AH Gears
AH Gears provides industrial gearbox design and manufacture services, up-tower maintenance and inspection on existing gearboxes, and has gear manufacturing, profile gear grinding, and machining capability.

In August 2013, NZWEA talked to Andy Horsfall, Managing Director of AH Gears, an Associate Member of NZWEA.

Andy started his apprenticeship in a gear shop in the UK 48 years ago, before moving to NZ where he worked in a gear manufacturing shop. In 1981 he set up a successful gear business in the Bay of Plenty then in 2000 he sold that business to form AH Gears Ltd. AH Gears provides quality industrial gearbox design and manufacture as well as gear cutting, computerised numerical control (CNC) gear grinding, and CNC machining, along with the repair and maintenance of existing gearboxes. Their specialist services include planetary, worm, bevel, splines and helical gears.

AH Gears are located in Auckland and made all the gearboxes for the 500 k/W wind turbines at Te Rere Hau.

How did you get into the wind energy sector?

AH Gears explained to NZWEA that some time ago, Andy attended a gear failure analysis course in Montana. The course was run by Robert Errichello, one of the world’s leading experts in gear failure analysis. During the course Mr Errichello explained the gearbox issues involved in the wind industry and recommended that anyone invited to get involved in that aspect of the gear industry should run a mile.

A week after Andy’s return, he was approached by Windflow Technology to design and build the torque limiting gearbox at the heart of the WTL 500 Wind turbine. Andy ignored the expert’s advice and took up the challenge.

It took around 18 months from the initial design to build the first gearbox, and, although the gearbox continued to evolve, one of the very early gearboxes continues to operate on the Port Hills in Christchurch. AH Gears has now built 97 of those gearboxes and the design and manufacturing processes have received International certification to the highest standard - approved to IEC class 1 edition 3 certification.

What percentage of your business does the wind industry make up?

According to Andy, wind has saved AH Gears from shrinking, which is rare among engineering shops these days as manufacturing in New Zealand continues to decline. AH Gears has up to 4 of their 16 employees working on wind-based projects at any one time utilising various precision CNC turning milling and gear manufacturing machines.

“We are now involved in retrofitting and repair of wind turbine gearboxes, working on Trustpower’s 660kW turbines where we incorporate all the latest modifications normally carried out in Europe to bring the rebuilt gearboxes up to the latest specifications. Once gearboxes are out of warranty we recommend improved bearing arrangements and lubrication modifications to extend the gearbox’s life. Trustpower has indicated we will be considered for the retrofit of their 3MW turbines when they come out of warranty.”

Andy’s dream is that, with NZ’s fantastic testing grounds among the roaring forties, they could develop and manufacture a successful 2–3 MW gearbox here in New Zealand.

How has being in the wind industry changed things for your company?

Since getting involved in the wind industry AH Gears has implemented AS/NZS ISO 9001; 2008. They have been audited by and received approval from both Vestas and Lloyds to manufacture components and manufacture or rebuild wind turbine gearboxes.

“The certification and approvals have improved our systems, processes and our reputation. Our ISO certification demands continuous improvement and we are constantly reviewing ourselves with that in mind. We reinvest a considerable part of our profits into upgrading our design and manufacturing capability, keeping up with the latest gear grinding technologies and design software.”

Do you have any innovations that have arisen because of being in the wind industry?

The final design of the WTL 500 gearbox incorporated three planetary stages, and one parallel stage, using flex pin technology that allows better load sharing between planet gears. This allows eight planets in stage one, four planets in stage two, and six planets in the output stage. The lubrication system had to deal with low speed high torque and high speed 'wheels within wheels' that challenged conventional lube systems and needed AH Gears to find an innovative solution using centrifugal force to get lubricant into the 4th stage planet bearings. The 4th stage planetary was used for the torque limiting system which allows the gearbox to effectively change ratio to cope with excessive torque generated during sudden wind gusts yet maintain continuous output speed allowing the use of a synchronous generator.

“We have also used our gear design software to predict deflections in the cantilevered yaw pinions and then ground lead corrections onto existing yaw pinions to extend the life of the yaw gears,” said Andy.

“We see opportunities arising for more innovation in existing turbines once we become accepted as credible wind turbine gearbox engineers. Wind farm owners are justifiably wary of making changes to the OEM supplied components before strong relationships and understanding have been built.”

What’s the best thing about wind energy?

“NZ has a fantastic wind resource and it would be a shame not to use it. Wind turbines are elegant works of art that minimize pollution and help maintain NZ’s “clean green” image. Wind is a great way of increasing New Zealand’s generating capacity to match our growth rate as well as being one of the most economic solutions for replacing older thermal generators.”

What’s the worst thing about wind energy?

“It seems to be hard to talk people into investing in this solution. I think the general public still resists wind energy because they think turbines are noisy and detract from scenery. For me though, from an engineer’s perspective, turbines are engineering masterpieces to be admired. If the media were to broadcast people’s positive experiences with wind energy then maybe the overall populace could be turned around to get on board.”

How can NZ get to 20% of our electriticy generated by wind by 2030?

AH Gears believes NZ needs to build local capability and expertise for repairing wind turbines since sending components offshore for repair is prohibitive.

“To make wind turbines economical in NZ, we have to run them in extreme conditions, which places very high stresses on the turbines. Local companies are best placed to develop understanding of those stresses and come up with cost effective solutions,” said Andy.

What would you like to see AH Gears achieve in the wind energy sector over the next year?

“We will ideally make good progress with building a wind turbine gearbox load test rig that will enable us to partial load test the 2.3 and 3 MW gearboxes. We have already invested in heavy lifting equipment and the load test rig is the next obstacle to overcome. The cost of removing and replacing these large gearboxes to and from the tower is huge and therefore it is important to have a reasonable load test carried out for everyone’s benefit. Unfortunately, building a reliable load test rig will cost a seven figure sum, but we are confident we can make it happen over the next couple of years.”