European mobile crane manufacturers are testing prototype crane models with a new ZF transmission. Following on from the now popular AS Tronic mobile crane transmission ZF has introduced the TC, aimed at larger and heavier mobile cranes. The TC Tronic combines the automatic (via a clutch) gear changing of the AS Tronic with a torque converter.
ZF has confirmed that TC-equipped mobile cranes were being tested by at least one European crane manufacturer.
Clutch wear is a particular consideration when heavy vehicles, with a low power to weight ratio, are pulling away from rest or manoeuvring slowly. A lighter vehicle, with a higher power to weight ratio, can be got moving without too much clutch slip so the clutch lasts a long time. A heavy vehicle with high rolling resistance from its many wheels, and perhaps on sand or mud, needs a lot of clutch slip to get it in motion, to overcome the resistance.
To better cope with this the new TC Tronic has a torque converter that can slip indefinitely if required (assuming the cooling system is up to it) instead of burning out a mechanical friction clutch. It gives a more cushioned drive take up than with a friction plate clutch and so is more likely to pull away smoothly and maintain traction between the tyres and the ground.
ZF claims further benefits for the TC including better fuel consumption than a manual transmission due to the automatically controlled torque converter lock up clutch and less excess load on the entire driveline. The friction clutch only operates during actual gear changes and the torque converter is bypassed under normal driving conditions. Gears can be shifted automatically or on demand from the driver but, as with the AS Tronic, he only has to operate accelerator and brake pedals and incorrect gear changes are prevented by the electronic control system.
The 12 speed (plus two reverse) 12 AS 3002 TC Tronic is suitable for cranes, heavy haulage and other special vehicles with input torque up to 2,700Nm. It is available with an integrated primary retarder, PTOs and gear selector unit with display.
