I'm getting on to building my motor mount and need some advice on tube size and cross bracing. It's for a Super Stinson Conversion on floats to an O-540.

The Stinson fuselage, where it mates to the engine mounts, is made of arc welded 5/8 .035 and 3/4 .035 which seems light but there are a ton of even heavier O-470 conversions around that are still hanging off those little straws so I want to know if I should be scaling my mount tubes to the airframe and/or beefing up my airframe.

One guy made his from 7/8 .049 which seems overkill but I would love to hear from an expert.

Cheers.

Hi,
if you’re looking for an engine mount for this kind of configuration, this is exactly what we design and manufacture — we’re actually building similar mounts right now.

We produce welded steel tube engine mounts for aircraft, including custom solutions for higher power engine conversions and float operations.

If you’d like to go with a properly engineered solution, feel free to reach out.

Best,
Andrea