Cooling Baffle Project

[VictorBravo]

In case anyone is interested, I have chosen to perform significant "repairs" to my cooling baffles. Some of the repairs were quite extensive, but should bring the temps down in hot weather very nicely.

I repaired the left and right inner plenum chamber baffles... they were so damaged that they were almost impossible to see without special optical equipment

I repaired the lower crankcase baffle, which was so badly worn that only a small part of it was remaining, not really enough to duct the air from the nose opening all the way back and then down over the oil tank. I even added a couple of stiffening flanges to prevent the cracks that happen on most of these pieces over the years. After repair, it will form a sealed tunnel under the engine so that virtually all of the oil return (drip) path on the bottom of the case will be bathed in cool airflow.

The other parts such as the cylinder baffle sections were so worn and damaged that it was almost impossible to discern the correct shape, that shape being fairly large so that the baffles ducted the airflow all the way around the cylinder on the bottom so as not to just allow the airflow to separate from the fins.

The outer plenum chamber baffles had been worn so badly that they no longer extended upward to contact the upper cowl. Also, many of the small baffling pieces that closeed off all the air gaps (so that ALL of the cooling air flow goes through the fins insteadof through gaps around the engine) were missing and had to have owner manufactured parts made to perform that vital function.

Although these newly repaired baffles have not flown yet, I have full expectation that they will function so well that the "winter baffle intake covers" can remain installed later in the year.

I will attempt to post photos of these newly repaired baffles below. I wouldn't be surprised if some other Forum Members' baffles are so worn and damaged that they bear little resemblance to these fully refurbished ones It may take a couple of posts to put up all the photos.

[VictorBravo]

Re: Cooling Baffle Project

First test of upload photos...

[VictorBravo]

Re: Cooling Baffle Project

Cyl. Baffles Photos Group 1

Bright red and green stuff is small dia. hi-temp silicone tubing, split and slipped over the edges of the metal as a bumper/gasket.

NOTE these photos were taken BEFORE final installation of the baffles, so NOT ALL parts are shown in these photos. The inter-cylinder baffles are not installed in these photos, nor are the lower hold-down plates and safety wire tie-downs.

AN470 AD 3 aircraft rivets were used on the joints except where the rubber material is held on with pop rivet "baffle rivets" which are standard for this function. The "baffle rivets" allow easier replacement of the rubber seals than AN rivets would.

[VictorBravo]

Re: Cooling Baffle Project

Cyl. Baffles Photos Group 2

Note 4th photo shows alum. spacers necessary to allow clearance between the intake spider hoses (not shown) and the baffle.

[VictorBravo]

Re: Cooling Baffle Project

Cyl. Baffle Photos Group 3

Red silicone 400 degree rubber (standard aircraft baffle seal material) forms the inboard wall of the cooling air exit duct at base of cylinders for smooth outflow into the lower cowl. Note 3rd photo that the baffling only touches the inboard (lower steel) portion of the cylinder cooling fins at one point, does not "hug" the contour of the cylinder. I believe this is to prevent the bottom of the cylinder from over-cooling where it does not need as much heat rejection as the cylinder head. Note 4th photo silicone hi-temp baffle material forming to the contour of the cyl. head to keep all the air flowing through the fins around a large part of the distance from top to bottom.

[Pearson]

Re: Cooling Baffle Project

Bill,

It sure looks purty. I like that green stuff, looks like the green hornet was there.

In the last photo you posted there are what looks like pieces of silicone rubber in the space in the top of the heads. What is that for. I thought those holes needed to be open for better cooling.

[VictorBravo]

Re: Cooling Baffle Project

Those holes only need to be open to let the air flow between the cooling fins inside the hole. But the fins only take up half of that hole, the other half is wasted flow. So covering the wasted part makes it so that the useful part (the fins) get almost twice as much air. What I did was not to cover the fins anywhwere (of course), but to cover everywhere other than the fins.

Bill

[astjp2]

Re: Cooling Baffle Project

Did you use T3 or O material? I perfer O because it wont crack as soon. I bought a horse blanket to get the felt to repair mine and used lockwire to secure it in the staple holes. Yours look good though!!!

Tim

[tim]

Re: Cooling Baffle Project

hey bill are u going to make up some drawings so we could use that design id like to try it with my c-85

[VictorBravo]

Re: Cooling Baffle Project

I mostly used O material on the parts I had to compound bend. There is some T-3 that I started using for straight bends because my hangar neighbor lets me use his brake

If I had it to do over again I'd probably put less compound bends in, and make the bent flanges smaller... I got too carried away with this set. The only place where there really needs to be a compound bend is at the root (small) end of the cylinder where the cylinder baffles meet the inboard wall. Even this is not absolutely needed.

Also, if I could do it all over I could make it with far less parts count, some pieces could be riveted together and not have to come apart.

i did make SOME tracings but they are not accurate. I had made paper patterns (usually two or more times) and then all the parts had to be hand-fitted anyway. So my patterns would not do much good unfortunately.

This project was far too much work, and it cost me months of flying. However, all indications point to it working very well... this time next week I'll have at least a rough opinion of how it worked. Because this is out there on the fuzzy edge of "repair", I feel the strong need to install a 4 probe CHT to make sure my repairs are working as well as I had hoped. If it does work I'll share that info, but considering my previous experience trying for a Field Approval I will likely not pursue that road.

All that being said, there is a good possibility you can get a significant improvement by starting with a good set of original baffles and making some "repairs" to those. If someone with cooling problems would simply remove, clean, reinstall, and properly seal the existing baffles you would probably solve most of your cooling problems. If all the intake air went though the fins instead of past them and leaked out through gaps, it would solve a lot of the problem IMHO.

Since I considered these baffles to be "repaired", and I am acting in sincere hopes that the powers that be will see it as that way as well, you will have to make a decision as to whether you think that the powers that be will also look kindly on such repairs on your airplane. I made the choice long ago that level one was what worked best for the airplane safety and reliability-wise... and that everything else was a distant level two. That will be an individual decision for each of us. My decision was made on the basis that very few bureaucracy types will be with me in the airplane if it overheats and I have to make a forced landing... and that NOT having it overheat justifies the means. But that's a choice I don't want to force on anyone, at least in a public forum.

[Hank Jarrett]

Re: Cooling Baffle Project

The other nice thing is most Feds don't have a clue what was on the plane in the first place. Had one guy thought my exhaust was home made. All he had seen on a 65 Cont was a Cub exhaust and he thought the muffler had been removed on mine. Show them a copy of the parts catalog with the original exhaust to end the argument. Had the same thing with the plywood instrument panel. Didn't catch any flack till I replaced it with the RIGHT one!
Do a professional looking repair and most likely any inspector won't know the difference anyway. I'm not advocating making changes to the plane, but the first requirement is that the plane be SAFE. I have yet to find a part I can't reproduce on a Taylorcraft (including stamped out instrument panels and post war wing ribs). I have yet to reproduce a part that wouldn't have been less expensive to buy a new one (if I can find one). The only hard part of the cooling baffles is the compound curved part over the cylinders.
Hank

[tim]

Re: Cooling Baffle Project

by the way dose any one know were i can find a baffle for the c-85 ?? hey bill im restoring my tcraft and id like to try and modify it to fit my c-85 if i can

[VictorBravo]

Re: Cooling Baffle Project

by the way dose any one know were i can find a baffle for the c-85 ?? hey bill im restoring my tcraft and id like to try and modify it to fit my c-85 if i can

The 65 baffles should be usable on an 85. Probably O-200 baffles would fit too.

What I learned in my project was that with a little extra effort you can make as good or better fitting of a baffle using flat sheet metal and rivets, than the stamped pieces. Even the big baffle in the back. The stampings (or hydroformed pieces) were easier for the factory to make but I do not believe they were ideal at all.

IF, and I say IF the flight experience shows that what I did is working, then I'll be glad to share some more details. But for right now it's all hot air and talk.

IMHO, make sure you have the baffle under the crankcase... this has been discussed recently in the Forum under another thread.

Like I said, I will give an educated guess that making sure all the flows through the fins instead of anywhere else would solve most of the problems. It's the holes and gaps that can be fixed most easily. In a pinch you can crumple up aluminum foil and stuff it in the holes, and safety wire it in place!

[tim]

Re: Cooling Baffle Project

ok thanks then i know were one is i think its some what damaged but ill fix it thanks bill