Oil cooler placement

[Battson]

Hey everyone,

Just wanted to note this here for the record. I have been bothered by issues with my oil cooler supporting bracket.
My oil cooler is mounted in the back of the baffle for cylinder #5. The bracket I used to mount it has cracked twice now.

The first time was over 100hrs into service, about 150 I guess, at which point I replaced it with a stronger bit of aluminium. The thicker / stronger metal only lasted about 50hrs, due to lower flexibility I suppose.
Fortunately I used a bracket instead of mounting it straight into the baffle. The second bracket has transferred the stresses to the baffles which are themselves showing the beginnings of fatigue cracking now.

The only solution for me is to move the oil cooler. This is an 11-pass oil cooler sized for an IO-540, so it's heavy and has a lot of heavy oil inside too. Having that much weight shaking around on the engine is simply proving too much for the baffles to take. I know lots of aircraft with smaller oil coolers mount them in the baffles, however this hasn't worked for me.

I considered a firewall mount as a solution, but that means using another aluminium bracket [which I feel like avoiding]. So I will be mounting it straight to the engine mount using adel clamps, and of course running a SCAT duct from the baffle to a diffuser in front of the cooler. I will search down cracks in the baffles, stop drill them on both ends, and add doubler plates.

Hopefully that information helps someone!

Jonathan

[Mark Goldberg]

Here is what I did Jonathan. My temps have been acceptable - and so far no issues with anything showing fatigue. 3" scat tube. Mark

[Battson]

Thanks Mark,
I have ordered 3" scat tube for my replacement job.

[rv8bldr]

I mounted the oil cooler in my RV-8 on the back of the baffle. 500 hours and all seems well.

[Battson]

Hi Mark,
Did you put a -540 in your RV-8?
Baffle mounting the smaller oil coolers on -360's seems a successful option, I have seen certified aircraft e.g. C172 which do it this way.

[N3UW]

I have a Piper Cherokee 235 that has a O-540. The oil cooler is also mounted to the rear baffle behind cylinder #5. The baffle if here is around 1/8" thick. it has lasted 2000 hours. I can take some photos if anyone is interested,

I mounted the oil cooler in my RV-8 on the back of the baffle. 500 hours and all seems well.

[rv8bldr]

Hey Jonathon

Nope, I have an IO-360-A3B6D 200hp in my -8. This is the larger of the oil coolers for 360's, but I don't know it's size in comparison to what I'll need for a 540. However, I used some serious aluminum angle material (.125) to make the baffle reinforcement and mounting tangs. Probably overkill, but so far so good.

[Battson]

Yes - the area you have mounted yours looks much less-prone to stress concentrations.

[rv8bldr]

BTW, I hate Tripod for web hosting (mostly because I can't seem to reliably post images from it), but I am too lazy to move my RV-8 site. If you want to see the whole oil cooler mount fabrication and mounting, here is a link to my engine page: http://rv8bldr.tripod.com/the_engine.html

[jaredyates]

Can you find the diffuser pre-made or are you going to have to lay it up yourself? I'm on about the third iteration of oil cooler configuration and mine is still not ideal.

[Battson]

I will make a diffuser myself. What has caused you to keep iterating your design Jared?

My whole installation runs very cool, especially the oil. Currently I have the cooler over 50% blocked off. I feel I can afford to give away some airflow over the cooler.

[jaredyates]

In my first mount I used a smaller cooler and had it right up next to the cylinder. Version 2 used a larger cooler and moved it back an inch, but then I developed some cracks in the 1" spacing brackets, and I had the cooler oriented in such a way that it could trap air. Version 3 has the cooler oriented correctly to self-purge the air, but I had to disconnect the pressurized air outlet that I had originally connected to the cabin heat muff inlet. I like the idea of getting such a heavy item off of the baffles though. I beefed mine up considerably, and also ran a steel support from the crankcase back to the cooler.

[Battson]

That is very interesting to read.
I presume that you had some high oil temp issues with the first version?
I think my summer temps were 180F in the climb and 160F in cruise, in winter they got much too low until I made winterisation adjustments. Now they hover around 160F again. I would like to see 200 in the climb, just to be sure I am drying the oil sufficiently.

[kestrel]

Mine is mounted to the engine mount, a lot like Mark's. Instead of a scat tube, I have a constructed, square cross section aluminum duct with a flexible connection perhaps made of baffle material? It works extremely well. My oil temps are always 180F as mine is equipped with one of those regulator thingies that control how much oil goes through or bypasses the cooler. There is about 450hrs on the plane. I've had it since 300 hrs with no issues.

[Battson]

Yeah it would be great to have a thermostatic valve. On the other hand, one more thing to break I suppose. But I would like one.

[AKKen07]

Hello All, to resurrect this thread I would like to ask for a survey of sorts. Would those who have already found a successful arrangement for a -540 powered 4 place please post which make/model of oil cooler is installed and which method of installation you have used (I.E. installed on the baffle, engine mount, firewall, etc.)? I am curious if the answer I am looking at is also where most others have wound up, especially those with multiple iterations. Thank you much!

[svyolo]

I am working on the Vans baffle kit right now. I really want to mount the cooler right to the aft left baffle, but haven't sorted out how to support the inboard side of the rear baffling. If I can't figure it out, I will mount it to the engine mounts with Adel clamps/aluminum angle.

[Bcone1381]

The photo below shows that Bob Barrows placed the oil cooler in the left cowl intake of his Patrol. I don't see many do this, but I dont know why. Bob likes it place here. Its just another data point to consider.

IMG_3721.jpg

[AKKen07]

That is interesting...

[Steve W]

[whee]

If you guys would get real engines that put out some good horse power this wouldn't be an issue/question; the cooler would be bolted to the engine case...








Totally kidding by the way

[Battson]

How many horses did you say you have in there Jon, tell me again