A sawmill suitable for Nitens and other hardwood logs

The way he was … Karl Goiser operating the gang frame saw in 1955

While we are talking, or sleeping, our Tasmanian nitens forest plantations are growing and growing, bringing forward the day when they need to be harvested. As is obvious and also has been well documented (R Washusen, Technical Report 2009) our hardwood sawmills are not suitable for this upcoming resource due to low recovery of about 25% and low productivity due to a number of factors.

Sawn timber produced from niten logs is of vastly lower dollar value compared with that from old growth forests. Therefore a mass production process should be used, coupled with a much better recovery. Ideal for this is the gang frame saw, the common sawmilling machine throughout Europe. However, for our application not cutting whole logs, but quarter section logs, introduced into the machine with the round side at the top or at the bottom, by this method producing 100% quarter sawn boards as required by the market.

Typically up to about twenty saw blades may be used, usually of 2 mm thickness, tensioned by a hydraulic tensioner rigidly tensioning all the blades simultaneously at about 4 t each. While gang frame saw blades make a kerf of only 3 mm, circular saws may make a much wider cut. Resulting in 3% loss of recovery per mm of wider cut when cutting 30 mm boards. Furthermore, because the boards produced by a gang frame saw are of exact thickness there is no need to over-cut, saving about 6% recovery. Also, there is no need for face cutting because there is no problem with spring since all the boards from a quarter log are cut in the one pass.

Such a sawmill would not require log sorting. First a log would be lengthwise cut in half with a single blade bandsaw or a saw with circular blades. Then each half would be lengthwise cut in half by a single blade bandsaw or a flat-top circular blade saw. The resulting quarter logs are then introduced into the gang frame saw, end to end in a continuing process, with the sawn surfaces of the quarter log at 45 degrees to the top or bottom feed roller of the gang frame saw. The boards that arrive in batches out of the gang frame saw can now be edged in a multi blade semi automatic edger, or stacked for drying and later processing.

The recovery rate for logs of 30 cm and bigger is expected to be between 45% and 60% depending on log size and dimension of sawn timber to be produced. Every unit in the production line is used in one pass only, all without reciprocation.

It should be noted that this sawmilling process (Innovation Patent 2012101038, 11 July 2012) is equally suitable for any other old growth or regrowth forest hardwood. Also, the gang frame saw could also be used for milling whole pine logs.

Small niten logs, or any other, could be processed whole in one pass through the gang frame saw. For example: for logs of 15 cm diameter plus the machine may be set up for two boards 20 mm in the centre (quarter sawn), outside of which on each side one 35 mm board for edging to 90 x 35 mm studs, ten on either side two more saws for 20 mm (back sawn). Expected recovery about 42% to 55%.

Due to my many years of experience in sawmilling both in Europe and here in Australia I feel compelled to submit my article on this subject as follows below.

Shortly after WW2 I served a three year apprenticeship in Austria as a sawmiller, which included two months of each year attending the Austrian Sawmilling School at Kuchl near Salzburg. Passed the exams with distinctions.

1954 was accepted for immigration to Australia as a sawyer. After four months at a sawmill north of Brisbane was offered and accepted the position of gang frame sawyer at their then new sawmill of Burnie Board & Timber. The following picture shows me operating the gang frame saw in 1955. This machine unfortunately was the wrong choice for hardwood and was soon replaced with a European model with intermittentt feed.

Part time agent for a Melbourne machinery company, then own business. Started and operated Burnie Machinery, then at Cooee, Tas Chainsaws at Wellington Street Launceston, and Machinery International (Machines for Wood) at Kings Meadows. Retired in 2007.