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Thread: Tubing Size Advice. Motor Mount O-540

  1. #1

    Tubing Size Advice. Motor Mount O-540


    I'm building an experimental O-540 Super Stinson Conversion on floats.

    I'm getting on to building my motor mount and need some advice on tube size and cross bracing.

    The Stinson fuselage, where it mates to the engine mounts, is made of arc welded 5/8 .035 at the top mounts and 3/4 .035 at the bottom which seems light but there are a ton of even heavier O-470 (+100lbs over Franklin) conversions around that are still hanging off those little straws. I want to know if I should be scaling my mount tubes to the airframe (3/4".035) or going beefier. I'm not wanting to add unnecessary weight as the O-540 is about 65 lbs heavier than the Franklin.

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

    I'm also interested in the mount loop that holds the engine mount ears in many dynafocal mounts I've seen. Why is a loop needed since the engine is such a stiff unit on it's own?


  2. #2

    Join Date
    Dec 2013
    Name:  Lycoming O-540 Number 1 DYNA (70456 Mount Ear) Engine mount Ring.jpg
Views: 247
Size:  20.2 KB

    I purchased a 0-540 engine mount ring (only) from "VANS" for their RV-10........Be advised that it is for a 0-540 with the "30" degree mount ears (Part # 70456) with a 1.385 inch center mount hole used on the following engines......D4A5,G1D5,K1A5,K1A5D,K1B5,K1D5,K1E5,K 1G5,K1G5D,T4A5D,T4B5D.........I would
    ask "VANS" what size tubes are used on their RV-10 mount from firewall to the mount ring..........
    Last edited by keltro; 04-16-2020 at 07:14 PM.

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