On-site calibration keeps torque tests running

Torotrak has reduced its downtime and increased the efficiency of its test programme by installing HBM's TB2 torque reference transducer for calibrating its T10F torque transducers on site.

Torotrak, the UK developer of the infinitely variable transmission (IVT), has reduced its downtime and increased the efficiency of its test programme by installing HBM's TB2 torque reference transducer for calibrating its T10F torque transducers from HBM on site.

Torotrak uses HBM's T10F torque transducers to ensure a high degree of accuracy in the design and testing of its IVT technology.

The Torotrak IVT enables 20% fuel economy compared with standard four-speed automatic transmission systems by enabling vehicle engines to run at optimum power conditions without compromising vehicle design.

Torotrak uses a total of 14 HBM T10F torque transducers ranging in size from 200 to 5000Nm.

These are fitted to a variety of test rigs ranging from full power transmission and engine dynamometers to component test rigs.

Rigs at Torotrak include two chassis dynamometers for passenger cars with full emissions measurement.

Each of the Torotrak's torque transducers demands a different level of accuracy depending on usage.

For some of the component efficiency tests, Torotrak needs an accuracy class of 0.05 allowing it to measure variations of below 1Nm.

On its full power test rigs an accuracy class of 0.1 is more suitable.

Each torque transducer has to be calibrated at least once a year to ensure the instrument's accuracy.

By installing a HBM TB2 torque reference transducer on site the calibration has become much quicker with the test rig downtime reduced to a single day.

Previously the cost and time constraints meant that torque flanges were only calibrated once per year.

Because Torotrak can now undertake calibration in-house it has reduced the calibration period to every six months allowing any units that are subject to heavy usage, or where concerns over accuracy have been raised in the past, to be monitored more frequently.

According to Graham Riding, Manager Test Rigs and Facilities, Torotrak (Development): "For some rigs with specific test requirements we will calibrate immediately prior to the test programme and again at the end to ensure high quality standards are maintained".

Having the calibration rig on site gives Torotrak's test engineers greater flexibility when their test results are unexpected.

Remarks Riding: "Sometimes, part way through a series of tests, engineers would question the validity of results that was usually the fault of the test piece and not the torque transducer".

"In the past they have had to balance the inevitable delay in sending the flange to Germany for calibration against the possibility of working with inaccurate readings".

Now Torotrak can quickly check the torque transducer without delaying the test programme.

The TB2 torque reference transducer, calibrated by HBM to DKD standard, and the HBM ML38 amplifier enable Torotrak to achieve easily calibration to ISO9000 standards on its T10F torque flanges.

The ML38 is a stable high-accuracy carrier frequency amplifier that is housed in one of Torotrak's modular HBM MGCplus housings allowing the transducer and ML38 combination to be used as a traceable calibration kit.

States Riding: "One of the reasons we were attracted to the TB2 torque reference transducer is that the calibration procedure is straight forward and relies upon a comparison between a known reference and the T10F test transducer".

This means that there is no need to use calibration weights of exact known characteristics.

Because the reference transducer is compared directly to the test transducer, any method of applying the load can be used.

This means that the test engineers can calibrate the T10F torque transducers from their own test rig giving them much greater responsibility and control over the test results.

Torotrak has used HBM's torque transducers for several years.

Says Riding: "We have found the equipment to be reliable, robust, accurate and repeatable so there is no reason to choose another manufacturer".

Torotrak's IVT technology is critical to the European car market where companies are committed to delivering a significant average fuel saving in new cars before the end of 2008.

Similarly, increased pressures facing US car companies to reduce dependency on foreign oil supplies are driving the demand for accessible fuel economy technology.

A typical new car programme takes 36 months to deliver from production commitment through to market launch.

The production commitments for cars being delivered in 2007 and 2008 will be made through 2004 and 2005.

Adds Riding: "Torotrak aims to be included in at least one of the new car programmes".

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