Centrifugal Clutch for Go-Kart Racing

Design and Prototype by . . .


Problem Statement

To design and manufacture a high performance centrifugal clutch prototype for competitive go-kart racing. The clutch must engage within an externally adjustable range. The clutch must also be lightweight, reliable, and engage smoothly.

Specifications

  • The clutch will transfer up to 6.5 ft-lbs of torque at the stall-engagement point.
  • All replaceable components will be designed for 230 cylces.
  • Non replaceable components will be designed for "infinite" life.
  • The total overall weight will not exceed 20 oz.
  • The stall-engagement point will be adjustable to speeds of 6500-9000 RPM.
  • The stall-engagement speed will not vary more than +/- 50 RPM.
  • The clutch will be able to withstand speeds up to 14,000 RPM.
  • The internal air gap will be adjustable from 0.000 to 0.035 inches.
  • The clutch will be able to dissipate 8,000 Watts to maintain reasonable operating temperatures.


Test Stand and Prototype

Summary

In the course of this project we designed, prototyped, and tested a centrifugal clutch for competitive Go-Kart racing. These karts are configured such that there is no transmission. Instead, a clutch which drives a chain and sprocket on the rear axle, is attached directly to the engine output shaft. When the engine reaches an optimum speed the clutch engages. The design utilizes the centrifical force of levers mounted to spinning pressure plates to engage a drum connected to the output driver sprocket.

Much of the prototype design was done using CadKey 7.5 for windows in 3D. We produced working drawings and CAM part programs. The majority of the machining was on a CNC mill in the mechanical engineering machine shop.

In order to evaluate the design we fabricated a dynamic test stand (see Figure 1.) A salvaged automobile differential and rear axle assembly was used as a differential load. Output shaft and engine speed were measured using an incremental shaft encoder and magnetic sensor respectively. The magnetic sensor was targeted at an aluminum disk and measured engine speed by sensing the frequency of irregularities in the target. We used a stepper motor to control the engine throttle. The data was used to identify engagement start and stall points to compare our design to existing products.

Based in part on our testing, we developed an improved design using Solid Works. The improved design meets weight specifications, improved the clutch lever expansion force, and increased the clutch's heat dissipation rate.

Us
The Intuitive Design Team


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