The Snowy Mountain Scheme onwards
This month we complete the story of the Concrete Transit Mixer in Australia.
The First Fleet of Rex Mixers were found to be defi-cient by the Snowy Mountains Authority. The main problem was their mixing efficiency was outside the Authority’s allowable limits. The Authority moved quickly to bring to a halt all concrete mixing on its affected tunnel project.
Meanwhile Americans on-site suggested that U.S. made mixers would not experience the same diffi-culties experienced by the Australian-made Rex mixers and their unsuccessful modifications to overcome the Authority’s stop order.
A timely visit by a delegation was made to the U.S. to investigate how American-made mixers per-formed on U.S. Bureau projects. Their study found conversely that the Bureau of Reclamation (the American Authority for Civil Works), had never used truck mixers on any critical works and that they didn’t consider it possible for any truck mixer to meet their strict efficiency requirements!
As a result, Fowler Wood were thrown back on their own resources and got back into their overalls and climbed inside their drums on the Snowy. The issue of mixer efficiency to meet the Authority’s standard was finally resolved after considerable trial & error and some good luck, together with the cooperation of Mick Ryan, Concrete Control Engineer for the Snowy Authority. Finally, these Mixers were on the job and actually set a new world record for Transit Mixing efficiency. This in turn led to their use on other major projects and Dams requiring 3” rock!
The trials and tribulations of the Snowy Scheme proved in the end to be highly beneficial to mixer manufacturers and the pre-mixed industry. The end result was an industry code of performance similar to those achieved on the Snowy – a commercial standard probably not achieved anywhere else in the world.
Following the achievements at the Snowy, Marlak & R.M.C. Ltd. had been working hard to overcome problems with low slumps down to 1” as well as speeding up the charging of dry batch materials. Their elementary solution was to make the drum mouth larger in diameter. All Australian manufacturers followed suite and with subsequent improvements in blade pitch and angle developed by Fowler Rex, a zero-slump suitable for extruded Kerb & Gutter machines like the Kerbmaker (which Fowlerex also marketed to the USA), finally became a reality.
Meanwhile while Australian manufacturers were concentrating on improving performance at the back end; overseas manufac-turers were concentrating on the development of improved drive mechanisms, such as mechanical Truck Drive Power Take Offs (P.T.O.’s) and hydraulic drives at the front end of the Mixer unit. These improvements eventually led to the disappearance of the separate engine drive in the USA and the ultimate adoption of the hydraulic drum head drive – pioneered in Australia with the Rheem Challenge drum head drive and the Fowlerex 770 Rex drum head drive, both hydrostatic systems driven from the front end of Flywheel P.T.O. on the truck.
Separate Engine Drive Developments
There was little in the way of engine drive development until a Holden with automatic transmission was successfully tested in a Mixer rebuilt by Forbes Engineering in Queensland. The unit had a belt drive through to a 10:1 reduction gear and chain drive. This was followed soon after by the introduction of the Chrysler automatic in the Rheem Challenge Mixer. This arrangement was well engineered and gained enthusiastic acceptance from the industry.
The change to automatic transmission brought significant operational improvements such as single lever control, first intro-duced by Rheem. Both the Chrysler and Holden automatic units achieved many of the benefits of a full hydraulic machine in operating simplicity, smoothness and lower maintenance costs.
In late 2016, Cesco Australia (originally evolv-ing out of the Forbes years); introduced the Weight$aver Mixer to the Australian market. A 7.6m3 mixer, weighing on average approx. 350kgs. lighter than comparable mixers. Previ-ously weight saving mixer development came at a price – those being through loss of quality, structural integrity and/or performance lon-gevity. These issues were overcome by the design engineering team at Cesco, providing a sturdy, lower and more durable platform. Coupled with the recent, newly-designed CML10 Gearboxes from ZF Australia, the Weight$aver supports a formidable drive ca-pacity. A feature of the CML10 is its unique gearbox ratio when coupled with a larger pump (like the Rexroth 90cc EDC Pump); only requires the truck to Rev at 1400 PRM to achieve the 16 to 18 barrel RPM to meet the Australian Standard. This not only preserves the hydraulics, mixer gearbox and truck engine, but represents a 22% efficiency saving when loading and slumping.
Following the successful take up of the Weight$aver to the Australian market, Cesco again was at the forefront of the next ma-jor development in Transit Mixer development in Australia – releasing the Frameless ”Low Rider” Mixer to the market in late June, 2017. Cesco, along with its design partners Mack Trucks and Boral Concrete worked togeth-er to deliver the first Lower Centre of Gravity (LCG) Truck and Transit mixer combination. This LCG mixer was designed to improve the vehicle’s natural road holding ability, reduce the risk of rollovers and introduce a low mainte-nance capacity for hydraulics and drive parts.
The pioneers of the pre-mixed, transit mixer industry laid the foundations for the current industry we are occupied in today. Engineers like Aspdin of Portland Cement fame, Brunel, Hyatt, Monier and Ransome are some of the leading lights that laid the footings for the local equipment manufacturers to imagine the pre-mix possibilities and perfect the machines.
Then Australian entrepreneurs took the baton to promote this new Australian technology to all levels of industry on these shores; but also to many parts of the world where pre-mixed concrete had not existed. Even creating new technologies to ex-port back into the USA, where the technology had initially originated from.
* Pictures, content and excerpts sourced & edited from: 1/ The Australian Truck Mixer – Its Origin and Development, published by NRMCA (National Ready Mixed Concrete Association of Australasia).