New swingarm designed using Autodesk's generative design tools.
On June 30th 2013, Richard Hatfield, CEO of a small motorcycle company, stood, quietly confident, at the foot of Pike's Peak, Colorado, alongside his fully electric bike and racer Carlin Dunne. Two years previously Lightning Motorcycles made waves by becoming the first electric powered bike to break the 200 mph park, and Richard knew the LS-218 was about to make history again in the race to the clouds.
"Next year, you should bring batteries,” Hatfield quipped after the bike smashed not only the rest of the electric field’s times but beat the fastest gas-powered bike by almost 21 seconds. The posted time of 10:00.694 remains a record for an electric motorcycle, in spite of the wet and snowy conditions at the peak 5,000-foot ascent. Lightning Motorcycles had a distinct advantage over some of the more well-established names in motorcycling, all of which were competing to bring the fastest electric bike to the mountain. Lightning was starting from scratch, unencumbered by traditional preconceptions of how one manufactures a bike. Using a suite of Autodesk software and 3D printing technologies Lightning was able to be agile in its iteration process.
"We can make quick changes and have a working part on the bike within a day," Hatfield said.
Amongst the software Lightning was deploying was Autodesk's Project Dreamcatcher - a demonstrator of its much talked about generative design capabilities, now available as a technology preview with Autodesk Fusion 360 and Autodesk Netfabb. Generative design tools allow you to explore a multitude of design solutions based on goals and constraints, unlike optimisation software which only allows for refinement of a known design. By cutting the weight of the bike without compromising performance, Lightning is now aiming to make the LS-218 even faster by deploying new design methods, additive and a manufacturing process that has been around for hundreds if not thousands of years, casting.
Heading up the project on the Autodesk side is Andreas Bastian, whose previous work on a magnesium aircraft seat frame using Autodesk Generative Design and Netfabb, was shortlisted for a TCT Award in 2017. The seat frame recorded a 56% weight saving and is on its way to being approved as flight-safe by the FAA.
Lightning had previously attempted to lightweight the bike's swingarm using composite 3D printing technologies, although the designs worked in theory the material properties were unlikely to withstand the forces required when riding such a powerful machine. For Andreas, it was logical to start with some of the techniques picked up on the seat frame project.
"We have looked at the swing arm because it is a nice scale of a problem," Andreas tells TCT. "It is traditionally made of three parts bolted together, it is made of known materials using known manufacturing processes, and it was developed by engineers, who know a ton about motorcycling."
Previous generatively designed projects had clear goals in that they needed to be both lightweight and structurally sound. However, the swing arm required both those quantitative goals as well as one more qualitative one; maintaining the allusive 'ride feel,' that is crucial to experienced riders.
It was determined using the simulation tools in Autodesk Generative Design, that there were five primary load cases, and to sustain ride feel the swingarm needed to match as many of these as possible, while at the same time reducing weight.
"What's interesting is you want a different amount of stiff ness for different behaviours," states Bastian. "You need high stiff ness for normal operating mode because if you are riding and hit a speed bump and your swingarm is floppy, then you will momentarily lose contact with the road and therefore bike. Whereas under race conditions when banking at angles of up to 50 degrees vertical you need a more deflection."
The generatively designed swingarm matched its original counterpart in four of the five load cases, with the fifth outperforming by as much as 55%.
Casting Aspersions
While a generatively designed part may look impressive onscreen and perform under Autodesk's rigorous simulation tools, manufacturing is another issue entirely. Although generative design tools and additive manufacturing (AM) have grown up together, for this particular project, Andreas knew that AM wasn't going to be able to produce the final part. Enter casting.
"We haven't seen a whole lot of shapes like those of generative design and a manufacturing process like casting overlap," he comments. "That is largely just cultural; it is not a technical reason. A lot of these new design capabilities are conceptually tied to additive and specifically direct metal additive, but casting has an incredible amount of shape flexibility too."
Casting also benefits from being a mature manufacturing process with qualification pathways for hundreds of materials including application specific alloys. Direct metal additive's value proposition against casting is centred around lead times and agility but by using what Andreas describes as 'No Tool Casting' this argument all but evaporates.
"Most of the lead time and cost in casting is in the tooling," Andreas states. "The foundry we are working with on this project use a voxeljet sand printer to directly print their moulds. Using this method, you effectively get all the value proposition of direct metal additive plus all of the advantages of casting."
Although sand printing for foundries is not new, it is the addition of Autodesk Generative Design that takes this project to another level. The foundry in question is Tooling & Equipment International (TEI), based out of Livonia, Michigan, and its President, Oliver Johnson concurs with Andreas on casting's future for generatively designed parts.
"We have combined advanced simulation and computer controlled casting with 3D sand printing to produce a fast and reliable method for casting almost any geometry," he states. "The potential of applying these technologies is vast, and we are working on expanding our capabilities even further to cast products that were previously unachievable."
The generatively designed swingarm was printed, cast in A356 aluminium, cleaned, heat treated, machined and inspected within three weeks, with the whole process taking only a few months. This kind of agility of manufacturing gives Lightning its speed on the track before anybody else.
"The democratisation of technology will enable new ideas to be brought to market quicker and allow startups to compete with large legacy enterprises." CEO, Richard Hatfield told TCT.
Earlier this year, an electric vehicle made by Tesla just 15 miles down the road from Lightning's headquarters in San Carlos, California is hurtling at 24,500mph towards Mars. While we might not match that here on earth, you can be sure Lightning Motorcycles and Autodesk will continue to push the limits of what is possible.
