Reinforcement needed on aft left baffle corner?

[alpinelakespilot2000]

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.

[andrew phillips]

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.

[Mark Burns]

Originally Posted by andrew phillips

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 That's 1/8" thick angle!

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[alpinelakespilot2000]

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!

[shuttle]

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

[Mark Burns]

Originally Posted by alpinelakespilot2000

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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[Ironflight]

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

[N941WR]

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 Burns]

Originally Posted by N941WR

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
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

[Ironflight]

Originally Posted by Mark Burns

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!



Paul