Paul Hammerstrom Design, Llc

Phone: 603 801 4411
Address: 14 Columbia DriveAmherst NH, 03031USA

Alter Cycles Project

Paul Hammerstrom Design > Alter Cycles Project

Alter Cycles Project

Alter cycles approached us about helping them with their new bike concept. Mark Groendal, a bike industry legend who designed the famous Slingshot bike, had a new frame concept based on his original Slingshot bike. This time, he wanted the down tube to BE the spring instead of adding an actual spring in place of the downtube. They had a rideable concept, however, they needed it refined. They needed it modeled in CAD so that they could have proper 2d drawings sent to the manufacturer and they needed FEA done so that the frame would pass the ISO frame standards. They wanted the frame designed so that the flexible downtube would be identical on all the frame sizes. The frame modeling included doing some surfacing on the top tube and designing the top tube so that it flexed along with the downtube but needed to keep the stress low so as not to fatigue during testing. We also used  our bike industry experience to help them source dropouts, make sure cranks would clear the chainstays, optimized  the cable routing, once we had the overall design fleshed out and we had the drawings in place, we set up an FEA model. This was a pretty complex task because the downtube was removable, had special high strength Zytel connectors, and the ends could rotate. We started with simple constraints and loads and gradually made them more complex. We also mimicked each ISO frame test such as pedal fatigue and horizontal fatigue. We were able to build really robust models that allowed us to quickly change frame size and frame geometry so that we could optimize the tubeset. We used our experience with materials and designing lightweight structures for high cycle fatigue to come up with a design that would meet their flex criteria and pass fatigue testing.

This was a great project and our combined efforts culminated in a product that we are all proud of. Currently Alter is selling bicycles in dealerships and is looking to expand to as many dealerships as possible. So if you are interested in carrying them give them a shout! It obviously is a robust product! 🙂 More information about Alter Cycles can be found at

Check the Alter Cycles in action in the video bellow