Wayne Keith has driven 250,000 miles in vehicles powered by wood gas over the past 10 years (see Vol. 33, No. 2). Little chunks of wood work best in his wood-powered trucks. So, he designed a "chunkier" that busts scrap wood into easy-to-handle pieces.

    "If I had to buy wood, driving my trucks around would cost less than a penny a mile. But because I use waste from my sawmill, I am driving around for free," he says. "My home-built chunker can chop enough sawmill slabs into fist-size chunks in a morning to take me to California and back."

    The wood chunker is crude, but it gets the job done. Keith used a rear axle from an International truck and attached a cutting surface to one end with the other end welded solid so it doesn't rotate. A pto shaft attached to the differential extends through a heavy cast brake drum that serves as a flywheel.

    "The flywheel smoothes out the power requirements and allows faster operation," says Chris Saenz, Keith's assistant.

    The axle is reinforced by several pieces of channel iron. Other channel iron pieces serve as legs to provide a comfortable working height, bringing the pto shaft level with the small tractor that powers it.

    The chunking action is provided by the inner edge of a heavy steel rim mounted on the axle. The inner rim edge has been trimmed on the bias like a spiral, so as it rotates, the edge varies from nothing to full width.

    A length of cross-reinforced channel iron mounted just ahead of the cutting rim serves as an anvil. A steel plate welded perpendicular to the channel iron is a backstop for pieces of wood inserted into the blade.
    As the drum rotates, Keith inserts a branch or piece of slab wood. As the drum edge rotates, it breaks off chunks at a rate of 70 to 80 per min.

    A small nipper blade on the other side of the drum rotates through a notch in the anvil. "The nipper starts a split in wide boards," explains Saenz. "Once inserted into the chunker, the split will continue down the length of the board, making two pieces instead of one."

    As chunks come off the machine, they are scooped into piles for storage. Saenz says green wood cuts easiest. Dry wood can be cut, but it's harder on the machine.

    No plans are available for the machine at this time. However, Keith is marketing plans for his wood gas system and has written a book about his work with wood gas. He also operates a website with restricted access for those who have purchased plans, though other parts of the site are open to all.

    Keith recently set a world speed record of 73 mph for biomass-powered trucks. For videos related to the wood chunker and Keith?s wood gas-fueled trucks, go to www.farmshow.com.