UL260i Flies High, Thanks to ZW3D
In 2004, Russel Pescod, partner in ULPower Aero Engines (www.ulpower.com), was working on a helicopter project, an...
In 2004, Russel Pescod, partner in ULPower Aero Engines (www.ulpower.com), was working on a helicopter project, and he was having a problem. The performance simply wasn’t what he and his collaborators had hoped it would be. After attempting to improve the performance of the experimental light helicopter for nearly a year, they began to suspect that the engine, which had been purchased from a third-party vendor, was the culprit. They took the engine to a performance shop, put it on a dynamometer, and found that the horsepower was significantly less than the manufacturer had promised.
A Momentous Decision – Let’s Build Our Own Engine
“We needed more power, so we talked to an engine specialist,” Pescod says. “We found there were basically two routes to the power we needed. We could buy an existing engine, strip it, refit it and rebuild it, or, we could build our own engine from scratch. Ultimately, we decided to design and build our own engine because we could control all the variables.”
With that decision made, Pescod began looking for a suitable CAD package to be used in designing the new aircraft engine. After much research he selected ZW3D. He says, “We chose ZW3D software for several reasons. One, we’re a small company with limited resources, so our choice had to be cost-effective. Two, ZW3D doesn’t skimp on performance; it had all the tools we needed, and then some. And finally, ZWSOFT was very supportive of what we planned to do.”
From Start to Design in a Month – with ZW3D
Pescod set out to build a flat-four, fuel-injected aircraft engine. The flat four is a proven configuration and fuel injection would deliver a lot of advantages over a carbureted engine: lower maintenance, plug-and-play computer-control performance, better fuel economy, immunity to pilot adjustment, elimination of carburetor icing, and better aerobatic performance.
“I designed the entire engine in complete detail before we cut a single piece of metal for the prototype, and it took just under a month with ZW3D.” Pescod says. “I created my own library of nuts and bolts so that when I specified that a certain bolt goes in a particular location, I knew that it would fit exactly.”
With ZW3D software, Pescod was able to move pieces around to make sure that everything fit correctly, that the holes lined up, and even that tools will fit when it comes time to maintain the engine.
“The ability to make pistons, connecting rods, crankshaft, camshaft, and valve train move in unison facilitated checking for interferences between any of the moving parts” he says. “ZW3D allowed us to optimize the engine design so that it would fit into the smallest possible area, saving both space and weight, which is critically important for an aircraft engine.” Mass properties were used to calculate the weight of individual components and made it easy to get a quick answer on the weight of subassemblies even when the components were not on hand.
Another handy feature of ZW3D became apparent when Pescod was designing the cylinder heads. The inlet ports are curved to get the air to “swirl”, and one of the key measurements that Pescod needed to know was the thinnest point between the inlet and exhaust ports. If that wall is too thin, the heat of the exhaust can melt it, with disastrous results. Fortunately, ZW3D made it easy to obtain that measurement and to adjust the wall dimension as needed.
Dynamic cross-sectioning was also very important to make sure that sufficient material was present between bolt holes and various passages in the cylinder heads. Area calculations for complicated parts such as cylinder heads were used for checking price quotes for aluminum anodizing.
Pescod notes that the ability to “virtually” build the entire engine in ZW3D software saves money when it comes time to build prototypes because the designer can eliminate so many potential errors. He is quick to point out that one of the advantages of ZW3D is that the design files can be cleanly exported and used to drive milling machines to make the parts. This is important for design-only companies that cannot take advantage of ZW3D’s integrated machining. He also says that some customers request that they design the aerodynamic cowling that covers the engine, and ZW3D excels at that difficult task.
From the day that Pescod first sat down at the computer to the day that the first proof-of-concept prototype was fired up was less than seven months. Today, numerous light aircraft around the world are powered by the UL260i, the remarkable engine that ZW3D helped to build.
Note:VX CAD/CAM software and technology has been acquired by ZWCAD Software Co., Ltd. VX CAD/CAM has been rebranded as ZW3D. All the testimonials of ZW3D refer to its predecessor.