Moving from glow to petrol (or the reverse) is about more than just the engine — it changes the whole weight and vibration profile of the model, and that has knock-on effects for landing gear that are easy to overlook.
Petrol engines are generally heavier for a given displacement than an equivalent glow engine, and that extra weight sits right up at the nose — which shifts the model’s all-up weight and often its centre of gravity, both of which affect how hard the gear works on every landing, not just take-off roll.
Vibration characteristics differ too. Petrol twins in particular can have a different vibration signature to a comparable glow four-stroke, and while that mostly affects things like fuel tank mounting and radio gear, it’s also a contributing factor to fastener loosening over time — including the bolts holding your landing gear on, which is one more reason the torque checks mentioned in Day 5 are worth doing as routine maintenance, not just at initial fitting.
If you’re converting an existing glow model to petrol, don’t assume the original landing gear rating still applies once you’ve added engine, ignition, and fuel system weight. It’s worth recalculating your new all-up weight and checking it against your gear’s rated range (see Day 1) rather than assuming the original gear specification still has headroom.
The reverse conversion (petrol to glow) is less commonly an issue, since you’re generally removing weight rather than adding it — but it’s still worth a sanity check against your gear’s original design weight, particularly if you’re also changing fuel tank size or battery specification as part of the conversion.
None of this means a conversion is complicated — it just means treating the gear as part of the weight-and-balance conversation, not a fixed item you carry over unchanged.
Our CRRC GF40i Kit engine. is a good reference point if you’re shopping around.