resistance or non frictional elasticity*1 as the sieve swings freely under gravity.
  5. The tripod can be used in a far more relaxed manner, such as sitting down comfortably (photograph in field trip report)
  6. The stand can even be leaned upon when shaking to allow different muscle groups to take over
  7. When a patch has been located and diggings have been dry sieved the stand can be adapted very easily to immerse sieve remains in water for further sieving, scrubbing and examination without having to hold sieves up to the sun and squint.

*1: A problem with single leg stands is that the sieve set needs to be moved against the support force of the stand, unlike with a tripod stand. Even when energy is stored through elasticity (such as a thin rod in ground) the conserved energy is not necessarily released in a way that can be fully harvested to conserve human energy.