Liebherr, in a revision of its truck mixer models, adopted steel of higher quality and introduced design improvements. As a result, there were improvements in reliability and operation life, and a reduction in the level of maintenance, it said.

The company said it was now using QSTE 500 steel, proven for its quality in truck chassis fames, for the mixer frame as well.

"Liebherr has responded to the favourable experience gained by chassis manufacturers with this innovative material, which has particularly good resistance to mechanical stress and wear," said the company. The mixer drum and spirals have been manufactured at Liebherr for many years from a special 27 Mn B5 manganese-chromium alloy steel.

"In order to reduce contamination from concrete deposited on the truck mixers during operation, a number of design modifications have been made - first for the HTM 904 on a four-axle chassis, one of the most popular models in Europe.

"The swivel chute support is now a close, single-arm bracket. An additional option is a two-sided cover for the rear drum mounting. As a result, there are only straight, smooth surfaces in the area most liable to deposits, and concrete is scarcely able to collect there. A sealing lip on the upper edge of the discharge hopper prevents concrete deposits on the drum from that side.

"The rear mudguards have been widened by 50mm towards the truck frame. A cover available as an option seals off the remaining space over the entire length of the mudguard.

"The outer wall of the discharge hopper has been extended outwards considerably and also raised. This provides on the one hand about 30 per cent more room for the discharged concrete and on the other hand reduces the danger of blockages with thick mix consistencies.

The tried and tested drum sizes along with their water volumes remain unchanged. As a result of the carefully positioned mountings and the drum geometry the centre of gravity is very low, which benefits the truck mixer's handling, according to the manufacturer.