Every year when the annual comes around, there always seems to be a handful of cracks and wear to address on engine baffles.

To get away from those repetitive nuisance fixes, couldn't baffles couldn't be made from stainless? A quick google search turns up zip, although there are several source of aftermarket aluminum baffles.


Chris

Never heard of stainless baffles, but I replaced my baffles with a new set from Airframes Alaska that were slightly heavier gauge of aluminum than the originals from Cessna.

If you’re having that much trouble with baffles, either get whatever is causing this fixed and/or buy a new set of baffles.

I wouldn’t consider stainless. Been flying airplanes a while and owned one plane for near 20 years and never touched the baffles. Something shaking in there?

MTV

mtv wrote:If you’re having that much trouble with baffles, either get whatever is causing this fixed and/or buy a new set of baffles.

I wouldn’t consider stainless. Been flying airplanes a while and owned one plane for near 20 years and never touched the baffles. Something shaking in there?

MTV

Perhaps you’ve been lucky and I’ve not, but I’ve never seen a set of baffles without some cracks/drill stop holes/reinforcing patches.

The 180/182 carb air box comes to mind....everyone has issues with those. When they get rebuilt, they’ll often end up with a stainless top skin to help with crack resistance. Why not for baffles?

Chris




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Dale Moul wrote:Never heard of stainless baffles, but I replaced my baffles with a new set from Airframes Alaska that were slightly heavier gauge of aluminum than the originals from Cessna.

The cub fuselages and bushwheels come from Airframes. The baffles come from Airforms.

They are mostly aluminum, but use stainless doublers in high wear places. They are a PMA part, but hold up better.

airChris wrote:

mtv wrote:If you’re having that much trouble with baffles, either get whatever is causing this fixed and/or buy a new set of baffles.

I wouldn’t consider stainless. Been flying airplanes a while and owned one plane for near 20 years and never touched the baffles. Something shaking in there?

MTV

Perhaps you’ve been lucky and I’ve not, but I’ve never seen a set of baffles without some cracks/drill stop holes/reinforcing patches.

The 180/182 carb air box comes to mind....everyone has issues with those. When they get rebuilt, they’ll often end up with a stainless top skin to help with crack resistance. Why not for baffles?

Chris

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I put 3500 hours on a Cessna 185. Three engines, same set of baffles. The baffles on my 170 were good for well over a thousand hours.

If you get a good set of baffles, and they should last a long time.

But, have you had your engine/prop dynamic balanced.

Carb air boxes are a different deal, no doubt, but send one to Randy Rubbert in ND, and it’ll come back bomb proof.

MTV

Baffles are a wear item. The baffles get sacrificed so your engine cylinder heads don't get the fretting wear. Stainless baffles would wear your engine, which would you rather have? If your baffles are getting excessive wear, vibration, as others have pointed to may be the root cause. You might also check your engine mounts. Soft worn mounts allow your engine to move more freely and exaggerate the vibration all engines naturally have. Good fresh mounts dampen the vibration. So check your mounts and then balance the prop.

Everyone seems to jump on the 'excessive vibration' idea here. That's not the case.

I'd ask anyone to look at their baffles after years of use and there are guaranteed to be issues that need addressing.

I'm simply putting the question out there: when it comes time to replace baffles, is there a better way? Stainless is used regularly in other areas to eliminate stress cracking, so why not baffles?

Is it the cost/benefit ratio?

Or perhaps as dogpilot pointed out, is it a engine wear vs. baffle wear issue?

Chris

airChris wrote:Everyone seems to jump on the 'excessive vibration' idea here. That's not the case.

I'd ask anyone to look at their baffles after years of use and there are guaranteed to be issues that need addressing.

I'm simply putting the question out there: when it comes time to replace baffles, is there a better way? Stainless is used regularly in other areas to eliminate stress cracking, so why not baffles?

Is it the cost/benefit ratio?

Or perhaps as dogpilot pointed out, is it a engine wear vs. baffle wear issue?

Chris

I agree with Dogpilot, baffles are a wear item. Baffles made of stainless thin enough to match the weight of aluminum baffles would crack as well.

On the 2 C-180 floatplanes that Kenmore operates on floats we change the baffles out with new ones every 3000-4000 hours.

I feel you may be trying to fix something isn't really broke, just repair the baffles as needed and replace them when they're worn out. As Dogpilot said it's much better to have a worn out baffle than a cylinder or case with a groove worn in it.

At the risk of doing a little buzz-marketing I can endorse McFarlane's Baffle Saver material: https://www.mcfarlaneaviation.com/products/product/BAFFLE-KIT-1BF/ this stuff works good at keeping the inherent vibration out of the baffles themselves

I have a roll of the McFarlane material in the hangar waiting for the baffle supports to go back on as well. I can't attest to it living up to the hype yet, but everything else I've bought from them is quality stuff.

I wouldn't discount vibration prevention in baffle survival. The cracks form as a result of metal fatigue, which happens from the metal flexing back and forth a tiny amount hundreds of thousands of times until the metal starts to fracture. As the engine vibrates, it moves - simple as that. Since it's bolted to the mount, that motion is going to pivot from that point. Baffles are about as far away from the mount pivot as you can get, meaning a tiny motion at the base will be amplified at the baffle.

The McFarlane seals transfer less force to the cowl, which equals less cowl wear and tear and likely less vibration felt inside; it probably also means less force on the baffle supports themselves since there isn't as much friction to pull on them, but they're still going to flex a bit every time that engine moves relative to the airframe.

The moral here is two-fold: First, make sure the isolation mounting is in good shape. LORD mounts wear out over time; see the other thread on rigging for some examples we've found in that area. Those mounts are *the* thing keeping the engine from shaking your airplane apart, but can be neglected, especially in airplanes that don't fly so much since a lot of people don't change them except at overhaul time. Second, prop balancing is worth every penny. About the simplest thing vibration can break is your baffle supports, since it also transfers into everything else (instruments, systems, attachments, people). I was able to get a good dynamic balance done for $180 and we got it down to 0.04 IPS which is fantastic; I also had zero regrets as soon as I flew it away, it was quite smooth. I plan to get it done again immediately following sign-off's once the airplane is back together.

I agree with Dogpilot, baffles are a wear item. Baffles made of stainless thin enough to match the weight of aluminum baffles would crack as well.

This has been my experience with ag planes as well, any panels exposed to constant vibration will crack in short time if made out of stainless. The aluminum panels take the vibration a little better and are cheaper, just have to stay on top of corrosion.

If you are looking for answers to questions that most folks aren't asking, look no further that EAA, but every now and then you can pick up something useful.

For example, there was a writeup I read recently concerning building custom baffles for your homebuilt. They suggested using 6061 aluminum rather than 2024-T3 like we use for EVERYTHING else on these old beaters. They claimed that 6000 series was more resistant to cracking,

I can't tell you if it's any better, but that ought to be decent fodder for another page or two beating this horse.

AEROPOD wrote:If you are looking for answers to questions that most folks aren't asking, look no further that EAA, but every now and then you can pick up something useful.

For example, there was a writeup I read recently concerning building custom baffles for your homebuilt. They suggested using 6061 aluminum rather than 2024-T3 like we use for EVERYTHING else on these old beaters. They claimed that 6000 series was more resistant to cracking,

I can't tell you if it's any better, but that ought to be decent fodder for another page or two beating this horse.

Thanks for the fodder, here's some info not relevant to the original topic. Alloy 2024 is about the worst alloy of aluminum for any bending, right up there with 7075. They are strong but crack easily, and lose most of the strength they originally had.Alloys 5052, 6061, and 3003 bend much better. We use 6061 for almost everything, but still switch to 5052 for structural components that need to be formed/bent, even 6061 cracks easily. We don't use 3003 simply because it's just another thing to keep stocked in the machine shop that we won't use that much of, but it bends like butter. If butter bent.