that minimised meshing interferencewhile at the
same time decreasing backlash by 45–50percent
over the HTD beltand substantially more over roller chain.
well-known Poly Chain tooth profile.
"
Synchronous belts feature carbon fibre tensile cord
Paul Boughton
In today’s high performance driven worldpower transmission parts that need to be incredibly strong and lightweight are not made of steel. They are made of premium grade carbon fibre.
First used by NASA in rockets and space capsulesnow used in everything from high-end racing bicycles to high performance race cars to the newest passenger aircraftcarbon fibre composites have superseded the use of metallic materials in many highly demanding applications.
Gates has incorporated these premium grade carbon fibres in synchronous belts.
Synchronous belt design underwent substantial development since the 1940s. Early synchronous belts could not handle the torque of chain drives at low RPMs.
Second generation synchronous beltswhich are known as HTD beltswere developed during the 1970s to displace chain drivesbut they were not found to be a practical alternative in most low speedhigh torque applications. This was because the belt had to be four to five times wider than the chainand it cost significantly more.
Curvilinear tooth profile
It took another 15years for the materials and technology to evolve to a stage where a synchronous belt could compete with a chain drive.
The first of these beltsthe Gates Poly Chain GT beltincorporated a patented curvilinear tooth profile
Made with polyurethane compounds combined with aramid fibre tensile cordsthis belt provided a truly suitable replacement for many chain drives.
The Gates Poly Chain GT belt underwent several evolutions in design since its introduction over 20years ago.
The latest evolutionthe Poly Chain GT Carbon beltincorporates a carbon fibre tensile cord that gives the belt greater strengthflexibilitymoisture resistance and power density.
Why carbon cords?
Research and development surrounding carbon fibre has progressed steadily over the past three decades.
Gates has pioneered the use of carbon fibre in a dynamic applicationin the tensile member of a synchronous belt.
This patented carbon cord design gives the belt performance attributesincluding: high flex fatigue resistance (better than aramid)dimensional stabilityhigh power density for more compact drive designshigh strength to weight ratio.
At the same timethe stretch of the belt is virtually zeroresulting from the high E-module of carbon fibres. As a resultthe tensioning of the belt remains constant during the whole service life (provided drive installation is correct).
The engineer can save space as well: The high power density allows for the use of narrower beltsand the optimised fatigue strength is key to the use of smaller pulleys.
With a Poly Chain GT Carbon belt of only 22mm wide the same power transmission can be acquired where before a rubber synchronous belt of 170mm (HTD)85mm (GT) or a previous generation polyurethane Poly Chain belt (GT) of 37mm had to be used.
Maintenance is virtually eliminated with carbon synchronous belt technology. Assuming that the belt is properly installedit will never need to be retensioned. No lubrication is required. The absence of chordal action makes the belt smooth-runningreducing wear and tear on other drive components.
Practical applications
The first practical applications confirm the advantages of the new belt. In a UK water utilityfour 4SPA belts driving a 30kW fan have been replaced by Gates carbon belts.
In this case the plant is running 24hours per dayseven days a week and 50weeks in the year. Motor efficiency is 94percent.
At energy costs of 6.65 Cent per kWh and a replacement of the belt twice a yeartotal operational costs of the drive amount to £13560.59peryear.
For the replacement a single 12mm Poly Chain GT Carbon 14MGT belt was sufficient and furthermore this belt needs replacement only once in three years.
As a resulttotal cost is reduced by £2 440.9 and this number refers to one single drive in a period of just three years. In the given example60 drives of that kind were replacedresulting in yearly savings of £146428.58 representing 20percent of the total cost.
Drive technology
Gates sees the application range of Poly Chain GT Carbon in the whole industrial drive technology as well as in automotive applicationsmotorcycles and the auxiliary drives of forestry machines and construction equipment.
This product is not only relevant for the OEM business; the replacement of existing drives is no problem because the new belt makes use of the
Enter 57 or at www.engineerlive.com/ede
Matthias Farrenkopf is Technical DirectorGatesGmbHAachenGermany. www.gates.com/europe/pti
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