billets and part tolerances can be as tight as 0.0005" (0.013 mm). However, the motorcycle frames are made from 4130 Chrome molybdenum tubing with walls that must be at least 0.058" (1.5-mm) thick, and ODs are between 0.875–1.000" (22.2–25.4 mm). There is also some oval-shaped tubing used. Sentry and its racing work both started when Yates recon- nected with long-time neighbor and friend Ed Grothus, team owner of Grothus Racing and current vice president at Sentry Industries. Grothus Racing is also the exclusive retailer of Sentry’s high-performance racing parts and assemblies. Yates had always been interested in drag bikes and was at a race when Grothus’s team broke a very expensive, tough-to-replace transmission part. Yates suggested mak- ing the part themselves and offered his and Rabbit Tool’s machining services because at the time he was still working for Birkestrand.
After that initial part, Yates helped build drag bike chassis as well as several other components and assemblies. He then realized he could offer these same components and as- semblies for retail sale, and officially launched Sentry in 2014.
Seizing the Opportunity “Grothus knew how to build a good chassis himself, but he was at the mercy of vendors and outside suppliers for other parts,” said Yates. “These included front-end assem- blies, aluminum billet parts, engine components and a lot more. So, I offered more of Sentry’s help, and we now build complete race-ready rolling chassis—frame, front and rear wheels, handlebars, carbon fiber bodies and other parts—for other teams that just have to bolt-on their own engines.” Sentry’s first big commercially available product was a drag bike front-end assembly. This consisted of the fluid-filled lower legs, plungers, outer and inner parts, axle and triple clamps (upper and lower) that attach the assembly to the bike frame’s head tube. A drag bike’s front wheel lifts off the ground at the start of a race and, for the most part, stays that way for about half of the run. When it does return to the track surface, the front- end assembly must completely dampen the impact. Sentry initially tooled up to produce 15 to 20 front-end assemblies, just to see how well they’d be received in the marketplace. They proved quite popular, mainly because of the significantly reduced cost yet very high-quality workman- ship and performance. The shop was able to reduce its pro-
duction costs, and thus pass the savings on to customers. Acquiring its Mazak VCU 500C allowed Sentry to machine the assembly lower axle blocks, the one part that had been farmed out and was very expensive to have produced.
Digital Dashboard
As a unique aspect of its front-end assemblies, Sentry’s triple clamp set includes a complete IQ3 race pack digital dashboard. It displays a variety of gages to monitor every- thing from engine rpm to oil pressure, as well as any other sensors used on a racing bike.
The dash attaches to the clamp set without brackets. In the past, teams had to make custom brackets to mount these gages to their existing front ends. The setups were often so bulky, that some teams would run without a dashboard. Some of Sentry’s more complex components are those
for its throttle assemblies. The shop is one of a few able to machine the challenging parts and do so cost effectively. “Throttle assembly parts require high CNC machine capa-
bility, such our Mazaks deliver, and very skilled machinists,” said Yates. “These are a perfect example of the complex parts we chase. Any shop can machine simple wheel axles, but it’s a whole different ball game to produce these throttle parts. Once we got going on the assemblies, they flew off the shelf and continue to be hot sellers.” The individuals involved with Sentry are a close-knit
group. In fact, the Sentry name is a combination of the three key players. The “S” is for Scott Yates, the “E” for Ed Grothus and the “N” for Norman Korte, treasurer at Sentry Indus- tries—all followed by the word “try.” Yates and Sentry still work closely with Rabbit Tool and Birkestrand, and together both shops have ventured into the wind energy sector. They plan to produce residential wind turbines that are compact and built to mount on rooftops. If all goes according to plan, their specific design will not only generate electricity, but also heating and cooling for homes. Sentry will be the main parts supplier for this project. The shop also plans to further expand its presence in the high- performance racing industry by producing some of the larger components for drag bikes, which, according to Yates, will mean more Mazaks at Sentry.
Edited by Yearbook Editor James D. Sawyer from information provided by Mazak Corp.
69 — Motorized Vehicle Manufacturing 2015
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