Image of pageindex72008.gif

Image of knobscover.jpg

In the 1960s and '70s, Miss Hurst Shifter, LindaVaughn, a busty blond, was the pin-up queen of auto racing. Specifically, she represented Hurst Shifters, making every hotrodder in the country want to have the company's signature T-handle shifter grip in his or her car. A hallmark of the Hurst shifter was the muscle it could withstand, where burly guys could take out their aggression while slamming the shifter from one gear to the next, living out their hotrod fantasies. The combination of Miss Hurst Shifter as a poster girl, and the signature T-handle that could be manhandled, arguably tied into male psyche at its most primal levels, making Hurst Shifters a wildly-successful brand.

The Hurst Shifter legacy continues, where hotrodders not only still place Hurst shifters in their cars, but some power wheelchair users seek adding true shifter knobs to their power wheelchairs for a touch of hotrod coolness. However, many power wheelchair users don't realize that adding a shifter knob to a power wheelchair joystick can be both damaging and dangerous.

How Shifter Knobs are Harmful
Power wheelchair joystick construction is fairly universal, consisting of a joystick post that leads to a centering spring, then a ball of sorts that contacts directional input sensors. When you push the joystick in the direction that you wish, it compresses the spring, contacts sensors, and steers the power wheelchair, accordingly.  

While power wheelchair joysticks are tested as reliable in the millions of cycles (movements), they are designed within specific leverage and force constraints. Joystick posts are commonly only 2” in height, and the rubber knob usually only adds 1” or less of additional height, with virtually no weight. These numbers are important because they maintain the correct leverage levels and weight on the joystick, reducing the likelihood of damaging the joystick with too much force or weight.

By contrast, adding a tall, heavy shifter knob radically changes the forces on the joystick. Adding height increases leverage, creating greater force on the entire joystick, and adding weight can compromise the spring, as well as increase directional forces. As a result, durability and safety can be compromised, where the extra leverage and weight can stress the components overall, and the added top-heaviness can inhibit the joystick from returning to center, its neutral position. The literal results are damaged sensors, commonly called “dead spots,” where your joystick no longer responds in positions, as well as a joystick that won't return to center (and, if a joystick isn't centered when it's powered-up, an error code occurs and the power wheelchair won't drive).

The Correct Solution
For those needing an alternative to a typical “carrot” joystick knob, there are a myriad of specialty knobs available. These knobs are of an appropriate height, and super lightweight, ensuring that they don't compromise the joystick's structural integrity:

Image of joystickknobvariations.jpg

Joystick knob variations are listed on most power wheelchair order forms, as well as ordered through providers. If you're seeking to order a joystick knob variation online, manufactured by companies like Body Point, you need to know if your joystick's post is 3/16” or 1/4”, as they vary by vintage and manufacturer.

Don't Get Behind the 8-Ball
Sure, putting an 8-Ball shifter knob on one's power wheelchair joystick may seem cool or cute; however, the toll that it can take isn't so much fun, diminishing reliability and safety. If you need an adaptive joystick knob, pick one made for the application, not a shifter knob. A specifically-designed joystick knob may not be as seemingly cool as a Hurst shifter or 8-ball, but it will get you to the races without harming your mobility.

Published 5/09, Copyright 2009,