A truck-bed mount stands the gasifier upright on a frame behind the cab, fixed to the chassis rather than the bed panels, with the gas line running along the chassis to the intake, and a trailer mount carries the whole system on its own sturdy running gear. On a trailer, put the unit’s weight just ahead of the axle so the tongue carries roughly 10% of the load, and run the gas line on a flexible, braided connection; a 4 m line of 45 mm pipe costs only about 0.12% of the engine’s intake, so the length is a leak and tar problem, not a power one.
Part of Vehicle Mounting
Truck-bed and trailer mounting place the gasifier system on a chassis-fixed frame or on its own towed running gear.
Truck Bed: The WWII Standard For Trucks
The carrier describes the gasifier upright in the bed or on a frame behind the cab, with gas piping along the chassis to the engine intake. Build a frame that bolts or welds to the chassis rails, because the bed panels cannot carry a 175-315 kg unit under braking and bumps (Weight & Space Constraints). Behind the cab, the unit also screens the cab from the hot surfaces, provided a gap and a shield remain.
Trailer: Any Vehicle, But Mind The Tongue
A trailer lets any vehicle run on wood gas and lets the unit be unhitched. Its costs are length, reversing, and a trailer that must be sturdy enough to carry a hot unit. Tongue load (the downward load at the hitch) is a statics question. Taking moments about the axle, with the hitch at distance h ahead of it and each weight W at distance c ahead of the axle, the tongue carries ΣW × c ÷ h.
- Take a 100 kg trailer frame with its centre 0.3 m ahead of the axle, a 250 kg unit with fuel 0.2 m ahead, and a hitch 2.0 m ahead of the axle.
- Tongue load = (250 × 0.2 + 100 × 0.3) ÷ 2.0 = 80 ÷ 2.0 = 40 kg.
- Total weight 350 kg, so the tongue carries 40 ÷ 350 = 11%. Towing practice commonly aims for about 10% (recalled).
- Move the unit to 0.6 m ahead of the axle and the tongue load becomes (150 + 30) ÷ 2.0 = 90 kg, 26% of the total, which overloads the hitch. Put it behind the axle and the tongue lifts, and the trailer sways.
The Gas Line Over The Hitch
The gas has to cross from trailer to vehicle. Use a metal-braided or hose connection with enough slack for tight turns, clamped at both ends, fitted on the cool side of the train so it is not exposed to hot gas, and with a way to close it off before unhitching. A long run costs little suction. For 60 Nm³/h at 40 °C in 45 mm pipe:
- Flow: 60 × 313 ÷ 273 = 68.8 m³/h = 0.0191 m³/s; pipe area π/4 × 0.045² = 0.00159 m²; speed 12.0 m/s.
- Dynamic pressure ½ρv² with ρ ≈ 0.99 kg/m³ (the gas at 40 °C): 0.5 × 0.99 × 12.0² = 71 Pa.
- A 4 m run, friction factor 0.02 (an assumption): 0.02 × (4 ÷ 0.045) × 71 = 126 Pa = 0.13 kPa, or about 0.12% of atmospheric pressure.
So length is not a power problem if the bore is generous. It is a problem of leak points, vibration and condensate that must drain.
Method
- Build the frame to the chassis (truck) or a trailer with proper brakes and lights for its weight.
- Position the unit by the tongue-load arithmetic for a trailer, by the axle arithmetic for a truck.
- Fix at several points; add safety chains and stops so a failed mount cannot drop the unit.
- Route the gas line with a fall to drains and flexible joints at the hitch and at the engine.
- Test it moving, with the gas flared at each halt.
Common Mistakes
- Fixing to the bed panels. They tear free.
- Letting the trailer unit sit behind the axle. The trailer sways.
- A tight, kinked line over the hitch. It chokes, leaks or tears when turning.
Safety
A towed or bed-mounted unit is a moving carbon monoxide source
Producer gas is about 18-22% carbon monoxide by volume. Never light, warm or park the vehicle or trailer in a garage, shed or enclosed yard with the gasifier lit, and never let anyone sleep in the cab. When coupling or uncoupling, close the gas valve and let the system stand outdoors. A unit that breaks loose at speed is catastrophic. See Carbon Monoxide Risks.
What’s Next
- Learn next: Vibration Isolation — mounting on the frame without shaking it apart
- Combine with: Heat Shielding — protecting the cab and the load