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Machine Design

Curvy robo-caddy takes shape with CAD

Designer Mark Stewart at Stewart Golf in England, turned to surface and solid-modeling CAD software to make their electric golf caddy stand out on the course.

The X1R (with remote control) weighs about 14 kg. There is also a model steered manually which weighs
about 12 kg.

Designer Mark Stewart at Stewart Golf in England (, turned to surface and solid-modeling CAD software to make their electric golf caddy stand out on the course. "Designs began with 2D drawings, but something like the caddy must be designed in 3D because there is not a flat surface on it," says Stewart. The curves complicate measurements and that led the company to Delcam Plc. (, developer of design and manufacturing software.

The caddy carries a bag of golf clubs, accessories, and sports a remote control that lets golfers direct it while walking behind. The X1R can be set to match a golfer's walking pace. "A keypad controls the caddy from up to 50 m away," says Stewart. "So you play your shot, hit the remote, and the cart goes off at your pace. You have to guide it left and right with the remote but that's quite easy," he says.

The remote-control caddy has two motors so the rear wheels work independently. This lets the caddy turn on a dime. The keypad control has simple stop and go, and left and right arrows to steer the cart. "Press the 10, 25, or 50 on the caddy's handle and it goes that distance and stops. So when putting out, you can send the caddy out of the way," says Stewart.

The 140-W, 12-Vdc motor draws power from a gel-pack battery. There's enough charge for 18 holes. "If the battery goes flat, you can put the wheels into a freeturning position and push the cart to a charging unit," he adds. An emergency stop signal turns the motors into generators and stops the caddy instantly. "It brakes the wheels," says Stewart. "Say it's headed into a lake or bunker, you can turn the brakes on."

Many components are injection molded, though the process can be limiting because of the materials. Early models appeared metallic, but don't look great. All silver parts on recent models, however, are thermoformed. And there are many more decorations for thermoforming that make surfaces look like wood veneers, for example. "Thermoforming the aesthetic pieces lets us customize the caddy for buyers," says Stewart. The material is a five-layer composite with a thin acrylic top layer for scratch and fade resistance.

Control electronics is coded to each machine so if multiple units turn up on the same course, each golfer controls only his own caddy. There are 64,000 different codes. "Even without marketing in the U.S., we still get one or two people a week wanting to buy one," says Stewart.

The caddy folds for storage. The rear wheels also come off to further lower its height.

The keypad for the remote-control unit has arrow keys for steering and numeric inputs to select a walking speed.



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