CAD/CAM Speeds Design And Machining For Cycle Shop

In the 1950s, George Smith had one goal: to make American motorcycles faster. At that time, high-performance aftermarket motorcycle parts weren't available. Therefore, Mr. Smith decided to design and manufacture his own performance parts for Harley Davidson engines. Demand for his components grew so Mr. Smith established S & S Cycle (Viola, Wisconsin) in 1958. Over the years, the company has produced parts that include power kits, carburetor and fuel systems, transmissions, gaskets, seals, valves, heads and complete V-Twin engines.

Today, George Smith Jr. races in the National Hot Rod Association with fellow racer, George Bryce. Their team does on-track testing with their V-Twin motorcycle engines.

“Our engines compete with the Japanese four cylinder engines, which has been challenging for the R&D team and George in particular,” remarks Barry Peterson, a prototype R&D CNC machinist.

To stay competitive on the street and the strip, S & S Cycle takes advantage of CAD/CAM software to develop customized racing parts that it would otherwise not be able to produce. The company relies on Mastercam CAD/CAM Mill Level 3 with Solids software from CNC Software, Inc. (Tolland, Connecticut). This software enables S & S to design more complex products and parts and machine them faster.

S & S Cycle has also found that the software allows it to bring in a model from CAD software and generate tool paths for basic contouring, drilling and tapping, in addition to complicated profiles and intricate surfaces that are continually changing in surface finishes.

“Mastercam is making a difference when dealing with complex surfaces,” says Mr. Peterson. “It has allowed us to make difficult parts with complex surfaces that weren't practical or previously possible for us to do.”

The company's V-Twin engines are made with billet, cast and forged parts. The bulk of the prototype parts are made from billet material to save on the time and cost of producing castings and forgings. S & S Cycle's most complex surfaces are found in its racing cylinder heads that contain the combustion chamber, valves and ports.

“Cylinder heads have been an interesting R&D project because of the ports for the air/fuel mixture and exhaust,” says Mr. Peterson. “The key to producing a lot of horsepower is to have a good cylinder head with ports that flow air and fuel efficiently and produce a good burn pattern in the combustion chamber. This is something that we are always working to improve.”

The billet Pro Stock heads start out as aluminum rectangular blocks that weigh 68 pounds. After machining, they weigh between 12.5 pounds and 13.0 pounds. For racing, it is crucial to eliminate as much extra weight as possible, but at the same time, the heads must be durable. Wall thickness between the outside of the head and the ports has to be constant. Ports also need the appropriate surface finish to reduce flow turbulence and allow the air/fuel mixture and exhaust to move quickly. The company roughs with a ¾"- ball-tip end mill and finishes with a “mini-master” ½"- ball-tip end mill. A handwork operation is performed to smooth out the port's walls. “These heads are more like a sculpture with unusual surfaces, which are machined and blended together,” remarks Mr. Peterson. “Roughing a port might take 9,000 to 10,000 blocks of G code, and finishing requires even more code.”

“Machining ports with a five-axis Fadal is something we've been able to do now that we have Mastercam,” says Mr. Peterson. “The software allows us to produce a tool path for a spiral cutting pattern in the ports and then duplicate it.” Now Fadal's digitizing option can be used. Points from digitizing are imported into Mastercam. Then, surfaces are created from which a tool path can be produced. Ports can be duplicated that were originally done by hand. After checking the flow pattern, the user can duplicate the pattern and machine it. The company says this is more consistent than doing the ports by hand.

The company also relies on the software's ability to import and export various files. The engineers design 2D drawings and 3D surface models and can save the files in IGES or DWG format.

S & S Cycle chose the CAM software to address needs such as improving surface machining and cutting ports in heads, along with the ability to make customized parts without producing castings. Although S & S uses Mastercam primarily for R&D work, its part programmers plan on using it for production components. “Our production group believes that the program can potentially help us make programming more efficient,” adds Mr. Peterson.