A gasifier on a vehicle is mounted on rubber isolators cut from old engine mounts or tyre sections, with a flexible section in the gas line and several attachment points, so that road and engine vibration do not crack its welds or loosen its fittings. Choose isolators that compress about 5 mm under the unit’s weight, which puts the mounting’s natural frequency near 7 Hz, keep the rubber away from hot surfaces, and add steel tethers so a failed mount cannot drop the unit.
Part of Vehicle Mounting
Vibration isolation decouples a gasifier from chassis and engine shake with rubber mounts and flexible gas connections.
What The Parent Carrier Asks For
Road vibration shakes loose everything, so the carrier says to mount the gasifier on rubber isolators, put flexible connections in the gas piping (a 15 cm section of heat-resistant silicone hose or a bellows joint), and secure all components with multiple attachment points, because a gasifier that breaks loose at speed is catastrophic.
A Rubber Mount Is A Spring: Choose It By Its Deflection
An isolator and the mass it carries form a spring and weight with natural frequency fₙ = (1 ÷ 2π) × √(g ÷ δ), where δ is the static deflection under the weight and g = 9.81 m/s².
- δ = 2 mm: fₙ = (1 ÷ 6.283) × √(9.81 ÷ 0.002) = 11.1 Hz.
- δ = 5 mm: fₙ = (1 ÷ 6.283) × √(9.81 ÷ 0.005) = 7.05 Hz.
- δ = 10 mm: fₙ = 4.99 Hz.
Vibration transmitted is reduced only above √2 × fₙ, and in an undamped model the transmissibility is 1 ÷ |(f ÷ fₙ)² − 1|. With fₙ = 7.05 Hz:
- Engine firing of a four-cylinder four-stroke at 3,000 rpm is 2 × 3,000 ÷ 60 = 100 Hz: (100 ÷ 7.05)² = 201, so transmissibility 1 ÷ 200 = 0.005, a 99.5% reduction.
- At idle (800 rpm) the firing frequency is 26.7 Hz: (26.7 ÷ 7.05)² = 14.3, transmissibility 1 ÷ 13.3 = 0.075.
- Near the mounts’ own resonance of 7 Hz the vibration is amplified instead. Road-input frequencies of about 10-15 Hz (recalled for wheel hop) sit just above that, where transmissibility is about 1.0 at 10 Hz, 0.5 at 12 Hz and still 0.3 at 15 Hz.
So soft mounts clean up engine vibration well but do little against wheel hop, which is why the unit must also be tethered and the pipework flexible. This is a one-degree-of-freedom model without damping; real rubber has damping and the figures are guides, not measurements.
Sizing For The Unit
For a 250 kg unit on four mounts, each carries 62.5 kg. For δ = 5 mm the stiffness per mount is 62.5 × 9.81 ÷ 0.005 = 123 kN/m. Under a 3 g bump the deflection scales to 3 × 5 = 15 mm, so each mount needs a travel stop at about that distance so the unit lands on metal, not on a stretched rubber.
Keep Rubber Cool
Natural rubber degrades at modest temperatures, about 70-80 °C in continuous use (recalled). Isolators belong on the frame, away from the hot shell, behind the heat shield (Heat Shielding). Silicone hose in the gas line belongs on the cool side, after the cooler (Material Selection for Mobile Use); tar and condensate attack many rubbers, so inspect it.
Method
- Weigh the unit and divide by the number of mounts.
- Choose mounts that deflect 5-10 mm at that load.
- Fit travel stops and steel tethers of cable or chain.
- Put flexible sections in the gas line between the isolated unit and the rigid vehicle, at both ends of the run.
- Check every fixing after the first 50 km and then regularly.
Common Mistakes
- Rigid pipes from an isolated unit. The pipe fatigues and cracks.
- Mounts that are too soft. The unit rocks on every bump and hits things.
- Rubber next to the reactor. It chars.
Safety
A cracked pipe on a shaking unit leaks carbon monoxide at the driver
Producer gas is about 18-22% carbon monoxide by volume. Never run the unit in a garage, shed or enclosed yard. If you feel headache, nausea or confusion in a vehicle with a gasifier, stop and get out upwind at once. A gasifier that drops off at speed is catastrophic, so tether it. See Carbon Monoxide Risks.
What’s Next
- Learn next: Heat Shielding — keeping heat from the mounts and cab
- Combine with: Trailer Mounting — the frame the isolators sit on