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Reinforcement needed on aft left baffle corner?

alpinelakespilot2000

Well Known Member
In the old RV6 baffle plans, the aft left outside corner is shown with a piece of angle running top to bottom, through which the two outboard oil cooler bolts run. However, on the newer OP-27 drawing, that angle is not shown. The oil cooler bolts run only through the oil cooler flanges, the oil cooler opening doubler, the aft baffle, an 0.63 spacer, and then finally the aft-most left side baffle flange. No angle is used. It appears that this is a newer design that supercedes the old RV6 plans. For those who used OP-27, can that angle be safely left out without fear of baffle cracking down the road?

Thanks for any input.
 
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add the angle

I thought the new system would be good enough. I discovered the cracks 3 days ago. In my opinion, the oil cooler needs a diagonal brace (search forums) and the angle should be mandatory. I will be doing both of these on my repairs after less than 100 hrs.
 
I thought the new system would be good enough. I discovered the cracks 3 days ago. In my opinion, the oil cooler needs a diagonal brace (search forums) and the angle should be mandatory. I will be doing both of these on my repairs after less than 100 hrs.

Andrew,
I also thought the new system would be ok since I installed a diagonal brace.
At 140 hours it cracked at the rear corner flange. See the before and after photos. I may have gone a little overboard on the repairs.
But I don't see it cracking here again:D That's 1/8" thick angle!

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Thanks for the tips, guys.

Mark, were the aft corner baffles that cracked T3 or the newer, supposedly strongerT6? Also, do you by chance have a picture of your diagonal brace? Did the crack that formed give you any thoughts about how you might have located the diagonal brace differently?

After seeing that picture I'm thinking whether it needs it or not, it might be worth going ahead and putting the angle on anyway!
 
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I'm assembling my baffles at the moment and looking to beef up this area right from the start.
Has anyone ever used stainless steel (FW) sheet stock to fabricate reinforcements in this area?

Is this a good or bad idea? Would be interested in hearing from those more experienced than I what they think of this.

I'd incorporate dissimilar metal protections and also implement a brace from the engine case to the oil cooler bolt too.

Steve
RV-7 TMX-IO-360-M1B
West Sussex
UK
 
Thanks for the tips, guys.

Mark, were the aft corner baffles that cracked T3 or the newer, supposedly strongerT6? Also, do you by chance have a picture of your diagonal brace? Did the crack that formed give you any thoughts about how you might have located the diagonal brace differently?

After seeing that picture I'm thinking whether it needs it or not, it might be worth going ahead and putting the angle on anyway!

Steve,
I don't know if my baffle material is T3 or T6.

I found a photo of the brace I installed.
It's just a copy of ones I had seen others do. It's 3/8" stainless hydraulic tubing with a .035 wall. After crimping the ends I heated them cherry red and let air cool in hopes to aneal the area to prevent cracking. It has not cracked yet. I think the brace works good to support and prevent a lot of vibration on the inboard side of the oil cooler.

That left rear baffle being .032 material is just not enough.

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That's a very nice looking installation Mark - very neat. I also am a believer in the diagonal brace, but I ran it from the same corner on the rear baffle to a boss on the crankcase Between the front and rear cylinder pushrods). My reasoning was that the cylinder heads might move ever so slightly relative to the rear of the engine, wereas the spine of the case and the rear baffle should form a pretty much rigid triangle. 920 hours - no cracks!

I also, of course, reinforced the heck out of the left rear corner and cooler mount. I spent a lot of time chasing baffle cracks in my old Grumman baffles, and vowed that I'd carry an extra half-pound on the RV if I had to in order to stop THAT madness!

Paul
 
Mark,

I have to agree with Paul on this one, you don't want to tie the two cylinders together because they do move independent of each other.

Here's how I solved the problem:


240 hours and not a crack in sight.
 
Mark,

I have to agree with Paul on this one, you don't want to tie the two cylinders together because they do move independent of each other.

Here's how I solved the problem:


240 hours and not a crack in sight.

Hi Bill,
You probably won't be able to crack a baffle with only 135HP :eek:
Not to mention that smoooth Catto prop.:)

Your bracing does look good and strong though.

The cylinders are not really "tied together" with my brace where it is.
There is plenty of fore/aft movement available in the rear baffle to allow for thermal expansion/contraction of the cylinders. In fact, that's why I put the brace there in the first place as it seemed to be the area that had the most flex.

I read a post somewhere a long time ago where someone said the oil cooler mount needs to be so strong you can move the plane around by tugging on the cooler.

The outboard corner seemed strong enough when built per the plans but it wasn't.

Paul,
Thanks for the kind words. I remember looking at that boss between the cylinders and for some reason I didn't go that route. Maybe you can post a photo of your brace sometime to show us how it's done. It does sound better.

Mark
 
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Paul,
Thanks for the kind words. I remember looking at that boss between the cylinders and for some reason I didn't go that route. Maybe you can post a photo of your brace sometime to show us how it's done. It does sound better.

Mark

Well, I wouldn't say it's "how it's done"....but here's how I did it!

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Paul
 
Well, I wouldn't say it's "how it's done"....but here's how I did it!

Paul


Paul,

That was a quick picture post! I see that you attached the brace high on the rear baffle.
That looks like it would do a good job for sure. I think my problem was that I didn't consider mounting it that high and if you don't the brace will hit the pushrod housing.

This thread should be very helpful for those preparing to tackle the "dreaded baffles" !

Mark
 
A few suggestions

I had the earlier non-prepunched baffle kit and made a lot of changes at the oil cooler connection due to the fact that I have spent so much time repairing baffles on certificated aircraft. The standard Vans design is virtually guaranteed to fail in that area. This is what I did.

1. I threw out the standard Vans oil cooler "flange" and fabricated a new beefier one from 0.032 sheet. See pix 1.

2. I fabricated an outboard corner reinforcement angle from 0.064 sheet. See pix 2.

3. I fabricated an infill section above the oil cooler to stiffen up the area and allow the rubber to run in a straight line in that area (this infill was ultimately provided with the newer prepunched kit). See pix 4.

4. I used 3 bolts on the outboard side and 2 bolts on the inboard side of the oil cooler. See pix 3.

5. I fabricated special "washers" to distribute the bolt/tube loads at the oil cooler flanges. See pix 3.

6. I fabricated a brace to triangulate the oil cooler back to the #4 cylinder head.

I have a few additional comments on this last detail. .

a) I wouldn't run this brace to the #2 cylinder as some have done due to the thermal expansion of the engine (as others on this thread have rightly pointed out).

b) The optimum place to connect the brace at the oil cooler end is onto the oil cooler bolts themselves. This ensures that no oil cooler loads are transmitted through the baffle sheeting at all.

c) It is ideal to pick up 2 bolts at the oil cooler and fabricate the attachment bracket such that the brace strut is coincident with the centre-line of the oil cooler bolts. This will eliminate any eccentric forces that might tend to produce cracking over time.

I've attached a few pix to show these details.


Pix 1. New oil cooler flange.



Pix 2. 0.064 corner angle.



Pix 3. Five bolts used on cooler (note load distribution "washers".



Pix 4. Cooler brace to #4 cylinder (note also infill above cooler for extra stiffness). Note that temporary nylock nuts will be replaced with metal locknuts.
 
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I'm assembling my baffles at the moment and looking to beef up this area right from the start.......Steve.
Steve,

Given the significant number of builders who have reported some degree of baffle failure in the oil cooler area, I did beef up this older, now superceded baffle kit from the start. With minimal modification to the basic baffle assembly, I can happily report no hint of cracking or other failure of any kind has been detected in approximately 250 hours of operational service. The major change was to beef up the left rear corner of the baffle assembly by adding an .063 strap doubler sandwiched between the baffle parts. I extended the doubler downward an inch or so more than strictly necessary and took advantage of the extra length to help support a primer line. The steel brace idea came from others and does seem to work as advertised. Of course supporting those very soft oil cooler flanges (I used cut down AN970-3 area washers) is always a good idea.

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Maybe wrong material!?

Hello,

In the EAA Sport magazine from January 2009, on page 86 is an article that is written about Engine Baffles.

The autor, Richard Koehler is mentioning that you should not use 2024 aluminum, because it will crack under vibration and heat. Better to use 6061.

As I remember correctly, the hole RV is produced out of 2024.

Regards, Dominik
 
Hello,

In the EAA Sport magazine from January 2009, on page 86 is an article that is written about Engine Baffles.

The autor, Richard Koehler is mentioning that you should not use 2024 aluminum, because it will crack under vibration and heat. Better to use 6061.

As I remember correctly, the hole RV is produced out of 2024.

Regards, Dominik

The aluminium sheet used in the rear left quadrant of the Vans baffle kit where the oil cooler attaches is not 2024 alclad. It's a softer more ductile aluminium alloy (and not alclad). At least it was on my pre-punched baffle kit that I bought a couple of years ago. The rest of the baffle seems to be 2024 alclad.
 
How to repair cracked oil cooler baffle

OK during my first annual I have found the same flange cracks that most people have had on the rear baffle oil cooler mount:mad:, also the top flange is cracked and the inner flange between the top two rivets. I did fabricate a brace out of spare 3/4 angle that came with the kit when I built the plane and that angle had also broken where it was bent to bolt to the rear baffle (the front was bolted to the center case a la Paul Dye)
So the question to the group is did people fab a new rear baffle and beef it up as noted in this thread or did you repair the existing baffle?
As I only have 90 hours on the plane I would like to fix this so it lasts.
Would like to point out that the fix to replace the lower cowl hinges with the extruded hinge seems to be working like a champ with no signs of failure so that is a change I think should go in the plans.
 
repeat discussion on baffle cracks

Not to resurrect a dead horse and beat it some more, but.. I finally decided to fix the enlarging crack on the #4 cylinder baffle flange. I saw some high speed footage of an aircraft engine running showing the cylinders moving more than I would anticipate and wondered is it wise to try to firmly attach the preferred stationary mass of an oil cooler to the movement of the cylinder. It appears beefing up that corner with enough bracing seems to work, but why not try to separate the cylinder from the rear bulkhead while supporting the oil cooler to the case. Instead of a hard connection to the corner, why not try a rubber flashing connection? It is used in industry to separate vibration in drive systems. A short heavy section of flashing can support some weight, but also absorb some vibration.
 
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