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Marv and I are making a new set of baffles for his narrow deck 160 hp. The 200 hour old oil cooler had cracked.. reinforced with 0.032” stainless and made 4 spacers to evenly load the flanges on the oil cooler.. bit heavier than needed as the bolt should have been number three not four.. machined all four to the same length ...within a thousand and a half..
What is the thermal coefficient of the aluminum radiator vs the steel standoffs so carefully machined? In other words, at highest potential operating temperatures, will the radiator grow more than the sell clamps securing it will safely allow?
Ha! One reason...well two. Wanted to transfer the load so to speak. Wanted larger surface area when the assembly was put under compression. This transmitted more potential bending force to the stainless plate...and somebody..is somehow....this eliminated any concerns. Maybe...a re-do.....vibration isolation mounts....I joke. If we had ordered AN3 bolts...would have done the same thing, used the same 4130 3/4” round stock and smaller diameter 4130 tubing and larger OD washers at the bolt heads.
Nope...nada.. looked through all the log books and the FAA CD for the aircraft. Stewart’s STC calls for a .040” thick aluminum doubler...I duplicated Airforms Inc’s PMA’d baffle reinforcements using stainless. Waiting on a call from the A/I.
Marv and I are making a new set of baffles for his narrow deck 160 hp. The 200 hour old oil cooler had cracked.. reinforced with 0.032” stainless and made 4 spacers to evenly load the flanges on the oil cooler.. bit heavier than needed as the bolt should have been number three not four.. machined all four to the same length ...within a thousand and a half..
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Bit of explanation......was going to just patch up the old baffles and work up a new set when I got home. When I got the plane, the baffles were cracked where the oil cooler was mounted as no doubler was installed. I made a .040 doubler, as I understand is called for in the Stewart STC, and installed it, with sign off by the AI. But the baffles were in such bad shape that they did not hold the doubler, which resulted in the oil cooler cracking. Ordered a new cooler and realized that we were going to have to rebuild the baffles or it would happen again. We duplicated the old baffles, but fit the new pieces a lot better, and used the Air Forms cooler mounting as a pattern for the oil cooler installation to prevent future fatigue cracking of the oil cooler ears.
Anyone have Stewart Drawing number 10012 for the oil cooler reinforcement on the rear baffle? Bought the STC but wanted to get started on it before it arrives via snail mail.
Would you mind sharing this? I am having baffle cracking issues on my rear mounted oil cooler installation and would like to compare the differences between my field approved installation and Stewarts. In my instance the field approval only calls out for a 0.040 doubler on the engine side of the left rear baffle.
Here is how Steve solved the cracking problem on my field approved installation. He broke a pierce of 0.030 steel and riveted into the corner.
Attachment 17574Attachment 17574
I do have a small crack in the corner of the 90 degree bend at the bottom of the opening.
I believe it’s caused by vibration as there is no structural load there.
Last edited by Gilbert Pierce; 08-03-2020 at 10:23 AM.