Brace the OIL COOLER, not the baffle
gmcjetpilot said:
If you want to stay with the baffle mount you can install a diagonal brace over the cylinders going from the inside corner of the baffle (joggle) and to an engine case bolt (two fwd of where the lift strap is). Here is another idea:
http://www.rvproject.com/20040721.html
In my opinion the absolute
KEY if you decide to use a brace, is that the brace must attach as directly as possible to the oil cooler itself. If you simply brace the baffle, still allowing even a minute amount of flex where the oil cooler attaches to the baffle, you can expect to see cracking.
As long as your brace ties the oil cooler itself to the engine case or cylinder boss or what not, then you should be OK.
FWIW, I had a brace running from the baffle to the engine, and I still had cracking occur. It wasn't until I braced the oil cooler itself that I solved my baffle cracking problems.
I have had over 500 hours on my current setup with not a single crack or issue.
To illustrate this with photos...here was my initial setup, with the brace attached to the BAFFLE, not the oil cooler:
That design failed in two ways -- first of all, the "crimped end" stainless tubing broke at the crimp. But more importantly and more to the point, this design braced the baffle, not the oil cooler. There was still flex at the back baffle wall and it cracked like crazy.
Enter the next and "final" design:
The key here is that this brace totally immobilizes the inboard edge of the oil cooler. The baffle happens to be braced as well, but the key is that the oil cooler cannot flex the baffles.
An experienced builder once told me: "If you can push and pull the plane around by the oil cooler, you done good. If yanking on the oil cooler causes any visible flex on the baffles at all, you
will eventually see cracking." I have lived by this credo since.
If I were starting over, I would probably mount the oil cooler on the engine mount, and provide a short semi-flexible duct to it...alleviating the baffles of any stress that the oil cooler causes. The oil cooler will be completely immobilized by virtue of being attached to the engine mount. No stress on the baffles. No heat conduction, or at least
less heat conduction, from the HOT cylinder head to the adjacent oil cooler. At least that's what I tell myself I will do next time.
But I am happy with my current setup, and the baffles haven't cracked at all in the oil cooler area since redesigning it with the brace that ties directly into the oil cooler.
)_( Dan
RV-7 N714D (683 hours)
http://www.rvproject.com