No, these were used in corn planter drives. Not sure how they'd use air or elec clutches for weed whackers. Most don't have dc electric supply or air pump. They're heavy enough to carry around without having battery-air pump-and a Insight monitor attached.

Corn planters & tractors can stand the burden however.

I think most weed whackers have centrifugal clutches anyway, don't they?

Maybe you were at a different show.