A wood gas unit can stand upright in the truck bed or on a frame behind the cab, on a small trailer towed behind any vehicle, or on a steel frame bolted to the rear of a car, and each trades something: the bed mount is the wartime standard for trucks, the trailer suits any vehicle but complicates reversing, and the rear frame makes a car rear-heavy. Whichever is chosen, the unit must be fixed at several points, isolated from vibration and shielded from heat.
Part of Wood Gas Vehicles
Vehicle mounting is where and how a gasifier, its cleaning train and its fuel are fixed to a car, truck or trailer.
Three Mounting Options From The Carrier
| Option | How | For | Against |
|---|---|---|---|
| Truck bed | Gasifier upright in the bed or on a frame behind the cab; gas piping runs along the chassis to the intake | The WWII standard for trucks | Takes payload space; hot unit close to cab and load |
| Trailer | Entire system on a small trailer towed behind | Any vehicle can use it; easy to disconnect | Adds length, complicates reversing, trailer must be sturdy; long gas line to engine |
| Rear frame (cars) | Steel frame bolted to the rear, extending behind the boot | Works for passenger cars | Rear-heavy handling and reduced visibility |
Detail on the first two is in Trailer Mounting.
What To Settle Before Fixing Anything
- The gas path. Shorter is better, but for leak points, vibration and condensate more than for power: a 4 m run of 45 mm pipe costs only about 0.1% of the engine’s intake ( Trailer Mounting). Keep the pipe wide and smooth, sloped to drains.
- The operator’s position. The lighting port, hopper lid and drains should be reachable from the side of the vehicle, standing upwind, without leaning over the unit.
- Clearances from the cab and the petrol system. The petrol tank, lines and battery still exist because the engine starts on petrol; keep them well clear of the hot parts (Heat Shielding).
- Where the exhaust and any leaking gas go. A cab downwind of a leaking unit fills with carbon monoxide. Mount the unit so that wind and travel carry leaks away from the cab, and keep cab windows and vents in mind.
Method
- Weigh the parts and choose the mounting position from the axle arithmetic in Weight & Space Constraints.
- Build the frame first and fix it to the chassis at several points, not to the body panels.
- Mount the units on the frame through isolators (Vibration Isolation).
- Run the gas line with flexible joints on the cool side and a continuous fall to the drains.
- Fit shields where hot surfaces face fuel, wiring or the cab.
- Road-test outdoors with the gas flared and checked at each stop.
Common Mistakes
- Mounting on body panels. They tear off.
- Putting the lighting port where the operator must lean in. That is the worst place to breathe start-up gas.
- Ignoring the cab. Carbon monoxide leaks and exhaust enter an occupied cab.
Safety
Never sleep, idle or warm up in or near a vehicle with a lit gasifier
Producer gas is about 18-22% carbon monoxide by volume, odourless and colourless, and it mixes through a space rather than layering. A parked vehicle with a lit gasifier in a shed, garage or enclosed yard, or with someone asleep in the cab, is a recognised way these systems have killed people. Never warm one up inside, even briefly. A gasifier that breaks loose at speed is also catastrophic. See Carbon Monoxide Risks.
What’s Next
- Learn next: Trailer Mounting — the two commonest options in detail
- Combine with: Vibration Isolation — keeping the unit from shaking apart